循环荷载下长短桩桩网复合地基变形试验研究

通过长短桩桩网复合地基的模型试验，分析有、无土工格栅及不同幅值循环荷载下复合地基沉降、长短桩桩身应变及土工格栅应变的特性. 试验结果表明，土工格栅的加入会改善循环荷载下复合地基的整体性能. 复合地基沉降、桩身应变及土工格栅应变主要发生在循环荷载作用前期. 增大循环荷载幅值不仅会增大复合地基总沉降，还会加快沉降发展的速率. 复合地基的沉降与循环次数的关系可以用指数函数表示. 土工格栅的拉膜效应将部分荷载由桩间土传递到桩上，相比于没有土工格栅的复合地基，有土工格栅的复合地基中长短桩的应变更大，且此时长桩桩帽处的土工格栅会承受更大的拉力，应变相较于桩间土处更大；循环荷载下的长桩上部应变增量较大，下部应变增量较小.

Experimental research on deformation of pile-net composite foundation with long-short piles under cyclic load

The model test was conducted on geosynthetic-reinforced pile-supported composite foundation with long-short piles. The characteristics of settlement, pile strain and geogrid strain of the composite foundation were analyzed under cyclic load with different amplitudes with or without geogrid. Results show that the addition of geogrid can improve the overall performance of composite foundation under cyclic load. The foundation settlement, pile strain and geogrid strain mainly occur in the early stage of cyclic load. Increasing the amplitude of cyclic load not only increases the final settlement, but also increases the increasing rate of the settlement. The relationship between composite foundation settlement and number of load cycles can be expressed by exponential function. The membrane effect generated by the geogrid causes the stress of the soil among piles to transmit to the pile top. The strain of long-short piles in composite foundation with geogrid is larger than that without geogrid. Geogrid near the pile top takes more tension and has larger strain than that near the soil among piles. The strain increment of long pile is larger in the upper part of the pile under cyclic load, which is smaller in the lower part.