露天采场边坡岩体抗剪强度参数确定及稳定性分析

Determination of Shear Strength Parameters and Stability Analysis of Slope Rock Mass in Open-Pit Mine

为了探究露天矿边坡在不同抗剪强度参数测定方法下的边坡稳定性变化情况,分别通过室内直剪试验、RMR岩体质量分级和Hoek-Brown强度准则等方法测定了岩体抗剪强度参数,结合二维极限平衡法和三维有限元强度折减法对采场边坡进行了稳定性分析。研究结果表明,基于室内直剪试验和Hoek-Brown强度准则获得的岩体内摩擦角相近,而黏聚力前者大于后者;所获得抗剪强度参数用于边坡稳定性分析时,基于室内直剪试验和Hoek-Brown强度准则获得的抗剪强度参数所计算的二维稳定性系数前者比后者高出了30.09%,三维稳定性系数前者比后者高出了9.33%,并且三维稳定性系数比二维稳定性系数在两种抗剪强度参数测定方法下分别高出了8.12%和28.85%。基于Hoek-Brown强度准则计算出的抗剪强度参数考虑了岩石的非均质性和裂隙分布,能够更准确地反映岩体在自然状态下的强度特征;三维稳定性分析全面地考虑了边坡的空间效应、复杂几何形状和边界条件,对于几何形状复杂、地质条件多变的复杂边坡,宜采用三维稳定性分析。

In order to explore the change of slope stability under different methods of measuring shear strength parameters,the shear strength parameters of rock mass were measured by indoor direct shear test,RMR rock mass quality classification and Hoek-Brown strength criterion.The stability analysis of stope slope was carried out by combining two-dimensional limit equilibrium method and three-dimensional finite element strength reduction method.The results show that the internal friction angle of rock mass obtained based on indoor direct shear test and Hoek-Brown strength criterion is similar,while the cohesion of the former is larger than that of the latter.When the obtained shear strength parameters are used for slope stability analysis,the two-dimensional stability coefficient calculated by the shear strength parameters based on the indoor direct shear test and the Hoek-Brown strength criterion is 30.09%higher than the latter,and the three-dimensional stability coefficient is 9.33%higher than the latter.And the three-dimensional stability coefficient is 8.12%and 28.85%higher than the two-dimensional stability coefficient under the two shear strength parameter determination methods.The shear strength parameters calculated based on Hoek-Brown strength criterion take into account the heterogeneity and fracture distribution of rock,which can more accurately reflect the strength characteristics of rock mass in natural state.The three-dimensional stability analysis comprehensively considers the spatial effect,complex geometry and boundary conditions of the slope.For complex slopes with complex geometry and variable geological conditions,three-dimensional stability analysis should be adopted.