勘察参数与本构模型参数转换关系初探

摘要

对于包括地铁明挖基坑和矿山竖井等地下工程的数值仿真分析,其结果可靠度取决于两个关键的因素,一是模拟基坑周边岩土体采用的本构模型,二是这些本构模型参数的可靠程度.而常规岩土勘察工作不能提供高级岩土本构模型(例如修正剑桥模型、小应变应变模型)参数,分析人员一般根据经验确定参数的取值,这为分析结果带来极大的不确定性和随意性.以施工实测位移响应反演确定岩土本构模型参数则较为准确,但是确定的岩土参数通常只适用于单一目标地质情况,不能推广应用到其他工程.本文基于岩土本构参数和常规勘察物理指标和力学试验结果的内在关联性,以及岩土参数的地区特性,拟以北京地区一定数量的明挖基坑工程为分析样本,在通过反演确定岩土本构模型参数的基础上,进一步考察常规勘察物理指标及力学试验结果与岩土本构模型参数之间的关系,拟探索两者之间是否存在强相关性并初步建立相关公式.研究结果希望从表观层次,为基坑或竖井支护设计,由常规勘察物理指标和基本力学试验结果来确定高级岩土本构模型参数,提供基础数据资料和方法初步探索.%For the numerical simulation analysis of underground engineering including underground excavation and mine shaft ,the reliability of the results depends on two key factors ,one is the constitutive model used to simulate the surrounding rock and soil ,the other one is the reliability of these constitutive model parameters .Conventional geotechnical survey can't provide parameters for advanced geotechnical constitutive model (such as modified Cambridge model ,small strain model ,etc .) ,analysts generally determine the value of the parameters according to experience ,which brings great uncertainty and randomness to the analysis results .It is more accurate to determine the parameters of the constitutive model of rock and soil by the inversion of the measured displacement response ,but the determined parameters of rock and soil are usually only applicable to a single target geological situation ,and can not be extended to other projects .In this paper ,based on the intrinsic relationship between the constitutive parameters of rock and soil and the physical indexes of conventional investigation and the results of mechanical tests ,as well as the regional characteristics of the parameters of rock and soil ,a certain number of open excavation foundation pit projects in Beijing area are taken as analysis samples .Based on the determination of the parameters of the constitutive model of rock and soil by inversion ,this paper further investigates the relationship between the parameters of the constitutive model of rock and soil and the physical indexes of conventional investigation and the results of mechanical tests ,and tries to find out whether there is a strong correlation between them and to establish the relevant formulas .The results of the study hope to determine the parameters of the advanced rock and soil constitutive model from the surface level for the design of the foundation pit or shaft support by the general survey physical index and the basic mechanical test results , and to provide the basic data and methods of preliminary exploration .