桩网复合地基的模型试验加固效果对比研究

为了探究不同形式的桩网复合地基加固软土的效果，设计了3组复合地基进行室内模型试验。第1组为PVC管材加固软土地基，第2组为桩承式复合地基，第3组为PVC管材与砂桩复合地基。在模型箱钢板内侧壁涂上黄油，并覆以塑料薄膜来减小边界效应；在PVC管材和土工编织网（格栅）上粘贴应变片，来测试PVC桩体应力及加筋拉力；在桩间土、砂桩顶部安装土压力盒，在路面的中心、路肩处安装百分表来测定相应的变形。试验结果表明：1）对于路面、路肩的沉降及二者的差异沉降，第3组沉降值最大，第2组沉降值最小；2）PVC桩与土应力比中，第2组应力比与其它2组比较则大得多；3）格栅应变变化规律较紊乱，在相应测点的格栅应变则是第2组最大。3组试验的结果说明在软土路段，在条件允许时，宜采用桩承式路堤来加固，加固效果更好。

Contrast Analysis of the Reinforcement Effect of Pile-Net Composite Foundation

To investigate the effect of consolidation soft soil, three groups of model tests were designed. The first group was PVC pile-net composite foundation, the second was pile-cap-net composite foundation, and the third was PVC and sand pile composite foundation. Butter was coated and plastic membrane was covered on inner side wall of model cast to reduce border effect. The gauges were glued with epoxy on the surface of the model with PVC piles and geogrids to measure the stress of PVC piles and geogrids. Soil pressure cells were installed in the middle of piles and the top of the sand piles, and dial indicators were installed in the middle of road and road shoulder to measure deformations. It is that shown： 1） as for the distribution of the road settlement and the differential settlement, the settlements of the third group are the largest and those of the second group are the least; 2） in terms of the stress ratio of PVC pile and soil, the values of the first group and the third group are similar, while the value of the second group is much larger; 3） the change of geogrid strain is disorderly. There are periodic peaks in the strain of geogrid of pile top and periodic troughs in the soil between the piles. The geogrid strain of the second group measured in the corresponding spot is much larger than those of the other two groups. The results of three groups of tests illustrate that if the condition is permitted, it would be the best to adopt the scheme of pile-cap-net composite foundation, which has better reinforcement effect for soft soil.