中文摘要：

我国土木、水利、交通和矿山工程建设中广泛存在着由于开挖卸荷引起的土体位移及稳定问题,传统的极限平衡方法不能考虑土体应力应变关系和应力历史等因素,安全系数的计算与工程实际存在偏差。以变形量为失稳判据的有限元强度折减法,考虑了土体应力应变关系,一定程度上可以弥补传统方法的缺陷,但目前针对开挖卸荷应力路径条件下土体应力应变规律研究偏少,限制了有限元强度折减法的作用,导致开挖卸荷相关问题不能很好地解决。因此本文针对卸荷土体应力应变规律研究工作给出了相应的思路和方法：采用室内卸荷应力路径试验,寻找合适的土体卸荷本构模型,在探索采用常规试验获取模型计算参数的实用方法和取用原则的同时,对开挖土体应力变形进行分析,进而结合有限元轻度折减法对实际开挖工程进行有限元数值模拟,与现场监测结果相比较,对模型和参数确定方法进行修正。应用这种方法,可以得到反映开挖卸荷实际的土体本构模型及其参数确定方法。

英文摘要：

In China,many construction projects including civil engineering,water conservancy,transportation and mining are widely puzzled by the soil displacement and stability problems from excavation unloading,the traditional limit equilibrium method could not consider the factors such as the soil stress-strain relationship and stress history,and there is a deviation between the calculation of safety factor and engineering reality.The FEM strength reduction method,with deformation for its instability criterion and considering the stress-strain relationship of soil,could make up for the shortcomings of traditional methods to a certain degree,but the research on stress-strain law of the soil under excavation unloading stress path is few,which would more or less limit the fuction of the FEM strength reduction method,and lead to the unsatisfactory solution for excavation unloading problems.So,some ideas and methods for the research on the stress-strain law are proposed here： The indoor unloading stress path tests are used to find out the right unloading soil constitutive model,and analyze the stress deformation while exploring the practical methods and access principles used to get the model parameters from conventional tests,then the numerical simulation is made for the excavation engineering by using the FEM strength reduction method,at the same time,through comparing the outcome with monitoring results,the model and parameters are modified.Using this approach,the better soil constitutive models and the methods to confirm its parameters could be acquired.