降雨诱发滑坡机理及相应的评价方法研究

滑坡是一种常见的自然灾害，其诱发因素很多，降雨是其中最常见最重要的一个，已有资料显示60％以上的边坡失稳是由于降雨引起的。降雨诱发滑坡机理及相应的评价方法研究历来是学术界、工程界十分关注，而又难以解决的一个课题。然而，目前岩土工程界尚无可资利用的研究成果。因此，这一方面的研究，具有重大的理论意义和工程意义。本文研究取得以下主要研究成果。(1)针对降雨诱发滑坡的机制以及相应的评价方法进行了系统地研究，采用“由现场变形监测分析→室内物理力学试验→模型机理分析→边坡降雨渗流场数值模拟→降雨诱发边坡失稳评价”的方法，结合雅安峡口滑坡，进行系统的分析探讨。(2)在查明峡口滑坡体的基本地质及水文条件的基础上，深入分析了峡口滑坡的工程地质特征及变形特征，进而对其破坏机制进行了分析。通过峡口滑坡降水量、地表位移、深部位移及地下水水位的两年多的现场监测资料分析，发现滑坡变形大小与降雨量的多少有很好的对应关系。坡体位移季节性变化明显，在雨季坡体变形明显，进入枯水季节，则位移减缓，趋于稳定。分析还发现，坡体前部位移较大，中部及中后部变缓，后部和外围更缓一些。(3)利用二项逻辑斯蒂回归模型建立了降雨诱发区域滑坡降雨临界值及降雨对滑坡的影响概率表达式。通过滑坡点与降雨量及降雨过程之间的统计分析，建立了同时考虑降雨强度和前期降雨的降雨临界值表达式。研究表明，雨城区滑坡发生与4天的降雨量有关，即当日降雨量、前第1天降雨量、前第2天降雨量、前第3天降雨量，其中当日降雨量对滑坡发生的影响最大。雨城区降雨诱发区域滑坡降雨临界值表达式：雨城区滑坡发生与4天的降雨关系密切，通过SPSS计算，得到考虑4日降雨量的滑坡发生概率表达式为：(4)运用基于有限差分理论的Visual-Modflow软件，对峡口滑坡在不同降雨情况件下坡体内渗流场进行了数值模拟，揭示了在降雨入渗的条件下，坡体地下水位的变化规律。(5)通过对滑体及滑带粉质粘土在不同含水状态下的剪切试验，表明强度参数随含水率的增加而降低的效应是非常显著的。但不同类型土体，水的浸泡效应并不完全一样，粗碎石土反应较弱，而细粒土则反应明显。(6)在一定的假设条件下，利用拉普拉斯(Laplace)正逆变换，推导了在降雨及河水位升降时，土质边坡地下水浸润线计算公式，为了应用方便并对其进行了多项式拟合，得到简化公式。(7)对降雨诱发边坡失稳的机制以及相应的边坡稳定性评价方法进行了探讨，并据此对峡口滑坡在不同降雨入渗条件下的稳定性进行分析、评价。
电加热器
Landslide is a common natural disaster, caused by many factors. Rainfall is the most common of which the most important one. However, more than 60% of slope instability is caused by rainfall. The rain-induced landslide mechanism and the corresponding method of evaluation is always academics, engineering concern, and difficult to resolve an issue. However, at present there is no available geotechnical engineering research results. Therefore, this study is of great theoretical significance and engineering significance.In this paper, the following main research results are made.(1) Against rain-induced landslide mechanism and the corresponding methods for the evaluation system of research. Initial set up a "scene from the deformation monitoring and analysis→indoor physical and mechanical tests→model Mechanism→rainfall seepage slope Numerical simulation→rainfall induced slope instability evaluation, "the system. In combination with Ya’an Xiakou landslide, using the above method for system analysis.(2) Identify Xiakou landslide in a basic geologic and hydrological conditions on the basis of in-depth analysis of the Gap landslide engineering geological characteristics and deformation characteristics, thereby undermining its mechanism of analysis. Gap landslide through precipitation, surface displacement, displacement and deep groundwater level in more than two years of on-site monitoring data analysis, Landslide found that the deformation of the size and number of rainfall in a very good relationship. Slope displacement apparent seasonal variations and in the rainy season, the slope deformation and entered the dry season, the displacement slowed down, become more stable. The analysis also found that the slope in front of larger displacement, the central and rear China slowdown, and the external rear alleviate some more.(3) Establish an expression for landslide critical value of rainfall induced area and probability rainfall influences landslide on basis of logic regression model. Make a quantitative survey on expression for rainfall critical value of induced area on basis of logic regression coefficient. Establish an expression for rainfall critical value with consideration of rainfall intensity and process by statistic analysis of landslide, rainfall and rainfall process. Study indicates that landslide in rainy urban area is related with rainfall within the latest 4 days, namely, rainfall on that day, rainfall on the day before, rainfall of two days ago and rainfall of three days ago, among which 1st day rainfall makes fundamental impact on landslide. Rainfall critical value is determined to be the amount of rainfall on four days. Expression for landslide critical value of rainfall induced area in rainy urban area:Landslide in rainy urban area is closely related with rainfall on that day and that on the latest three days. After calculation by SPSS, an expression for probability of landslide related to four days’ rainfall is obtained as follows:(4) By the software of Visual-Modflow, which is based on definite difference theory, numerical modeling has been taken for saturated and unsaturated seepage field at Xiakou landslide on different rainy conditions. The result shows regularity for change of groundwater level at landslide site after the rain saturates the ground.(5) The result shows the effect that intensive parameter reduction along with the water content increase is very notable, by the shearing test for landslide aspect and slippery belt silty clay under the different containing water states, But the soaking effect of water is not equally complete to the different type soil aspects. The thick crushed stone soil reaction is weaker, but the thin soil reacts clearer.(6) Calculating formula for saturation line of groundwater at slope when rainfall and water level rises or descends is reasoned by converting forward and backward Laplace on certain assumption. For convenient application, this formula is simplified by merging of polynomial.(7) Make discussion on mechanism of landslide on slope induced by rainfall, as well as evaluation of stability of the slope. According to this, analysis and evaluation has been made on the stability of Xiakou landslide on varied rainfall conditions.