节理岩质边坡稳定性分析改进Sarma法

Improved Sarma method for stability analysis of jointed rock slopes

在节理岩质边坡稳定性分析中,传统Sarma法仍存在如下几个方面的不足:(1)未合理明确节理块体间剪切力方向;(2)未有效处理节理块体间及其滑动底面被拉裂;(3)未可靠保证节理块体滑动底面剪切力方向与边坡整体滑动趋势相符。因而,传统Sarma法的分析模式不能完全满足受力合理性原则。为此,在传统Sarma法的基础上,进行以下改进:(1)构建相对运动趋势下节理块体间剪切力方向判别关系式;(2)引入拉伸截断技术,可靠估计线性Mohr-Coulomb强度准则下岩体节理面抗拉强度;(3)容许节理块体间被拉裂,建立节理块体间拉裂计算机制;(4)提出增大块间安全系数以及节理块体两侧裂缝式退化处理方式,合理解决节理块体滑动底面被拉裂问题;(5)虚设反向滑动块体间裂缝,有效应对顺滑节理块体滑动底面剪切力反向情况。进而,提出节理岩质边坡稳定性分析改进Sarma法。通过后续算例对比分析,本文方法的可靠性与有效性得到验证。此后,进一步详细探讨改进方法中相关新参数对节理岩质边坡稳定性的影响。

In the stability analysis of jointed rock slopes,the traditional Sarma method still has the following deficiencies:(1)The direction of the shear force between joint blocks is unreasonably defined.(2)The tensile cracking between joint blocks and their bottom surfaces(i.e.,the slip surface)is ineffectively treated.(3)The requirement that the direction of the shear force on the sliding bottom surface of joint block is consistent with the overall sliding trend of the slope can not be reliably guaranteed.Therefore,the analysis model of the traditional Sarma method cannot fully satisfy the principle of rationality for force analysis.Hence,the following improvements are made on the basis of the traditional Sarma method as:(1)The relation-equation for determining the direction of the shear force between joint blocks under the trend of relative motion is constructed.(2)The technique of tensile strength cut-off is introduced to reliably estimate the tensile strength of rock joints under the linear Mohr-Coulomb strength criterion.(3)The calculation mechanism is established for allowing the tensile cracking between joint blocks.(4)The treatment approach of increasing factor of safety between joint blocks and degrading with the use of cracks on both sides of joint blocks are proposed to reasonably solve the problem of the bottom surface of joint blocks being cracked.(5)The virtual crack at the side of the reverse sliding blocks is set to effectively deal with the case of the reverse of shear force on the bottom surface of slumping joint block.Thereby,the improved Sarma method for stability analysis of jointed rock slope is proposed.Through the comparison and analysis on some existing examples,the reliability and effectiveness of the present method are verified.Thereafter,the influence of relevant new parameters in the Improved Sarma method on the stability of jointed rock slope is further discussed in detail.