【作者】 肖坚；

【导师】 罗晓辉；

【作者基本信息】 华中科技大学 ， 岩土工程， 2005， 硕士

【摘要】 基坑工程涉及领域广,技术难度大,工程事故多,且造成的损失严重。基坑失事不仅给工程项目本身造成严重的经济损失,而且会危及到周围的建筑物、地下管线、道路等的安全。软土地区由于土体强度低,地下水位高,流塑性强,基坑失稳事故频发。极限平衡条分法由于不能考虑土体内部的应力应变关系,无法分析边坡破坏的发生和发展过程。有限元法则从本构关系入手,可以求解真实的应力分布,也可以方便的显示破坏区的开展过程,是当前边坡稳定性分析的一个新途径。本文以某软土基坑的失稳事故为研究背景,根据作者提出的塑性区贯通作为衡量边坡破坏的依据,运用强度折减弹塑性有限元法,对无支护条件下软土基坑的失稳破坏进行了数值模拟分析,得出了软土基坑变形和失稳破坏的一般规律。分析表明,刚体转动假设并不完全适用于软土边坡,边坡滑动面形状也并非一般的圆弧面,基于极限平衡理论的各种条分法得到的稳定系数与实际边坡的稳定程度并不一致。以塑性区贯通为失稳判据的强度折减有限元法,可以很好的求解真实的应力分布和模拟软土边坡破坏过程,是一种值得提倡的方法。常规的边坡稳定性分析中大多没有考虑建筑基桩对土体变形的抑制作用。事实上,基桩在其允许变形范围内,可以起到抗滑桩的作用。本文在考虑桩土共同作用的基础上,对基桩这一有利影响进行了初步的探讨和定量的分析,得到了一些有意义的结论。更多还原

【Abstract】 The excavation engineering involving technologies of wide fields is so difficult to deal with that engineering accidents are frequently happened and brought about a great loss. Besides the great economic loss to the engineering project itself, it jeopardizes the safety of building, underground pipeline, road around, etc. Due to low soil strength, high underground water level and strong soil plasticity flow , unstability accidents happened frequently in soft soil area. Because the strain-stress relation of soil is unable to taken into consideration, the limit equilibrium slice method cannot analyze the process of slope failure. The finite element method (FEM) which has considered the constitutive relation of soil can obtain the actual stress distribution and display the expand process of failure zone. It is a new approach in slope stability analysis nowadays. Based on a excavation accident in soft soil area, and according to the unstability criterion which was suggested by author, the collapse of foundation pit without timbering was analyzed by strength–reduction FEM, and some common characteristics of slope deformation have been obtained. It is shown that the rigid rotation assumption is inadequately fit for soft soil slope, and the shape of slip surface is also not general circular arc surface. Stability coefficient gained by various slice methods cannot meet the demand of actual slope stability. The strength reduction FEM, taking the run-through of plastic zone as unstability criterion, can obtain actual stress distribution and simulate the process of slope failure. It is a method deserving to be advocated Conventional slope stability analysis has not considered the inhibition effect to soil deforming of foundation pile. Actually, foundation pile can be used as anti-slide pile in its deformation allowance. This helpful effect has been discussed preliminarily based on pile-soil interaction , and some significant conclusions have been drawn.更多还原