本科毕业论文（设计）
题目： 降雨对斜坡稳定性的影响 ——以南平市斜坡为例
姓 名： 刘莹 学号： 2114481 院 （系）： 环境学院 专业： 地下水科学与工程 指导老师： 湖沉 职称： 讲师 评 阅 人： 赵锐 职称：
2014 年 06 月
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本人以信誉声明：所呈交的毕业论文（设计）是在导师指导下进行的研究工作及取得的研究成果，论文中引用他人的文献、数据、图件、资料均已明确标注出，论文中的结论和结果为本人独立完成，不包含他人成果及为获得中国地质大学或其他教育机构的学位或证书而使用过的材料。与我一同工作的同志对本研究所做的任何贡献均已在论文中作了明确的说明并表示了谢意。
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摘 要
斜坡失稳破坏是多山地区常见的一种自然灾害，而降雨是斜坡失稳破坏最重要的触发因素。降雨通过以下方式影响斜坡的稳定性：降雨时，雨水入渗使原本的非饱和土变成饱和土，孔隙水压力增大也即基质吸力减小，使斜坡的抗剪强度降低；其次，雨水入渗会增加土壤的重度，加大下滑力；同时，长时间的雨水入渗会抬高地下水位，当地下水位达到或超过潜在滑动面时，地下水会软化滑面从而降低斜坡的抗剪强度。在此文中，利用Geostudio2007软件主要分析降雨条件下，孔隙水压力的变化（也即基质吸力的变化）对斜坡稳定性的影响。
本文以福建省南平市西芹镇兴华街道后山比较有代表性的Ⅲ区房后斜坡为例，首先对其进行斜坡变形的宏观分析及敏感性因素的分析并计算得到天然条件下的斜坡稳定性系数。后取Ⅲ区房后斜坡28-28’号地质剖面，使用Geostudio2007软件建立了边坡饱和非饱和降雨入渗有限元计算模型，得到不同降雨条件下雨水入渗时孔隙水压力的变化情况，并计算得到不同降雨强度和不同降雨历时下的斜坡稳定性系数，进而分析降雨对斜坡稳定性的影响。经过分析得到如下结论：
（1）Ⅲ区房后斜坡受降雨或者其他不利因素影响时，中上部岩土体仍存在崩塌或滑坡的可能。计算结果表明，在天然情况下，此斜坡能基本保持稳定，稳定性系数为1.294。
（2）在相同降雨时长的条件下，降雨强度越大，斜坡的稳定性系数减小得越快。但在降雨强度大于雨水渗透系数时，各种不同降雨强度对斜坡稳定性的影响趋于相近。
（3）在相同降雨强度的条件下，降雨历时越长，斜坡的稳定性系数减小得越快。 （4）通过模拟斜坡监测点中孔隙水压力的变化可知，随着降雨的持续，孔隙水压力会一直升高，而斜坡的稳定性系数下降。因此降雨引起的孔隙水压力增大是导致斜坡失稳的重要原因。
关键词：降雨入渗 斜坡稳定性 Geostudio2007 孔隙水压力
Abstract
Slope instability and failure is a common natural disaster in mountainous areas, and rainfall is the most important trigger factor. Rainfall affects the slope stability in the following ways. Firstly, rainwater infiltration will make the original unsaturated soil become saturated soil so that pore water pressure increases ( ie, matric suction decreases) which will then reduce the shear strength of the slope. Secondly, rainwater infiltration will increase the soil's density and the pore water pressure and hence increase decline in force. What's more, prolonged rainfall infiltration will raise the water table and when the water table reaches or exceeds the potential sliding surface, the groundwater will soften the slip surface which will reduce the shear strength. In this paper, Geostudio is used to analyze how the changes of pore water pressure affects the stability of slope.
This paper takes the example of a representative Ⅲ district slope in Fujian Province, Nanping, Xiqin town, Xinghua Street. The macro-deformation of the slope and sensitivity factors are analyzed and the slope stability coefficient under the natural condition is calculated. By using Geostudio, a saturated-unsaturated finite element model of rainfall infiltration is built in taking the 28-28' geological section of the Ⅲ district slope. I get the results of changes in pore water pressure and slope stability coefficient under different rainfall intensity and duration. Then I analyze the rainfall's impact on slope stability. Following are the conclusions.
1. Ⅲ district slope is possible to collapse or landslide in the upper and middle part of the slope after another rainfall or other unfavorable factors. The calculation results show that under natural condition, this slope can basically stay stable and the slope stability coefficient is 1.294. 2. Under the same rainfall duration, the higher the rainfall intensity, the faster that slope stability coefficient decreases. However, when the rainfall intensity is greater than rainwater permeability coefficient, the impact of various different rainfall intensity is the barely the same on the stability of the slope no matter what the rainfall intensity is.
3. under the same conditions of rainfall intensity, the longer that rainfall lasts, the faster stability of the slope coefficient decreases.
4. Through monitoring changes in simulated pore water pressure, we can know that with rainfall continues, pore water pressure increases and it leads to decrease of the slope stability coefficient. Therefore increase in pore water pressure caused by rainfall is an important factor that triggers the slope instability .
Keywords: rainfall infiltration; slope stability; Geostudio2007; pore water pressure
目 录
第一章 前言 .............................................................................................................................. - 1 -
第一节 选题意义和依据 .................................................................................................. - 1 - 第二节 国内外研究现状 .................................................................................................. - 1 - 第三节 存在的问题和展望 .............................................................................................. - 2 - 第四节 研究内容及技术路线 .......................................................................................... - 3 - 第二章 自然地理及地质概况 .................................................................................................. - 5 -
第一节 自然地理条件 ...................................................................................................... - 5 - 第二节 斜坡基本特征 ...................................................................................................... - 6 - 第三节 斜坡岩土体特征 .................................................................................................. - 7 - 第三章 斜坡稳定性分析 .......................................................................................................... - 9 -
第一节 斜坡变形宏观分析 .............................................................................................. - 9 - 第二节 斜坡稳定性敏感因素分析 .................................................................................. - 9 - 第三节 天然条件下的斜坡稳定性 ................................................................................ - 10 - 第四章 降雨条件下的斜坡稳定性对比分析 ........................................................................ - 13 -
第一节 基本原理 ............................................................................................................ - 13 - 第二节 计算模型 ............................................................................................................ - 15 - 第三节 数值模拟结果分析 ............................................................................................ - 26 - 第五章 结论和建议 ................................................................................................................ - 30 -
第一节 结论 .................................................................................................................... - 30 - 第二节 建议 .................................................................................................................... - 30 - 致 谢 ...................................................................................................................................... - 31 - 参考文献 .................................................................................................................................. - 32 -