考虑水–岩作用特点的典型岸坡长期稳定性分析

大型水库库岸边坡长期经受库水位升降变化的影响,其作用效应主要表现为两个方面,一方面是水压力升降变化的影响,另一方面是岸坡消落带岩土体的水–岩作用劣化效应。基于此,在前期研究基础上,考虑消落带水–岩作用的影响深度及时间效应,建立了岩体强度劣化模型,并结合典型库岸边坡进行了计算分析。研究表明:库水位变化对库岸边坡稳定性影响明显,尤其在一定时期以后,在高水位运行期间安全系数将会出现骤减后迅速恢复的现象,说明坡体下滑力与阻滑力的平衡被打破后又得到调整至新的平衡,随着水–岩作用次数的增加,这种骤减在年循环周期内,逐渐向前推移,且频率与减幅均有所增大,进一步说明当水–岩作用程度越大时,岩体平衡越容易被打破且库岸边坡稳定性越差,而新的平衡对应的安全性逐年降低。这一现象符合重力背斜型滑坡在库水作用期间的破坏堆积过程,研究成果对库区岸坡的稳定性计算具有一定指导意义。

Long-term stability of bank slope considering characteristics of water-rock interaction

In large reservoirs, the bank slopes experience the effect of water level variation for a long time. This effect mainly contains two aspects: 1) the influence of hydraulic pressure going up and down; 2) the water-rock degradation effect of rock mass in hydro-fluctuation belt. Based on the above and the previous studies and considering the depth and time of water-rock effect, the strength degradation model for rock mass is established and used to analyze a typical bank slope. The study shows that water level variation has distinct influence on the stability of bank slope. Especially after a period of time, the safety factor decreases dramatically and regains quickly during high water level operating period. It is indicated that the balance of sliding force and anti-sliding force in the bank slope is broken and then comes to a new balance. With the increasing times of water-rock effect, the dramatic decrease of safety factor appears forward during a cycle time of a year, and the frequency and decrease amplitude both increase. Furthermore, the greater the degree of water-rock interaction is, the more easily the balance of rock mass is broken and the worse the stability of bank slope is. The safety factor of bank slope in the new balance decreases year by year. This phenomenon conforms to the damage accumulation process of gravity anticline type landslide during the period of reservoir water fluctuation. This study is of a certain guiding significance to the stability calculation of bank slopes in reservoirs.