软土基坑离心模型试验及数值模拟研究

CENTRIFUGAL MODEL TEST AND NUMERICAL SIMULATION OF SOFT SOIL FOUNDATION PIT

针对2组具有不同支护形式的软弱基坑进行离心模型试验,测试基坑开挖卸荷过程中支护结构内力和变形,以及坑周土变形,并进行相应的数值计算。试验结果表明:水平支撑对基坑的稳定性影响较大,未加水平支撑的基坑易发生由于支护结构与坑侧土体变形过大所导致的失稳;加水平支撑后基坑的稳定性提高,但要注意由于坑底土体隆起变形所导致的支护结构底端移动和坑顶支撑松弛,进而造成整个支护结构失稳。通过对基坑周边土体在开挖过程中形成的不同应力路径和蠕变参数分析,采用ABAQUS中的扩展D-P模型,对试验模型的原型基坑进行数值计算,计算结果和离心模型试验吻合较好,且可反映基坑周边土体的蠕变效应。

Two series of centrifugal model tests were performed on soft soil foundation pit with different supporting structures. The deformation of soils and supporting structure was measured, and the internal force of structure was analyzed. On the basis of the tests, the numerical calculation was carried out. Test results show that the lateral bracing is very important for the stability of foundation pit; if not, the deformation of supporting structure and soils around the foundation pit would increase quickly with increasing excavation depth, and leading to slope instability. When lateral bracing was added in the foundation pit, the stability of foundation pit was improved. But if the uplift deformation of the basal soil increased, the supporting structure on the bottom will move and lateral bracing will relax; then the entire supporting structure will failure. The soils around the foundation pit have different stress paths and different creep parameters during excavation. For the model and prototype, the numerical calculations were carried out by adopting the extended D-P model in ABAQUS. It is shown that the numerical results accord with the centrifugal model test results, and also show the soil creep properties.