库水升降作用下灰岩岸坡稳定性数值研究

Numerical study on the stability of limestone bank slopes under the influence of reservoir water fluctuation

基于现场调研与采样,采用室内力学试验测定灰岩力学参数与干湿循环下强度劣化规律;基于UDEC建立库岸边坡数值模型,研究了三峡库区反倾岸坡、顺层岸坡、近水平层状岸坡及含危岩体岸坡在库水升降作用下的失稳演化过程及消落带劣化深度与岩层厚度对岸坡稳定性的影响规律。结果表明:库水升降作用下岸坡的失稳过程可以分为裂隙萌生发育、裂隙发展贯通和坡体失稳破坏阶段;随着消落带劣化深度的增加,4种岸坡稳定性系数降低;随着岩层厚度的增加,4种岸坡的稳定性系数升高。近水平层状岸坡稳定性系数受以上2种因素影响最大,而随着干湿循环次数增加发生的变化最小;当劣化深度大于10 m以及岩层厚度大于5 m时,含危岩体岸坡稳定性系数随影响因素水平变化而产生的变化量较小。长远来看,受库水影响的4种典型岩质岸坡稳定性从大到小依次为反倾岸坡、近水平层状岸坡、顺层岸坡、含危岩体岸坡。

Based on field investigation and sampling,the mechanical parameters of limestone and the degradation characteristics of strength under dry-wet cycles were determined by mechanical tests.Through the establishment of a numerical model of the shoreline slope utilizing UDEC,this study examined the process of instability evolution and the impact of weathered zone degradation depth and rock layer thickness on the stability of various shoreline slope types in the Three Gorges Reservoir region.Specifically,the anti-dip bank slope,parallel-layer bank slope,near-horizontal layered bank slope,and shoreline slope containing dangerous rock masses were included in the analysis under the influence of reservoir water level fluctuations.The findings demonstrate that the failure process of the shoreline slope under reservoir water level fluctuations can be categorized into stages of crack initiation,crack propagation,and slope failure.Additionally,an increase in the degradation depth of the weathered zone leads to a decrease in the stability coefficient of the four types of shoreline slopes,while an increase in rock layer thickness results in an increase in their stability coefficient.Of note,the stability coefficient of the near-horizontal layered bank slope is significantly influenced by these factors,and with minimal changes arising from the increase in the number of dry-wet cycles.Subsequently,when the degradation depth exceeds 10 meters and the rock layer thickness surpasses 5 meters,the variation in the stability coefficient of the shoreline slope containing dangerous rock masses due to changes in influencing factors is relatively minor.In the long term,the stability of the four typical rocky shoreline slopes influenced by reservoir water level fluctuations from large to small is:anti-dip bank slope,near-horizontal layered bank slope,parallel-layer bank slope,bank slope containing dangerous rock masses.