北川县筲箕窝滑坡复活机制及稳定性研究

发布时间：2018-02-05 00:28

本文关键词： 筲箕窝滑坡成因机制数值模拟复活机制稳定性评价　出处：《成都理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：筲箕窝老滑坡位于四川省绵阳市北川羌族自治县三坪村,处于龙门山构造带内,构造背景复杂,为中陡倾千枚岩质顺层斜坡失稳破坏后堆积而成,其变形破坏类型为“滑移-弯曲-溃决”型,失稳规模约700万m3。在“5.12”汶川地震中,老滑坡堆积体体上出现若干条短小的张拉裂缝;地震后经过多年降雨作用,尤其为2013年7月的特大暴雨后,坡体上发育多条横向的长大张拉裂缝,复活迹象明显。老滑坡复活将危及坡体上的居民生命和财产安全,中断通向上游村落的重要交通道路,并对老麂沟沟口居民造成威胁。因此,研究该滑坡的复活机制及稳定性具有重要的实际意义,同时补充了地震引发滑坡堆积体复活的研究,对类似老滑坡堆积体的复活及稳定性的分析具有一定的参考价值。本文在收集研究区相关地质关资料,整理勘查资料,对滑坡区工程地质条件、滑坡结构特征、变形破裂特征进行分析的基础上,采用地质-力学的方法分析老滑坡的形成机制,通过地质分析与数值模拟相结合的方法研究了滑坡在地震与暴雨作用下的复活机制,进而用定性与定量两种方法对滑坡整体与局部的稳定性进行评价,并提出了防治措施。主要研究成果如下:(1)分析滑坡的基本特征与滑坡外围的类似千枚岩斜坡的变形特征,并结合滑移-弯曲的地质力学模型计算极限弯曲段长度,确定筲箕窝滑坡为中陡倾千枚岩质顺层斜坡失稳破坏后堆积而成,变形破坏模式为“滑移-弯曲-溃决”。(2)“5.12”地震中,老滑坡堆积体在地震波作用下变形破坏主要变现为松动、破裂,在后部高陡的部位与前部微地貌呈凸起形的部位产生若干条短小的横向裂缝;地震后受多年降雨作用影响,尤其在2013年7月特大暴雨期间,滑坡有明显的复活迹象,主要表现坡体上出现多条长大的横向裂缝与下错陡坎,并具有一定分区性。根据坡体结构特征与变形破裂特征将老滑坡分为1#、2#、3#三个复活区。(3)老滑坡体结构较松散,为滑坡复活提供了不良的地质基础;在地震作用下,坡体出现裂缝,且结构更加松散,为后期降雨入渗提供良好的渗流通道。降雨入渗坡体后转化为地下水,对坡体加载,产生静水压力与渗透力,并且软化滑带,造成下滑力增加而抗滑力减小,滑坡堆积体开始出现蠕滑变形,导致老滑坡的复活。根据滑坡的变形特征,推断滑坡度堆积体变形破坏的模式为“蠕滑-拉裂-剪断”模式。利用Flac3D(有限差分法)模拟分析在地震与暴雨作用下滑坡堆积体复活机制,通过对数值模拟结果分析得出:在地震作用下,堆积体的位移较小,塑性变形几乎在整个滑坡堆积体出现,塑性破坏在坡体上零星出现;老滑坡堆积体在降雨作用下位移量较大,出现一定区域的塑性破坏,并且在滑坡后部与前部形成相对集中的剪切应变带,降雨作用诱发堆积体复活。(4)通过定性分析与采用Morgenstern-Price极限平衡法分析老滑坡堆积体局部及整体稳定性。老滑坡整体在天然工况下处于稳定状态,在暴雨与地震工况下处于基本稳定状态。各复活体在天然工况下处于基本稳定-稳定状态,除1#复活体在暴雨工况下处于不稳定,其余在暴雨与地震工况下基本处于欠稳定-基本稳定状态。通过稳定的敏感性分析,稳定性系数随内聚力与内摩擦角呈上升趋势,其中内摩擦角对滑坡稳定性的影响更大。二维渗流场与应力场耦合数值模拟分析五十年一遇的单次最大降雨与5天连续最大降雨条件下的稳定性情况。单次降雨结果显示:单次最大降雨方式为垂直入渗,引起坡表的应力应变改变,容易引发表层的溜滑。5天连续降雨结果显示:降雨前2天雨水作用方式为垂直入渗为主引起滑体容重增加,降雨后3天雨水作用形式为渗透作用和一定的浮托作用;耦合计算显示降雨作用使坡体整体应力增加,滑带处最大剪应力增大,在后部与前部形成两个贯通的剪应变带,后部的最大剪应变量值较前部的大,剪应变带未整体贯通,验证滑坡失稳破坏为“蠕滑-拉裂-剪断”模式。(5)在滑坡稳定性计算结果的基础上,并结合滑坡变形特征、失稳破坏模式、岩土特征、空间发育特征及受害对象的分布等特点提出滑坡的防治方案为抗滑桩+排(截)水沟。
[Abstract]:The old landslide is located at three Shaoji nest village in Sichuan city of Mianyang province Beichuan Qiang Autonomous County, is located in the Longmen mountain tectonic belt, tectonic background complex, as the steep bedding layer phyllite slope instability damage accumulation, deformation and failure type "slip bending outburst" type, instability of the size of about 7 million m3. in the "5.12 Wenchuan earthquake", the old landslide body appeared on a number of short cracks; after the earthquake, after years of rainfall, especially for the torrential rain in July 2013 after the slope on the development of a number of horizontal tensile cracks grew up, raised significantly. Signs of revival of old landslide will endanger the slope residents on the safety of life and property, important way to interrupt traffic upstream of the village, and pose a threat to the old Deer Valley residents. Therefore, it has important practical significance to study the stability and the revival mechanism of the landslide, and adding earthquake Study on the resurrection of the landslide, which has a certain reference value for similar analysis of old landslide accumulation and stability of resurrection bodies. Based on the relevant data collected in the study area geological exploration data, consolidation, engineering geological conditions of landslide, landslide structure, foundation deformation and fracture characteristics were analyzed, using the method of geomechanics the analysis of the formation mechanism of old landslide, based on geological analysis and numerical simulation study of the landslide revival in the earthquake and rainstorm under the action mechanism, and then using qualitative and quantitative methods of two landslide overall and local stability evaluation, and puts forward the preventive measures. The main results are as follows: (1) the deformation characteristics of slope and landslide characteristics similar to phyllite surrounding landslide analysis, combined with the geological mechanics model of slip - bending length limit calculation, determine the Shaoji nest Landslide is steep bedding layer phyllite slope instability damage accumulation, deformation and failure mode of "sliding and bending - break." (2) "5.12" earthquake, the old landslide under earthquake wave deformation and failure of the mainshow is loose, broken, several short transverse cracks in the rear part and the front of the high and steep micro landforms were convex parts; after the earthquake affected by years of rainfall, especially in July 2013 during the torrential rain, landslides have obvious signs of resurrection, a plurality of transverse cracks and grew up under the fault scarp occurred mainly on the slope, and has a certain area according to the. Structural characteristics of slope deformation and fracture characteristics of the slope is divided into 1#, 2#, 3# three wards. (3) the old landslide body structure is loose, provides a good foundation for the geological landslide; in the earthquake, cracks in the slope, and the structure is more loose, For the latter part of the rainfall infiltration provide good seepage channel. Rainfall infiltration into slope groundwater, the slope of loading, hydrostatic pressure and penetration, softening and sliding zone, sliding force caused by increased anti slide force, landslide began to creep deformation, leading to the old landslide according to the resurrection. The deformation characteristics of the landslide, landslide accumulation of inference of the deformation and failure model for creep cracking and shearing "model. Using Flac3D (finite difference method) simulation analysis of landslide debris in the earthquake and rainstorm revival mechanism, based on the numerical simulation results show that under the earthquake, the accumulation of small displacement of body the plastic deformation accumulation almost throughout the landslide, the plastic damage in sporadic slope; the old landslide in rainfall displacement is large, plastic damage area, and in the rear and front landslide Formation of shear strain is relatively concentrated, the effect of rainfall induced accumulation of resurrection. (4) through the qualitative analysis and the Morgenstern-Price method of limit equilibrium analysis of the old landslide is local and overall stability. The old landslide is in the stable state in the natural condition, is in a stable state in the rainstorm and seismic conditions. The complex in vivo the natural condition is stable and stable state, in addition to 1# resurrection is unstable in heavy rain conditions, the rest in the heavy rain and earthquake conditions is less stable to stable state. Through the sensitivity analysis of stability, stability coefficient with the cohesion and internal friction angle increased, the influence of internal friction angle of landslide the stability should be greater. And simulate the stability of the single maximum rainfall analysis of fifty years and 5 days of continuous maximum rainfall conditions numerical two-dimensional seepage field coupling force field The single rainfall situation. Results show that the single biggest rainfall pattern for vertical infiltration, slope surface caused by stress and strain change, easily lead to slippery surface.5 days of continuous rainfall showed that rainfall 2 days before the rain to the role of vertical infiltration mainly caused by landslide bulk density increased, the 3 day after the rain drop rain effect for the penetration and float over certain extent; coupled calculation shows that the effect of rainfall the slope stress increases, the slide zone of maximum shear stress increases in the rear and the front two through the formation of shear strain, maximum shear strain value than the rear part, the shear strain with the overall link up verify the landslide failure as "creep cracking and shearing" model. (5) based on the calculation result of landslide stability, and combined with the characteristics of landslide deformation, failure modes, geotechnical characteristics, the characteristics of spatial distribution characters and victims etc. The prevention and control scheme of the landslide is the anti slide pile + row (cut) ditch.

【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P642.22

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