摘 要

降雨入渗是尾矿坝边坡失稳的重要致灾因子，持续降雨诱发的尾矿坝失稳案例非常多。目前，由于对降雨条件下尾矿坝失稳机制认识不够，致使事故频发。针对上述问题，论文对铜山口尾矿库进行现场勘察、试验、取样、室内土工试验等一系列测试，系统地研究了尾矿的物理力学特性，对不同饱和度的尾矿材料进行三轴固结不排水试验，得到抗剪强度随饱和度的变化规律；理论分析了降雨入渗对边坡稳定的影响机理，在Biot理论的基础上得到了渗流和应力场直接耦合的公式。通过Geo-Studio的专门模块对该尾矿坝在典型剖面在各种降雨作用下尾矿坝内浸润线进行模拟，得到不同降雨作用下浸润线的变化规律；在系统总结当中利用的基本理论，方法还有SEEP/W渗流分析结果和不同含水量下尾矿强度的变化规律，采用SLOPE/W稳定分析模块进行边坡稳定性分析。主要结论如下：

（1）当含水量小于一定值时，含水量的变化对尾矿的黏聚力影响不大。高于该时，尾矿黏聚力急剧下降，其对数与含水量呈线性关系。因此，在尾矿边坡稳定性计算中，含水量小于黏聚力值取小值，并作为常数；含水率大于该值，可按黏聚性对数和含水量呈线性关系考虑。考虑到含水量的变化对尾矿的内摩擦角影响不大，可以不考虑其对边坡稳定性的影响。

（2）采用Geostudio软件对铜山口尾矿库的一个剖面进行分析，分析对其进行稳定渗流和在不同降雨条件下的瞬态渗流分析，在此基础上，分别对其进行了稳定性计算，并得出相应的结论如下：

①边坡稳定计算表明：通过与相关的计算方式相比较发现Bishop计算方式安全系数相对较大一点，更安全一点，而Janbu计算法则则正好相反。

②在降雨持时的条件控制不变得情况下，单位时间内降水量增加的时候去会出现浅层岩土含水增大，基层吸水能力下降，土坝稳定系数也会随着下降的的现象。但随着降雨继续扩大则慢慢这个趋势变得相对减小。但是持时增加时候有所变化，稳定性持续下降。

③当边坡的渗透系数较小时，在降雨强度不变的条件下，随着降雨历时的增大，边坡的安全系数不断减小。

通过对不同降雨条件下尾矿坝边坡稳定性的分析，理论分析了降雨入渗诱发岩土体边坡的失稳机制，研究结果可为尾矿坝边坡稳定分析、滑坡灾害预报和边坡治理等方面提供有用的参考数据，具有一定的理论意义和实用价值。

关键词：尾矿坝；降雨；铜山口尾矿库；力学特性；稳定性

Abstract

The rainfall infiltration is a significant hazard factor for the failure of tailings dam slope. There are many tailings dam which is damaged due to continuous rainfall. At present, due to the lack of understanding of the stability mechanism of tailings dam instability, it results in many accidents frequently. In view of the above problems, a series of tests on the scene investigation, test and sampling and of Tongshankou tailings dam are implement. The physical and mechanical properties of tailings are systematically studied in order to grasp the shear strength of tailings material under different moisture content. A series of isotropically consolidated undrained triaxial tests are conducted on the tailings materials with different saturation in order to obtain shear strength of saturation; The influence mechanism of rainfall infiltration on slope stability is analyzed theoretically. Based on the Biot consolidation theory, the mechanism of seepage and stress field interaction is analyzed, and equation of direct coupling method for seepage field and stress field is proposed; The infiltration line of tailings dam under different rainfall in the typical profile of tailings dam is simulated based on the finite element analysis software of GEO-SLOPE OFFICE ( SLOPE/ W module). What's more, the variation law of infiltration line under different rainfall is obtained; The paper systematically summarizes by basic theory and analytical methods in the analysis of slope stability and completes the seepage calculation. Meanwhile, based on the analysis result of SEEP/W and different strength of tailings under different moisture content, software SLOPE/W stability analysis module is utilized for slope stability analysis.The main conclusions are as follows.

(1) When the water content is less than a certain value, the change of water content has little effect on the cohesion of the tailings. When the water content is higher than a certain value, the tailings cohesive force drops sharply, its logarithm and the water content has the linear relation. Therefore, in the tailings slope stability calculation, when the water content is smaller than a certain value, the cohesion value can be taken as a constant. When the water content is greater than the value, the cohesion logarithm and water content is linearly. Because the variation of water content has little effect on the internal friction angle of tailings, it can't consider the influence on the slope stability.

(2) The Geostudio software is used to analyze a section of the tailings pond of the Zhelamuqin mine. The steady seepage and the transient seepage analysis are analyzed under different rainfall conditions. On this basis, the stability analysis is analyzed. The main conclusions are as follows.

①The slope stability calculation shows that the safety factor calculated by Bishop method is the biggest compared with Morgenstern-Price method. The Janbu method has the smallest safety factor.

②When rainfall is constant, with the increase of rainfall intensity, the water content of shallow rock mass is increasing, the suction of matrix is ​​decreasing and the stability coefficient of soil slope is decreasing. When the rainfall intensity increases to a certain value which is more than the infiltration capacity of rock and soil, this trend is decreasing. When the rainfall intensity is constant with the continuous growth of rainfall, soil slope stability is also constant reduce.

③When the permeability coefficient of the slope is small, the safety factor of the slope decreases with the increase of rainfall duration under the same rainfall intensity.

By analyzing the stability of tailings dam slope under different rainfall conditions, the failure mechanism of rock-soil slope induced by rainfall infiltration is theoretically analyzed. The results can be used to analyze the stability of tailings dam slope, landslide hazard forecast and edge Slope control and other aspects to provide useful reference data. It also has a certain theoretical significance and practical value.

Key words: Tailings dam; Rainfall; Tongshankou tailings dam; Mechanical property; Stability

第一章 绪论

1.1 研究背景

尾矿是指采矿作业中产生的矿物废物，采用管道或沟槽输送到尾矿库。尾矿由水力填充沉积，逐年增加形成。尾矿坝是尾矿的重要组成部分，由初期坝和堆积坝组成。初期坝分为透水堆石坝、均质土坝和废石坝等；堆积坝一般由尾矿堆积而成。据堆积坝筑坝工艺的不同，尾矿坝分为上游式尾矿坝、下游式尾矿坝、中线式尾矿坝、干式堆存和水库式尾矿坝等。

由于地形等条件的限制，尾矿坝下游地区都是很重要的区域，如果发生溃坝的话，将对下游区人民群众造成重大伤亡，影响矿区的正常生产，污染环境。据统计，国内2005年以前发生的尾矿坝溃坝灾害约有80多起，且近年来尾矿坝发生灾害的频率有上升的趋势。因此，如何防治尾矿坝溃坝灾害具有重大的意义。

通过以往尾矿坝溃坝事故的调查表明，尾矿坝溃坝与降雨密不可分。在降雨作用下，一方面，随着雨水的不断入渗，尾矿材料的含水量增加，降低了尾矿材料的抗剪强度，另一方面，坝体内浸润线上升，增加了滑面的下滑力，在某些情况下，在水头梯度作用下，还会产生动水压力。总之，降雨条件下尾矿坝的稳定性是一个复杂的过程，涉及了流体力学固体力学耦合作用，且表现出多路径和相互作用的动态特征。目前，国内外对于降雨条件下尾矿坝边坡稳定性鲜有报道。因此，揭示降雨条件下尾矿坝边坡稳定性是矿山工程灾害防治的基础，是我国矿山尾矿坝防灾减灾中的核心问题。