Numerical and Field Evaluation of Pile Behavior in Sandy Soil Underlain by Clay

摘要

When the building loads are relatively small, challenges often faces the foundation design especially when inappropriate soil conditions exist. These may be represented in the existence of soft soil in the upper layers of soil while sandy soil or firm cohesive soil exists in the deeper layers. In such cases, the design becomes infeasible if the piles are extended to the deeper layers, especially when there are sandy layers at shallower depths underlain by stiff clayey soil. In this research, models of piles resting in a sand layer underlain by clay soils are numerically simulated by different modelling theories. Finite element software, Plaxis 3-D Foundation was used to evaluate the pile behavior under different loading scenarios. The standard static load test, (SSLT), according to ASTM D-1143, was simulated and compared with the real-life loading, (RLL), scenario. The results showed that the pile behavior obtained from the current static load test are not realistically represented compared with that obtained from real-life loading. Attempts were carried out to capture the proper numerical loading scenario that simulates the pile behavior in real-life loading including the long-term effect. A new method called Modified Quick load Test, (MQLT_(1.3)), based on the findings of this research is proposed for the pile static load test. Field loading tests were carried out to validate the new method. Results obtained from both numerical and field tests by using MQLT_(1.3) prove that this method is more accurate in predicting the pile behavior in sand soil underlain by clay than the current standard static load.