砂性土中桩端荷载-沉降关系的模拟

Modeling on pile-tip performance in sandy soils

提出了一个基于球形孔扩张理论的模型,用于模拟砂性土中长桩的桩端变形性状。该模型对Vesic(1972)的解答作了改进,同时考虑了砂性土强度指标在高应力下的衰减和在高密度下的增长。模型参数可通过土的初始竖向有效应力及标准贯入试验N值求得。球孔塑性区的平均体积应变不再需要通过土工实验,而是利用有限应变理论计算获得。在考虑了孔扩张过程中的能量守恒原理后,可得桩端土的特征变形值,从而进一步推出桩端的荷载–沉降关系。该模型计算结果与两根静压长桩的现场试验比较,结果一致性较好。

Based on the spherical cavity expansion solution developed by Vesic （1972）, a model was proposed for the analysis of long piles embedded in sandy soils. Unlike the Vesic＇s model, the reduction of strength under high stress and the increase of strength under high density were both taken into account in the tip present model. The strength parameters could be derived from the effecitive overburden pressure and SPT-N value at the pile tip. The mean volumetric strain in the plastic zone was determined analytically by adopting the finite strain theory, and therefore, it was no longer necessary to estimate such strain from laboratory test results. By incorporating the energy conservation principle, the model was further extended to allow prediction of the load-settlement behavior of piles. The accuracy of the model was assessed by using two case histories. It had been demonstrated that the present model could provide fairly accurate prediction of the end-bearing capacity and the settlement of long piles.