非饱和黄土边坡水气交换及其稳定性研究

发布时间：2018-02-22 11:45

本文关键词： 非饱和黄土降雨入渗蒸发边坡稳定性　出处：《兰州交通大学》2015年硕士论文　论文类型：学位论文

【摘要】：黄土大多数是含水量低的非饱和土,气候变化对地表附近黄土的含水量影响很大。黄土在受水浸湿作用前处于非饱和状态,非饱和黄土在降雨作用下极易达到局部饱和状态,由此引起抗剪强度快速减小,孔隙水压力为负值(由于大部分情况下孔隙气压力为零,所以其值等于基质吸力),进而引起边坡的安全系数减小,甚至导致黄土边坡产生滑坡。通过研究发现,水分渗入是引起滑坡的主要原因,但是人们对于这种关系的认识和理解还不够充分。在滑坡整治过程中,如果能科学合理地确定滑坡体所在边坡的水分场和温度变化趋势,这将极大节省工程投资。本文在学习、归纳非饱和黄土边坡理论研究的基础上,以兰州马兰黄土为研究对象,结合室内物性试验和模型试验,定性与定量分析相结合,对水气交换作用下的非饱和黄土边坡稳定性进行了系统研究,取得了一些有价值的研究成果。首先,对所选用的非饱和黄土的填土土样进行了室内物理特性的测试,测定了其级配曲线、最优含水率、最大干密度、液塑限指数、渗透系数等,为下一步试验做好准备工作。其次,设计了非饱和黄土边坡的室内模型,通过利用手动喷雾器对坡体进行水分入渗和保暖灯模拟日照,进行边坡土体内水气变化及边坡稳定性的试验研究。模型试验采用水分测试装置、温度测试装置、位移测试装置对模型内土体进行联合监测,记录了水分入渗及模拟日照的情况下模型内土体的水分、温度、位移变化过程。对其进行了系统详实研究,旨在研究非饱和黄土边坡在水分入渗和日照条件下的水分场及温度场的规律,对非饱和黄土边坡地质灾害的形成机制进行分析,为边坡破坏机理提供理论支持,并为在建工程提供设计依据。再次,在前述非饱和黄土水气交换模型试验的基础上,通过非饱和渗流软件SEEP/W模拟了兰州九州石峡口南部的黄土高边坡在不同降雨强度和降雨持时条件下的降雨入渗,得出了计算模型不同层位的的孔隙水压力和体积含水量。最后利用之前的非饱和渗流分析结果,耦合到SLOPE/W中进行边坡稳定性分析,通过对不同降雨强度变化研究,来探讨抗剪强度和孔隙水压力随深度的变化。
[Abstract]:Loess is mostly unsaturated soil with low water content, and climate change has a great influence on the water content of loess near the surface. The loess is in unsaturated state before being soaked by water, and unsaturated loess is easy to reach local saturation state under the action of rainfall. As a result, the shear strength decreases rapidly, and the pore water pressure is negative (because in most cases the pore gas pressure is zero, so its value is equal to the matrix suction, thus causing the slope safety factor to decrease. Through the research, it is found that water infiltration is the main cause of the landslide, but the understanding of this relationship is not enough. If the water field and temperature change trend of the slope where the landslide body is located can be determined scientifically and reasonably, the project investment will be greatly saved. In this paper, on the basis of studying and summarizing the theoretical research of unsaturated loess slope, taking Ma Lan loess in Lanzhou as the research object, Combined with indoor physical property test and model test, combined with qualitative and quantitative analysis, the stability of unsaturated loess slope under the action of water and air exchange is studied systematically, and some valuable research results are obtained. The indoor physical properties of the unsaturated loess filled soil samples were tested, and the gradation curve, optimal moisture content, maximum dry density, liquid-plastic limit index, permeability coefficient and so on were determined. The indoor model of unsaturated loess slope was designed, and the water infiltration and heat preservation lamp were simulated by manual sprayer. In the model test, the moisture test device, the temperature test device and the displacement test device are used to monitor the soil mass in the model. The changes of soil moisture, temperature and displacement in the model were recorded under the condition of water infiltration and simulated sunshine. The purpose of this paper is to study the regularity of water field and temperature field of unsaturated loess slope under the condition of water infiltration and sunshine, to analyze the formation mechanism of geological hazard of unsaturated loess slope, and to provide theoretical support for the failure mechanism of unsaturated loess slope. And provide the design basis for the project under construction. Thirdly, on the basis of the above unsaturated loess water and gas exchange model test, The infiltration of loess high slope in the south of Shixiakou, Jiuzhou, Lanzhou was simulated by unsaturated seepage software SEEP/W under different rainfall intensity and duration. The pore water pressure and volume water content of different layers of the model are obtained. Finally, using the results of unsaturated seepage analysis before, the slope stability is analyzed by coupling to SLOPE/W, and the variation of different rainfall intensity is studied. To study the variation of shear strength and pore water pressure with depth.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU411;TU444

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