建筑物掏土纠倾法孔周土压力和破坏特性试验研究

Experimental study on soil pressure and failure mode of holes for under-excavation in building rectification

掏土孔孔周土受力与变形以及破坏模式是建筑物纠倾研究的关键问题,影响纠倾设计中掏土孔直径及掏土孔间距等参数的确定。为了研究建筑物掏土纠倾法掏土孔周土压力变化、掏土孔破坏模式以及地基的沉降情况,设计并制作了可用于模拟掏土纠倾的模型箱,对掏土孔直径为200mm,孔间距分别为400、600、800mm的纠倾模型进行试验,分析了由于掏土孔开挖引起的地基土沉降及倾斜率。研究结果表明:掏土孔的破坏呈现立式椭圆、卧式椭圆及近似圆形三种破坏模式;通过孔侧和孔上部压力的变化,发现孔周土压力发生转移,从孔上部土压力向孔侧边土体转移,孔顶土压力减小,孔侧土压力增加,形成土拱效应;随着孔间距增加,土体形成稳定拱脚,从而不利于纠倾工程回倾;通过试验结果,建议孔间距为2~3倍掏土孔直径。

In the design of building rectification process,the stress,the deformation and the failure mode of the excavation holes are the key problems.They affect the determination of the key design parameters such as the diameter and spacing of excavation holes etc.In this regard,some model experiments were carried out to study the soil pressure variation around the holes,the failure mode of the excavation hole and the soil settlement after excavation.A simulation model box was designed and made to simulate the soil excavation.The soil excavation was then done with the hole diameter of 200 mm;three cases with the hole spacing of 400 mm,600 mm,and 800 mm,respectively,were considered.The soil settlement and tilt ratio due to the excavation holes were analyzed.The results show that there are three failure modes of the excavation holes: vertical irregular oval,horizontal irregular oval,and irregular circle. Further,it is found that the soil pressure transfers from above the hole to the side of the hole,which accords with the soil arching effect.Furthermore,it is found that with the increase of hole spacing,the soil between the holes forms a steady arching foot,which is unfavorable to the building rectification.It is suggested based on the test results that the proper hole spacing should be 2-3 times of the hole diameter.