Study On Landslide Stability Based On GPS Monitoring Technology

Huanglianshu landslide is located in Fengjie County, the Three Gorges Reservoir area of the Yangtze River. The landslide volume is 754 x 104m3 and the type belongs to the large-scale soil landslide. It is a direct threat to 53 households 255 people life and property safety and the Yangtze River waterway safety. Huanglianshu landslide began to be professional monitoring from July 2003, accumulated nearly ten years of valuable GPS landslide displacement monitoring data. From the monitoring results, the fluctuation of the impoundment and the volatility of the reservoir water level of the Three Gorges Reservoir has greatly affected the stability of the Huanglianshu landslide, resulting in the transition from the steady state to the critical state or the creep state, Even appear many times to slide.Talking Huanglian landslide as the research background, using the theory of GPS landslide displacement monitoring as the technical support, combined with landslide topography, stratigraphic assemblage and landslide composition characteristics, based on the full collection of existing data, the use of the engineering geology, surveying and mapping science, statistics, and so on theory and methods, based on the monitoring data of the existing research, This paper focuses on the formation and evolution of landslide, the factors that affect the stability of landslide and the formation mechanism of landslide. Due to the principle of two-dimensional rigid-body limit equilibrium method, the stability of landslide is evaluated on the basis of existing monitoring data., To optimize the monitoring program, the establishment of monitoring and early warning, Huanglian landslide for the status quo gives comprehensive measures and recommendations. The main achievements of the paper are:(1) The landslide plane shape is typical ring-shaped features, length of about 600 m,width of 550?700m,front and rear edge height difference 315m,sliding body thickness of 7.2?35.4 m,landslide volume 754 × 104m3, for large landslides.(2) The sliding body is a Quaternary residual slope (Q4el+dl), landslide accumulation layer (Q4del), lithology is silty clay, crushed stone mixed composition; slip belt exists in the geotechnical interface, lithology (J1-2z). The lithology is mainly composed of silty mudstone,sandstone and siltstone. The lithosphere is a kind of silty mudstone, sandstone and siltstone.The Huanglianshu landslide is a soil landslide that slides along the interface between the bedrock and the Quaternary loose bulk.(3) Combined with the macroscopic investigation and monitoring data analysis,Huanglianshu landslide can be divided into strong and weak deformation area, the main deformation area is located on the west side of the landslide body, and has the characteristics of gradually decreasing the deformation rate from west to east and from top to bottom. In the strong deformation zone, the maximum horizontal deformation rate of FJ004 monitoring point is up to 73.87mm/d, and the macroscopic deformation is especially obvious. The horizontal deformation rate of FJ009 is 8.01mm/d. In the weakly deformed area, the deformation rate of the whole landslide is less than 1mm/d, local 1-5 mm/d, and there is no sign of surface deformation.(4) The monitoring data shows that the change of the water level of the Three Gorges reservoir area and the increase of the rainfall are the most important limiting factors for the landslide deformation. After the reservoir is impounded, the groundwater level in the slippery body is lifted, and the slippery soil and the slippery soil are weakened in the reservoir water level for a long time, and the water level of the reservoir is large and the change is frequent,and a large water level difference is formed between the two , The sliding water pressure inside the body suddenly changed, especially in the reservoir water level continues to decline in the case, the sliding body stress repeatedly adjusted to promote the deformation and damage to the slope, causing landslides. The landslide deformation and displacement curve shows that the sliding deformation of the landslide decreases with the decrease of the reservoir water level, but the deformation of the landslide is weakened until the stability is stable. The relationship between the displacement of the landslide and the rainfall during the sliding period shows that the displacement of the landslide is positively correlated with the rainfall, and the sliding displacement will increase with the increase of the rainfall:?Based on the characteristics of landslide deformation and landslide factors, the formation mechanism of Huanglianshu landslide is analyzed from the angle of landslide evolution. Firstly, the Huanglianshu landslide is a kind of ancient landslide formed by the erosion and tectonic uplift of the bedrock. Because of the impoundment of the Three Gorges reservoir area, a new eroded sliding surface is formed and instability sliding under the influence of rainstorm, belonging to the creep - pull-type landslide.?Based on the principle of two-dimensional rigid body limit equilibrium method, the stability of landslide shows that the overall Huanglianshu landslide is in stable state at present. Wherein the sliding surface in nature and working conditions in each reservoir level,stability factor greater than the safety factor, in a steady state; the sliding surface and the stationary surface decline and the water level drop in a substantially stable condition - less stable state. The deformation of Huanglianshu landslide is slowing down in the short term,but the influence factors of landslide stability are especially complicated in the case of rainstorm and the change of water level in the Three Gorges reservoir area, and it is likely to slip again and even cause the slip of the old slip surface. In the case of Huanglianshu landslide has been included in the follow-up project management planning, the existing monitoring has been optimized to establish professional monitoring and early warning classification, so as to ensure the safety of life and property.?Based on the stability calculation of Huanglian landslide and the geological characteristics of landslide, the paper puts forward the measures of landslide control of"support + backfill gully + front edge slope + perfect drainage system".