Physical simulation of the excavation deformation response of counter-tilt slope with rigid layers on the soft
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摘要: 现有上硬下软边坡的研究大都集中在压缩挤出变形的近水平泥岩、页岩基座型边坡变形演化过程，针对倾倒变形的板岩基座型边坡开挖响应研究甚少，本文以西藏玉曲河某水电站厂址边坡为研究对象，根据现场地质调查建立符合坡体实际情况的地质结构模型，采用物理试验的方法模拟原型边坡开挖。通过试验揭示上硬下软反倾边坡在开挖条件下的变形响应特征及破坏模式。研究结果表明：（1）开挖条件下上硬下软型边坡变形破坏过程分为a）下部软岩倾倒弯曲加剧；b）软岩倾倒折断，上部卸荷硬岩沿已有裂隙剪切；c）倾倒软岩滑移，卸荷硬岩剪断岩性分界部位，折断面贯通3个阶段。其变形破坏模式为下部软岩倾倒—上部硬岩剪断组合滑移型破坏；（2）开挖强倾倒区岩体会使下部软岩迅速失稳并促使上部硬岩剪切破坏；开挖引起的反倾上硬下软边坡大变形在短时间内完成，前期变形和能量积累是一个较长的过程；（3）开挖时需避免对坡脚倾倒岩体“大开挖”施工。Abstract: Most of the existing researches on counter-tilt slope with rigid layers on the soft focus on the deformation evolution process of near-horizontal mudstone and shale pedestal type slopes with compression and extrusion deformation, and the excavation response of the slab-pedestal type slope with toppling deformation were seldom examined. This paper takes the slope of the Yuqu Hydropower Station in Tibet as the research object. Based on the field geological investigation, the geological structure model conforming to the actual situation of the slope is established, and the prototype slope excavation is simulated by using the physical test method. The deformation response characteristics and failure modes of counter-tilt slope with rigid layers on the soft under excavation conditions are revealed through experiments. The results show that (1) the process of deformation and failure of counter-tilt slope with rigid layers on the soft under excavation conditions is divided into three stages: (a) lower soft rock topping is intensified; (b) soft rock toppling fracture and the upper unloading hard rock along the existing crack shear; and (c) dumping soft rock slip, unloading hard rock shearing lithologic boundary points, break through the surface. The deformation failure mode is the lower soft rock toppling-upper hard rock shear-combination slip failure. (2) The large deformation caused by excavation of counter-tilt slope with rigid layers on the soft is completed in a short time, and the deformation and energy accumulation in the early stage is a long-time process. (3) During the excavation, it is necessary to avoid the “large excavation” construction of the rock mass toppling on the slope foot.
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