基于RMR与H-B准则估算大型洞室岩体力学参数敏感度分析

Sensitivity Analysis on the Estimation of Mechanical Parameters for Rock Mass Around Large Cavern Based on RMR and H-B Criterion

利用RMR(岩体质量分级)与Hoek-Brown(H-B)准则估计岩体力学参数可作为大型地下洞室围岩参数确定的有效途径.考虑到输入参数不确定性引起岩体力学参数估计精度受影响的问题,依托白鹤滩水电站地下厂房工程,基于原位测试、室内试验与数值模拟等,研究H-B准则输入参数与估计岩体力学参数间的敏感性关系,并采用敏感度因子定量描述.结果表明,岩体力学参数对输入参数的敏感性排序为RMR>σ_(ci)(岩石单轴抗压强度)>m_(i)(岩石材料常数),当RMR取值误差为±5%时,弹性模量、内摩擦角及黏聚力估计结果分别产生约20%,22%与13%的偏差;当σ_(ci)与m_(i)的测定误差小于±20%时,其对于内摩擦角与黏聚力估算结果的影响分别小于4%与10%.该研究可为类似大型地下洞室工程岩体力学参数估计精度评价提供借鉴.

Using RMR(rock mass rating)and Hoek-Brown(H-B)criterion to estimate mechanical parameters of rock mass is an effective way to determine parameters of the surrounding rock mass around large underground cavern.Considering that the uncertainty of input parameters directly affects the estimation accuracy of mechanical parameter of rock mass,relying on the large underground powerhouse engineering of Baihetan Hydropower Station,the sensitivity between the input parameters of H-B criterion and mechanical parameters of rock mass is studied through in-situ test,laboratory test and numerical simulation,in which the sensitivity factor is used to describe the sensitivity relationships.The results show that the sensitivity of mechanical parameters of rock mass to input parameters is ranked as RMR>σ_(ci)(uniaxial compressive strength of rock)>m_(i)(rock material constant),and the influence of RMR is the most significant.The error of±5%in the determination of RMR would result in a deviation of about 20%,22%and 13%in the estimated results of elastic modulus,internal friction angle and cohesion,respectively.When the error ofσ_(ci)and m_(i)is less than±20%,the influence of them on the estimation results of internal friction angle and cohesion is less than 4%and 10%,respectively.This research can provide reference for the accuracy evaluation on estimation of mechanical parameter of rock mass around similar large underground caverns.