红层地区滑坡滑带处水—岩（土）化学作用研究

发布时间：2018-09-03 14:47

【摘要】：四川省南江县位于川东北边缘地区,其县城中南部为典型的红层区,2011年“9.16”因为遭到强降雨作用的影响,该研究区域发生了数以千计的土质滑坡,其中尤其以缓倾角土质滑坡居多。而滑坡的演化过程都贯穿着滑坡体能量动态平衡的一系列极为复杂的物理—化学变化,尤其是在滑带处的地球化学条件对“滑带土”的形成与聚集具有重要的控制作用进而影响滑坡的发展与演化过程。滑带土是滑坡形成、发展以及滑动过程中的重要产物,也是滑坡的重要组成部分,滑带土的形成和聚集与滑坡的发展演化、变形历史以及滑坡的稳定性等都具有密切的内在联系。本文基于现场调查,通过大量的室内试验,研究了滑带土的赋存条件,结合水文地球化学基本原理,对斜坡中的从基岩—挤压破碎带—软弱泥化夹层—滑带土逐步演化的整个过程中水—岩(土)化学作用进行分析,探讨了滑带赋存环境改变对滑带土的影响过程。滑带作为一个相对隔水层,能对上部入渗的降水进行截留,形成了一个独立的水文地质单元,同时,造岩矿物的黏土化过程往往在滑带处形成一个较为“开放”而又相对“封闭”的环境,在这样一个相对封闭性的环境下,由于环境中的微生物的呼吸作用等,形成了一个缺氧的还原性环境。通过对滑带土及上下岩土体的元素组成及矿物成分对比分析,结合基本水文地球化学作用原理,可知,在滑带的形成时期,最主要的作用是造岩矿物的黏土化过程,使泥化夹层的泥化程度不断加强,从而在斜坡内部形成连续的泥化带的同时,也满足了滑带土的赋存条件。分别采用通入氧气的有氧环境和通入氮气的无氧环境进行模拟实验,探究滑带赋存的环境改变,对滑带土的影响。在有氧环境中,主要表现为:早期低价态的变价金属元素发生氧化作用,且低浓度溶液的加入使溶液中可溶盐类的溶解作用增强,使得溶液中SO42-以及Cl-离子的浓度升高,溶液中由于氧化作用产生的H+结合,形成强酸物质,使得溶液中的PH值降低,直至溶液呈酸性。但是随后体系中所发生的硅酸盐类矿物的转化以及碳酸盐的矿物的溶解作用使得溶液中的PH值上升,产生碱化作用。在无氧环境中主要发生的是可溶盐类矿物的溶解作用以及缓慢的硅酸盐类矿物的转化,即伊利石向化学稳定性更好的高岭石发生转化,因此在该体系中水溶液的PH值主要呈斜率较小的稳步上升趋势。根据此次试验中对不同环境下滑带土的抗剪强度衰减程度分析,结合南江地区2011年“9.16”强降雨诱发大量滑坡的实例,对滑坡的发生机制及过程进行讨论,即连续的降雨不仅改变了滑带土还原性的环境,地下水往下渗入与滑带土发生氧化反应,使黏土矿物聚集,与此同时由于离子浓度较低的地下水的参与,也使得土中胶结物发生溶解,使得滑带土的剪切强度降低且厚度增加,而滑带中的粘土矿物的隔水边界效应,使斜坡的负载增大,由于降雨对滑带土所产生的化学作用对抗剪强度的降低需要一个较长期的作用,并且需要一次较强的降雨使斜坡的负载增加到一定的范围,因此可以推断,久雨之后暴雨是红层地区该类缓倾角浅层土质滑坡大规模群发性发生的必要条件。
[Abstract]:Nanjiang County, Sichuan Province, is located in the northeastern edge of Sichuan Province. The central and southern part of Nanjiang County is a typical red bed area. In 2011, thousands of soil landslides occurred in the study area due to the impact of heavy rainfall, especially the gentle dip angle soil landslides. The evolution of landslides is permeated by the dynamic balance of landslide energy. A series of extremely complex physical-chemical changes, especially the geochemical conditions at the sliding zone, play an important role in controlling the formation and accumulation of the "sliding zone soil" and thus affecting the development and evolution of landslides. The formation and accumulation of slip zone soils are closely related to the development and evolution of landslides, the deformation history and the stability of landslides. Based on field investigation and a large number of laboratory tests, the occurrence conditions of slip zone soils are studied in this paper. The chemical action of water-rock (soil) during the gradual evolution of muddy intercalation-sliding zone soil is analyzed, and the influence of the change of the occurrence environment of the sliding zone on the sliding zone soil is discussed. In this relatively closed environment, an anoxic reductive environment is formed due to the respiration of microorganisms in the environment. According to the basic hydrogeochemical principle, the most important role of the slip zone is the claying process of the rock-forming minerals during the formation of the slip zone, which makes the degree of mudding of the muddy intercalation strengthened continuously, thus forming a continuous muddy zone in the interior of the slope and satisfying the occurrence conditions of the slip zone soil. In the aerobic environment, the main manifestations are as follows: oxidation of low-valent metal elements occurs in the early stage, and the dissolution of soluble salts in the solution is enhanced by the addition of low-concentration solution, which makes SO42-and Cl-in the solution. With the increase of ion concentration, the H + produced by oxidation in the solution binds to form strong acidic substances, resulting in the decrease of pH value in the solution until the solution is acidic. However, the subsequent transformation of silicate minerals in the system and the dissolution of carbonate minerals lead to the increase of pH value in the solution, resulting in alkalization. The dissolution of soluble salt minerals and the slow transformation of silicate minerals, i.e. illite to kaolinite with better chemical stability, are the main occurrences in the environment. Therefore, the PH value of the aqueous solution in the system shows a steady upward trend with a small slope. According to the shear resistance of slip zone soils in different environments in this experiment. Based on the analysis of intensity attenuation degree and a large number of landslides induced by "9.16" heavy rainfall in Nanjiang area in 2011, the occurrence mechanism and process of landslides are discussed, that is, continuous rainfall not only changes the reducing environment of slip zone soil, but also causes clay minerals to accumulate due to the oxidation reaction between groundwater infiltration and slip zone soil. The participation of groundwater with lower sub-concentration also causes the dissolution of cements in the soil, which reduces the shear strength and increases the thickness of the sliding zone soil. However, the water-proof boundary effect of clay minerals in the sliding zone increases the load on the slope. The reduction of shear strength due to the chemical action of rainfall on the sliding zone soil requires a longer-term operation. In addition, a strong rainfall is needed to increase the slope load to a certain extent. Therefore, it can be inferred that heavy rain after long rains is the necessary condition for large-scale mass occurrence of such gently inclined shallow soil landslides in red beds.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P642.22

【相似文献】