持续降雨入渗非饱和黏土边坡失稳机理及其应用研究

发布时间：2018-01-27 17:32

本文关键词： 持续降雨非饱和黏土边坡入渗方式失稳机理模型试验　出处：《兰州大学》2014年博士论文　论文类型：学位论文

【摘要】：降雨入渗是天然边坡和工程边坡失稳的重要诱因,多雨地区的黏土边坡因持续降雨诱发的滑坡灾害十分严重。降雨渗入原本稳定的黏土边坡,加速了边坡变形破坏。因此,进行持续降雨入渗黏土边坡的入渗规律分析和失稳机理研究对多雨地区边坡滑坡灾害防治具有重要的意义。本文将非饱和-饱和土边坡极限平衡理论和土壤水渗流理论相互融合,运用强度折减数值计算方法,并结合模拟试验和工程实际进行分析,主要进行了以下几方面的研究：首先,本文结合降雨诱发工程边坡破坏的现状,探讨了雨水入渗作用下的边坡黏土工程特性和边坡稳定机理。将不同含水量的黏土进行室内试验,获得了不同含水量黏土的抗剪强度及相关参数,并通过基质吸力试验数据拟合发现该黏土SWCC曲线指数拟合式更合理。接着,探讨了持续降雨条件下坡面雨水入渗深度以及入渗方式。结合黏土饱和入渗原理和Green-Ampt入渗方式,考虑坡内黏土初始含水量相同和有规律变化两种情况,分别计算雨水饱和入渗与非饱和入渗下坡面积水时间、积水时的入渗深度和入渗率。进而,利用极限平衡理论和有限差分强度折减法,考虑非饱和黏土基质吸力和渗流力,建立了持续降雨入渗非饱和黏土边坡极限平衡条分法的计算式、强度折减法的计算式。研究了持续降雨过程引起的含水量和容重增加、粘聚力和内摩擦角减小,从而诱发土坡的安全系数快速下降。综合分析了黏土边坡稳定性的影响因素,建立了黏土物理力学参数对边坡稳定性影响的理论计算式。通过数值方法计算各参数影响下的安全系数和最大水平位移,得到黏土含水量、粘聚力、内摩擦角、基质吸力、边坡高度和坡角等参数的灵敏度,从而确定了非饱和黏土边坡重要物理力学参数的灵敏程度顺序。通过各种黏土屈服准则参数的相互变换,可得到持续降雨工况下的黏土内摩擦角φ=16.5°可作为其屈服准则选取或调整的临界点。然后,通过边坡模拟试验直观展现了模型边坡在持续降雨工况下的变形破坏过程,验证了持续降雨入渗过程存在非饱和入渗方式。获得了持续降雨过程中坡顶、坡中和坡脚三个位置不同深度处黏土基质吸力,并分别以坡顶或坡中入渗深度和坡脚点确定的潜在滑面进行模型边坡的稳定性计算,得到了以坡中位置入渗深度15cm左右的潜在滑面安全系数最小。最后,结合工程实际,探讨了持续降雨条件下边坡平台、坡高和坡率的设置效果。系统研究了雨水不同入渗深度时的边坡安全系数和边坡可能的失稳时间,并分析了持续降雨入渗条件下工程边坡的稳定性。
[Abstract]:Rainfall infiltration is an important cause of instability of natural slope and engineering slope. The landslide disaster induced by continuous rainfall is very serious in the clay slope in rainy area. Rainfall infiltrates into the originally stable clay slope. Accelerate the slope deformation and damage. It is of great significance to study the infiltration law and instability mechanism of continuous rainfall infiltration clay slope for slope landslide disaster prevention in rainy area. In this paper, the limit equilibrium theory of unsaturated saturated soil slope and soil water infiltration are introduced. The flow theory merges with each other. Using the numerical calculation method of strength reduction, combined with the simulation test and engineering practice, the following aspects of the research are mainly carried out: Firstly, combined with the current situation of slope failure induced by rainfall, the engineering characteristics of slope clay and slope stability mechanism under the action of Rain Water infiltration are discussed. The clay with different water content is tested in laboratory. The shear strength and related parameters of clay with different moisture content were obtained, and the fitting formula of SWCC curve index was found to be more reasonable by fitting the matrix suction test data. Then, the paper discusses the infiltration depth and infiltration mode of Rain Water on slope under the condition of continuous rainfall, combined with the saturated infiltration principle of clay and Green-Ampt infiltration mode. Considering the same initial water content and regular variation of the clay in the slope, the water time of the slope area under the Rain Water saturated infiltration and the unsaturated infiltration, the infiltration depth and the infiltration rate are calculated respectively. Then, by using the limit equilibrium theory and the finite difference strength reduction method, considering the suction and seepage force of unsaturated clay matrix, the calculation formula of limit equilibrium strip method for unsaturated clay slope with continuous rainfall infiltration is established. The calculation formula of strength reduction method. The increase of water content and bulk density caused by continuous rainfall, the decrease of cohesion and internal friction angle are studied. Therefore, the safety factor of soil slope decreases rapidly, and the factors influencing the stability of clay slope are comprehensively analyzed. A theoretical formula for calculating the influence of physical and mechanical parameters of clay on slope stability is established. The safety factor and maximum horizontal displacement under the influence of each parameter are calculated by numerical method, and the water content, cohesive force and internal friction angle of clay are obtained. The sensitivity order of important physical and mechanical parameters of unsaturated clay slope is determined by the sensitivity of matrix suction, slope height and slope angle. The critical point of selecting or adjusting the yield criterion can be obtained that the angle of internal friction of clay is 16.5 掳under the condition of continuous rainfall. Then, the deformation and failure process of the model slope under the condition of continuous rainfall is demonstrated intuitively through the slope simulation test. The unsaturated infiltration mode was verified in the process of continuous rainfall infiltration, and the clay matrix suction at three different depths of slope top, slope and foot of slope was obtained during the process of continuous rainfall. The stability of the model slope is calculated with the potential slip surface determined by the infiltration depth of the top or middle slope and the slope foot point, and the minimum safety factor of the potential slip surface with the infiltration depth of 15 cm in the middle position of the slope is obtained. Finally, combined with engineering practice, the setting effect of slope platform, slope height and slope rate under the condition of continuous rainfall is discussed, and the slope safety factor and the possible instability time of slope under different infiltration depth of Rain Water are systematically studied. The stability of engineering slope under the condition of continuous rainfall infiltration is analyzed.
【学位授予单位】：兰州大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU43

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