砂土地基和粉质黏土地基基坑悬臂开挖离心模型试验

分别开展砂土和粉质黏土两种典型土质条件下基坑悬臂式开挖离心模型试验，详细叙述试验过程中所要解决的关键问题，并提出合理的解决方案。通过对比分析两组试验结果，得到以下结论：非饱和土地基制备中参数控制困难，分层夯实法有待进一步改进，而砂雨法制备的砂土地基参数可控性更好；两组试验的结果有差异，砂土地基试验所呈现的土压力、地基变形、支护弯矩的变化规律更好，因此，岩土离心试验可适当考虑以砂土代替非饱和土；对于采用悬臂式支护结构的基坑，开挖引起的地表沉降曲线在砂土中呈指数型，而在粉质黏土中呈直线型；开挖引起的粉质黏土地基土体位移范围较砂土地基更大；开挖引起的砂土中挡墙弯矩较粉质黏土更大，砂土和粉质黏土中最大弯矩位置都随开挖逐渐下移；在砂土试验中开挖引起主动区土压力各处均减小，而在粉质黏土试验中开挖引起土压力在挡墙底有增大趋势。该基坑工程离心模型试验过程及数据处理方法可为进一步试验提供参考。

Centrifuge model tests on cantilever foundation pit engineering in sand ground and silty clay ground

Two centrifuge model tests on foundation pit engineering with cantilever retaining wall in sand and silty clay ground are carried out respectively. Test procedures and some feasible solutions to the key problems in the tests are introduced, and results of the two tests are listed and compared in this paper. It can be summarized that the preparation of unsaturated soil ground is difficult because it is hard to control parameters of remolded soil. Therefore, stratified compaction method needs to be improved. In contrast, sand ground prepared by sand-rain method is easier to control parameters.Evolution of soil pressure, foundation deformation, and bending moment in the sand ground test is better than that in the silty clay ground test. Therefore, geotechnical centrifuge model tests in unsaturated soil ground can be replaced by the tests in sand ground appropriately. In foundation pit engineering with cantilever supporting structures, the induced surface settlement curve is an exponential pattern in sand ground but a linear pattern in silty clay ground according to test results, and the induced ground deformation range is larger in silty ground than that in sand ground. The induced bending moment of the retaining wall is larger in sand ground than that in silty ground, and the positions of the maximum bending moment for both grounds move down during the excavations. In sand ground, soil excavation causes decrease of the earth pressure behind the retaining wall, while in silty clay ground, there is an increase at the bottom of the wall. The complete test procedures and data processing methods presented in this study provide technical premises and guidance for further tests.