【作者】 李玉林；

【导师】 向喜琼；

【作者基本信息】 贵州大学 ， 地质资源与地质工程， 2023， 硕士

【摘要】 2019年10月14日下午16时左右,安顺市镇宁县发生了一起由冲沟侧向补给地下水诱发的缓倾土质滑坡,由于特殊地理条件,坡体两侧存在两条季节性冲沟,沟内节理裂隙发育,局部可见岩土接触面,常规条件下滑坡不可发生。为研究滑坡形成机理,本文以许荒滑坡为研究对象,展开硕士论文研究,在收集前人研究资料和现场实地踏勘的基础上,对许荒进行区域地质调查、水文地质调查,通过采用工程地质分析法、野外精细化调查及历史变形监测、数值模拟等方法手段,对许荒滑坡变形破坏特征及形成机理进行系统性研究。现将研究的主要成果和认识总结如下:(1)许荒滑坡平面形态近似呈舌形,南东高北西低,后缘以坡体下错为界,前缘民房修建导致剪出口不易被识别,位于两条季节性冲沟之间,变形特征较明显,主要以裂缝为主,呈弧形展布,可见深度、裂缝宽数厘米至数十厘米,延伸数米至数十米。滑坡主滑方向337°,体积约1.22×10~5m~3,滑坡规模中型。(2)根据滑坡形态特征以及变形破坏特征,将许荒滑坡分为启动区、牵引区,知地下水是滑坡诱发的主要影响因素,坡脚民房修建及道路加载导致斜坡内地下水运移通道被阻挡,地下水在坡体内部淤积雍高,坡脚处会出现暂时性承压现象。(3)基于永久散射体的SBAS-In SAR技术,在2017年1月1日～2021年12月31日这一监测时间段内,坡体变形明显,主要集中于滑坡前缘、中后部以及冲沟两侧,平均地表形变速率-9～8mm/a,最大沉降速率为9mm/a。将滑坡发生时间为节点,通过时序变形分析显示发生前后坡体变形差异较大。(4)结合数值模拟结果,许荒滑坡形成主要经历两个阶段,一是在启动区由地下水承压起主要作用,静水压力与超孔隙水压力起推进作用的应力集中阶段,坡脚先行发生溃屈破坏,后部滑体前缘临空;二是随冲沟侧向不断补给地下水,坡体潜在滑移面被软化,相继向下发生牵引滑动,变形破坏模式为蠕滑-拉裂。(5)对于冲沟侧向补给地下水条件下滑坡稳定性计算,在计算过程中应综合考虑不同承压水位下滑面处水压力分布形式。(6)有承压水作用的边坡,其稳定性对承压水位比较敏感,尤其在连续降雨季节,承压水位会因坡脚受堵而抬升,在预防与防治中要注意保持坡体前缘渗出段的畅通,同时注意减少或阻止后缘裂缝、冲沟侧向补给地下水,以降低滑面孔压,减少降雨对斜坡稳定性的影响。更多还原

【Abstract】 On October 14,2019,at about 16:00 p.m.,a gently dipping soil landslide induced by lateral recharge of groundwater from an alluvial ditch occurred in Zhenning County,Anshun City.Due to the special geographical conditions,there are two seasonal alluvial ditches on both sides of the slope body,and the joint fissures are developed in the ditch,and the rock-soil contact surface is locally visible,and the landslide cannot occur under conventional conditions.In order to study the formation mechanism of landslide,this paper takes Xuhuang landslide as the research object and starts the master’s thesis research.Based on the collection of previous research data and field investigation,the regional geological survey and hydrogeological survey are conducted on Xuhuang,and the deformation and damage characteristics and formation mechanism of Xuhuang landslide are systematically studied by using engineering geological analysis method,field refinement survey and historical deformation monitoring,numerical simulation and other methods.The main results and understanding of the research are presented.The main results and understanding of the research are summarized as follows:(1)Xu desolate landslide planform is nearly tongue-shaped,south east high north west low,the back edge of the slope body for the boundary,the front edge of the construction of residential buildings led to shear exit is not easily identified,located between two seasonal drains,deformation characteristics are more obvious,mainly fissures,arc-shaped spreading,visible depth,fissure width of a few centimeters to tens of centimeters,extending a few meters to tens of meters.Landslide main slip direction337°,the volume of about 1.22×10~5m~3,landslide scale medium-sized.(2)According to the morphological characteristics of the landslide and the deformation and damage characteristics,the Xuhuangli landslide is divided into the initiation area and the traction area,and it is known that groundwater is the main influencing factor of landslide initiation.The construction of the residential houses at the foot of the slope and the loading of the road lead to the obstruction of the groundwater transport channel in the slope,and the groundwater is silted up inside the slope body Yonggao,and the temporary pressure bearing occurs at the foot of the slope and the collapse and damage occurs.(3)Based on the SBAS-In SAR technique of permanent scatterer,during the monitoring time period from January 1,2017 to December 31,2021,the slope deformation is obvious,mainly concentrated in the front edge,middle and rear of the landslide and both sides of the wash,with an average surface deformation rate of-9 to8mm/a and a maximum settlement rate of 9mm/a.Taking the landslide occurrence time as the node,the time series deformation analysis shows that The difference of slope deformation before and after the occurrence is large.(4)Combined with the numerical simulation results,the formation of Xuhuang landslide mainly goes through two stages,one is in the initiation area by groundwater bearing pressure plays a major role,hydrostatic pressure and super pore water pressure plays a propulsive role in the stress concentration stage,the foot of the slope first collapse damage,the back slide front edge of the hollow;the second is with the lateral gully continuously recharge groundwater,the slope body potential slip surface is softened,followed by downward traction sliding,deformation damage mode for creep slip-pull crack.(5)For the calculation of landslide stability under the conditions of lateral recharge groundwater in the flushing ditch,the form of water pressure distribution at the sliding surface of different pressure-bearing water levels should be taken into consideration in the calculation process.(6)The stability of slopes with pressurized water is sensitive to the pressurized water level,especially in the season of continuous rainfall,the pressurized water level will be raised due to the blockage of the foot of the slope.In the prevention and control,attention should be paid to keep the seepage section of the front edge of the slope unobstructed,and at the same time,attention should be paid to reduce or stop the lateral recharge of groundwater from the cracks and gullies at the back edge to reduce the pore pressure of the slippery surface and reduce the influence of rainfall on the stability of the slope.更多还原