山西省黄土崩塌地质灾害的现状及水敏感性分析

发布时间：2019-03-12 16:36

【摘要】：以山西省黄土崩塌灾害为例,通过对山西省临汾、吕梁、长治、忻州四市的灾害频发区的黄土地质灾害点的实地调查和所收集资料的分析得出:一、山西省境内地质环境复杂,黄土地质灾害具有种类多、分布广、频率高的特点,其中以崩塌为主,崩塌数占黄土地质灾害总数的73%以上。且崩塌灾害受当地地形地貌、气象水文、地质构造的影响,且随着山西省经济的发展,人类活动对地质灾害的发生影响越来越大;除已发生的地质灾害外,山西省还存在大量潜在的黄土崩塌灾害隐患点,这些灾害隐患对人民群众生命财产安全构成了极大威胁。二、黄土崩塌的发生是多种因素综合作用的结果,包括黄土土体自身因素以及外部触发因素。其中而黄土崩塌外部触发因素即诱因主要为降雨、土壤冻融、地下水侵蚀、河流冲蚀、人类活动及生物活动等。其中降雨和冻融对黄土崩塌的影响最为严重。而降雨、冻融作为黄土崩塌的两种诱发因素的共性是:灾害发生前期,土壤含水量急速增大,导致土体抗剪强度不断降低,且自重持续增大,土体间抗剪强度不足以维持自身重力,土体发生下落,形成崩塌灾害。针对黄土崩塌的水敏感性分析研究,对三个地质灾害频发县:吉县、永和、临县的灾害点进行现场取样,并对所取的原状土样在不同含水量下进行室内直剪抗剪强度实验,分别对土体黏聚力和内摩擦角这两抗剪强度指标进行与含水量关系分析。结果表明吉县与永和两县土样实验规律相似,表现为:黄土抗剪强度在界限含水量时达到最大,此时两县界限含水量分别为ωCJ为(17±2.00)%,ωCy为(15±2.00)%。而崩塌灾害发生时,往往土体含水量远高于此界限含水量,抗剪强度随含水量的增加急剧下降。此界限含水量可作为灾害地区灾害预警值。临县的实验结果为:区别于吉县与永和的实验规律,抗剪强度总体上随含水量增加呈下降趋势,区别的原因在于临县黄土自然状态下含水量低,孔隙率大,为支架大孔隙黄土,土骨架强度随结构强度贡献率不大,结构强度主要取决于颗粒间胶结物及晶体结构的性质。这些物质中的可溶性盐及部分有机质能在水中溶解,导致黄土中胶结物及晶体结构溃散,粘聚力丧失;而吉县永和黄土含水量高,空隙率低,强度主要取决于骨架强度与颗粒之间的胶结作用,当土壤的含水量非常低时,土粒间胶结力不能完全发挥其作用,土壤黏聚力较低;而随着含水量不断增大,胶结作用力发挥作用且不断增大,进而土壤黏聚力不断增加。
[Abstract]:Taking the loess collapse disaster of Shanxi Province as an example, it is concluded that the geological environment in Shanxi province is complicated and the loess geological hazard has many kinds, The distribution is wide and the frequency is high, in which the collapse is the main and the number of collapse accounts for more than 73% of the total number of geological disasters in the loess area. and with the development of Shanxi's economy, the impact of human activities on the geological disasters is becoming more and more serious; in addition to the geological disasters that have taken place, a large number of potential hidden danger points of the loess collapse in Shanxi are also existed, The hidden danger of these disasters poses a great threat to the lives and property of the people. 2. The occurrence of loess collapse is the result of the comprehensive effect of various factors, including the self-factors of loess soil and the external trigger factors. Among them, the external trigger factors of loess collapse are rainfall, soil freeze-thaw, groundwater erosion, river erosion, human activities and biological activities. The effect of rainfall and freeze-thaw on the collapse of loess is the most serious. In the early stage of the disaster, the water content of the soil is rapidly increased, the shear strength of the soil is continuously reduced, and the self-weight is continuously increased, and the shear strength between the soil bodies is not sufficient to maintain the self-gravity and the soil mass can fall, And the collapse hazard is formed. In view of the water sensitivity analysis of the collapse of the loess, the field sampling is carried out on the disaster points of three geological disasters, namely, Jixian, Yongand and Linxian, and the experimental results of the shear strength of the indoor direct shear under different water content are carried out on the original undisturbed soil samples. The relationship between the cohesive force and internal friction angle of the soil and the water content were analyzed. The results show that the experimental rules of the soil samples in Jixian and Yongand two counties are similar, and the results show that the shear strength of the loess reaches the maximum in the limit water content, and the water content of the two counties is respectively (17-2.00)% and (15-2.00)% respectively. In the event of collapse, the water content of soil is much higher than the water content of this limit, and the shear strength decreases sharply with the increase of water content. The water content of this limit can be used as the early warning value of the disaster area. The experimental results of Linxian County are as follows: the experimental law of Jixian and Yonghe is different, and the shear strength decreases with the increase of the water content, and the difference is that the water content in the natural state of the loess in Linxian is low and the porosity is large, which is the large-pore loess of the support. The strength of the soil skeleton is less than that of the structural strength, and the structural strength depends on the properties of the interparticle bond and the crystal structure. The soluble salts and some of the organic matter in these materials can be dissolved in water, and the cement and the crystal structure in the loess are broken and the cohesion is lost; and the water content of the permanent and loess in the Jixian County is high, the void rate is low, and the strength is mainly determined by the cementation effect between the strength of the skeleton and the particles, When the water content of the soil is very low, the bonding force between the soil and the soil can not fully play its role, and the cohesive force of the soil is low; and as the water content is increasing, the binding force of the soil is increased, and the cohesive force of the soil is increased.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P642.21

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