黄土边坡降雨条件下破坏机理室内模型试验研究

发布时间：2018-04-18 07:28

本文选题：黄土边坡 + 降雨条件　；参考：《兰州交通大学》2017年硕士论文

【摘要】：降雨是引起各种地质灾害的重要因素之一,尤其是黄土塬、梁、峁等地形发育完全的黄土地区,为黄土边坡的地质灾害提供了天然条件。通过建立室内边坡模型,控制雨强、作用时间、边坡坡脚等研究降雨引起的黄土边坡失稳过程,并利用土压力盒、水分及孔隙水压力传感器等监测土体内部各项参数的变化,结合降雨过程和边坡破坏发展过程进行了针对性的分析。同时,运用数值分析软件建立与室内模型试验同尺寸的数值模型,分析孔隙水压力、渗流方向、抗剪强度等随降雨的变化。主要研究内容或成果如下:(1)浸润线发展规律:相同边界条件下,40°与55°边坡模型的浸润线推移规律保持一致:降雨前期,边坡各处浸润线向土体推移速率基本保持一直,为0.11m/hr;随降雨边坡表面土体饱和,坡脚处产生积水,坡顶、坡面的浸润线推移速率下降,且坡面下降的更为严重,而在坡脚处的浸润线推移速率受积水影响大于坡顶及坡面处的;40°边坡模型的浸润线推移速率较55°边坡模型的快;同时,数值计算模型得出饱和-非饱和区域分界线对下方土体影响深度约5cm,且不随外界条件变化;坡面处的雨水入渗方向随降雨与坡面夹角不断减小,甚至保持平行。(2)室内模型监测数据变化特性:通过对两个模型试验土体内部埋设监测元件,再结合边坡破坏发展过程,着重分析了不同点含水量、应力与孔隙水压力随降雨时间的变化特征。(3)黄土边坡的失稳过程:降雨入渗→上部土体容重和水压增加→裂缝产生、发展→坡脚软化坍塌和土体内部孔隙缓慢贯通并不断扩大→形成上下贯通的通道→边坡体下滑力增加及抗剪强度降低→沿孔隙贯通的通道形成软弱层→产生破坏。并针对边坡破坏形态得出其对应的破坏模式:40°和55°边坡模型都属于由坡脚软化坍塌引起的牵引式破坏。(4)在一定循环间歇降雨雨强下,边坡的安全系数与降雨时间有着直接的关系,边坡的安全系数随着降雨时间的增长而降低。稳定系数减小的速率存在明显的分界点:降雨初期,安全系数减小的速率相对较大,随着降雨时间的持续,当达到某时刻时,此时的最危险滑动面完全处于饱和区,且在随后的时间段内,时刻变化的最危险滑动面也完全处于饱和区时,边坡稳定系数依然有下降的趋势,但相对平缓。
[Abstract]:Rainfall is one of the important factors that cause various geological disasters, especially in loess areas with well-developed terrain, such as loess plateau, beam and knoll, which provides natural conditions for geological disasters of loess slope.Through establishing indoor slope model, controlling rain intensity, acting time, slope foot and so on, the process of loess slope instability caused by rainfall is studied, and soil pressure box, moisture and pore water pressure sensor are used to monitor the change of soil mass internal parameters.Combined with rainfall process and slope failure development process, targeted analysis was carried out.At the same time, the numerical model with the same size as the indoor model test is established by using the numerical analysis software to analyze the variation of pore water pressure, seepage direction and shear strength with rainfall.The main research contents or results are as follows: (1) the law of the development of the infiltrating line: under the same boundary conditions, the infiltration line of 40 掳slope and 55 掳slope model is the same, and the moving rate of the infiltration line from the different parts of the slope to the soil is basically maintained at the beginning of the rainfall period.When the surface of the slope is saturated with rainfall, there is water at the bottom of the slope, and the velocity of the infiltration line of the top and slope decreases, and the slope decreases more seriously.However, at the foot of the slope, the velocity of the infiltration line is faster than that of the model of 40 掳slope at the top of the slope and the slope at the slope surface, and the velocity of the infiltration line is faster than that of the model of 55 掳slope at the foot of the slope, and at the same time,The numerical model shows that the depth of the boundary between saturated and unsaturated region is about 5 cm, and the depth of the boundary does not change with the external conditions, and the infiltration direction of Rain Water on the slope decreases with the angle between the rainfall and the slope.Even maintain parallelism. 2) change characteristics of indoor model monitoring data: by installing monitoring elements inside the soil mass of two model tests and combining with slope failure development process, the water content of different points is analyzed emphatically.The change of stress and pore water pressure with rainfall time) the unstable process of loess slope: the increase of bulk density and water pressure of the upper soil mass and the formation of cracks in the upper part of the loess slope by rainfall infiltration.The soft collapse at the foot of the slope and the gradual penetration and expansion of the internal pores of the soil to form a channel through which the downward force increases and the shear strength decreases and the weak layer is formed along the channel through which the pores are perforated will be destroyed.According to the failure pattern of slope, the corresponding failure modes: 40 掳and 55 掳are both tractive failure caused by slope foot softening and collapse.The safety factor of slope is directly related to rainfall time, and the safety factor of slope decreases with the increase of rainfall time.At the beginning of rainfall, the rate of safety factor decreases is relatively large. With the duration of rainfall, the most dangerous slip surface is completely in the saturation zone when the rainfall time is reached.And in the following time period, when the most dangerous sliding surface is in the saturation zone, the slope stability coefficient is still decreasing, but relatively flat.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU411

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