A-BQ,一种基于BQ 的各向异性岩体质量分级系统

A-BQ,a classification system for anisotropic rock mass based on China National Standard

自然界中岩体的力学行为多数表现为各向异性,现有的岩体质量分级方法大多是基于各向同性假设,因此远远难以满足工程要求。本研究在中国岩体质量分级标准BQ的基础上,提出了一种各向异性岩体质量分级系统A-BQ。该系统可用来评估岩体的各向异性程度,同时还可以对各向异性岩体的质量进行评估分级。系统中考虑了岩石的固有各向异性和岩体结构的各向异性,分别采用岩石强度的各向异性和岩体完整性系数的各向异性表征。岩体的各向异性程度通过不同作用方向下岩体的最好与最差质量得分之比确定,并由围岩应力进行调整。基于岩体各向异性结构的产状,结合岩体最好和最差质量得分,可计算各向异性岩体的基本得分,再通过应力状态和地下水因子的校正,获得各向异性岩体的ABQ值,在此基础上将岩体质量分为5级。针对不同岩体质量级别给出了隧道和边坡工程可能的稳定性状态和破坏模式。最后以实际的各向异性岩体隧道和边坡工程为例,对该分级方法进行了应用。

The rock mass in nature is in most cases anisotropic,while the existing classifications are mostly developed with the assumption of isotropic conditions that not always meet the engineering requirements.In this study,an anisotropic system based on China National Standard of BQ,named as A-BQ,is developed to address the classification of anisotropic rock mass incorporating the anisotropy degree as well as the quality of rock mass.Two series of basic rating factors are incorporated including inherent anisotropy and structure anisotropy.The anisotropy degree of rock mass is characterized by the ratio of maximum to minimum quality score and adjusted by the confining stress.The quality score of rock mass is determined by the key factors of anisotropic structure occurrence and the correction factors of stress state and groundwater condition.The quality of rock mass is characterized by a quality score and classified in five grades.The assessment of stability status and probable failure modes are also suggested for tunnel and slope engineering for different quality grades.Finally,two cases of tunnel and slope are presented to illustrate the application of the developed classification system into the rock masses under varied stress state.