Early Identification And Risk Assessment Of Landslide Induced By Mined Out Area Breakdown In Hejiadi,Panzhou City,Guizhou Province

Guizhou is a well-known province of mineral resources in my country,but due to the backward mining technology and lack of mine safety awareness,a large area of mining subsidence has been formed,which has resulted in a large number of mine geological disasters.By summarizing the experience and lessons of the three goaf landslides in Pusa Village,Dazhai landslide,and Fuquan Daoping Town landslide,it is found that the goaf landslide has the characteristics of suddenness,concealment,large-scale and serious damage,and conventional Early identification methods and risk assessment methods are difficult to accurately determine and evaluate potential landslides induced by goaf collapse.This paper takes Hejiadi mined-out subsidence area as the research area,and focuses on early identification and risk assessment of landslides induced by mined-out subsidence.It uses multi-temporal optical satellite remote sensing dynamic monitoring,radar satellite time series In SAR deformation analysis,and UAV aerial measurement,Detailed on-site investigations of various methods to analyze and monitor the deformation of the study area,use Geostudio,Flac3 D,PFC3D numerical simulation software to carry out risk assessment of landslide hidden danger points.The following main understandings and conclusions have been formed.(1)By using the Sentinel-1A satellite down-orbit image data from October 2014 to December 2019 for differential interference,the deformation area of the goaf of Hejiadi was identified,and then the high-precision and three-dimensional images of the drone Model remote sensing interpretation and ground investigation and verification,the deformation is divided into left and right sides.There is a landslide H2 on the upper edge of the deformation zone,and a large number of collapses on the lower edge.At the same time,a large number of tensile cracks develop on the slope,and the deformation zone is on the right.Chair-shaped cracks developed on the upper edge,large-scale landslide H1 occurred on the lower edge,and various types of cracks developed on the slope.According to the deformation survey,it is judged that the left side of the deformation area is the goaf subsidence and the right side of the deformation area is the hidden danger point of the landslide.According to the topography and the damage of the slope,it is determined that the upper edge of the ring chair-shaped crack is the landslide trailing edge,and the left and right sides of the valley are The left and right boundaries of the landslide,the cutting exit is the front landslide H1.(2)The three phases of drone high-precision images in November 2018,March2019,and July 2019 were used to monitor and analyze the hidden danger points of the landslide,and it was found that the vegetation of the landslide H1 March 2019 showed a relatively obvious bright white crack texture.,In July 2019,the crack collapsed at this place,and the cracks in the brown loess can be clearly seen.Compared with March,the back edge ring chair-shaped cracks in July have obvious tension and widening,which indicates that the hidden danger point of the landslide is further aggravating the deformation.(3)Select the mined-out deformation area for 5 years,that is,from October 28,2014 to October 26,2019.Sentinel-1A ascending orbit image data is used for In SAR time series deformation analysis,and ten monitoring points are selected.The results show that since 2014 From October 28,2010 to December 25,2019,the 10 monitoring points showed a trend of continuous settlement and deformation.Among them,P5 and P9 points have the largest deformation,P5 point LOS direction deformation can reach 160 mm,P9 point deformation can reach 157 mm,P3,P8 points have a tendency to rise first and then settle,which may be caused by vegetation.The other deformation points have a fair value.In addition,it can be seen from the deformation curve that since June 2019,the deformation rate of 10 In SAR monitoring points has shown a decreasing trend.According to on-site investigation and analysis,the decreasing trend is caused by backfilling in the mining area.(4)Use Geostudio and FLAC3 D numerical simulation software to simulate the deformation and failure mode of landslide hidden danger points under saturated conditions,simulate the most dangerous slip surface of landslide in two-dimensional and three-dimensional forms,and evaluate the stability of landslide hidden danger points.,Get its safety and stability coefficient.Use PFC3 D numerical simulation software to simulate the instability stage of landslide hidden danger points,obtain the instability movement process of landslide hidden danger points,and finally obtain the threat range of landslide hidden danger points,and verify the accuracy of the simulation results by fitting the landslide movement distance empirical formula for risk assessment.According to the failure mode of landslide deformation and failure,corresponding control measures are formulated.