不同型式复合地基试验对比分析

基于相似理论，设计并完成了土工格室加筋垫层、砂井、散体材料桩、柔性桩等九组复合地基模型试验，并对其加固效果进行对比分析，分析结果表明：水平加筋垫层的设置可扩散上部荷载，提高复合地基承载力，土工格室的加强效果优于土工格栅；桩体复合地基须考虑群桩效应的影响，其承载能力明显好于加筋垫层复合地基；不同加载范围下桩和土体的承载能力发挥程度不同，单桩加载下桩体承载能力发挥较三桩、七桩加载时大，碎石桩桩顶桩土应力比>碎石桩+土工格栅>碎石桩+土工格室，而柔性桩+土工格室的桩顶桩土应力比>柔性桩+土工格栅>柔性桩；砂井和各种型式的碎石桩复合地基桩底桩土应力比在1左右，各种型式的柔性桩桩底桩土应力比较大，最大达24；软基浅部较深部孔隙水压力大、消散速度快；桩体复合地基孔隙水压力较土工格室复合地基和软土地基小，砂井和碎石桩复合地基的排水速度明显快于柔性桩复合地基。

Comparative analysis of model tests on different types of composite foundations

Nine groups of model tests on the geocell-reinforced cushion, bag-sand well, gravel pile and flexible pile composite foundation are completed to analyze the consolidation effect of different types of composite foundations based on the similarity theory. Some conclusions are drawn as follows: (1) the inclusion of horizontal reinforcement can spread the upper load and raise the bearing capacity, and the reinforced effect of geocell is superior to that of geogrid; (2) the effect of pile groups cannot be neglected when analyzing composite foundation with piles and their bearing capacity is superior to that of horizontal reinforcement composite foundation obviously; (3) the volatility of bearing capacity of piles and soil changes under different loading ranges, and that under single-pile loading range is higher than that under three piles and seven piles. The pile-soil stress ratio of the pile head of gravel pile composite foundation is larger than that of gravel pile + geogrid composite foundation. The smallest is gravel pile + geocell composite foundation, but for the foundation of flexible pile types is flexible pile + geocell composite foundation larger than flexible pile + geogrid composite foundation, and the smallest is flexible pile composite foundation; (4) the pile-soil stress ratio of bottom pile of bag-sand well and gravel pile composite foundation is about 1 and for the flexible pile composite foundation it is much larger and the largest value is about 24; the pore-water pressure is larger and the velocity of dispersion is faster in shallow foundation than those in deep foundation of pile. The pore-water pressure, and that is bigger of piles composite foundation is larger than that of soft soil foundation and geocell-reinforced composite foundation, and the outflow velocity of bag-sand well and gravel pile composite foundation is faster than that of flexible pile composite foundation.