三峡库区巫峡段反倾岩石边坡的破坏机制及判据

 三峡库区巫峡段龚家坊2#斜坡属反倾岩石边坡，发育薄厚互层和软硬相间的岩体结构，在库水位抬升后发生了大型滑塌。为了研究该类岩石边坡的破坏机制和判据，基于龚家坊2#斜坡岩体结构的调查成果，分析厚薄互层的反倾岩石斜坡弯曲变形过程，及库水作用下斜坡的破坏机制。基于叠合悬臂梁模型、独立悬臂梁模型，提出薄厚互层反倾岩石斜坡各破坏阶段的应力判据。采用有限元分析库水软化作用下，龚家坊2#斜坡岩石的强度折减参数及变形破坏规律。研究结果表明：(1) 上硬(嘉陵江组)下软(大冶组)的沉积结构和快速下切的河谷，是巫峡龚家坊至独龙段反倾斜坡普遍发育弯曲变形的关键因素；(2) 厚薄相间的岩层结构，使反倾岩石边坡表现为多阶段破坏，其中，薄层弯曲岩层和厚层坚硬岩层，分别以叠合悬臂梁模型和独立悬臂梁模型建立破坏判据；(3) 库水对该区薄层泥灰岩软化后的抗剪强度小于天然强度的85%，斜坡发生自下而上的渐进式破坏。

FAILURE MECHANISM AND CRITERION OF COUNTER-TILT ROCK SLOPES AT WUXIA GORGE SECTION IN THREE GORGES RESERVOIR AREA

Gongjiafang slope #2 is a counter-tilt slope consisted of thick/thin and soft/hard rocks layers at Wuxia Gorge section in the Three Gorges Reservoir area. It had undergone a complicated failure process of bending to slipping. In order to study its failure mechanism and criterion，the rock structures of the counter-tilt slope were investigated and its deformation process and failure mechanism influenced by rising water level of the reservoir were analyzed. A set of analysis models，i.e. superposed cantilever model，independent cantilever beam model were proposed to decide the failure criterions of the counter-tilt slope by comparing the slope stresses with the rock strength. The finite element method was employed to analyze the parameter reduction of rock and the laws of deformation and failure. The strata structure of the upper hard rock strata and the lower soft rock strata and the deep and steep river are the key reasons to induct bending deformation onto the counter-tilt slope in the Wuxia Gorge area. The counter-tilt slope with different layer thicknesses has multiple failure stages and different criteria with the superposition cantilever model appropriate for thin soft rocks and the independent cantilever beam model fit for thick rocks. The shear strength of thin marlstone may be reduced to 85% of its normal strength after the rock softening and the slope failure developes from the lower part to the upper part.