Abstract
The stress and displacement boundary conditions of excavation retaining structures affect the deformation mechanism and movement of the retained soil mass. The soil movement disturbs the load sharing performance and structural integrity of cement-fly ash-gravel (CFG) pile composite foundations existing in the vicinity, which merits considerable research work. This article presents results from 3D finite element analyses performed to study the influence of retaining wall rotation on the load sharing characteristics of adjacent CFG pile composite foundation comprising long and short piles. To verify the numerical model, a relatively large-scale 1 g physical model test was conducted. It is revealed that to arrive at a new static equilibrium during progression of wall rotation, the percentage load sharing ratios of the long and short piles change increasingly while the load proportion carried by the upper soil reduces remarkably. The percentage load sharing characteristics of CFG pile composite foundation are more affected in immediate proximity to the wall than those located at far distance. For the foundation having 3 × 3 long and short piles placed at 3.0–15.0 m away from the wall, the location resulted in a reduction of soil bearing capacity ranging between 1.4 and 7.5% of the total imposed load while the corresponding increase in the % load borne by the long and short pile range was 0.83–4.15 and 0.59–3.36%, respectively. For the other parameters considered in this article viz. pile spacing, subsoil stiffness, cushion stiffness and thickness, and applied working load, the increment in % load sharing of the long and short pile range was 3.45–4.15, 1.3–5.79, 1.48–3.36, 4.15–4.79, and 3.67–4.15% and 3.36–4.67, 1.43–4.99, 1.48–3.36, 3.36–3.64, and 1.38–3.36% of the imposed load, respectively. Moreover, the long piles’ load sharing proportion was higher than that of short piles, and peripheral piles received larger load proportion.
Highlights
Escalating urban land demands and growing population size in emerging cities have promoted the quest for possible alternative solutions to prevailing geotechnical problems, notable among which is enhancing poor ground conditions to make them suitable for construction
If the group having 15 m long piles and 10 m short piles is taken, the shielding effect resulted in a 53% and 109% higher bending moment in the front long pile as compared to that of the bending moment developed in the central and rear corner pile, respectively, whereas the rear short pile sustained a bending moment 53% less than that of the short pile adjacent to the wall
The percentage load sharing of piles increased, ranging between 0.83–4.15 and 0.59–3.36%, respectively, for the long and short piles depending on the location of the foundation behind the wall, as the proportion of the subsequent decrease in stress borne by the soil between piles transferred to the piles
Summary
Escalating urban land demands and growing population size in emerging cities have promoted the quest for possible alternative solutions to prevailing geotechnical problems, notable among which is enhancing poor ground conditions to make them suitable for construction. Is is because of the lateral reinforcement effect of CFG piles that cannot be ignored and has to be acknowledged to optimize the rigidity and working mechanism of foundation pit support structures [34] When it comes to the active earth pressure acting on the wall, studies have shown that the calculation results obtained from the conventional theories are normally larger than experimental observations [33, 35] and numerical findings [36] due the shielding effect of the CFG piles. Physical model test results of Li et al [40] on the load distribution of rigid-pile composite foundation revealed the same characteristics under the condition of soil displacement arising from retaining wall rotation about the base Even though such studies highlighted the effects of soil displacement on the load bearing behaviour, they were limited to equal length piles. A large-scale indoor 1 g model test was carried out to verify the finiteelement model used
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