【作者】 赵权利；

【导师】 尚岳全；

【作者基本信息】 浙江大学 ， 防灾减灾工程及防护工程， 2013， 博士

【摘要】 缓倾滑坡是指主滑动面倾角小于20°的一类滑坡,承压水对缓倾滑坡的滑动破坏有重要影响。平推式滑坡是缓倾滑坡的一种特例。本文采用工程地质分析方法、理论分析方法、数值分析方法、物理模型试验方法等手段,综合分析缓倾滑坡中承压水的作用机理,探讨承压水产生的水文地质条件,研究平推式滑坡中承压水作用区间、渗透参数对滑坡稳定性的影响、平推式滑坡启动判据的修正、缓倾滑坡中承压水孔压的时空分布规律和承压水对缓倾滑坡作用的滞后效应。通过以上研究,获得以下主要成果和认识：(1)基于对新昌县下山滑坡的工程地质分析,探讨承压水的形成机理及其对该滑坡的作用,通过监测资料分析发现该滑坡体内承压水的作用范围小于底部滑面长度范围。结合下山滑坡的地质环境条件,构建典型平推式滑坡地下水渗流分析模型,提出通过计算承压水作用范围,使边坡稳定计算结果更合理。根据承压水一维稳定渗流理论,推导出承压水作用范围的计算公式；同时计算分析承压水作用范围各影响因素的敏感性。计算结果表明,在一定范围内各影响因素有如下规律：①承压水作用范围随着渗透系数增大而线性减小；②承压水作用范围随渗流量增大而线性增大；③承压水作用范围和透水层厚度呈抛物线关系,且随着透水层厚度的增加呈加速趋势减小。最后分析了承压水作用范围大小对滑坡稳定系数的影响规律,结果表明滑坡稳定性系数随着承压水作用范围增大而线性减小。(2)对平推式滑坡启动判据的传统研究往往忽略滑块后缘的静水压力沿滑面法向的分力及承压水作用的具体范围,因而导致计算结果不准确。通过对平推式滑坡进行全面的受力分析,同时引入了承压水作用范围的概念,最终推导出修正后的平推式滑坡启动判据。将所得的修正判据应用于模型试验的结果分析,验证了修正判据的准确性,同时对平推式滑坡启动临界水头的模型试验结果和修正计算值之间的差异进行了机理分析。(3)目前滑坡稳定性分析中对承压水作用的模拟过于简化,从而会导致分析方式不当。考虑到部分已有研究对地下水作用的理解比较混乱,提出用滑面附近孔隙水压力指示承压水的作用,分析了承压水孔压的时空变化规律及其对缓倾滑坡稳定性的影响。根据不同渗透条件下边坡稳定性计算结果分析,提出了渗透系数比的概念,分析了随渗透系数比的变化,枯水期孔压在空间维度上的具体分布及其所对应的边坡稳定性变化规律。分析了在丰水期前缘有无堵塞的两种情况下,随降雨时间持续期的变化,滑面附近孔压的时空变化规律,以及其对边坡稳定系数的影响。通过工程实例分析,验证了丰水期降雨及其产生的承压水作用对边坡稳定性的作用规律。(4)通过工程实例分析,发现缓倾滑坡变形相对滞后于承压水状态的改变。构建缓倾滑坡物理模型试验,对滑坡施加承压水作用,测量坡体不同层位的体积含水量、坡体变形、坡面变形、坡前推力等特征参量,通过对测量结果进行归一化处理,分析这各参量相对于承压水作用时间的滞后关系。结合模型试验,从应力应变变化规律、坡体蠕变规律、滑带土长期强度、含水量对滑带土强度的影响等几方面,对承压水致滑坡失稳的滞后效应进行机理分析。更多还原

【Abstract】 Gently inclined landslide is a kind of landslide, sliding surface obliquity of which is less than20degrees. Influence of confined groundwater is very important to sliding damage of gently inclined landslide.Translational landslide is a special case of gently inclined landslide. Methods of engineering geology analysis, theoretical analysis, numerical simulation and physical model test are used to study the influence mechanism of confined groundwater in gently inclined landslide. The hydrogeology condition and the action range of confined groundwater are analyzed. Effect of permeability parameters variation on landslide stability is analyzed. The start-up criterion of translational landslide is modified. The temporal and spatial variation of pore water pressure induced by confined groundwater is analyzed. The hysteresis of confined groundwater effect which acting on gently inclined landslide is analyzed. Finally, the main results and new ideas in this study are as follows:(1) Based on engineering geology analysis of Xiashan landslide, formation mechanism and its effect on this landslide are analyzed. Monitoring data shows that the acting of the action range of confined groundwater is less than the length of sliding surface. Combining with geological environmental condition of Xiashan landslide, the typical groundwater seepage model of translational landslide is established, and the result of slope stability calculation becomes more reasonable considering action range of confined water. Based on one-dimensional steady seepage theory, calculation formula of action range caused by confined groundwater is deduced, and then parameter sensitivity of this formula is analyzed. The calculation result shows that action range of confined groundwater follows established law within a certain range of each parameter:①Action range of confined groundwater decreases linearly with the increase of permeability coefficient.②Action range of confined groundwater increases linearly with seepage discharge.③Action range of confined groundwater takes on parabola shape with thickness of permeable layer, and it is accelerated decreasing trend with increase of permeable layer thickness. Calculation result also shows that the stability coefficients of slope decreases linearly with the increase of action range of confined groundwater.(2) The existing research about start-up criterion of translational landslide neglects two aspects:one is the normal component force of hydrostatic pressure at posterior border of slope, which acts on slip surface, the other is the action range of confined water. Therefore the calculation results of start-up criterion of translational landslide are inaccurate. Overall force analysis are exerted on translational landslide, meanwhile the conception of action range of confined water is introduced, then the modified start-up criterion is deduced. The modified start-up criterion is applied to analyze the results of physical simulation, and proved to be accurate. Mechanism analysis is applied on the differences of critical hydraulic between test results and calculation results obtained from the modified start-up criterion of translational landslide.(3) The present simulation of confined groundwater effect in slope stability analysis is too simplified to guarantee an appropriate analysis mode. Considering that some existing research has given confusing interpretation about the groundwater effect, this thesis proposes a concept of using pore water pressure near the slip surface to indicate this effect, and then analyzing the temporal and spatial variation laws of pore water pressure induced by confined groundwater and the consequent influence on slope stability caused by this variation. According to the analysis of slope stability results under different permeability conditions, the concept of seepage coefficient ratio is proposed, and the spatial distribution of pore water pressure in dry season with various seepage coefficient ratios is analyzed, and then the variation laws of slope stability corresponding to different seepage coefficient ratios are obtained. Under two conditions including the permeable layer blockage condition and non-block condition at front edge in wet season, the temporal and spatial variation laws of pore water pressure and effect on the slop stability factor caused by the variation with different rainfall duration are analyzed. Through analyzing engineering practice, the effect on slope stability caused by the variation of confined groundwater is verified, and the variation of confined groundwater is induced by the rainfall in wet season.(4) Via engineering examples analysis, the hysteresis of gently inclined landslide failure caused by confined groundwater effect is analyzed. A physical slope model including confined groundwater is constructed to measure volume water content, slope body deformation, slope surface deformation and slope thrust in different position of this model. According to the test results which are processed using normalization method, the hysteresis of slope deformation relative to confined groundwater effect is analyzed. The mechanism of slope failure hysteresis caused by confined groundwater is discussed from some aspects, such as stresses and strain redistribution law, slope creeping law, long-term strength of slip soil and impact of water content on the strength of slip soil.更多还原