花岗岩残积土农村边坡安全监测预警关键技术研究与应用

Research and application of key technologies for rural slopesafety monitoring and early warning of granite residual soil

基于已有边坡防灾减灾项目,对典型花岗岩残积土农村边坡开展安全监测与预警研究。研究表明:监测剖面应根据坡度、坡高和削坡方式,选择在易发生破坏且具代表性的部位,必要时可增加监测剖面,共设置两条剖面;边坡安全监测内容宜包含降雨量、坡体含水率、边坡位移、坡脚挡墙倾斜观测和视频监控设备组合;边坡监测设备应布置在坡体的不同部位、不同高程,以便对坡体的稳定性在空间上进行整体控制,至少在监测剖面顶部和中部设置位移监测点;变形监测站点的埋设位置应选在岩土体性能较差、预计变形较大的位置;此类边坡规模较小且易发生失稳破坏,宜采用成本较低、安装位置灵活的GNSS方法开展此类边坡位移监测;边坡安全预警指标宜采用降雨量和坡顶位移量双指标,增加容错率,必要时可增加坡体含水率指标;报警方式除采用常规的短信提醒外,应设置诸如声音、光照等设立在现场的报警装置,增强报警效果。降雨对花岗岩残积土边坡的稳定性存在直接的和主要的影响,随降雨量上升,坡体含水率及边坡位移量相应提高并存在一定的滞后现象。采用有限元分析软件Geo-studio软件中的SIGMA/W模块和Slope/E模块对该边坡进行渗流分析和稳定性分析,岩土体力学参数、水土特征曲线、渗透系数等来源于实测勘察数据,网格单元的大小为1 m,单元网格的形状为正方形和三角形相结合。模型校正调试选取监测期间内降雨量最大时间段进行拟合,模型坡顶位移量与实测值误差为5%,满足可行性校验。选用70 mm降雨强度定义模型降雨边界,观测边坡稳定系数变化,选择预警稳定性系数为1.1。最终设定边坡降雨量预警值为70 mm/d,坡顶位移量5 mm/d。本项研究提高了农村消坡建房危险边坡安全监测和预警的有效性和经济性,为解决该类边坡的监测和预警问题提供理论和实践指导。

Based on the existing slope disaster prevention and mitigation projects,the safety monitoring and early warning of typical granite residual soil slope in rural areas are studied.The results show that the monitoring profile should be selected according to the slope,slope height and slope cutting method,and the representative parts that are prone to failure can be added when necessary.The content of slope safety monitoring should include rainfall,slope moisture content,slope displacement,slope foot retaining wall inclination observation and video monitoring equipment combination;The slope monitoring equipment should be arranged in different parts and elevations of the slope so as to control the stability of the slope as a whole in space.At least the displacement monitoring points should be set at the top and middle of the monitoring profile.The buried location of deformation monitoring station should be selected in the location where the performance of rock and soil mass is poor and the deformation is expected to be large.This kind of slope is small in scale and prone to instability failure,so GNSS method with low cost and flexible installation position should be adopted to carry out displacement monitoring of this kind of slope.The slope safety warning index should adopt the double index of rainfall and slope top displacement,increase the fault tolerance rate,and increase the slope water content index if necessary.In addition to the conventional SMS reminder,alarm devices such as sound and light should be set up at the scene to enhance the alarm effect.Rainfall has direct and major influence on the stability of granite residual soil slope.With the increase of rainfall,slope moisture content and slope displacement increase correspondingly and there is a certain lag phenomenon.The SIGMA/W modules and Slope/E modules in the finite element analysis software Geo-studio were used to conduct seepage analysis and stability analysis of the slope.The geotechnical physical parameters,soil and water characteristic curves,and permeability coefficient were derived from the measured survey data.The size of the grid unit was 1m,and the shape of the grid unit was a combination of square and triangle.Model calibration and debugging selects the maximum rainfall period during the monitoring period to fit,and the error between the displacement of the slope top of the model and the measured value is 5%,which meets the feasibility verification.The rainfall intensity of 70mm was used to define the rainfall boundary of the model,the slope stability coefficient was observed,and the early-warning stability coefficient was selected as 1.1.The forewarning value of slope rainfall is 70mm/d and the displacement of slope top is 5mm/d.This study improves the effectiveness and economy of safety monitoring and early warning of dangerous slope in rural slope construction,and provides theoretical and practical guidance for solving the problem of such slope monitoring and early warning.