一种确定节理岩体残余强度参数方法的探讨

A METHOD FOR DETERMINING RESIDUAL STRENGTH PARAMETERS OF JOINTED ROCK MASSES

岩体的地质强度指标(GSI)集中考虑岩体结构和结构面表面特征2个方面的因素,已被广泛地应用于岩体强度参数与变形参数的计算中。在GSI系统的基础上,采用残余GSI量化评价方法,通过对峰值地质强度指标GSI进行折减,以得到残余地质强度指标GSI r,据此来计算节理岩体的残余强度参数。首先,结合岩体分类指标法(RMi),在Vb和J c的基础上探讨残余岩块体积Vb r和残余节理条件系数J cr取值的确定方法;然后,由Vb r和J cr计算出GSI r,据广义Hoek-Brown准则计算出节理岩体的残余强度参数,重点对4种典型岩体的残余强度取值进行分析,讨论残余岩体体积对岩体残余强度参数的影响;最后,通过对岩体原位剪切实验数据和一桥墩承台开挖边坡的稳定性反分析,证实基于GSI r指标的节理岩体残余强度参数确定方法的合理性和可靠性,为节理岩体残余强度参数的确定提供一条新的思路。

The geological strength index（GS/） system concentrates on the description of two factors, rock structure and block surface conditions, which has been widely used in the estimation of strength parameters and deformation parameters. The guidelines given by the GSI system are for the estimation of the peak strength parameters of jointed rock masses. There are no guidelines given by the GSI, or by any other system, for the estimation of the rock mass＇s residual strength that yield consistent results. In order to make up the paucity of research, on the basis of GSI system, in this paper, using the GSI quantitative evaluation method by means of adjusting the peak GSI to the residual GSIr with two factors： residual block volume Vb and residual joint condition factor jr. Firstly, according to rock mass index（RMi）, methods to obtain the rock block volume Vb and joint condition factor Jc values are discussed. Then, on the basis of Vb and Jc , the accessor method for Vb and jr are probed. Finally, calculating the GSIr value by Vb and Jc, to determine the residual strength parameters by generalized Hock-Brown criterion. The proposed method for estimating rock mass＇s residual strength is validated using in-situ block shear test data from two tunnels and data from back-analysis of rock slopes, so as to provide a new idea to obtain the residual strength parameters of the jointed rock masses.