Analysis on deformation characteristics of a cutting high bedding rock slope with multiple weak layers based on physical model tests
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摘要:
含有多层软弱夹层的开挖边坡具有坡体结构复杂、稳定性评价及治理难度大的特点。以黔西地区现场开挖高边坡为研究对象,建立室内物理试验模型,通过不同的工况开挖,呈现变形破坏演化过程,分析变形破坏模型及形成机理,确定失稳破坏范围。结果显示:开挖边坡裂隙产生由表及里,由上及下,由最初的陡倾短小裂隙扩展延伸,最终贯通,形成近似平行岩层的长大裂缝;缓坡度开挖变形破坏为浅表层,整体稳定性较好,失稳范围及规模较小;陡坡度开挖变形破坏规模大,稳定性较差,以滑移-拉裂深层失稳为主;浅层滑坡滑面以层间泥化夹层剪切为主,基本呈直线状;深层滑坡滑面以层间泥化夹层剪切以及陡倾裂隙组合形成阶梯状。该研究成果对于黔西地区的顺层开挖高边坡设计、稳定性评价、治理措施选择等具有重要的指导意义。
Abstract:The excavated slope with multi-layer weak interlayer has the characteristics of complex slope structure and difficult stability evaluation and treatment. Based on the on-site excavation of high slope in western Guizhou, an indoor physical test model is carried out. Through excavation under different working conditions, the evolution process of deformation and failure is presented. The deformation and failure model and formation mechanism are analyzed to determine the instability and failure range. The results show that the fissures in the excavated slope extend from the surface to the inside, from top to bottom, from the initial steep short fissures, and finally through to form a long fissure approximately parallel to the rock layer; the deformation and failure of gentle slope excavation is shallow surface, the overall stability is good, and the instability range and scale are small; the excavation deformation and failure scale of steep slope is large, and the stability is poor, mainly in the deep instability of slip tensile fissure; the slip surface of shallow landslide is mainly sheared by interlayer argillaceous interlayer, which is basically linear; the sliding surface of deep landslide is stepped by the combination of interlayer argillaceous interlayer shear and steep inclined fractures. The research results have important guiding significance for the design, stability evaluation and treatment measures of bedding excavation high slope in western Guizhou.
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Key words:
- weak interlayers /
- high slope excavated /
- deformation instability /
- physical model test
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表 1 试验主要物理量相似比取值
Table 1. The ratios of main physical quantities in tests
物理量 相似比符号 相比取值 几何相似 Cl 60 重度相似 Cr 1 泊松比相似 Cμ 1 摩擦系数相似 Cf 1 黏聚力相似 CC 60 摩擦角相似 Cφ 1 应变相似 Cε 60 时间相似 Ct=(Cl)1/2 7.75 表 2 边坡变形破坏分析与评价
Table 2. Comprehensive analysis and evaluation of slope deformation and failure
工况 变形破坏特征 稳定性及评价复杂性 失稳规模及范围 失稳模式及机理 工况一 变形破坏特征以滑移-拉裂为主。裂缝产生由表及里,通常先产生竖向或垂直坡面的陡倾短小裂缝,然后裂缝进一步扩展延伸形成近似平行坡面的长大裂缝,最终贯通引起变形破坏。缓坡度开挖,滑面最终呈现沿软弱夹层剪切的平直滑面;陡坡度开挖则形成分级变形破坏、滑面呈现折线、台阶形态。 稳定性相对较好,滑面短小,最终贯通后整体呈折线型,局部出现台阶,易于识别,评价简单。 规模较小,最大深度为一般4.0~8.0 m,位于3~4级坡面,易形成多级失稳。支护方便、简单。占地面积大,不利于工程建设规划。 缓坡度开挖条件下,坡体沿层面剪切滑移,变形破坏模式为渐进牵引式的滑移-拉裂。重力和开挖临空面是形成失稳破坏的主要影响因素,陡倾裂缝及软弱夹层剪切滑移是形成机理的重要条件。 工况二 稳定性差,滑面长大,形状连续多变,以阶梯状、直线状或混合状为主。变形失稳演化过程复杂,评价难度较大。 规模较大,最大深度为一般为20.0~50.0 m,位于4~5级边坡。易形成1~2级失稳。支护复杂,难度大。占地面积小,利于工程建设规划。 陡坡度开挖条件下,坡体呈现多级变形破坏,通常是上部滑移-拉裂坡体对下部坡体形成一定的推力,整体变形破坏模式为渐进推移式。边坡开挖后,在重力和临空面的作用下,首先沿着层间软弱夹层剪切滑移,由于滑面埋深较大,同时竖向裂隙发育,在滑移错动过程中形成折线、台阶式滑面。 工况三 稳定性较差,滑面长大,形状多变,阶梯状、直线状或混合状,以台阶形态为主。变形破坏演化过程复杂,评价难度大。 规模较大,最大深度为一般为30.0~60.0 m,位于4~5级边坡。易形成1~2级失稳。支护复杂,难度大。占地面积较小,较利于工程建设规划。 陡-缓相结合的开挖条件下,坡体上部坡体沿层间软弱夹层剪切滑移形成滑移-拉裂变形破坏,下部则在上部失稳坡体推力以及自身重力作用下,产生渐进推移式变形失稳。而坡体中部变形破坏则兼含了牵引式和推移式,形成机理复杂。 -
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