上部覆盖层下伏页岩一类潜在滑坡演化变形机制分析

为研究上部覆盖层下伏页岩这一类型的滑坡失稳变形,需要确定其变形的潜在影响因素,从定量角度上分析这一类型滑坡灾害的变形演化问题。以容县六王镇西流河潜在滑坡为研究对象,借助钻孔勘探、室内试验和地质调绘,详细分析了西流河滑坡的工程地质概况,并推测其可能的变形演化机制,然后利用Geostudio数值软件建立西流河滑坡的渗流模型,模拟其在不同降雨工况下的渗流规律。研究发现:西流河滑坡在持续降雨过程中稳定性系数从1.224逐步降低至1.09,稳定性系数不断下降,滑坡体内由垂直入渗逐步转化沿滑动带稳定渗流;当遭遇极端暴雨情况(50年重现期)时,滑坡体内稳定渗流场显著增厚,饱和滑带土增多,滑坡安全储备达到极限。由此可以得出:上部覆盖层下伏页岩一类滑坡变形演化过程主要分滑坡体上部覆盖层堆积阶段,垂直入渗至页岩富水软化阶段和稳定渗流至潜在滑动带软化蠕变这3个阶段;其中上部覆盖层的高渗透性和下伏页岩的隔水特征是导致页岩风化带软化蠕变和稳定渗流场形成的关键因素。研究结果为上部覆盖层下伏页岩这一类滑坡影响因素的研究提供了一些证据,对研究滑坡演化变形机制具有借鉴意义。

Analysis on evolutionary deformation mechanism of a potential landslide such as underlying shale in the upper overburden

In order to study the landslide instability deformation of the shale under the upper overburden, it is necessary to determine the potential influencing factors of the deformation and analyze the deformation evolution of this type of landslide disaster from a quantitative perspective.Taking the potential landslide of Xiliu River in Liuwang Town, Rongxian County as the research object, with the aid of drilling exploration, indoor test, geological annotation, the general situation of engineering geology of Xiliu River landslide was analyzed in detail, and the possible mechanism of deformation evolution was speculated. Then, the seepage model was established by using Geostudio numerical software to simulate its seepage law under different rainfall conditions. The results show that the stability coefficient of Xiliu River landslide gradually decreases from 1.224 to 1.09 in the process of continuous rainfall and the landslide body gradually changes from vertical infiltration to the stable seepage flow along the slip zone; When extreme rainstorm is encountered (50-year recurrence period), the stable seepage field in the landslide body thickens significantly, the saturated slide zone soil increases, and the landslide safety reserve reaches the limit. It can be concluded that the evolution process of the landslide deformation of the underlying shale in the upper overburden is mainly divided into three stages: The accumulation stage of the overburden of the landslide body, the vertical infiltration stage to the water-rich softening stage of the shale, and the stable seepage stage to the softening creep stage of the potential sliding zone. The high permeability of the upper overburden and the water-proof characteristics of the underlying shale are the key factors leading to the formation of in the shale weathering zone. The results of this study provide some evidence for influencing factors and evolutionary deformation mechanism of the landslide such as the underlying shale in the upper overburden.