山西某矿山高边坡马兰黄土非饱和特性及稳定性研究

发布时间：2018-09-08 14:23

【摘要】：马兰黄土是一种广泛分布于我国西北地区的土体,总分布面积约64万m2。其本身的物理力学性质导致水土流失、滑坡、等地质灾害对人类的生产建设均有不同程度的影响,涉及矿山工程、水利水电工程、路桥工程、铁道工程等诸多领域。随着我国西部大开发战略的实施,在我国西北的黄土覆盖地区,工程建设的规模及难度均逐年扩大,针对黄土的物理力学性质以及西北黄土高原地区工程地质条件的研究亦逐年深入。河曲县位于西北黄土高原的东部边缘,县城西面紧靠黄河干流,与内蒙、陕西交界,是毗邻三省的经济、文化重镇。并且近几年,在此基础上发展了水力资源、矿产资源、电力开发等新兴工业。经过几十年不断的人类工程活动,以及黄土高原日益严重的水土流失的影响,河曲的矿山工程地质条件日益恶化,在降雨、人类活动等条件下,滑坡,崩塌等地质灾害发生次数逐年上升。由于河曲的矿山大多在露天情形下开采后人工削坡,因此在矿区的采场边坡形成了许多马兰黄土高边坡,随着开采深度的加深以及开采技术的提高,矿山对边坡开挖设计以及稳定性验算、后期治理成为一个亟待解决的问题。对河曲矿山黄土高边坡的工程地质研究将有效的解决矿区采场边坡稳定性问题,保证矿区采矿的安全生产,有效促进河曲以及类似西北地区黄土高边坡矿山地质环境治理恢复问题的解决。本论文以山西河曲的工程开挖边坡作为研究对象,研究了非饱和马兰黄土高边坡的土体非饱和物理性质以及对应边坡稳定性,对马兰黄土进行室内实验、室内模型实验,研究基质吸力、含水率对黄土体颗粒的微观影响,得到土体体积含水量与基质吸力的关系曲线,利用非饱和土强度系数的计算公式,对非饱和马兰黄土边坡的稳定进行了分析计算,得到了不同工况下非饱和马兰黄土高边坡的稳定性系数与安全系数,对各工况下矿山边坡的稳定性做出了评价与优化。结合室内模型试验以及FEFLOW有限元软件进行数值模拟,分析马兰黄土边坡在降雨状态下的饱和过程,降雨入渗深度以及边坡破坏过程,建立了对应的数值模型,同时结合室内人工降雨试验,提出非饱和马兰黄土高边边坡的稳定性评价方法,给出各种因素影响下边坡的稳定性情况,给出合理的优化方案。论文的主要研究内容和成果如下：1.在野外地质调查以及研究区基础水文地质、工程地质资料收集的基础上,总结河曲县梁家碛矿山的自然地理条件以及矿山研究区的工程地质特征,以及马兰黄土高边坡的变形破坏特征。矿山内边坡马兰黄土裂隙较发育,由于长时间的煤矿开采,导致采场边坡普遍高陡,且受人工开挖和降雨等外力的影响,往往导致坡体存在不稳定因素。根据现场勘查,区内马兰黄土高边坡的变形破坏主要表现为局部崩塌。矿山内马兰黄土边坡坡角高陡、节理裂隙发育、降雨侵蚀以及开挖坡面使坡角发生破坏是边坡局部破坏的主要内在因素。在边坡开挖以及降雨等因素的影响下,边坡土体向临空方向卸荷,在坡脚、坡肩等区域发生局部破坏最终诱发滑坡。2.为分析非饱和马兰黄土高边坡内部土体稳定性参数变化情况,在微观方面研究了马兰黄土的土体体积含水量、基质吸力的关系曲线；在宏观上进行室内降雨实验、强度实验,坡体渗流场数值模拟等手段综合分析。基于上述研究思路,从现场采集了马兰黄土的试样,并根据土样的干密度的不同,制备了4组重塑试样。以V-G模型为依据,对脱湿状态下试样的基质吸力数据进行拟合,绘制土水特征曲线(SWCC)。探讨不同干密度对应的坡体高度吸力变化曲线,并结合统计学的V-G模型对脱湿状态下非饱和马兰黄土的渗透系数曲线进行了计算模拟。3.为将前面的实验结果更好的耦合到稳定性分析中,分析马兰黄土高边坡在降雨、坡高及坡比因素下的失稳情况,利用实验槽以及降雨设备等器材进行试验设计,建立不同降雨以及坡体条件下的边坡模型。按照工程经验结合相关文献设计了45。、60°、70°三个坡度等级的边坡,坡高范围设计在45cm、60cm、70cm以1：100的模型相似比例以及天然状态下的含水率12%建立滑坡模型。降雨强度则按大雨～暴雨的等级设置了60mm、90mm、120mm三个区间。为了直观反映降雨对于坡体内部孔隙水压力以及含水率的影响,在室内降雨模型边坡的坡脚、坡顶、中部以及坡体内部中埋设孔隙水压力计以及水分仪,通过连接数据采集系统,观察在不同工况下,孔压计以及水分仪数据的变化。通过试验槽的网格以及高清摄像头、照相机等设备,观察坡体变形—破坏情况。通过设计正交试验对不同工况下边坡的破坏情况以及利用spss软件进行因素方差分析。结果表明：三个影响因子坡比、降雨、坡高,对边坡的稳定性影响程度依次为雨强坡度坡高。因此在实际工程中,较大的雨强,较高的坡高以及高陡的坡度将使非饱和马兰黄土高边坡产生滑坡的概率大大的增加。4.为直观的显示所有参数间的联系,分析室内人工降雨模型实验数据是否符合实际情况,将非饱和马兰黄土高边坡人工降雨模型试验的数据导入FEFLOW中进行模拟观察,建立边坡的渗流场模型,以观察坡体在降雨条件下,坡体内部孔隙水压力以及含水率的变化情况,以时间步长为1天、5天进行模拟计算,结果发现边坡在强降雨条件下降在表层土体中将产生一个暂态的土体饱和带,短期内边坡降雨难以影响浸润线以下的土体；坡脚以及坡肩产生的饱和带的扩大将使整个非饱和马兰黄土边坡的稳定系数降低。5.总结了国内外饱和—非饱和土边坡稳定的研究方法,针对采场非饱和马兰黄土高边坡在接受降雨的条件下进行了稳定性验算设计,并在验证之后对坡体的优化方案提出了相关建议东部海拔高程1040m边坡坡体几何参数设计值为：单级坡高为10m,坡角55°,台阶宽度按照相关规范采用6m、lOm间隔布置,将达到良好的稳定效果。
[Abstract]:Malan Loess is a kind of soil widely distributed in Northwest China, with a total area of about 640,000 m2. Its physical and mechanical properties lead to soil erosion, landslides, and other geological disasters on human production and construction have varying degrees of impact, involving mine engineering, water conservancy and Hydropower projects, road and bridge engineering, Railway Engineering and many other fields. In the loess-covered areas of Northwest China, the scale and difficulty of engineering construction have been enlarged year by year. The study on the physical and mechanical properties of loess and the engineering geological conditions in the Loess Plateau area of Northwest China has been deepened year by year. The main stream, bordering Inner Mongolia and Shaanxi, is an economic and cultural center adjacent to the three provinces. In recent years, on this basis, new industries such as hydraulic resources, mineral resources and electric power development have been developed. Deterioration, under the conditions of rainfall, human activities, landslides, landslides and other geological hazards occur year by year, the number of times increased. Because most of the mine in Hequ in the open-pit mining situation after artificial slope cutting, so in the mining area of the stope slope formed a lot of Malan loess high slope, with the deepening of mining depth and mining technology to improve the mine slope. The excavation design and stability checking calculation have become an urgent problem to be solved. The engineering geological study of the loess high slope in Hequ mine will effectively solve the problem of the stability of the stope slope, ensure the safe production of the mining area, effectively promote the geological environment control of the loess high slope in Hequ and similar northwest areas. In this paper, the unsaturated physical properties and the corresponding slope stability of unsaturated Malan loess high slope are studied. Laboratory experiments and model experiments are carried out on Malan loess to study the micro-effects of matrix suction and water content on Loess particles. The relationship curve between soil volume water content and matrix suction is obtained. The stability of unsaturated Malan loess slope is analyzed and calculated by using the formula of unsaturated soil strength coefficient. The stability coefficient and safety coefficient of unsaturated Malan loess high slope under different working conditions are obtained. The stability of mine slope under different working conditions is made. The saturation process, rainfall infiltration depth and slope failure process of Malan loess slope under rainfall condition are analyzed by numerical simulation combined with indoor model test and FEFLOW finite element software. The corresponding numerical model is established, and the unsaturated Malan loess high-side slope is proposed by combining with indoor artificial rainfall test. The main contents and achievements of this paper are as follows: 1. On the basis of field geological survey, basic hydrogeology and engineering geological data collection, the natural geographical conditions of Liangjiaqi mine in Hequ County are summarized. And the engineering geological characteristics of the mine research area, as well as the deformation and failure characteristics of the Malan loess high slope. The Malan loess fissure is well developed in the mine slope. Because of the long-term coal mining, the stope slope is generally high and steep, and is influenced by external forces such as artificial excavation and rainfall, which often leads to the existence of unstable factors. The deformation and failure of Malan loess high slope is mainly manifested by local collapse.The slope angle of Malan loess slope is high and steep,the joints and fissures are developed,the rainfall erosion and the slope angle destroyed by excavation are the main internal factors of the local failure of the slope.Under the influence of slope excavation and rainfall,the soil mass of the slope is in the air direction. In order to analyze the variation of soil stability parameters in unsaturated Malan loess high slope, the relationship curves of soil volume water content and matrix suction were studied in microscopic aspect; in macroscopic aspect, indoor rainfall experiment, strength experiment and slope body suction were carried out. Based on the above research ideas, the samples of Malan loess were collected from the field and four groups of remolded samples were prepared according to the different dry densities of the samples. Based on V-G model, the matrix suction data of the samples were fitted and the soil-water characteristic curves (SWCC) were drawn. The suction curve of the slope height corresponding to the density is calculated and simulated with the V-G model. 3. In order to better couple the experimental results to the stability analysis, the instability of Malan loess high slope under rainfall, slope height and slope ratio is analyzed. According to the engineering experience and the relevant literature, the slope of grade 45, 60, 70 is designed. The range of slope height is designed to be 45 cm, 60 cm, 70 cm in the same proportion of 1:100 model and natural condition. Landslide model is established with 12% water content. Rainfall intensity is divided into three sections of 60mm, 90mm and 120mm according to the grade of heavy rain to heavy rain. By connecting the data acquisition system, the data changes of pore pressure meter and moisture meter under different working conditions are observed. The deformation and failure of slope body are observed through the grid of test trough, high-definition camera, camera and other equipment. The failure of slope under different working conditions is designed by orthogonal test and the variance of factors is carried out by SPSS software. The results show that the slope ratio, rainfall, slope height, and the degree of influence on slope stability are rainfall intensity and slope height in turn. Therefore, in practical engineering, the larger rainfall intensity, higher slope height and high steep slope will greatly increase the probability of landslide of unsaturated Malan loess high slope. The relationship between parameters is analyzed, and whether the experimental data of artificial rainfall model in laboratory conform to the actual situation is analyzed. The artificial rainfall model test data of unsaturated Malan loess high slope are imported into FEFLOW for simulation observation, and the seepage field model of slope is established to observe the change of pore water pressure and water content in slope body under rainfall condition. The results show that a transient saturated zone will be formed when the slope falls on the surface soil under the condition of heavy rainfall, and it is difficult to affect the soil below the saturated line in the short term. The stability coefficient of slope decreases. 5. The research methods of saturated-unsaturated soil slope stability at home and abroad are summarized. The stability checking design of unsaturated Malan loess high slope in stope is carried out under the condition of accepting rainfall. After verification, the relevant suggestions on slope geometry of 1040 m East elevation slope are put forward. The design parameters are as follows: the height of single-stage slope is 10m, the slope angle is 55 degrees, the width of step is 6m and the interval of lOm is arranged according to relevant specifications, which will achieve good stability effect.
【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P642.131

【参考文献】