刚性桩复合地基尺寸效应试验研究

Experimental study on scale effect of rigid pile composite foundation

为了研究刚性桩复合地基承载性状受基础尺寸大小变化的影响规律,自主研制一个模型箱试验装置,开展4个不同尺寸压板的地基土以及复合地基载荷试验和单桩载荷试验等相关模型试验,获得一套模型试验测试成果。试验结果表明,在基底应力和置换率相同的条件下,复合地基沉降随压板尺寸增大而增大,桩–土应力比随压板尺寸增大而增大,桩分担的荷载随压板尺寸增大而增大。在试验成果的基础上,从理论上对刚性桩复合地基尺寸效应进行分析,所揭示的规律与试验结果也是一致的。由于尺寸效应的存在,现场载荷试验承载性状不能代替实际基础复合地基承载性状,进而提出由桩–土组合叠加计算模型的方法,来解决复合地基尺寸效应问题,模型试验及工程实例计算结果证明了该方法是可行的。结果可为解决复合地基尺寸效应问题及探讨复合地基承载能力检测方法提供参考。

In order to study the influence of foundation scale on the bearing capability of rigid pile composite foundation,several groups of model tests such as the load tests under four different scale plates,foundation soil load test,composite foundation load tests and single pile load tests,were carried out using a model test apparatus made in-house. A series of test results were acquired. The results showed that with the same loading stress and pile replacement ratio,the composite foundation settlement and pile-soil stress distribution ratio increased with the increasing of loading plate scale. The load carried by the pile increased at the same time. Based on the test results,the scale effects of rigid pile composite foundation were analyzed from a theoretical point of view. The composite foundation load test did not perfectly represent the load bearing characters of the actual composite foundation because of the scaling effects. A new method to calculate the bearing capacity of the ground by overlapping the single pile and soil p-s curves were put forward to solving the problems of scale effects of composite foundation. Calculated results of model tests and engineering example showed that the method was feasible.