西宁市泥岩及碎石土滑坡成因机理研究

发布时间：2018-02-25 17:39

本文关键词： 泥岩滑坡碎石土滑坡成因机理数值模拟稳定性分析　出处：《青海大学》2017年硕士论文　论文类型：学位论文

【摘要】：西宁市位于湟水河河谷内与山间丘陵边缘地区,为低山丘陵及河谷平原,特有的地形地貌、地质构造等地质环境,使得西宁市内多种地质灾害频发。通过现场实地地质调查及结合调查报告研究结果表明:新近泥岩滑坡共有49处占西宁市地区的新近总滑坡的73.1%;新近碎石土滑坡共有10处占新近总滑坡的14.9%,成为威胁人类生命财产的主要地质灾害之一。因此,西宁市泥岩及碎石土滑坡成因机理研究对西宁市滑坡地质灾害的评价、分析、预警和防治可提供参考,具有实际意义。本文选取以张家湾砖厂滑坡为代表的泥岩滑坡及以付家寨滑坡为代表的碎石土滑坡为研究对象,通过实地滑坡剖面勘查和已有的调查报告,确定滑坡模型以及模型力学参数,结合FLAC3D强度折减法及SLIDE极限平衡法,对典型的泥岩及碎石土滑坡在天然和饱和条件下做出系统而全面的稳定性及成因机理分析。取得的认识如下:(1)西宁市地质灾害调查统计新近滑坡共有67处,按滑体性质可分为土质滑坡、泥岩滑坡、碎石土滑坡三类,其中泥岩滑坡地层主要以古近系(E)、新近系(N)、白垩系(K)的泥岩、砂岩及石膏岩为主,占新近总滑坡的73.1%;碎石土滑坡地层母岩均为古近系(E)泥岩、砂岩、石膏岩地层,岩性主要为碎屑岩、含盐矿物为主,占新近总滑坡的14.9%。(2)西宁市泥岩及碎石土滑坡,在构造运动影响下,受控于北川河西岸断裂、湟水河断裂、南川河断裂、沙塘川断裂带。(3)泥岩及碎石土滑坡成因机理:张家湾砖厂泥岩滑坡,由于后缘陡坡在自重应力影响下形成拉裂缝,岩体内发育的节理裂隙面成为优势拉裂和剪切面,为降水提供了下渗通道,使得滑坡后缘上部黄土的孔隙水、含水量大大增加,破坏了滑坡的稳定性,最终滑坡后缘失稳发生崩塌;付家寨碎石土滑坡,由于湟水河的快速下切使得坡体内盐分的流失加剧,且泥岩本身遇水软化特性较强,变形能不易积累,坡体便以小规模崩塌的形式不断释放能量并堆于坡脚,形成了坡体现有的这一特殊物质结构特征,在集中降水等条件下坡体内盐分不断释出,并于相对隔水层形成滑动剪切面,最终产生滑坡灾害。(4)泥岩及碎石土滑坡稳定性分析结果表明:在天然及饱和条件下,张家湾砖厂滑坡整体稳定性系数分别为1.290、1.160,说明滑坡整体处于稳定状态,在强度折减法与极限平衡法对比分析中,初步判断3个监测点中,可以得出监测点A处于随时失稳状态,监测点B、C稳定性较好,但不排除人为开挖边坡及强降水等因素对该滑坡的影响,而导致的再次灾害,这与实地野外调查结果一致;付家寨滑坡整体稳定性系数分别为1.110、1.080,说明滑坡整体处于稳定状态,在强度折减法与极限平衡法对比分析中,初步判断监测点A,滑坡后缘中部的稳定性较差,属于随时失稳状态,这与特殊的地层岩性及降水有直接的关系。
[Abstract]:Xining City is located in the Huangshui River Valley and the hilly margin of the mountains. It is a low mountain hill and valley plain with unique topography and geomorphology, geological structure and other geological environments. The results of field geological investigation and investigation report show that there are 49 new mudstone landslides which account for 73.1% of the total recent landslide in Xining city and 73.1% of the new gravel landslide in Xining City, and the results of field geological investigation and investigation report show that there are 49 new mudstone landslides in Xining City, which account for 73.1% of the total recent landslide. A total of 10 landslips accounted for 14. 9% of the total recent landslides, becoming one of the major geological hazards threatening human life and property. Study on the genetic Mechanism of mudstone and Gravel landslide in Xining City the evaluation, analysis, early warning and prevention and control of landslide geological hazards in Xining City can be used as a reference. This paper selects the mudstone landslide represented by Zhangjiawan Brick Factory landslide and the gravel landslide represented by the Fujiazhai landslide as the research object, and through the field landslide section survey and the existing investigation report, this paper selects the mudstone landslide as the representative of Zhangjiawan brick factory landslide and the gravel landslide represented by the Fujiazhai landslide. The landslide model and its mechanical parameters are determined, combined with FLAC3D strength reduction method and SLIDE limit equilibrium method. A systematic and comprehensive analysis of the stability and genetic mechanism of typical mudstone and gravel landslides under natural and saturated conditions is made. According to the nature of the sliding body, it can be divided into three types: soil landslide, mudstone landslide and gravel landslide. The mudstone landslide strata are mainly composed of mudstone of Paleogene, Neogene, Cretaceous K), sandstone and gypsum rock. 73.1% of the total recent landslide; the parent rock of the lithotriptic landslide is Paleogene (E) mudstone, sandstone, gypsum rock formation, lithology is mainly clastic rock, salt mineral is dominant, and it accounts for 14.9.2% of the recent total landslide) Xining mudstone and macadam landslide. Under the influence of tectonic movement, controlled by the fault in the west bank of Beichuan River, the Huangshuihe fault, the Nanchuan River fault, the Shatangchuan fault zone and the sand Tangchuan fault zone, the formation mechanism of mudstone and gravel landslide: Zhangjiawan Banchang mudstone landslide, Due to the formation of tensile cracks in the steep slope of the rear edge under the influence of gravity stress, the fracture plane developed in the rock body becomes the dominant tensile crack and shear surface, which provides a seepage channel for precipitation, which makes the pore water and water content of the loess in the upper part of the landslide increase greatly. It destroyed the stability of the landslide, and finally the instability of the back edge of the landslide collapsed. Due to the rapid downcutting of the Huangshui River, the loss of salt in the slope was aggravated, and the mudstone itself was characterized by strong softening of water, and the deformation could not be easily accumulated. The slope body releases energy continuously in the form of small scale collapse and heaps on the foot of the slope, which forms the special material structure characteristic of the slope. Under the condition of concentrated precipitation and other conditions, the salt in the slope body is continuously released, and the sliding shear surface is formed in the relative water-isolated layer. The results of landslide stability analysis of mudstone and gravel soil show that under natural and saturated conditions, the overall stability coefficient of Zhangjiawan brick factory landslide is 1.290 / 1.160, which indicates that the whole landslide is in a stable state. In the comparative analysis of strength reduction method and limit equilibrium method, it can be concluded that the monitoring point A is in a state of instability at any time, and the stability of monitoring point BCC is good, among the three monitoring points, it is preliminarily judged that the monitoring point A is in a state of instability at any time. However, the influence of man-made excavation slope and heavy precipitation on the landslide is not excluded, which is consistent with the field investigation results, and the overall stability coefficient of the Fujiazhai landslide is 1.110 ~ 1.080, which indicates that the whole landslide is in a stable state. In the comparative analysis of strength reduction method and limit equilibrium method, the stability of monitoring point A and the middle of the back edge of landslide is poor, which is in the state of instability at any time, which is directly related to the special stratigraphic lithology and precipitation.
【学位授予单位】：青海大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P642.22

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