Study On The Hydrological Response And Stability Of The Rainfall-type Accumulation Landslide Based On The Field Monitoring

Qinba Mountain Area in Shanxi Province is one of the geological hazard-prone areas in China,the landslide disaster induced by rainfall has seriously affected the normal production activities of the people and hindered the economic development of the area for a long time.Therefore,the paper relies on the Institute of Exploration Technology of the Chinese Academy of Geological Science.Based on a variety of technical means such as field surveying,geological mapping,geophysical exploration,exploration and mapping,as well as a large number of laboratory tests,taking the Shai Zhiliang landslide in Qinba Mountain of Shaanxi Province as a typical slope,and based on the landslide multi-factor monitoring data,the hydrological response law and seepage mechanism of the slope soil under rainfall conditions are analyzed,and the deformation mechanism and mode of the slope are revealed.At the same time,Geostudio software is used to simulate and verify the above rule.The main results are as follows:1.Through field comprehensive exploration and indoor physical and mechanical tests,the reasonable monitoring slope body is synthetically evaluated and selected,and the soil properties and stratification characteristics of the slope are discussed.At the same time,a omni-directional,high-precision,automated multi-factor integrated comprehensive real-time monitoring and analysis system combining meteorological hydrology and GPS/BDS surface deformation displacement is established.2.The hydrological response and seepage mechanism of the slope are analyzed in detail by using meteorological and hydrological real-time monitoring system.(1)Distribution regularity of rainfall and temperature and humidity: Rainfall is mainly concentrated in May to September,especially in June to July.Rainfall frequency is the most concentrated and intensity is the greatest,while in October to April,rainfall frequency is relatively low and intensity is relatively small.Temperature fluctuates and rises from April to July,and the temperature is maintained at two months in July and August.Starting in September,the temperature fluctuates and decreases in the region.The overall humidity in the area is high,air humidity is positively correlated with rainfall and negatively correlated with temperature.(2)Distribution characteristics of volumetric water content: under rainfall conditions,rainfall intensity and duration are directly proportional to the depth of the affected soil layer;the maximum volumetric water content formed in soil layer is positively related to the depth of soil layer and rainfall intensity;At the same time,it is confirmed that the existence of cracks will affect the saturated and unsaturated zone of the monitoring area,which explains the mechanism of the superficial landslide in the Qinba Mountain area,that is,the slip zone is usually located at the saturated and unsaturated layer interface of the soil;(3)Response speed analysis of volumetric water content: Under normal conditions,the response speed of soil to rainwater is inversely proportional to its depth,and when there is a dominant seepage surface in the soil layer,the response speed of volumetric water content in the deep layer is faster than that in the shallow layer.(4)Transient saturation zone analysis: the stability of the upper slope region is higher than that of the lower slope region.The main reason is that the transient saturation zone occurs in the surface soil of the lower slope under the condition of continuous high intensity rainfall,while the surface soil of the upper slope region is loose and the cracks are more,and evaporation and drainage are relatively easy,so the transient saturation zone will not appear in the surface soil of the upper slope region.(5)The relationship between matrix suction and volume water content: the smaller the volume water content is,the greater the matrix suction is.The maximum matrix suction often exists in the surface soil,and the change of matrix suction tends to synchronize with the occurrence of rainfall events.While for the deep saturated soil,pore water pressure lags behind the occurrence of the first continuous rainfall with a lag time of about one or two days,and the continuous high-intensity rainfall will cause a sudden change in pore pressure;(6)Analysis of groundwater level variation law: with the occurrence of rainfall,the groundwater in the upper slope area has increased,while the groundwater level elevation in the lower slope area has remained basically unchanged,but the overall water level of the slope body is deeper and has no effect on the stability of the slope.;3.GPS/BDS real-time monitoring system of surface deformation and displacement is used,and the three-dimensional deformation and displacement of landslide is analyzed in detail,and the deformation mechanism and mode of landslide are summarized.(1)In the elevation direction,the deformation of the front edge,middle and lower parts of the slope is larger than that of other parts,which is a typical deformation feature.Under the condition of dry-wet circulation,the slope stability is characterized by intermittent slow sliding,in which the increase of matrix suction is beneficial to the overall stability of the slope,while the emergence of transient saturation zone can accelerate the deformation of the slope.(2)In the horizontal direction,the deformation of each part of the slope is small,so it can be judged that the slope has no trend of sliding in the horizontal direction.4.Based on the calculation model and boundary conditions constructed by fully restoring the engineering geological conditions and hydrometeorological conditions of the slope,Geostudio software is used to simulate and analyze the seepage field,the variation of pore pressure which in different depths of soil layers in different rainfall durations and slope stability under rainfall conditions.The results obtained verify the reliability of the relevant conclusions of Chapters four and five.