顺层缓倾复合介质边坡水力驱动型滑移破坏机制研究

为了对水力作用下顺层缓倾复合介质边坡稳定性进行定量研究，以沪蓉高速公路彭家湾某同类边坡为例，基于极限分析上限法原理建立针对性的简化力学计算模型。首先，根据位移协调条件以及塑性力学关联流动法则，构建出一个机构允许的应变速度场；其次，根据流体力学原理，在Hoek和Bray假设的基础上，建立适合顺层缓倾复合介质边坡的水压分布模型。通过边坡内水压分布特性分析，得出水力作用（潜滑面扬压力、潜滑面动水压、后缘张裂隙静水压）均与后缘张裂隙内充水高度直接相关；在此基础上，分别建立临界充水高度与临界降雨强度表示的边坡滑移失稳判据。通过该力学模型，计算工程案例边坡滑坡时后缘张裂隙临界充水高度值与临界降雨强度值，确定边坡滑移失稳时滑移面具体位置，并进行边坡稳定性的敏感性因素探讨。研究结果表明：当后缘水位达到临界充水高度或降雨强度达到临界值时，边坡沿着稳定性系数最小的潜滑面发生滑移破坏；底层滑体厚度仅影响底层滑体的稳定性；岩层倾角小于15°时，各潜滑面稳定性受倾角影响较大；水力作用下边坡稳定性下降主要由潜滑面扬压力与张裂隙静水压引起，动水压几乎没有影响。

Research on Sliding Failure Mechanism of Gently Inclined Bedding Compound Rock Mass Slope Under Hydraulic Drive

In order to conduct a quantitative research on the stability of gently inclined compound rockmass slope under the hydraulic drive, taking a similar slope in Pengjiawan of Shanghai-Chengdu Expressway as an example, a targeted calculation model of simplified mechanics was established on the basis of the upper bound method of limit analysis. In this calculation model, firstly, a strain velocity field allowed in institution was constructed according to the displacement coordination conditions and the plastic mechanics associated with the law of flow. Secondly, according to the principles of fluid mechanics, the hydraulic pressure distribution model suitable to the gently inclined bedding compound rockmass slope was established on the basis of E. Hoek and J. W. Bray's assumptions. Through the analysis of the features of hydraulic pressure distribution inside the slope, the hydraulics including the uplift pressure of potential sliding surfaces, the dynamic pressure of potential sliding surfaces and the fissured hydraulic pressure at the back edge, were directly related to the water filling height of the fissure at the back edge. On this basis, the criterion of sliding instability of slope expressed by the critical water filling height and the critical rainfall intensity was developed respectively. According to the criterion, it was clear that the slide failure of slope might occur along the potential sliding surface with the smallest stability coefficient when the water level at the back edge reaches the critical value or the rainfall intensity reached the critical value. Based on the mechanical model, the value of critical water filling height of the fissure at the back edge and the critical rainfall intensity at the slope landslide in the project case were calculated, and the specific position of sliding surface in sliding instability of slope was discussed. Meanwhile, the sensitive factors of slope stability were also carried out. The results show that the thickness of the bottom rock mass only affects its own stability, and when the dip angle of rock mass is less than 15°, the stability of each potential sliding surface is greatly affected by the dip angle. Under the hydraulic drive, the decline of slope stability is mainly caused by uplift pressure of the potential sliding surfaces and fissured hydraulic pressure, and the hydrodynamic pressure has almost no effect.