DOI : 10.17577/IJERTV9IS120109
- Open Access
- Authors : John Ngaya Mukabi
- Paper ID : IJERTV9IS120109
- Volume & Issue : Volume 09, Issue 12 (December 2020)
- Published (First Online): 21-12-2020
- ISSN (Online) : 2278-0181
- Publisher Name : IJERT
- License:
This work is licensed under a Creative Commons Attribution 4.0 International License
Quasi-Mechanistic Analyses of Impact of Vibrational Dynamic Loading on Characteristics of Clayey and Gravelly Geomaterials
John Ngaya Mukabi
R&D/Design Dept.
Kensetsu Kaihatsu Consulting Engineers Ltd.
Nairobi, Kenya
Abstract A desirably realistic modelling and simulation approach for pavement and related geo-structures is to effectively replicate the effects of vibrational dynamic loading (VDL), which is the prevalent mode of loading on practically all live load- imposed structures. In this Study, an innovative comprehensive testing regime was designed to simulate the vibrational dynamic loading commonly experienced during in-service of highway and airport pavements. Based on experimental test results simulating a variety of testing and loading conditions adopted for varying geomaterials, sophisticated analytical models, introduced in this paper, were developed. The validity, lucidity and rationality of the proposed TACH-MD VDL analytical models is pragmatically demonstrated through comparison with experimental testing results. Effective application of these models in the design of highway and airport pavements is ascertained based on tabulated results, graphical plots and analytical discussions. It is rationally derived that the proposed TACH-MD VDL analytical models can be effectively applied for natural and hydraulically stabilized clayey and gravelly geomaterials as well as unbound and bound crushed stone aggregates.
Keywords Vibrational dynamic loading, VDL, analysis, analytical models, quasi-mechanistic, clayey, gravelly, geomaterial.
-
INTRODUCTION
The application of effective quasi-empirical and analytical models that can facilitate for the precise analysis and structural evaluation of the effects of vibrational dynamic loading is indeed one of the most fundamental prerequisites in pavement engineering. In this Study, TACH-MD VDL analytical models that can simulate and account for the effects of vibrational dynamic loading commonly experienced during in-service of highway and airport pavements, are introduced as part of essential design tools [1].
Furthermore, consideration of the fact that some pavements will certainly not be subjected to high intensity dynamic loading, it is imperative that a more realistic approach based on a multi-stage loading regime that takes into account a rebound effect due to post-dynamic-static loading stress release, has been made accordingly. Consequently, a number of tests under sustained dynamic loading to simulate critical state conditions and consideration of future increase in load intensity were performed for this sake [1]. It is important to note that the Airports that can be appropriately characterized with due reference to the sustained dynamic loading model are the likes of Heathrow and JF Kennedy which have landings and take- offs every other minute [1]. Based on the foregoing considerations therefore, several modes of loading including sustained and multi-stage loadings were meticulously designed
and carried out on specimens that represent typical pavement and subgrade materials as well as structural layer configurations in due consideration of the intensity and direction of the impacted stresses [1]. The reliability and effectiveness of applying the proposed models is explicitly manifested in this paper whereby explicable discussions are made in retrospect to the pragmatic pavement structural design of aerodromes in Kenya and Somalia.
-
CORE TACH-MD MODELS FOR DERIVING SHEAR AND MAXIMUM IMPACT STRESSES
Rutting is one of the most important load-induced distresses frequently encountered in flexible asphalt pavements. The primary mechanism of rutting is associated with shear deformation rather than densification. Clearly therefore, shear stress is one of the critical factors affecting pavements performance, hence the serious need to fully comprehend its characteristics in asphalt pavements. Accordingly, therefore, it is imperative to comprehend the loading and stress induction characteristics. However, most conventional pavement design methodologies assume that tyre pavement contact stress is equivalent to tyre inflation pressure and is uniformly distributed over a circular contact area, a theory which fairly contradicts the actuality. In this Study, analyses of the mode of loading, load impact/intensity and loading characteristics are fastidiously carried out by employing the TACH-MD models presented in Equations 1 ~ 6. Equation 1 defines the correlations between shear stress, load intensity, and
pavement thickness, ; whilst Equation 2 expresses the same
for tyre pressure, instead of load intensity, . The relation between the maximum shear stress, . and maximum tyre pressure, , is delineated in Equation 3, while the location of the maximum shear stress, , is defined in Equation 4. On the other hand, Equations 5 and 6 are adopted in computing the maximum impact and contact stresses for simulating aircraft landing impact and vehicular contact stresses, respectively.
= [15.78() + 24.964]2 [2.1299() 3.648] + 0.0786() 0.092 () (1)
= [5.8792 7.7879 15.769 ]2 + [1.7817(0.7443)] + 0.094() +
0.2111 () (2)
. = 6 × 1082 , + 0.0001, +
Vertical Stress Distribution within the Baraawe Airport Runway Pavement and Subsurface Depth of Influence for Varying Design Contact Stresses
0.1454 (),
(3)
Required Design Vertical Stress Capacity, v (MPa)
0 0.5 1 1.5 2 2.5 3
0
, = 16.19(.) + 89.674 () (4)
= 0.01132 14.835 + 6065.2 () (5)
200
Depth of Influence (Thickness), DI (mm)
Depth of Influence (Thickness), DI (mm)
400
600
Near Subsurface Ground Depth Investigated
Range for Near Future Design Consideration
& Structural Performance Evaluation
= 0.0075712 9.93945
+ 4063.684 () (6)
800
1000
Boundary Limit For Structural Subgrade
Examples of the analytical results generated employing
Equations 2, 5 and 6 are provided graphically in Figures 1 ~ 3. Figure 1 depicts the shear stress profile within the upper pavement layers indicating the location and profile of the maximum shear stress.
Shear Stress – Tyre Pressure – Pavement Layer Thickness Relations
1200
1400
1600
1800
2000
DCS: Design Contact Stress in MPa; DCS = 1.250 MPa (1250 kPa)
DCS=1.25 DCS=1.5 DCS=2 DCS=2.6
Resulting Shear Stress, (MPa)
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2
Itp:
Infl (Hi
ated ghe
Tyr r Va
e P lue
ress s fo
ure r Air
in k cra
Pa ft
& Si
mu
lati
on)
td/> Pr
ofil Sh
e of ear
Ma Str
xim ess
um
AC
La
yers
BC
=
.
.
.
+
.
.
+
.
+
.
Itp:
Infl (Hi
ated ghe
Tyr r Va
e P lue
ress s fo
ure r Air
in k cra
Pa ft
& Si
mu
lati
on)
Pr
ofil Sh
e of ear
Ma Str
xim ess
um
AC
La
yers
BC
=
.
.
.
+
.
.
+
.
+
.
0
Pavement Layer Thickness, tP (mm)
Pavement Layer Thickness, tP (mm)
25
50
75
Fig. 2. Vertical stress distribution for varying pavement and subgrade layers.
Vertical Strain Distribution within the Baraawe Airport Runway Pavement and Subsurface Depth of Influence for Varying Design Contact Stress
Required Design Vertical Elastic/Resilient Strain Limit, [v]ELS (%) 0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007
0
200
100
125
150
175
200
225
Itp=200 Itp=300 Itp=400 Itp=460 Itp=500 Itp=600 Itp=700 Itp=810 Itp=900 Itp=1000 Itp=1050 Itp=1100 Itp=1200 Itp=1500 Itp=2000 Itp=2500 Itp=3000
Fig. 1. Shear stress profile within the upper pavement layers.
400
PDepth of Influence (Thickness), DI (mm)
PDepth of Influence (Thickness), DI (mm)
600
800
1000
1200
1400
1600
1800
2000
Range for Near Future Design Consideration
& Structural Performance Evaluation
DCS: Design Contact Stress in MPa; DCS = 1.250 MPa (1250 kPa)
Line of Initial Convergence
@ DI = 100mm
On the other hand, the influence of the magnitude of the tyre pressure and the initial impact stress on the stress and strain distributions and the resulting profile at varying depths is demonstrated in Figures 2 and 3, respectively. The following derivations can be made from these figures: i) the magnitude and characteristic profiles of the shear stress, vertical stress and vertical strain are dependent upon the contact tyre pressure; ii) the maximum shear stress occurs at approximately 0.5, where
represents the upper pavement thickness; the shear and vertical stress distribution profiles are distinctly different; iii) the magnitude of the impact elastic strain decreases with increased contact stress; and iv) on the contrary, the secant elastic strain limit increases with increased design/impact stress, which is in agreement with the concepts of dynamic loading effects on limiting elastic strain and KHSSS (kinematic hardening soil small strain) models ([2],[3], [4], [5] [6], [7]).
DCS=1.25 DCS=1.5 DCS=2 DCS=2.6
Fig. 3. Vertical strain distribution for varying pavement and subgrade layers.
-
VALIDATION OF THE QUASI-MECHANISTIC TACH-MD VDL ANALYTICAL MODELS PROPOSED/ADOPTED
-
TACH-MD VDL models for determining progressive deformation
The importance of developing reliable models for characterizing the progressive deformation of foundation ground, pavements and other geo-structures, cannot be overemphasized. The quasi-mechanistic TACH-MD VDL (vibrational dynamic loading) analytical models proposed/adopted in this Study are introduced hereafter. Characterization of progressive vertical (axial) and lateral (horizontal) deformation under sustained vibrational dynamic loading ([1], [6], [8],[9]) is achieved through the application of the models defined in Equations 7 ~ 14.
= [0.0279(0.0937)] × () 0.5045(0.057) (7)
. = {[0.0279(0.0937)] × () 0.5045(0.057)} × [0.864 0.063(0)] (8)
0
0
. = 0.000177782 0.16540 + 37.726 35% 0 400 (9)
. = (0.0735) (10)
-
Cumulative Dynamic Stress Strain PI Universal Model for Clayey Geomaterials
= 1 × 10149.0922 + 1.63 × 1095.003 +
0 0
0.33082 22.35 + 318.05 () (22)
0
0
.
0
0
. = 13.60544
(11)
Consequently;
-
Cumulative Dynamic Stress Cumulative Loading Cycles PI Universal Model for Clayey Geomaterials
= [0.0279(0.09370.000177782 0.16540 +
= (0.33082 22.35 + 318.05)( )
0
,
37.726 )] × ()
6.17882 + 231.55 2315.3 () (23)
0.5045(0.0570.000177782 0.1654 + 37.726 )
0 0
(12)
-
Cumulative Dynamic Stress Cumulative Loading Cycles PI Universal Model for Gravelly Geomaterials
0
0
= {0.0279(1.6658 × 1052 0.01550 +
3.53493 )} × () 0.5045{4.43346 × 1052
= 1 {
= 1097.81.612} ×
0
3 }
=1
and,
9.4278 × 10
0 + 2.50382
.
(13)
[0.0279(0.0937)] × (){ 0.5045(0.057) }
100 (24)
= {0.0279 [1.27483 (
0
0
0
)]} × ()
.
= 1 {
= 1097.81.612} ×
0
0
0.5045 [0.77551 (
)] (14)
p>=1
-
-
Other TACH-MD VDL models adopted
0
0
[0.0279(0.0937)] × (){ 0.5045(0.057) }
100 (25)
Other quasi-mechanistic TACH-MD VDL analytical models proposed/adopted in this paper are defined in Equations 15 ~ 25.
-
Secant Dynamic Stress – Cumulative Load Cycles – PI Model for Clayey Geomaterials
= [0.06042 + 1.2562 + 43.922] ×
(2×1052+0.0008+0.1208)
-
-
Validation of the TACH-MD models
The data that partially validates the TACH-MD models adopted in the characterization, modelling and simulation of vibrational dynamic loading is summarized in Table I.
Loading Time
Measured Values
Predicted Values
S/N
(Hrs.)
(mins.)
Loading Cycles (No.)
Neat BCS
BCS +
2% Lime
BCS +
Con Aid
+ 2%
Lime
BCS +
5% Lime
Neat BCS
BCS +
2% Lime
BCS +
Con Aid
+ 2%
Lime
BCS +
5% Lime
Loading Sequence
Vertical Deformation, a (%)
1
0.017
1
2800
1.15
0.43
0.12
0.1
1.315
0.429
0.564
-0.086
2
0.033
2
5600
1.703
0.672
0.831
0.053
3
0.050
3
8400
1.929
0.814
0.986
0.134
4
0.067
4
11200
2.22
1.21
0.87
0.23
2.090
0.914
1.097
0.191
5
0.083
5
14000
2.215
0.992
1.183
0.236
6
0.167
10
28000
2.603
1.235
1.450
0.374
7
0.250
15
42000
3.16
1.28
1.26
0.27
2.830
1.377
1.605
0.455
8
0.333
20
56000
2.991
1.478
1.716
0.512
9
0.417
25
70000
3.116
1.556
1.802
0.557
10
0.500
30
84000
3.28
1.22
1.59
0.506
3.218
1.620
1.872
0.593
11
0.667
40
112000
3.505
1.25
1.78
0.67
3.379
1.721
1.983
0.651
12
0.833
50
140000
3.503
1.799
2.069
0.695
13
1.000
60
168000
3.605
1.863
2.139
0.732
14
1.167
70
196000
3.692
1.917
2.198
0.762
15
1.333
80
224000
3.766
1.963
2.249
0.789
16
1.5
90
252000
3.832
2.005
2.295
0.813
17
2.0
120
336000
3.83
1.66
2.29
0.69
3.993
2.105
2.405
0.870
18
2.3
137
384000
5.33
2.152
2.457
0.897
19
3.0
180
504000
Neat BCS Failed After 0.364 Cycles
2.01
2.58
0.82
2.247
2.561
0.951
20
4.0
240
672000
2.16
2.57
0.86
2.348
2.672
1.008
21
5.0
300
840000
2.28
2.76
1.37
2.426
2.758
1.053
22
6.0
360
1008000
2.39
2.78
1.41
2.490
2.828
1.089
23
7.0
420
1176000
Testing Terminated after 1Million Cycles
2.544
2.887
1.120
23
19.0
1,140
3192000
2.894
3.271
1.319
24
59.5
3571
9998800
3.294
3.710
1.547
Loading Time
Measured Values
Predicted Values
S/N
(Hrs.)
(mins.)
Loading Cycles (No.)
Neat BCS
BCS +
2% Lime
BCS +
Con Aid
+ 2%
Lime
BCS +
5% Lime
Neat BCS
BCS +
2% Lime
BCS +
Con Aid
+ 2%
Lime
BCS +
5% Lime
Loading Sequence
Vertical Deformation, a (%)
1
0.017
1
2800
1.15
0.43
0.12
0.1
1.315
0.429
0.564
-0.086
2
0.033
2
5600
1.703
0.672
0.831
0.053
3
0.050
3
8400
1.929
0.814
0.986
0.134
4
0.067
4
11200
2.22
1.21
0.87
0.23
2.090
0.914
1.097
0.191
5
0.083
5
14000
2.215
0.992
1.183
0.236
6
0.167
10
28000
2.603
1.235
1.450
0.374
7
0.250
15
42000
3.16
1.28
1.26
0.27
2.830
1.377
1.605
0.455
8
0.333
20
56000
2.991
1.478
1.716
0.512
9
0.417
25
70000
3.116
1.556
1.802
0.557
10
0.500
30
84000
3.28
1.22
1.59
0.506
3.218
1.620
1.872
0.593
11
0.667
40
112000
3.505
1.25
1.78
0.67
3.379
1.721
1.983
0.651
12
0.833
50
140000
3.503
1.799
2.069
0.695
13
1.000
60
168000
3.605
1.863
2.139
0.732
14
1.167
70
196000
3.692
1.917
2.198
0.762
15
1.333
80
224000
3.766
1.963
2.249
0.789
16
1.5
90
252000
3.832
2.005
2.295
0.813
17
2.0
120
336000
3.83
1.66
2.29
0.69
3.993
2.105
2.405
0.870
18
2.3
137
384000
5.33
2.152
2.457
0.897
19
3.0
180
504000
Neat BCS Failed After 0.364 Cycles
2.01
2.58
0.82
2.247
2.561
0.951
20
4.0
240
672000
2.16
2.57
0.86
2.348
2.672
1.008
21
5.0
300
840000
2.28
2.76
1.37
2.426
2.758
1.053
22
6.0
360
1008000
2.39
2.78
1.41
2.490
2.828
1.089
23
7.0
420
1176000
Testing Terminated after 1Million Cycles
2.544
2.887
1.120
23
19.0
1,140
3192000
2.894
3.271
1.319
24
59.5
3571
9998800
3.294
3.710
1.547
TABLE I. SUMMARY OF DATA COMPARING MEASURED AND MODELLED DYNAMIC LOADING RESULTS.
0.612
(15)
= 10.978 () (16)
= 1097.81.612 () (17)
-
Secant Dynamic Static Stress Correlations for Clayey Geomaterials
[] = 8.1720.7838 () (18) -
Secant Dynamic Static Stress Model for Gravely Geomaterials
[] = 12.060.6304 () (19) -
Secant Dynamic Stress PI Model for Clayey Geomaterials
[ ] = 2321542.14 () (20) -
Secant Dynamic Stress PI Model for Gravely Geomaterials
[] = 75.660.896 () (21)On the other hand, the graphical depictions of the results tabulated in Table I are plotted in Figures 4 and 5 in both
Comparison of Impact of Vibrational Dynamic Loading on Resulting Modulus of Deformation of
Clayey Geomaterials Including Measured vs. Predicted Characteristic Curves for BCS
Comparison of Impact of Vibrational Dynamic Loading on Resulting Modulus of Deformation of
Clayey Geomaterials Including Measured vs. Predicted Characteristic Curves for BCS
3000
3000
= . .
= . .
2500
250
2000
2000
Modlus of Deformation, ED (kPa)
Modlus of Deformation, ED (kPa)
arithmetic and semi-log scales, respectively. The tabulated data and graphical figures also make a comparison between measured and modelled results. It can be can be noted that, in all cases, an appreciable fitting of the characteristic curves is achieved for the varying natural and stabilized black cotton soils from the Lake Victoria Region of Western Kenya.
1500
1500
Comparison of Measured vs. Predicted Deformation of Neat & Stabilized Black Cotton Soil
1000
1000
6
= . . × . .
500
500
5
0
1000
0
1000
Neat BCS
10000
10000
100000
100000
1000000
1000000
Axial Strain, a (%)
Axial Strain, a (%)
4 Failed @
Nvd=384000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Cycles
3
Neat BCS: Measured
Neat BCS: Predicted
Afmadow Silty Clay
Neat BCS: Measured
Neat BCS: Predicted
Afmadow Silty Clay
2
1
0
0 200000 400000 600000 800000 1000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Neat BCS: Measured Neat BCS: Predicted BCS+2% Lime: Measured BCS+2% Lime: Predicted BCS+Con Aid+2% Lime: Measured BCS+Con Aid+2% Lime: Predicted BCS+5% Lime: Measured BCS+5% Lime: Predicted
Fig. 4. Comparison of measured and modelled deformation results under dynamic loading (arithmetic scale).
Comparison of Measured vs. Predicted Deformation of Neat & Stabilized Black Cotton Soil
Fig. 7. Comparison of measured and modelled results for impact of dynamic loading on modulus of deformation [ = 1].
All the depicted graphs also include a comparison of measured and predicted results. It can be observed that, in conformity with their magnitude of initial stiffness, the Baraawe silty clay has the highest resistance to deformation, whilst the BCS registers the lowest. Measured vs. predicted BCS results show quasi-perfect superimposition.
Further validation of the TACH-MD VDL models is udertaken throughout this paper by comparing measured and
6
= . . × . .
5
Axial Strain, a (%)
Axial Strain, a (%)
4
3
2
1
0
Neat BCS
Failed @ Nvd=384000
Cycles
geo-mathematically modelled results.
-
-
-
PRINCIPAL RESULTS ADOPTED FOR VDL ANALYSES
-
Example of parametric principal design parameters adopted for VDL analyses
Table II presents a summary of the principal design
parameters adopted for dynamic loading analysis undertaken for Bardhere and Diinsoor gravels sampled from Somalia.
1000 10000 100000 1000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Neat BCS: Measured Neat BCS: Predicted BCS+2% Lime: Measured BCS+2% Lime: Predicted BCS+Con Aid+2% Lime: Measured BCS+Con Aid+2% Lime: Predicted BCS+5% Lime: Measured BCS+5% Lime: Predicted
Fig. 5. Comparison of measured and modelled deformation results under dynamic loading (semi-log scale).
20000
20000
15000
15000
Modlus of Deformation, ED (kPa)
Modlus of Deformation, ED (kPa)
Characteristics of the modulus of deformation of natural black cotton soil, Afmadow and Baraawe silty clays (Somalia) are graphically depicted in Figures 6 and 7 for loadings up to 10 million and 1 million cycles, respectively.
30000
Comparison of Impact of Vibrational Dynamic Loading on Resulting Modulus of Deformation of
Clayey Geomaterials Including Measured vs. Predicted Characteristic Curves for BCS
30000
Comparison of Impact of Vibrational Dynamic Loading on Resulting Modulus of Deformation of
Clayey Geomaterials Including Measured vs. Predicted Characteristic Curves for BCS
= . .
= . .
25000
25000
0
1000
10000
100000
1000000
0
1000
10000
100000
1000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Neat BCS: Measured
Neat BCS: Predicted
Baraawe Silty Clay
Afmadow Silty Clay
Neat BCS: Measured
Neat BCS: Predicted
Baraawe Silty Clay
Afmadow Silty Clay
10000
10000
5000
5000
Fig. 6. Comparison of measured and modelled results for impact of dynamic
Summary of Principal Parameters Adopted for Dynamic Loading Analysis
Construction Stage
Pre-Construction
Post-Construction
Parametric Description
Afmadow
Hudur
Bardhere
Diinsoor
Gravel Wearing Course (GCW) Bearing Capacity, CBR ( %)
45
20
32
14
Equivalent Base Course (EBC) Bearing Capacity, CBR ( %)
To Be Deterined During Design Stage
To Be Deterined During Design Stage
32
14
Equivalent Sub-Base (ESB) Bearing Capacity, CBR ( %)
32
14
Structural Subgrade Bearing Capacity, CBR ( %)
11
20
29
8
Gravel Wearing Course (GCW) Bearing Capacity, UCS (MPa)
1.087
0.483
0.771
0.338
Equivalent Base Course (EBC) Bearing Capacity, UCS (MPa)
To Be Deterined During Design Stage
To Be Deterined During Design Stage
0.771
0.338
Equivalent Sub-Base (ESB) Bearing Capacity, UCS (MPa)
0.771
0.338
Structural Subgrade Bearing Capacity,UCS (MPa)
0.700
0.193
Gravel Wearing Course (GCW) Elastic Modulus, Eo (Mpa)
232
95
147
72
Equivalent Base Course (EBC) Elastic Modulus, Eo (Mpa)
To Be Deterined During Design Stage
To Be Deterined During Design Stage
147
72
Equivalent Sub-Base (ESB) Elastic Modulus, Eo (Mpa)
147
72
Structural Subgrade Resilient Modulus, MR (MPa)
58
95
133
44
Mean Pavement Thickness Determined from DCP Tests, tdcp (mm)
To Be Deterined Durng Design Stage
To Be Deterined During Design Stage
263
205
Computational Models Adopted
Values Computed Based on Conventional SN/CBR Models
Values Computed Based on Quasi-Mechanistic Models
Structural Layer Designation
GWC
EBC
ESB
GWC
EBC
ESB
GWC
EBC
ESB
GWC
EBC
ESB
Computed Discrete Structural Layer Thickness, tstr. (mm)
To Be Deterined During Design Stage
To Be Deterined During Design Stage
107
62
94
100
48
57
Existing Thickness-Modulus Ratio (mm/MPa)
0.728
0.422
0.639
1.389
0.667
0.792
Required Discrete Structural Layer Stiffness, Eo (MPa) [To Achieve a PBBD (Performance Based Balanced Design)]
4573
4573
491
3953
3953
1188
Required Full Depth Composite Pavement Stiffness, Eo (MPa) [To Achieve a PBBD (Performance Based Balanced Design)]
1365
1365
Existing Full Depth (Composite) Structural Thickness, TFD (mm)
263
205
Example of Computed Values for Enhanced Structural Capacity Required for Fokker50 as Design Aircraft for Bardhere & Diinsoor Airstrips
Computational Models Adopted
Values Computed Based on Conventional SN/CBR Models
Values Computed Based on Quasi-Mechanistic Models
Allowable Full Depth (Composite) Pavement Thickness, TFD (mm)
To Be Deterined During Design Stage
To Be Deterined During Design Stage
300
420
Required Full Depth (Composite) Pavement Thickness, TFD (mm)
300
450
Structural Layer Designation
GWC
EBC
ESB
GWC
EBC
ESB
GWC
EBC
ESB
GWC
EBC
ESB
Computed Discrete Structural Layer Thickness, tstr. (mm)
To Be Deterined During Design Stage
To Be Deterined During Design Stage
100
100
100
150
150
150
Existing Thickness-Modulus Ratio (mm/MPa)
0.022
0.035
0.216
0.057
0.119
0.325
Required Discrete Structural Layer Stiffness, Eo (MPa) [To Achieve a PBBD (Performance Based Balanced Design)]
4573
2835
462
2635
1265
462
Required Full Depth Composite Pavement Stiffness, Eo (MPa) [To Achieve a PBBD (Performance Based Balanced Design)]
853
853
Legend: SE -Structural Evaluation; GWC -Gravel Wearing Course; EBC -Equivalent Base Course; ESF : Equivalent Structural Foundation
Summary of Principal Parameters Adopted for Dynamic Loading Analysis
Construction Stage
Pre-Construction
Post-Construction
Parametric Description
Afmadow
Hudur
Bardhere
Diinsoor
Gravel Wearing Course (GCW) Bearing Capacity, CBR ( %)
45
20
32
14
Equivalent Base Course (EBC) Bearing Capacity, CBR ( %)
To Be Deterined During Design Stage
To Be Deterined During Design Stage
32
14
Equivalent Sub-Base (ESB) Bearing Capacity, CBR ( %)
32
14
Structural Subgrade Bearing Capacity, CBR ( %)
11
20
29
8
Gravel Wearing Course (GCW) Bearing Capacity, UCS (MPa)
1.087
0.483
0.771
0.338
Equivalent Base Course (EBC) Bearing Capacity, UCS (MPa)
To Be Deterined During Design Stage
To Be Deterined During Design Stage
0.771
0.338
Equivalent Sub-Base (ESB) Bearing Capacity, UCS (MPa)
0.771
0.338
Structural Subgrade Bearing Capacity,UCS (MPa)
0.700
0.193
Gravel Wearing Course (GCW) Elastic Modulus, Eo (Mpa)
232
95
147
72
Equivalent Base Course (EBC) Elastic Modulus, Eo (Mpa)
To Be Deterined During Design Stage
To Be Deterined During Design Stage
147
72
Equivalent Sub-Base (ESB) Elastic Modulus, Eo (Mpa)
147
72
Structural Subgrade Resilient Modulus, MR (MPa)
58
95
133
44
Mean Pavement Thickness Determined from DCP Tests, tdcp (mm)
To Be Deterined During Design Stage
To Be Deterined During Design Stage
263
205
Computational Models Adopted
Values Computed Based on Conventional SN/CBR Modes
Values Computed Based on Quasi-Mechanistic Models
Structural Layer Designation
GWC
EBC
ESB
GWC
EBC
ESB
GWC
EBC
ESB
GWC
EBC
ESB
Computed Discrete Structural Layer Thickness, tstr. (mm)
To Be Deterined During Design Stage
To Be Deterined During Design Stage
107
62
94
100
48
57
Existing Thickness-Modulus Ratio (mm/MPa)
0.728
0.422
0.639
1.389
0.667
0.792
Required Discrete Structural Layer Stiffness, Eo (MPa) [To Achieve a PBBD (Performance Based Balanced Design)]
4573
4573
491
3953
3953
1188
Required Full Depth Composite Pavement Stiffness, Eo (MPa) [To Achieve a PBBD (Performance Based Balanced Design)]
1365
1365
Existing Full Depth (Composite) Structural Thickness, TFD (mm)
263
205
Example of Computed Values for Enhanced Structural Capacity Required for Fokker50 as Design Aircraft for Bardhere & Diinsoor Airstrips
Computational Models Adopted
Values Computed Based on Conventional SN/CBR Models
Values Computed Based on Quasi-Mechanistic Models
Allowable Full Depth (Composite) Pavement Thickness, TFD (mm)
To Be Deterined During Design Stage
To Be Deterined During Design Stage
300
420
Required Full Depth (Composite) Pavement Thickness, TFD (mm)
300
450
Structural Layer Designation
GWC
EBC
ESB
GWC
EBC
ESB
GWC
EBC
ESB
GWC
EBC
ESB
Computed Discrete Structural Layer Thickness, tstr. (mm)
To Be Deterined During Design Stage
To Be Deterined During Design Stage
100
100
100
150
150
150
Existing Thickness-Modulus Ratio (mm/MPa)
0.022
0.035
0.216
0.057
0.119
0.325
Required Discrete Structural Layer Stiffness, Eo (MPa) [To Achieve a PBBD (Performance Based Balanced Design)]
4573
2835
462
2635
1265
462
Required Full Depth Composite Pavement Stiffness, Eo (MPa) [To Achieve a PBBD (Performance Based Balanced Design)]
853
853
Legend: SE -Structural Evaluation; GWC -Gravel Wearing Course; EBC -Equivalent Base Course; ESF : Equivalent Structural Foundation
TABLE II. EXAMPLE OF PARAMETRIC PRINCIPAL DESIGN PARAMETERS ADOPTED FOR VIBRATIONAL DYNAMIC LOADING (VDL) ANALYSIS.
loading on modulus of deformation [
= 10].
-
Summary of results adopted for analyses of VDL impact
Summaries of the results adopted for analyses of vibrational dynamic loading impact are tabulated in Tables III ~ V for natural clayey geomaterials and Tables VI ~ VIII for natural gravelly geomaterials.
TABLE III. SUMMARY OF DATA ADOPTED FOR ANALYSIS OF DYNAMIC LOADING EFFECTS ON DEFORMATION CHARACTERISTICS OF CLAYEY GEOMATERIALS.
Dynamic Loading Effects on Deformation & Modulus of Deformation Characteristics of Clayey Geomaterials
Loading Cycles (No.)
Neat BCS: Measured
Neat BCS: Predicted
Neat Baraawe Silty Clay
Neat Afmadow Expansive Clay
Neat BCS: Predicted from Measured Values
Neat BCS: Predicted
Neat Baraawe Silty Clay
Neat Afmadow Expansive Clay
Vertical Deformation, a (%)
Resulting Modulus of Deformation, ED (kPa)
2800
1.15
1.315
0.564
876
706
2764
5600
1.703
0.831
466
1481
8400
1.929
0.986
381
1122
11200
2.22
2.090
1.097
304
334
945
14000
2.215
0.031
1.183
305
295015
837
28000
2.603
0.136
1.450
235
27510
603
42000
3.16
2.830
0.197
1.605
172
205
15102
512
56000
2.991
0.240
1.716
188
10954
460
70000
3.116
0.274
1.802
176
8867
425
84000
3.28
3.218
0.301
1.872
162
167
7600
400
112000
3.505
3.379
0.344
1.983
145
154
6118
364
140000
3.503
0.378
2.069
145
5265
340
168000
3.605
0.406
2.139
139
4702
32
196000
3.692
0.429
2.198
134
4299
308
224000
3.766
0.449
2.249
129
3992
297
252000
3.832
0.467
2.295
126
3750
288
336000
3.83
3.993
0.510
2.405
126
118
3250
267
383600
5.33
4.068
0.530
2.457
74
114
3054
258
504000
4.220
0.571
2.561
108
2708
241
672000
4.381
0.614
2.672
101
2407
225
840000
4.506
0.648
2.758
97
2209
214
1008000
4.608
0.676
2.828
94
2066
205
1176000
4.694
0.699
2.887
91
1956
199
3192000
5.253
0.849
3.271
76
1429
162
9998800
5.892
1.021
3.710
63
1061
133
Dynamic Loading Effects on Stress-Strain Characteristics of Clayey Geomaterials
Loading Cycles (No.)
Neat BCS: Measured
Neat BCS: Predicted
Neat Baraawe Silty Clay
Neat Afmadow Expansive Clay
Neat BCS: Predicted from Measured Values
Neat BCS: Predicted
Neat Baraawe Silty Clay
Neat Afmadow Expansive Clay
Strain, a (%)
Resulting Deviatoric Stress, (kPa)
2800
1.15
1.315
0.564
10.08
9.29
15.59
5600
1.703
0.831
7.93
12.30
8400
1.929
0.986
7.34
11.07
11200
2.22
2.090
1.097
6.74
6.99
10.37
14000
2.215
0.031
1.183
6.75
91.80
9.91
28000
2.603
0.136
1.450
6.11
37.29
8.75
42000
3.16
2.830
0.197
1.605
5.43
5.81
29.70
8.22
56000
2.991
0.240
1.716
5.61
26.29
7.89
70000
3.116
0.274
1.802
5.48
24.26
7.66
84000
3.28
3.218
0.301
1.872
5.31
5.37
22.88
7.48
112000
3.505
3.379
0.344
1.983
5.10
5.21
21.08
7.22
140000
3.503
0.378
2.069
5.10
19.91
7.04
168000
3.605
0.406
2.139
5.01
19.07
6.89
196000
3.692
0.429
2.198
4.94
18.43
6.78
224000
3.766
0.449
2.249
4.88
17.92
6.68
252000
3.832
0.467
2.295
4.82
17.50
6.60
336000
3.83
3.993
0.510
2.405
4.83
4.70
16.58
6.42
383600
5.33
4.068
0.530
2.457
3.94
4.65
16.19
6.33
504000
4.220
0.571
2.561
4.55
15.47
6.17
672000
4.381
0.614
2.672
4.45
14.79
6.02
840000
4.506
0.648
2.758
4.37
14.32
5.90
1008000
4.608
0.676
2.828
4.31
13.96
5.81
1176000
4.694
0.699
2.887
4.26
13.67
5.74
3192000
5.253
0.849
3.271
3.98
12.13
5.32
9998800
5.892
1.021
3.710
3.71
10.84
4.92
Equivalent Dynamic Strength (kPa)
135.6
474
193
Static Strength, UCS (kPa)
36.2
169
48.3
CBR (%)
1.5
7
2
Dynamic Loading Effects on Stress-Strain Characteristics of Clayey Geomaterials
Loading Cycles (No.)
Neat BCS: Measured
Neat BCS: Predicted
Neat Baraawe Silty Clay
Neat Afmadow Expansive Clay
Neat BCS: Predicted from Measured Values
Neat BCS: Predicted
Neat Baraawe Silty Clay
Neat Afmadow Expansive Clay
Strain, a (%)
Resulting Deviatoric Stress, (kPa)
2800
1.15
1.315
0.564
10.08
9.29
15.59
5600
1.703
0.831
7.93
12.30
8400
1.929
0.986
7.34
11.07
11200
2.22
2.090
1.097
6.74
6.99
10.37
14000
2.215
0.031
1.183
6.75
91.80
9.91
28000
2.603
0.136
1.450
6.11
37.29
8.75
42000
3.16
2.830
0.197
1.605
5.43
5.81
29.70
8.22
56000
2.991
0.240
1.716
5.61
26.29
7.89
70000
3.116
0.274
1.802
5.48
24.26
7.66
84000
3.28
3.218
0.301
1.872
5.31
5.37
22.88
7.48
112000
3.505
3.379
0.344
1.983
5.10
5.21
21.08
7.22
140000
3.503
0.378
2.069
5.10
19.91
7.04
168000
3.605
0.406
2.139
5.01
19.07
6.89
196000
3.692
0.429
2.198
4.94
18.43
6.78
224000
3.766
0.449
2.249
4.88
17.92
6.68
252000
3.832
0.467
2.295
4.82
17.50
6.60
336000
3.83
3.993
0.510
2.405
4.83
4.70
16.58
6.42
383600
5.33
4.068
0.530
2.457
3.94
4.65
16.19
6.33
504000
4.220
0.571
2.561
4.55
15.47
6.17
672000
4.381
0.614
2.672
4.45
14.79
6.02
840000
4.506
0.648
2.758
4.37
14.32
5.90
1008000
4.608
0.676
2.828
4.31
13.96
5.81
1176000
4.694
0.699
2.887
4.26
13.67
5.74
3192000
5.253
0.849
3.271
3.98
12.13
5.32
9998800
5.892
1.021
3.710
3.71
10.84
4.92
Equivalent Dynamic Strength (kPa)
135.6
474
193
Static Strength, UCS (kPa)
36.2
169
48.3
CBR (%)
1.5
7
2
TABLE IV. SUMMARY OF DATA ADOPTED FOR ANALYSIS OF DECAY STRESS CHARACTERISTICS OF CLAYEY GEOMATERIALS SUBJECTED TO VIBRATIONAL DYNAMIC LOADING EFFECTS.
TABLE V. SUMMARY OF DATA ADOPTED FOR ANALYSIS OF CUMULATIVE STRESS-STRAIN CHARACTERISTICS OF CLAYEY GEOMATERIALS SUBJECTED TO VIBRATIONAL DYNAMIC LOADING .
Summary of Dynamic Loading Effects on Stress-Strain Characteristics of Clayey Geomaterials
Loading Cycles (No.)
Neat BCS: Measured
Neat BCS: Predicted
Neat Baraawe Silty Clay
Neat Afmadow Expansive Clay
Neat BCS: Predicted from Measured Values
Neat BCS: Predicted
Neat Baraawe Silty Clay
Neat Afmadow Expansive Clay
Strain, a (%)
Resulting Deviatoric Stress, (kPa)
2800
1.15
1.315
0.564
10.08
9
16
5600
1.703
0.831
17
28
8400
1.929
0.986
25
39
11200
2.22
2.090
1.097
6.74
32
49
14000
2.215
0.031
1.183
38
92
59
28000
2.603
0.136
1.450
44
129
68
42000
3.16
2.830
0.197
1.605
5.43
50
159
76
56000
2.991
0.240
1.716
56
185
84
70000
3.116
0.274
1.802
61
209
92
84000
3.28
3.218
0.301
1.872
5.31
67
232
99
112000
3.505
3.379
0.344
1.983
5.10
72
253
106
140000
3.503
0.378
2.069
77
273
113
168000
3.605
0.406
2.139
82
292
120
196000
3.692
0.429
2.198
87
311
127
224000
3.766
0.449
2.249
92
329
134
252000
3.832
0.467
2.295
97
346
140
336000
3.83
3.993
0.510
2.405
4.83
101
363
147
383600
5.33
4.068
0.530
2.457
3.94
106
379
153
504000
4.220
0.571
2.561
111
394
159
672000
4.381
0.614
2.672
115
409
165
840000
4.506
0.648
2.758
119
423
171
1008000
4.608
0.676
2.828
124
437
177
1176000
4.694
0.699
2.887
128
451
183
3192000
5.253
0.849
3.271
132
463
188
9998800
5.892
1.021
3.710
136
474
193
Equivalent Dynamic Strength (kPa)
135.6
474.1
193.1
Static Strength, UCS (kPa)
36.2
169
48.3
CBR (%)
1.5
7
2
TABLE VI. SUMMARY OF DATA ADOPTED FOR ANALYSIS OF MODULUS OF DEFORMATION CHARACTERISTICS OF GRAVELLY GEOMATERIALS SUBJECTED TO VIBRATIONAL DYNAMIC LOADING.
Dynamic Loading Effects on Axial Strain & Modulus of Deformation Characteristics of Somalia Gravel Geomaterials
Loading Cycles (No.)
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Baraawe Silty Clay
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Baraawe Silty Clay
Vertical Deformation, a (%)
Resulting Modulus of Deformation, ED (MPa)
Post-
Construct
Pre-
Construct
Pre-
Construct
Post-
Construct
Post-
Construct
Pre-
Construct
Pre-
Construct
Post-
Construct
2800
5600
8400
11200
14000
0.031
295
28000
0.136
28
42000
0.197
15
56000
0.240
11
70000
0.274
9
84000
0.011
0.301
1569
8
112000
0.038
0.344
212
6
140000
0.018
-0.074
0.059
0.378
720
105
5
168000
0.034
-0.063
0.076
0.406
261
69
4.7
196000
0.005
0.047
-0.053
0.091
0.429
5527
153
52
4.3
224000
0.015
0.058
-0.044
0.104
0.449
917
107
42
4.0
252000
0.025
0.068
-0.036
0.115
0.467
433
83
36
3.8
336000
0.014
0.047
0.093
-0.018
0.142
0.510
1064
153
50
26
3.3
383600
0.023
0.057
0.104
-0.009
0.154
0.530
465
111
42
22
3.1
504000
0.043
0.078
0.128
0.009
0.180
0.571
176
67
30
2297
17
2.7
672000
0.063
0.101
0.153
0.027
0.207
0.614
94
45
23
363
14
2.4
840000
0.079
0.118
0.172
0.009
0.042
0.228
0.648
65
35
19
2029
183
12
2.2
1008000
0.092
0.132
0.187
0.020
0.054
0.245
0.676
51
29
16
593
123
11
2.1
1176000
0.103
0.144
0.201
0.029
0.064
0.260
0.699
43
25
15
326
93
10
2.0
3192000
0.174
0.221
0.286
0.088
0.128
0.354
0.849
18
12
8
55
30
6
1.4
9998800
0.256
0.310
0.385
0.156
0.202
0.462
1.021
10
7
5
22
14
4
1.1
TABLE VII. SUMMARY OF DATA ADOPTED FOR ANALYSIS OF SECANT STRESS DECAY CHARACTERISTICS OF GRAVELLY GEOMATERIALS SUBJECTED TO VIBRATIONAL DYNAMIC LOADING.
Dynamic Loading Effects on Deformation Characteristics of Somalia Gravel Geomaterials
Loading Cycles (No.)
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Baraawe Silty Clay
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Baraawe Silty Clay
Vertical Deformation, a (%)
Resulting Secant Deviatoric Stress, (kPa)
Post-
Construct
Pre-
Construct
Pre-
Construct
Post-
Construct
Post-
Construct
Pre-
Construct
Pre-
Construct
Post-
Construct
2800
5600
8400
11200
14000
0.031
91.80
28000
0.136
37.29
42000
0.197
29.70
56000
0.240
26.29
70000
0.274
24.26
84000
0.011
0.301
173.14
22.88
112000
0.038
0.344
81.01
21.08
140000
0.018
0.059
0.378
128.80
61.91
19.91
168000
0.034
0.076
0.406
87.66
52.97
19.07
196000
0.005
0.047
0.091
0.429
279.24
71.51
47.61
18.43
224000
0.015
0.058
0.104
0.449
141.19
62.54
43.98
17.92
252000
0.025
0.068
0.115
0.467
106.19
56.70
41.32
17.50
336000
0.014
0.047
0.093
0.142
0.510
149.39
71.49
46.94
36.28
16.58
383600
0.023
0.057
0.104
0.009
0.154
0.530
109.07
63.32
43.74
196.26
34.46
16.19
504000
0.043
0.078
0.128
0.009
0.180
0.571
75.40
52.22
38.65
200.09
31.35
15.47
672000
0.063
0.101
0.153
0.004
0.027
0.207
0.614
59.38
44.79
34.69
334.24
99.30
28.77
14.79
840000
0.079
0.118
0.172
0.009
0.042
0.228
0.648
51.78
40.64
32.26
190.87
76.59
27.12
14.32
1008000
0.092
0.132
0.187
0.020
0.054
0.245
0.676
47.20
37.92
30.59
119.68
65.77
25.94
13.96
1176000
0.103
0.144
0.201
0.029
0.064
0.260
0.699
44.06
35.96
29.34
95.29
59.24
25.04
13.67
3192000
0.174
0.221
0.286
0.088
0.128
0.354
0.849
31.97
27.64
23.60
48.51
38.56
20.72
12.13
9998800
0.256
0.310
0.385
0.156
0.202
0.462
1.021
25.29
22.49
19.70
34.27
29.18
17.61
10.84
Equivalent Dynamic Strength (kPa)
594
923
707
823
765
749
474
Static Strength, UCS (kPa)
483
1086
627
1070
852
701
169
CBR (%)
20
45
26
44
35
29
7
Plasticity Index, PI (%)
10
11
12
8
9
13
18
TABLE VIII. SUMMARY OF DATA ADOPTED FOR ANALYSIS OF CUMULATIVE STRESS-STRAIN CHARACTERISTICS OF GRAVELLY GEOMATERIALS SUBJECTED TO VIBRATIONAL DYNAMIC LOADING.
Cumulative Stress-Strain Characteristics Under Vibrational Dynamic Loading: Effects on Deformation Characteristics of Somalia Gravel Geomaterials
Loading Cycles (No.)
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Baraawe Silty Clay
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Baraawe Silty Clay
Vertical Deformation, a (%)
Resulting Secant Deviatoric Stress, (kPa)
Post- Construct
Pre- Construct
Pre- Construct
Post- Construct
Post- Construct
Pre- Construct
Pre- Construct
Post- Construct
2800
5600
8400
11200
14000
0.031
92
28000
0.136
129
42000
0.197
159
56000
0.240
185
70000
0.274
209
84000
0.011
0.301
173
232
112000
0.038
0.344
254
253
140000
0.018
0.059
0.378
129
316
273
168000
0.034
0.076
0.406
216
369
292
196000
0.005
0.047
0.091
0.429
279
288
417
311
224000
0.015
0.058
0.104
0.449
420
351
461
329
252000
0.025
0.068
0.115
0.467
527
407
502
346
336000
0.014
0.047
0.093
0.142
0.510
149
598
454
538
363
383600
0.023
0.057
0.104
0.009
0.154
0.530
258
661
498
573
379
504000
0.043
0.078
0.128
0.009
0.180
0.571
334
714
537
604
394
672000
0.063
0.101
0.153
0.004
0.027
0.207
0.614
393
758
571
633
409
840000
0.079
0.118
0.172
0.009
0.042
0.228
0.648
445
799
603
660
423
1008000
0.092
0.132
0.187
0.020
0.054
0.245
0.676
492
837
634
686
437
1176000
0.103
0.144
0.201
0.029
0.064
0.260
0.699
536
873
663
711
451
3192000
0.174
0.221
0.286
0.088
0.128
0.354
0.849
568
901
687
732
463
9998800
0.256
0.310
0.385
0.156
0.202
0.462
1.021
594
923
707
749
474
Equivalent Dynamic Strength (kPa)
594
923
707
823
765
749
474
Static Strength, UCS (kPa)
483
1086
627
1070
852
701
169
CBR (%)
20
45
26
44
35
29
7
Plasticity Index, PI (%)
10
11
12
8
9
13
18
-
-
VDL CHARACTERISTICS OF CLAYEY GEOMATERIALS Simulation of the Afmadow silty clay foundation ground is
undertaken by comparatively evaluating the dynamic loading characteristics of clayey subgrade geomaterials. This involves the comparative analysis of: i) load impact (maximum impact
upon contact) characteristics depicting the effects of lime stabilization on black cotton soil (BC) subjected to vibrational dynamic loading; ii) dynamic loading impact on the modulus of deformation of non-stabilized clayey geomaterials; iii) decay characteristics of secant stress as a result of cumulative dynamic loading effects; iv) deformation characteristics of clayey geomaterials under dynamic loading; and, v) cumulative stress- strain characteristics of neat clayey geomaterials subjected to vibrational dynamic loading.
-
Analysis of load impact characteristics of natural and hydraulically stabilized clayey geomaterials
A summary of the results of the impact of vibrational dynamic loading (VDL) on the characteristics of natural, lime and lime-conaid treated black cotton soil (BCS) and natural Afmadow silty clay is presented in Table IX, whilst the corresponding deformation characteristics are graphically depicted in Figures 8 and 9 for VD loadings within the range of 10 million and 1 million cycles, respectively.
The characteristic curves in these graphs show that: i) notwithstanding the geomaterial type, deformation is significantly impacted by the cumulative cycles of the VDL; ii) in conformity with their bearing strengths (CBRs), the Baraawe silty clay quantitatively exhibits the lowest deformation, whilst the BCS registers the highest (4 days soaked CBRs: Baraawe=7%; Afmadow=2% BCS=1.5%); ii) lime stabilization enhances deformation resistance of the BCS; and
iii) the Afmadow silty clay subgrade requires in-situ ground improvement.
TABLE IX. COMPARISON OF NATURAL AND STABILIZED CLAYEY GEOMATERIALS SUBJECTED TO VIBRATIONAL DYNAMIC LOADING RESULTS.
Comparison of Vibrational Dynamic Loading Effects on Deformation Characteristics of Clayey Geomaterials
Loading Cycles (No.)
Neat BCS: Measured
Neat BCS: Predicted
Neat Baraawe Silty Clay
Neat Afmadow Expansive Clay
Neat BCS: Predicted from Measured Values
Neat BCS: Predicted
Neat Baraawe Silty Clay
Neat Afmadow Expansive Clay
Vertical Deformation, a (%)
Resulting Modulus of Deformation, ED (kPa)
2800
1.15
1.315
0.564
876
706
2764
5600
1.703
0.831
466
1481
8400
1.929
0.986
381
1122
11200
2.22
2.090
1.097
304
334
945
14000
2.215
0.031
1.183
305
295015
837
28000
2.603
0.136
1.450
235
27510
603
42000
3.16
2.830
0.197
1.605
172
205
15102
512
56000
2.991
0.240
1.716
188
10954
460
70000
3.116
0.274/p>
1.802
176
8867
425
84000
3.28
3.218
0.301
1.872
162
167
7600
400
112000
3.505
3.379
0.344
1.983
145
154
6118
364
140000
3.503
0.378
2.069
145
5265
340
168000
3.605
0.406
2.139
139
4702
322
196000
3.692
0.429
2.198
134
4299
308
224000
3.766
0.449
2.249
129
3992
297
252000
3.832
0.467
2.295
126
3750
288
336000
3.83
3.993
0.510
2.405
126
118
3250
267
383600
5.33
4.068
0.530
2.457
74
114
3054
258
504000
4.220
0.571
2.561
108
2708
241
672000
4.381
0.614
2.672
101
2407
225
840000
4.506
0.648
2.758
97
2209
214
1008000
4.608
0.676
2.828
94
2066
205
1176000
4.694
0.699
2.887
91
1956
199
3192000
5.253
0.849
3.271
76
1429
162
9998800
5.892
1.021
3.710
63
1061
133
4.5
4
3.5
Axial Strain, a (%)
Axial Strain, a (%)
3
Comparison of Impact of Vibrational Dynamic Loading on Deformation of Clayey
Geomaterials
Neat BCS Failed @ Nvd=384000 Cycles
The results in Figure 10 show that: i) the mode and rate of secant deviatoric stress decay as a result of cumulative VDL is dependent upon the nature and stiffness of the clayey geomaterial; and ii) a very good agreement exists between the measured and modelled (predicted) results.
Figure 11 depicts the superimposed VDL stress-strain
2.5
= . . ×
. .
curves for varying clays. The graph also includes a comparison
2
1.5
1
0.5
0
of measured and predicted results for BCS. As was deduced form Figure 10, the Baraawe silty clay has the highest resistance to stress decay, whilst the BCS registers the lowest. Measured vs. predicted BCS results show quasi-perfect superimposition.
Comparison of Impact of Vibrational Dynamic Loading on Deformation of Clayey
Geomaterials Including Meausred vs. Predicted Results for BCS
Comparison of Impact of Vibrational Dynamic Loading on Deformation of Clayey
Geomaterials Including Meausred vs. Predicted Results for BCS
= . . × . .
= . . × . .
0 2000000 4000000 6000000 8000000 10000000
100
100
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
= . .
90
= . .
90
80
70
60
50
40
30
20
10
0
80
70
60
50
40
30
20
10
0
Neat BCS 2% Lime Stabilized Con Aid + 2% Lime Stabilized
Secant Deviatoric Stress, d (kPa)
Secant Deviatoric Stress, d (kPa)
5% Lime Stabilized Baraawe Silty Clay Afmadow Expansive Clay
Axial Strain, a (%)
Axial Strain, a (%)
Fig. 8. Comparison of impact of dynamic loading on natural and stabilized clays [ = 10].
4.5
Comparison of Impact of Vibrational Dynamic Loading on Deformation of Clayey
Geomaterials
= . . × . .
4.5
Comparison of Impact of Vibrational Dynamic Loading on Deformation of Clayey
Geomaterials
= . . × . .
4
Neat BCS Failed @ Nvd=384000 Cycles
4
Neat BCS Failed @ Nvd=384000 Cycles
0.01
0.1
1
10
0.01
0.1
1
10
Axial Strain, a (%)
Axial Strain, a (%)
Neat BCS: Measured
Neat BCS: Predicted
Baraawe Silty Clay
Afmadow Expansive Clay
Neat BCS: Measured
Neat BCS: Predicted
Baraawe Silty Clay
Afmadow Expansive Clay
0
200000
400000
600000
800000
1000000
0
200000
400000
600000
800000
1000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Neat BCS
5% Lime Stabilized
2% Lime Stabilized
Baraawe Silty Clay
Con Aid + 2% Lime Stabilized
Afmadow Expansive Clay
Neat BCS
5% Lime Stabilized
2% Lime Stabilized
Baraawe Silty Clay
Con Aid + 2% Lime Stabilized
Afmadow Expansive Clay
3.5
3
2.5
2
1.5
1
0.5
0
3.5
3
2.5
2
1.5
1
0.5
0
Fig. 9. Comparison of impact of dynamic loading on natural and stabilized clays [ = 1].
-
Analysis of secant stress decay resulting from cumulative dynamic load impact on natural clayey geomaterials
× + . + .
× + . + .
15
10
5
15
10
5
Secant Deviatoric Stress, kPa)
Secant Deviatoric Stress, kPa)
Modelled decay characteristics of the secant deviator stress of natural black cotton soil, Afmadow silty clay and Baraawe silty clay are graphically depicted in Figure 10 for loadings up to 1 million with comparison to measured data.
Secant Stress Decay resulting from Impact of Vibrational Dynamic Loading on Clayey
Geomaterials Including Meausred vs. Predicted Characteristic Curve for BCS
Secant Stress Decay resulting from Impact of Vibrational Dynamic Loading on Clayey
Geomaterials Including Meausred vs. Predicted Characteristic Curve for BCS
30
25
20
= . + . + . ×
30
25
20
= . + . + . ×
Neat BCS Failed @ Nvd=384000 Cycles
Neat BCS Failed @ Nvd=384000 Cycles
0
1000
10000
100000
1000000
0
1000
10000
p>100000
1000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Neat BCS: Measured
Neat BCS: Predicted
Baraawe Silty Clay
Afmadow Expansive Clay
Neat BCS: Measured
Neat BCS: Predicted
Baraawe Silty Clay
Afmadow Expansive Clay
Fig. 10. Decay characteristics of secant deviator stress under dynamic loading
[ = 10].Fig. 11. Stress-strain characteristics under dynamic loading [ = 10].
-
Deformation characteristics of natural clayey geomaterials subjected to VDL
Axial Strain, a (%)
Axial Strain, a (%)
Deformation characteristics under dynamic loading of natural black cotton soil, Afmadow silty clay and Baraawe silty clay are graphically depicted in Figures 12 and 13 for loadings up to 3.2 million and 100,000 (one hundred thousand) cycles, respectively; with a comparison of measured and predicted results for BCS. The results from these figures clearly indicate that: i) deformation, defined in terms of axial (vertical) strain is significantly influenced by the nature and stiffness of the clayey geomaterials; and ii) the impact of VDL is more intense within the initial phase of loading tending to a residual state with increased cumulative loading (Figure 13).
4.5
Comparison of Impact of Vibrational Dynamic Loading on Deformation of Clayey Geomaterials
Including Meausred vs. Predicted Characteristic Curves for Black Cotton Soil
4.5
Comparison of Impact of Vibrational Dynamic Loading on Deformation of Clayey Geomaterials
Including Meausred vs. Predicted Characteristic Curves for Black Cotton Soil
Neat
4 BCS
Failed @
Nvd=384000
3.5 Cycles
3
2.5
2
= . . × . .
Neat
4 BCS
Failed @
Nvd=384000
3.5 Cycles
3
2.5
2
= . . × . .
0
500000 1000000 1500000 2000000 2500000 3000000 3500000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
0
500000 1000000 1500000 2000000 2500000 3000000 3500000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Neat BCS: Measured
Neat BCS: Predicted
Baraawe Silty Clay
Afmadow Expansive Clay
Neat BCS: Measured
Neat BCS: Predicted
Baraawe Silty Clay
Afmadow Expansive Clay
1.5
1
0.5
0
1.5
1
0.5
0
Fig. 12. Deformation characteristics of clays under dynamic loading
[ = 3.2].Neat BCS: Measured
Neat BCS: Predicted
Baraawe Silty Clay
Afmadow Expansive Clay
Baraawe Silty Clay: PI=18%
Afmadow Expansive Clay: PI=28%
Neat BCS:PI=32%
3.5
3
3.5
3
Comparison of Impact of Vibrational Dynamic Loading on Deformation of Clayey Geomaterials
Including Meausred vs. Predicted Characteristic Curves for Black Cotton Soil
Neat BCS
Failed @ Nvd=384000
Cycles
Comparison of Impact of Vibrational Dynamic Loading on Deformation of Clayey Geomaterials
Including Meausred vs. Predicted Characteristic Curves for Black Cotton Soil
Neat BCS
Failed @ Nvd=384000
Cycles
2.5
2
1.5
1 = . . × . .
0.5
0
0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
2.5
2
1.5
1 = . . × . .
0.5
0
0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Effects of Cumulative Impact Stress on Deformation Characteristics of Clayey Geomaterials
Effects of Cumulative Impact Stress on Deformation Characteristics of Clayey Geomaterials
= × . + . × . + . . + .
= × . + . × . + . . + .
500
450
400
500
450
400
Cumulative Impact Stress @ Failure:
=135.6kPa @ 383,600Cycles Strain @ Critical State: =3.83% Strain @ Failure: =5.33%
Cumulative Impact Stress @ Failure:
=135.6kPa @ 383,600Cycles Strain @ Critical State: =3.83% Strain @ Failure: =5.33%
350
300
250
200
150
100
50
0
350
300
250
200
150
100
50
0
0
0
1
1
2
2
3
Axial Strain, a(%)
3
Axial Strain, a(%)
4
4
5
5
6
6
7
7
Axial Strain, a (%)
Axial Strain, a (%)
Cumulative Impact Stress, ci (kPa)
Cumulative Impact Stress, ci (kPa)
Neat BCS: Measured
Neat BCS: Predicted
Baraawe Silty Clay
Afmadow Expansive Clay
Baraawe Silty Clay: PI=18%
Afmadow Expansive Clay: PI=28%
Neat BCS:PI=32%
Fig. 13. Deformation characteristics of clays under dynamic loading
[ = 100000]. -
Analysis of cumulative stress-strain characteristics of natural clayey geomaterials subjected to VDL
The influence of dynamic loading on cumulative impact stress, for [. = 3.2] is depicted in Figure 14 for natural Baraawe and Afmadow silty clays as well as natural black cotton soil (BCS). It can be observed that the Baraawe silty clay exhibits the highest impact stress; a state that is
Influence of Vibrational Dynamic Loading on Cumulative Impact Stress of Clayey
Geomaterials
500
Cumulative Impact Stress @ Failure:
450 =135.6kPa @ 383,600Cycles
Strain @ Critical State: =3.83%
400 Strain @ Failure: =5.33%
350
300
250
200
150
Influence of Vibrational Dynamic Loading on Cumulative Impact Stress of Clayey
Geomaterials
500
Cumulative Impact Stress @ Failure:
450 =135.6kPa @ 383,600Cycles
Strain @ Critical State: =3.83%
400 Strain @ Failure: =5.33%
350
300
250
200
150
Cumulative Impact Stress, cid (kPa)
Cumulative Impact Stress, cid (kPa)
attributable to its lower plasticity index and higher stiffness (4 days soaked resilient moduli in : = 39; = 12 = 9).
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Baraawe Silty Clay: PI=18%
Afmadow Expansive Clay:PI=28%
Neat BCS:PI=32%
Baraawe Silty Clay: PI=18%
Afmadow Expansive Clay:PI=28%
Neat BCS:PI=32%
100
50
0
1000
100
50
0
1000
10000
10000
100000
100000
1000000
1000000
10000000
10000000
Fig. 14. Influence of dynamic loading on cumulative impact stress
[. = 3.2].On the other hand, the characteristics of the cumulative impact stress plotted against axial strain under vibrational dynamic loading are depicted in Figure 15. The results in these figures show that: i) the Afmadow silty clay subgrade requires ground improvement to enhance its resistance to impact stress and reduce the magnitude of deformation; and, ii) black cotton soil (BCS) exhibits the highest deformation strain due to its lower resistance to impact stress [lower stiffness (deformation resistance)].
Fig. 15. Cumulative impact stress-strain characteristics under dynamic loading.
-
Implication of results from this Section V: Simulation of foundation/subgrade ground characteristics for design
1.
Vibrational dynamic loading (VDL) has distinctly significant
1.
Vibrational dynamic loading (VDL) has distinctly significant
impact on the geotechnical engineering properties, characteristics and geotechnical quantities of clayey subgrade geomaterials.
-
As the dynaic loading increases, the deformation and impact stress resistance of the clayey subgrade geomaterials reduces exponentially with the most drastic reduction exhibited within the initial (primary) phase of loading.
-
The Afmadow silty clay subgrade requires in-situ ground improvement preferably using ND (Non-Destructive) GI techniques and/or replacement.
-
Designs based on comprehensive subgrade geomaterials and in- situ ground property analysis as well as high standards of QCA are imperative in ensuring achievement of Performance Based Value Engineering (PB-VE) pavement structures.
-
Both Afmadow and Hudur gravels require OPMC (Optimum Mechanical & Chemical) stabilization in order to achieve the geotechnical engineering properties required for the design & construction specifications for the designated design aircraft.
impact on the geotechnical engineering properties, characteristics and geotechnical quantities of clayey subgrade geomaterials.
-
As the dynamic loading increases, the deformation and impact stress resistance of the clayey subgrade geomaterials reduces exponentially with the most drastic reduction exhibited within the initial (primary) phase of loading.
-
The Afmadow silty clay subgrade requires in-situ ground improvement preferably using ND (Non-Destructive) GI techniques and/or replacement.
-
Designs based on comprehensive subgrade geomaterials and in- situ ground property analysis as well as high standards of QCA are imperative in ensuring achievement of Performance Based Value Engineering (PB-VE) pavement structures.
-
Both Afmadow and Hudur gravels require OPMC (Optimum Mechanical & Chemical) stabilization in order to achieve the geotechnical engineering properties required for the design & construction specifications for the designated design aircraft.
-
-
VDL EFFECTS ON GRAVELLY GEOMATERIALS The effects of vibrational dynamic loading on the
characteristics of gravelly geomaterials are analyzed in this Section VI. Essentially, this involves the analysis of: i) dynamic loading impact on the modulus of deformation of non-stabilized gravelly geomaterials; ii) decay characteristics of secant stress as a result of cumulative dynamic loading effects; iii) deformation characteristics of gravelly geomaterials under dynamic loading; and, v) cumulative stress-strain characteristics of neat gravelly geomaterials subjected to vibrational dynamic loading.
-
Analysis of VDL impact on modulus of deformation and axial strain of gravelly geomaterials: Comparative simulation of pre- and post-conctruction charatceristics
Simulated Pre-Construction (PrC) and Post-Construction (PoC) characteristics of the modulus of deformation and cumulative strain subjected to VDL on some typical Somalia gravels are graphically depicted and compared in Figures 16 and 17 for cumulative loadings of up to 10 million cycles.
500
Decay of Modulus of Deformation Due to Impact of Vibrational Dynamic Loading on Gravel
Geomaterials
Secant Stress Decay resulting from Impact of Vibrational Dynamic Loading on Gravel
Geomaterials
500
Decay of Modulus of Deformation Due to Impact of Vibrational Dynamic Loading on Gravel
Geomaterials
Secant Stress Decay resulting from Impact of Vibrational Dynamic Loading on Gravel
Geomaterials
450
= . .
140
= . .
450
= . .
140
= . .
400
350
PrC: Pre-Construction
PoC: Post-Construction
400
350
PrC: Pre-Construction
PoC: Post-Construction
300
250
200
150
100
50
0
100000
300
250
200
150
100
50
0
100000
1000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
1000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
10000000
10000000
Hudur PrC Afmadow PrC Bardhere PrC Bardhere PoC Diinsoor PrC Diinsoor PoC
Hudur PrC Afmadow PrC Bardhere PrC Bardhere PoC Diinsoor PrC Diinsoor PoC
120
100
80
60
40
20
0
100000
120
100
80
60
40
20
0
100000
1000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
1000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
10000000
10000000
Modlus of Deformation, ED (MPa)
Modlus of Deformation, ED (MPa)
Deviatoric Stress, kPa)
Deviatoric Stress, kPa)
Fig. 16. Impact of dynamic loading on modulus of deformation of gravels
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0.30
0.25
0.20
0.15
0.10
0.05
0.00
Axial Strain, a (%)
Axial Strain, a (%)
[. = 10].Deformation Characteristics of Somalia Gravel Geomaterials Under Vibrational Dynamic Loading
Deformation Characteristics of Somalia Gravel Geomaterials Under Vibrational Dynamic Loading
0.50
0.50
0.45
0.40
= . . × . .
0.45
0.40
= . . × . .
0.35
PrC: Pre-Construction
PoC: Post-Construction
0.35
PrC: Pre-Construction
PoC: Post-Construction
0
2000000
4000000
6000000
8000000
10000000
0
2000000
4000000
6000000
8000000
10000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Hudur PrC
Afmadow PrC
Bardhere PrC
Bardhere PoC
Diinsoor PrC
Diinsoor PoC
Hudur PrC
Afmadow PrC
Bardhere PrC
Bardhere PoC
Diinsoor PrC
Diinsoor PoC
Fig. 17. Cumulative strain characteristics of gravels under dynamic loading
[. = 10].It can be observed and derived, from Figures 16 and 17 that:
i) the rate of decay of the modulus of deformation is more drastic for the post-construction gravels implying that effects of reconstitution/remolding are visibly apparent and that these geomaterials may have been in varying degrees of weathered states culminating in the increase in fines contents, which implies loss in bearing capacity and stiffness; ii) resistance to deformation under dynamic loading is dependent on the magnitude of both plasticity index and the bearing strengths; iii) the mode of decay is influenced by both the magitude of the initial stiffness and number of cumulative loading cycles, whereas the charcteristic curves in Figure 17 show that the axial deformation (straining) is almost entirely dependent only on the initial stiffness; and iv) both stiffness dacay and straining are more acute within the initial stage of loading. Refer to Tables VII and VIII for further data correlation and verification.
-
Analysis of cumulative deviator stress decay resulting from cumulative VDL impact on gravelly geomaterials
Decay characteristics of the secant deviator stress of some
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Fig. 18. Deviator stress decay characteristics of gravels under dynamic loading [. = 10].
-
Influence of VDL and axial strain level on the cumulative impact stress of gravelly geomaterials
The influence of cumulative VDL on the cumulative impact stress is demonstrated in Figure 19, whilst its strain level dependency is depicted in Figure 20 for loadings of up to 10 million cumulative cycles. In both cases it can be observed that the cumulative impact stress increases with both cumulative loading and straining tending towards a residual state after approximately one million (1,00,000) loading cycles. However, it can be inferred that, whereas the threshold for the initiation of the residual state tendency is virtually clearly defined at this level, that of cumulative deformation occurs at varying strain levels depending on the magnitude of the initial stiffness, plasticity index as well as compressive and bearing strength (refer to Tables VII and VIII).
It can further be derived that reconstitution/remolding reduces the levels/thresholds of both cumulative loading and deformation resistance of the cumulative impact stress (compare Pre-Construction (PrC) and Post-Construction (PoC) characteristic curves in Figures 19 and 20).
Influence of Vibrational Dynamic Loading on Cumulative Impact Stress of Somalia Geomaterials
PrC:
PoC
Pre-Construction St
: Post-Construction S
age
tage (Reco
nstituted
/Rem
olded
Stat
e)
PrC:
PoC
Pre-Construction St
: Post-Construction S
age
tage (Reco
nstituted
/Rem
olded
Stat
e)
1000
900
Cumulative Impact Stress, ci kPa)
Cumulative Impact Stress, ci kPa)
800
700
600
500
400
300
200
100
0
100000 1000000 10000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
typical Somalia gravels are graphically depicted in Figure 18
Hudur PrC Afmadow PrC Bardhere PrC Diinsoor PrC Bardhere PoC Diinsoor PoC
for loadings of up to 10 million cumulative cycles. That drastic deviator stress decay occurs within the zone of initial loading can very well be observed from this figure.
Fig. 19. Cumulative impact stress characteristics of gravels under vibrational dynamic loading.
Effects of Cumulative Impact Stress on Deformation Characteristics of Somalia Gravel Geomaterials
Effects of Cumulative Impact Stress on Deformation Characteristics of Somalia Gravel Geomaterials
Degradation of Gravelly Geomaterial Stiffness Resulting from Cumulative Dynamic Loading Progression
1000
900
800
700
600
500
400
300
200
100
0
1000
900
800
700
600
500
400
300
200
100
0
140
= . . × . + . ×
Zone of Erratic Data
. . × . × + .
Cumulative Impact Stress, cid kPa)
Cumulative Impact Stress, cid kPa)
Secant Modulus of Deformation, Es (MPa)
Secant Modulus of Deformation, Es (MPa)
120
100
80
60
40
Due to Bedding Errors and System Compliance
MR: Resilient Modulus in MPa
20
PrC: Pre-Construction Stage
PoC: Post-Construction Stage (Reconstituted/Remolded State)
PrC: Pre-Construction Stage
PoC: Post-Construction Stage (Reconstituted/Remolded State)
0
1000 10000 100000 1000000 10000000 100000000
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
Axial Strain, a (%)
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
Axial Strain, a (%)
Vibrational Dynamic Loading, NA,VL (Cumulative No. of Cycles)
Diinsoor: Eoi = 44 Afmadow: Eoi = 58 Bardhere: Eoi = 87 Baraawe: Eoi = 91 Hudur: Eoi = 95 Diinsoor PC: Eoi = 63 Bardhere PC: Eoi = 133
Hudur PrC
Afmadow PrC
Bardhere PrC
Diinsoor PrC
Bardhere PoC
Diinsoor PoC
Hudur PrC
Afmadow PrC
Bardhere PrC
Diinsoor PrC
Bardhere PoC
Diinsoor PoC
Fig. 20. Cumulative impact stress-strain characteristics of gravels under vibrational dynamic loading.
the geotechnical engineering properties, characteristics and geotechnical quantities of the gravelly geomaterials designated for use in pavement construction.
-
As the dynamic loading increases, the deformation and impact stress resistance of thegravelly geomaterials reduces exponentially with the most drastic reduction exhibited within the initial (primary) phase of loading.
-
Both Afmadow and Hudur gravels require mechanical as well as chemical stabilization in order to meet design and construction specification requirements.
-
Designs based on comprehensive pavement geomaterials analysis of the effects of vibrational dynamic loading in retrospect to the maintenance of high standards of QCA are imperative in ensuring achievement of Performance Based Value Engineering (PB-VE) pavement structures.
-
Both Afmadow and Hudur gravels require OPMC stabilization in order to achieve the geotechnical engineering properties required for design & construction specifications of the designated design aircraft.
the geotechnical engineering properties, characteristics and geotechnical quantities of the gravelly geomaterials designated for use in pavement construction.
-
As the dynamic loading increases, the deformation and impact stress resistance of thegravelly geomaterials reduces exponentially with the most drastic reduction exhibited within the initial (primary) phase of loading.
-
Both Afmadow and Hudur gravels require mechanical as well as chemical stabilization in order to meet design and construction specification requirements.
-
Designs based on comprehensive pavement geomaterials analysis of the effects of vibrational dynamic loading in retrospect to the maintenance of high standards of QCA are imperative in ensuring achievement of Performance Based Value Engineering (PB-VE) pavement structures.
-
Both Afmadow and Hudur gravels require OPMC stabilization in order to achieve the geotechnical engineering properties required for design & construction specifications of the designated design aircraft.
-
Implication of results in this Section VI: Stress-strain and deformation resistance (geotechnical engineering) characteristics for design.
1.
Vibrational dynamic loading has distinctly significant impact on
1.
Vibrational dynamic loading has distinctly significant impact on
Fig. 21. Impact of vibrational dynamic loading on secant modulus of deformation of Somalia gravels [. = 30].
Impact of Dynamic Loading on Gravelly Geomaterials with Varying Resilient Moduli
7
MR: Resilient Modulus in MPa
Deformation (Axial Strain), a (%)
Deformation (Axial Strain), a (%)
6
5
4
3
2
1 = . . × . + . ×
. . × . × + .
0
0 5000000 10000000 15000000 20000000 25000000 30000000
Vibrational Dynamic Loading, NA,VL (Cumulative No. of Cycles)
MR= 100MPa Diinsoor: Eoi = 44 Afmadow: Eoi = 58 Bardhere: Eoi = 87 Baraawe: Eoi = 91 Hudur: Eoi = 95 Diinsoor PC: Eoi = 63 Bardhere PC: Eoi = 133
-
-
ANALYSIS OF STIFFNESS DECAY AND DEFORMATION OF
TYPICAL SOMALIA GRAVELS UNDER CUMULATIVE VDL
-
Decay and deformation characteristics
The impact of vibrational dynamic loading on the decay
Fig. 22. Deformation characteristics of Somalia gravels under dynamic loading [ = 30].
-
Analysis of VDL impact on modulusof deformation within the initial phase of loading
The characteristic curves depicting stiffness degradation resulting from progressive cumulative vibrational dynamic loading within the initial phase of loading [1000 100000 ] are graphically plotted in Figure 23.
Degradation of Gravelly Geomaterial Stiffness Resulting from Cumulative Dynamic Loading Progression
characteristics of secant modulus of deformation and the strain
= . . × . + .
×
deformation of Somalia gravels is depicted in Figures 21 and 22, respectively; for VDLs of up to 30 million cumulative cycles. It can be deduced that both the stiffness decay and straining deformation resistance largely depend on the magnitude of the initial stiffness (elastic modulus).
The results in these figures further make a comparison of the Pre-Construction and Post-Construction characteristics, which show that the Pre-Construction (PrC) Bardhere gravel with the highest initial elastic modulus [0 = 133] exhibits the highest resistance to deformation (note that the maximum strain
250
Secant Modulus of Deformation, Es (MPa)
Secant Modulus of Deformation, Es (MPa)
200
150
100
50
0
. . × . × + .
Zone of Erratic Data Due to Bedding Errors, System Compliance and Low Load Intensity
Eo: Elastic Modulus in MPa
for this gravel is; [] = 1.8%.
1000 10000 100000
Vibrational Dynamic Loading, NA,VL (Cumulative No. of Cycles)
Diinsoor: Eoi = 72 Bardhere: Eoi = 133 Hudur: Eoi = 163 Afmadow: Eoi = 232
Baraawe: Eoi = 278 Diinsoor PC: Eoi = 153 Bardhere PC: Eoi = 197
Fig. 23. Modulus of deformation decay characteristics Somalia gravels under dynamic loading [1000 100000].
Cumulative Impact Stress, ci (kPa)
Cumulative Impact Stress, ci (kPa)
The following observations and/or derivations can be made from the modelled results graphically plotted in Figure 23: i) there exists a zone of erratic data (within the region of very small strains), the causes of which may be attributable to bedding errors, system compliance and low load intensity (limitation of transducer resolution); ii) it can be explicitly confirmed that the mode and magnitude of impact of VDL is predominantly dependent upon the initial stffness of the geomaterial; iii) application of the TACH-MD VDL models, which were developed within a mechanistic-empirical framework based on experimental testing data, is limited within this zone; and iv) the limiting factor, which is the number of cumulative load cycles, depends on the magnitude of the initial stiffness with geomaterials of higher stiffness registering higher cyclic limits possibly due to the fact that bedding error correction requires higher load intensity for stiffer specimens.
-
Implication of Results in this Section VII: Simulation of pavement gravel characteristics within initial phase of VDL for design and construction
1.
Deformation resistance is predominantly dependent upon the
1.
Deformation resistance is predominantly dependent upon the
magnitudes of the initial/original stiffness (elastic modulus) and the plasticity characteristics.
-
Vibrational dynamic loading has distinctly significant impact on the geotechnical engineering properties, characteristics and geotechnical quantities of the gravelly geomaterials designated for use in pavement construction.
-
As the dynamic loading increases, the deformation and impact stress resistance of thegravelly geomaterials reduces exponentially with the most drastic reduction exhibited within the initial (primary) phase of loading.
-
Further research is required in order to determine a sustainable solution to the data collection and processing within the erratic zone which occurs within the region of very small strains (initial phase of the vibrational dynamic loading [ < 10000].
magnitudes of the initial/original stiffness (elastic modulus) and the plasticity characteristics.
-
Vibrational dynamic loading has distinctly significant impact on the geotechnical engineering properties, characteristics and geotechnical quantities of the gravelly geomaterials designated for use in pavement construction.
-
As the dynamic loading increases, the deformation and impact stress resistance of thegravelly geomaterials reduces exponentially with the most drastic reduction exhibited within the initial (primary) phase of loading.
-
Further research is required in order to determine a sustainable solution to the data collection and processing within the erratic zone which occurs within the region of very small strains (initial phase of the vibrational dynamic loading [ < 10000].
errors, system compliance, low load intensity (limitation of transducer resolution) and environmental factors (Sec. IX) during VDL testing.
errors, system compliance, low load intensity (limitation of transducer resolution) and environmental factors (Sec. IX) during VDL testing.
5.
5.
Both Afmadow and Hudur gravels require OPMC stabilization in order to achieve the geotechnical engineering properties required for design & construction specifications of the ATR72 design aircraft.
6.
Both Afmadow and Hudur gravels require OPMC stabilization in order to achieve the geotechnical engineering properties required for design & construction specifications of the ATR72 design aircraft.
6.
It is crucially vital to consider the adverse effects of bedding
It is crucially vital to consider the adverse effects of bedding
-
-
ANALYSIS OF CUMULATIVE STRESS-STRAIN CHARACTERISTICS OF CLAYS AND GRAVELS UNDER
PROGRESSIVE VDL
Under this Section VIII, cumulative stress-strain characteristics of specimens subjected to dynamic loading are analyzed. The analysis includes evaluation of the effects of reconstitution/remolding, which are outlined under several preceding sub-Sections. This is achieved by comparing Pre- Construction (PrC) and Post-Constrution (PoC) results.
-
Cumulative impact stress-strain characteristics of clayey geomaterials
Figure 24 shows the impact of vibrational dynamic loading on cumulative impact stress of clays subjected to dynamic loading [ = 3.2 ] . It can be noted that clayey geomaterials with lower plasticity indices (PIs) exhibit
higher cumulative impact stresses and that the Afmadow silty clay subgrade certainly requires ground improvement.
Influence of Vibrational Dynamic Loading on Cumulative Impact Stress of Clayey Geomaterials
Influence of Vibrational Dynamic Loading on Cumulative Impact Stress of Clayey Geomaterials
500
Cumulative Impact Stress @ Failure:
450 =135.6kPa @ 383,600Cycles
Strain @ Critical State: =3.83%
400 Strain @ Failure: =5.33%
350
300
250
200
150
100
50
500
Cumulative Impact Stress @ Failure:
450 =135.6kPa @ 383,600Cycles
Strain @ Critical State: =3.83%
400 Strain @ Failure: =5.33%
350
300
250
200
150
100
50
0
1000
10000
100000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
1000000
10000000
0
1000
10000
100000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
1000000
10000000
Baraawe Silty Clay: PI=18%
Afmadow Expansive Clay:PI=28%
Neat BCS:PI=32%
Baraawe Silty Clay: PI=18%
Afmadow Expansive Clay:PI=28%
Neat BCS:PI=32%
Fig. 24. Impact of dynamic loading on cumulative impact stress of Clays
[ = 3.2].The characteristics of the cumulative impact stress versus strain of clayey geomaterials are graphically depicted in Figure
Cumulative Impact Stress, ci (kPa)
Cumulative Impact Stress, ci (kPa)
25. It can be noted that the Baraawe silty clay with the lowest PI exhibits the highest resistance to deformation.
Effects of Cumulative Impact Stress on Deformation Characteristics of Clayey Geomaterials
Effects of Cumulative Impact Stress on Deformation Characteristics of Clayey Geomaterials
= × . + . × . + . . + .
= × . + . × . + . . +.
500
500
Cumulative Impact Stress @ Failure:
=135.6kPa @ 383,600Cycles Strain @ Critical State: =3.83% Strain @ Failure: =5.33%
450
400
350
300
250
200
150
100
50
Cumulative Impact Stress @ Failure:
=135.6kPa @ 383,600Cycles Strain @ Critical State: =3.83% Strain @ Failure: =5.33%
450
400
350
300
250
200
150
100
50
0.010
0.100
0
1.000
10.000
0.010
0.100
0
1.000
10.000
Axial Strain, a(%)
Axial Strain, a(%)
Baraawe Silty Clay: PI=18%
Afmadow Expansive Clay: PI=28%
Neat BCS:PI=32%
Baraawe Silty Clay: PI=18%
Afmadow Expansive Clay: PI=28%
Neat BCS:PI=32%
Fig. 25. Cumulative impact stress-strain characteristics of clays under dynamic loading.
-
Cumulative impact stress-strain characteristics of gravelly geomaterials
The impact of VDL on cumulative impact stress of gravels is graphically demonstrated in Figure 26 for loadings of up to [ = 10 ] . It can be noted that gravelly geomaterials with higher strengths and stiffness exhibit higher cumulative impact stresses (refer to results tabulated in Tables
VII & VII in Section IV). It can further be observed that the influence of cumulative VDL on the impact stress is more pronounced within the loading zone of 100,000 ~ 1000,000 (one hundred thousand to one million) cycles, after which practically all modelled curves tend to a residual state with increased loading. On the other hand, the characteristics of the cumulative impact stress versus strain for gravels are depicted in Figure 27. It can be noted that the gravels with lower PIs and higher strengths and stiffness (elastic moduli) exhibit the highest resistance to deformation (refer to summary results in Tables VII & VII in Section IV).
Influence of Vibrational Dynamic Loading on Cumulative Impact Stress of Somalia Gravels
Influence of Vibrational Dynamic Loading on Cumulative Impact Stress of Somalia Gravels
1000
900
800
700
600
500
400
300
200
100
0
100000
1000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
10000000
1000
900
800
700
600
500
400
300
200
100
0
100000
1000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
10000000
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Cumulative Impact Stress, ci kPa)
Cumulative Impact Stress, ci kPa)
Cumulative Impact Stress, ci kPa)
Cumulative Impact Stress, ci kPa)
Fig. 26. Impact of dynamic loading on cumulative impact stress of Somalia gravels [ = 10].
Effects of Cumulative Impact Stress on Deformation Characteristics of Somalia Gravel Geomaterials
Effects of Cumulative Impact Stress on Deformation Characteristics of Somalia Gravel Geomaterials
1000
900
800
700
600
500
400
300
200
100
0
1000
900
800
700
600
500
400
300
200
100
0
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
Axial Strain, a (%)
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
Axial Strain, a (%)
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Fig. 27. Cumulative stress-strain characteristics of Somalia gravels under vibrational dynamic loading.
-
Cumulative impact stress-strain characteristics of typical Somalia gravels under VDL: Effects of reconstitution/remolding
Cumulative Impact Stress, ci kPa)
Cumulative Impact Stress, ci kPa)
The effects of reconstitution/remolding are analyzed through the comparison of the Pre-Construction (PrC) and Post- Construction (PoC) results shown in Figures 28 and 29.
Influence of Vibrational Dynamic Loading on Cumulative Impact Stress of Somalia Geomaterials
Influence of Vibrational Dynamic Loading on Cumulative Impact Stress of Somalia Geomaterials
1000
900
800
700
600
500
400
300
200
100
PrC: Pre-Construction Stage
PoC: Post-Construction Stage (Reconstituted/Remolded State)
1000
900
800
700
600
500
400
300
200
100
PrC: Pre-Construction Stage
PoC: Post-Construction Stage (Reconstituted/Remolded State)
0
100000
1000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
10000000
0
100000
1000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
10000000
Hudur PrC
Afmadow PrC Bardhere PrC Diinsoor PrC Bardhere PoC Diinsoor PoC
Hudur PrC
Afmadow PrC Bardhere PrC Diinsoor PrC Bardhere PoC Diinsoor PoC
Fig. 28. Impact of dynamic loading on cumulative impact stress of gravels
Figure 28 and the correlation between cumulative impact stress and cumulative progressive strain depicted in Figure 29 clearly show that reconstitution of the gravelly geomaterials reduces strength/stiffness and that the magnitude of this reduction is dependent upon the original strength, stiffness and plasticity index (refer to summary Tables VII & VII in Section IV).
Effects of Cumulative Impact Stress on Deformation Characteristics of Somalia Gravel Geomaterials
1000
900
800
700
600
500
400
300
200
100
0
Effects of Cumulative Impact Stress on Deformation Characteristics of Somalia Gravel Geomaterials
1000
900
800
700
600
500
400
300
200
100
0
0.01
0.10
Axial Strain, a (%)
1.00
0.01
0.10
Axial Strain, a (%)
1.00
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Cumulative Impact Stress, ci kPa)
Cumulative Impact Stress, ci kPa)
Fig. 29. Cumulative impact stress-strain of Somalia gravels: LS
[ = 10]: Comparison of Pre-Construction (PrC) and Post-construction (PoC) characteristicsOn the other hand, Figures 30 and 31 show the impact of progressive loading on the magnitude of axial strain (deformation) graphically plotted both in arithmetic and semi- log scale for clarity of comparison of this VDL impact on Pre- Construction (PrC) and Post-construction (PoC) characteristics simulating the effects of reconstitution/remolding and to enable proper analysis thereof.
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0.30
0.25
0.20
0.15
0.10
0.05
0.00
Axial Strain, a (%)
Axial Strain, a (%)
It can also be inferred from these figures that: i) reconstitution reduces the deformation resistance of gravelly geomaterials; and ii) the magnitude of resistance is proportional to the magnitude of the initial stiffness.
Deformation Characteristics of Somalia Gravel Geomaterials Under Vibrational Dynamic Loading
Deformation Characteristics of Somalia Gravel Geomaterials Under Vibrational Dynamic Loading
0.50
0.50
0.45
0.40
= . . × . .
0.45
0.40
= . . × . .
0.35
PrC: Pre-Construction
PoC: Post-Construction
0.35
PrC: Pre-Construction
PoC: Post-Construction
0
2000000
4000000
6000000
800000
10000000
0
2000000
4000000
6000000
8000000
10000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Hudur PrC
Afmadow PrC
Bardhere PrC
Bardhere PoC
Diinsoor PrC
Diinsoor PoC
Hudur PrC
Afmadow PrC
Bardhere PrC
Bardhere PoC
Diinsoor PrC
Diinsoor PoC
Fig. 30. Impact of dynamic loading on cumulative axial strain of Somalia
[= 10]: Comparison of Pre-Construction (PrC) and Post-construction
(PoC) characteristics
gravels [ = 10]: Comparison of Pre-Construction (PrC) and Post- construction (PoC) characteristics.
Comparison of Impact of Vibrational Dynamic Loading on Deformation of Gravel Geomaterials
Comparison of Impact of Vibrational Dynamic Loading on Deformation of Gravel Geomaterials
-
Influence of moisture-suction variation
-
1.200
1.200
= . . × . .
= . . × . .
1.000
1.000
Axial Strain, a (%)
Axial Strain, a (%)
As can be observed from Figures 32 and 33, plasticity index and mechanical stability (particle size and distribution) have significant influence on both static and dynamic strengths of clayey geomaterials as well as gravels.
0.800
0.800
0.600
0.600
0.400
0.400
0.200
0.200
0.000
10000
100000
1000000
10000000
0.000
10000
100000
1000000
10000000
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Vibrational Dynamic Loading Cumulative Cycles, Nvd (No.)
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Baraawe Silty Clay
Hudur Gravel
Afmadow Gravel
Bardhere Gravel
Diinsoor Gravel
Baraawe Silty Clay
Fig. 31. Impact of dynamic loading on cumulative axial strain of Somalia gravels [ = 10]: Log Scale (LS): Comparison of Pre-Construction (PrC) and Post-construction (PoC) characteristics.
500
Unconfined Compressive Strength, UCS (kPa)
Unconfined Compressive Strength, UCS (kPa)
450
400
350
300
250
200
150
100
50
0
Comparison of Static and Dynamic Strength of Clayey Geomaterials
Baraawe Silty Clay
Afmadow Silty Clay
Black Cotton Soil
18 20 22 24 26 28 30 32
Plasticity Index, PI (%)
Static Dynamic
-
Implication of Results in Section VIII: Simulation of pavement gravel characteristics subjected to VDL
1.
Reconstitution/remolding impacts adversely on the geotechnical
1.
Reconstitution/remolding impacts adversely on the geotechnical
Fig. 32. Impact plasticity index on static and dynamic strengths of clayey geomaterials.
Comparison of Static and Dynamic Strength of Somalia Gravels
engineering properties of gravelly geomaterials by reducing strength and deformation resistance (stiffness) making the geomaterials more susceptible to the impact of dynamic loading.
-
Deformation resistance is predominantly dependent upon the magnitudes of the initial/original stiffness (elastic modulus) and the plasticity characteristics, particularly under dynamic loading.
-
Vibrational dynamic loading has distinctly significant impact on the geotechnical engineering properties, characteristics and geotechnical quantities of the gravelly geomaterials designated for use in pavement construction.
-
It is imperative to carry out further comprehensive analyses of the vibrational dynamic loading characteristics during the design stage in order to generate appropriate design parameters.
engineering properties of gravelly geomaterials by reducing strength and deformation resistance (stiffness) making the geomaterials more susceptible to the impact of dynamic loading.
-
Deformation resistance is predominantly dependent upon the magnitudes of the initial/original stiffness (elastic modulus) and the plasticity characteristics, particularly under dynamic loading.
-
Vibrational dynamic loading has distinctly significant impact on the geotechnical engineering properties, characteristics and geotechnical quantities of the gravelly geomaterials designated for use in pavement construction.
-
It is imperative to carry out further comprehensive analyses of the vibrational dynamic loading characteristics during the design stage in order to generate appropriate design parameters.
Unconfined Compressive Strength, UCS (kPa)
Unconfined Compressive Strength, UCS (kPa)
1200
1100
1000
900
Hudur: Bardhere: Afmadow: Diinsoor:
Afmadow Coarse Particle Effect:
D60 = 10.5mm; D10 = 4.5mm
-
PERFORMANCE EVALUATION OF VDL EFFECTS
800
700
600
500
400
Pre-Construction Data: Bardhere & Diinsoor
Hudur, Bardhee & Diinsoor: D60 < 9mm; D10 < 0.1mm
Structural performance simulation of subgrade and pavement geomaterials as well as discrete layers and composite pavement subjected to the effects of vibrational dynamic loading is to be carried out in [10] mainly in consideration of extreme changes in environmental conditions and factors in retrospect to the limiting design parameters.
Based on the prevailing climatic conditions in Afmadow and
8 9 10 11 12 13
Plasticity Index, PI (%)
Static Dynamic
Fig. 33. Impact plasticity index on static and dynamic strengths of Somalia gravels: Without consideration of particle size effect
Unconfined Compressive Strength, UCS (kPa)
Unconfined Compressive Strength, UCS (kPa)
Comparison of Static and Dynamic Strength of Somalia Gravels
Hudur, locations of the aerodromes to be designed in Somalia, it was deemed imperative that moisture ~ suction variation be analyzed for both suction and dilatancy characteristics under dynamic loading conditions; the comprehensive testing regime of which is included in the testing matrix, modules defining basic protocols and main testing procedure presented in Section
4.6 of Chapter 4 of [1].
One of the main influencing factors with regard to the impact of moisture ~ suction variation is the PI (plasticity index); refer to [10] for the functional and applicable models as well as validation and comprehensive analytical discussions. An introductory example of influence of PI and correlation with mode of loading (dynamic static) is subsequently provided.
1100
1000
900
800
700
600
500
400
8 9 10 11 12 13
Plasticity Index, PI (%)
Static Dynamic
Fig. 34. Impact plasticity index on static and dynamic strengths of Somalia gravels: Corrected particle size effect.
It can also be noted from these figures that, in general, the dynamic strengths are higher than static strengths for geomaterials with strengths lower than 700kPa ( 700). It can also be noted that whereas both static and
dynamic strengths (UCS) reduce consistently for clayey geomaterials (Figure 32), the characteristic curves in Figure 33 are rather sinusoidal. This is attributable to the effect of mechanical stability (particle size fines content) as indicated in Figure 33. This fact is verified in Figure 34, which depicts the characteristic curves corrected for particle size effects.
Simulation is therefore carried out, in [10], taking the effects of plasticity index, particle size, mechanical stability, agglomeration, among other factors, into account.
-
Overall performance evaluation
The overall structural performance evaluation of discrete layers and composite pavements is undertaken in [10].
-
-
CONCLUSIONS
-
Vibrational dynamic loading has distinctly significant impact on the geotechnical engineering properties, characteristics and geotechnical quantities of clayey subgrade and gravelly geomaterials for pavements.
-
As the dynamic loading increases, the deformation and impact stress resistance of the clayey and gravelly geomaterials reduces exponentially with the most drastic reduction exhibited within the initial (primary) phase of loading.
-
Designs based on comprehensive subgrade geomaterials, in- situ ground property and pavement geomaterials analyses of the effects of vibrational dynamic loading in retrospect to the maintenance of high standards of QCA are imperative in ensuring achievement of Performance Based Value Engineering (PB-VE) pavement structures.
-
Deformation resistance is predominantly dependent upon the magnitudes of the initial/original stiffness (elastic modulus) and the plasticity characteristics.
-
Reconstitution/remolding impacts adversely on the geotechnical engineering properties of gravelly geomaterials by reducing strength and deformation resistance (stiffness) making the geomaterials more susceptible to the impact of dynamic loading and environmental conditions/factors.
-
Deformation resistance is predominantly dependent upon the magnitudes of the initial/original stiffness (elastic modulus) and the plasticity characteristics, particularly under vibrational dynamic loading.
-
It is imperative to carry out further comprehensive analyses of the vibrational dynamic loading characteristics during the design stage in order to generate appropriate design parameters.
ACKNOWLEDGMENT
The author wishes to acknowledge, with utmost gratitude, the Japan International Cooperation Agency and Kajima Corporation (JICA) for substantially funding the initial stage of this research, the Materials Testing & Research Division (MTRD), Ministry of Transport, Infrastructure, Housing & Urban Development in Kenya, the University of Nairobi and Norconsult for carrying out the initial phase of testing as well as the Research Teams of Kensetsu Kaihatsu Engineering Consultants Limited and the Kenya Geotechnical Society (KGS) for their relentless efforts in providing the due assistance that culminated in the successful compilation of this paper.
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