Abstract
Objective/methods: Pile load test is commonly carried out at ground level assuming that using sleeve eliminates shaft resistance within the planned excavation area. But these tests do not capture the effect of stress relief due to excavation. So to study its effect on pile behavior, three numerical simulations were carried out using finite element method. The first simulation (L_Ground) was carried out at the ground level. The second simulation (L_Sleeve) was conducted using sleeve in the planned excavation area. The length of sleeve was taken equal to the depth of basement. The third simulation (L_ Excavation) was carried out after excavation at the formation level. Findings/application: It was found that QLE is 85% of QLS so when tests are conducted by using a sleeve, pile capacity is overestimated. QLG is 74% of QLS which is less than QLE. Because after excavation, soil particles around the pile are stiffer so capacity is increased. At ground level, at working load shaft carries about 77% load. When the load is increased and reaches the ultimate value end bearing contributes more than the shaft resistance. On the other hand, for sleeved pile, at working load shaft and end bearing carries about 80 and 20% load, respectively. But at ultimate load, shaft carries 55% load which is still greater than that carried by end bearing. While after excavation, at working load shaft carries about 86% load. When ultimate load is reached the load distribution is similar to sleeved pile. In the case of ground level and excavation, the shaft resistance has been fully mobilized at the load less than QLS that is about 74 and 86% of QLS, respectively. These results will help to estimate the pile capacity in a better way. Keywords: Stress Relief, Pile Capacity, Soft Clay.
Highlights
These days, tall structures have turned into a need to meet the housing requirements for the ever-increasing population
In Ref. [3], Peng studied the effect of stress relief on pile capacity and concluded that stress relief may cause the reduction in shaft resistance
When the load is increased and reaches the ultimate value end bearing contributes more than the shaft resistance
Summary
These days, tall structures have turned into a need to meet the housing requirements for the ever-increasing population. It is assumed that if a sleeve is used within the planned excavation depth, shaft resistance is eliminated Such a test cannot capture the effects of stress relief on pile behavior. It may affect the pile capacity under the deep excavation The effect of this stress relief on pile behavior is required to be studied. This brief literature review has revealed that the stress relief changes the shaft resistance which affects the pile capacity. Pile load tests were carried out at the ground surface, before excavation assuming sleeve completely eliminates shaft resistance. The objective of this research is to compare the pile capacity before and after stress relief due to excavation and to determine the changes in axial load distribution along the pile due to stress relief
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