基于扩展有限元方法的基坑突涌研究

传统理论基于弹塑性力学计算基坑内部的塑性区域并将塑性区域等价为破坏区域,无法获得具体的突涌位置。文中首次利用扩展有限元方法研究基坑突涌现象,模拟了一处位于加拿大的垃圾填埋场基坑的突涌现象,获得了3个突涌位置和与之对应的涌水通道,与现场结果吻合较好。对影响基坑裂纹扩展的参数进行了分析,结果表明,土体的渗透系数与孔隙率越小,流体粘度越大,则裂纹内孔压越大,最终的裂纹张开尺寸越大。通过对基坑开挖离心机实验进行扩展有限元模拟,确认了基坑突涌中裂纹属于I型张拉裂纹,且窄开挖基坑的突涌位置位于墙后,宽开挖基坑的突涌位置位于基坑内。

WATER BURST SIMULATION IN DEEP EXCAVATION PITS WITH EXTENDED FINITE ELEMENT METHOD

In the research of deep excavation water burst, traditional study figures out the area of plastic stress state of foundation pits and treats the plastic area as failure zone, but it fails to get the detailed burst location. This paper researches the burst problem with extended finite element method (XFEM) for the first time. Water burst of a landfill pit in Canada is simulated, three burst locations and corresponding full crack paths are obtained which match the reported locations very well. After the analysis of parameters which affect the crack propagation, it is found that with the smaller the permeability, coefficient void ratio and greater the viscosity of the fluid, the larger the crack width and crack open size is. For another example, Simulation of centrifuge test of deep excavation is conducted. It is found that cracks in pits burst belong to I type tension cracks and resulted water burst locations in narrow pits locate behind the walls while water burst locations in wide pits locate inside the excavations.