| Intense tectonic activity led to rapid uplift of the surface,and also caused serious damage to the integrity of the rock mass in the area.With the intensification of extreme climate events and the comprehensive impact of human activities,Zhouqu has become one of the most serious areas of geological disasters such as landslide and debris flow in China.In recent years,major disasters such as Yahuokou landslide and Guoye landslide have occurred successively in Zhouqu area.Landslides not only endanger the safety of people's lives and property,but also seriously restrict the local economic and social development in Zhouqu.Carrying out the whole-process monitoring and identification and stability evaluation of landslides in fault zones can provide important scientific references for landslide warning and disaster assessment in similar geological background and geomorphological environments.Synthetic Aperture Radar Interferometry(In SAR)technology has high precision and is not affected by weather,and has been widely used in landslide deformation monitoring and other fields.Coregistration of optically sensed images and correlation(COSI-COrr)technology extracts the horizontal displacement of large landslide through phase correlation,and it can solve the problem of incoherence when In SAR technology monitors large displacement.Combined with In SAR technology,it can monitor the whole process of landslide deformation.Therefore,this paper takes the Yahuokou landslide as the research object,uses the In SAR technology to study its deformation history,and uses the COSI-COrr technology to reproduce its sliding process.And summarize the deformation characteristics of the landslide to determine its failure mode.Combined with field investigation and engineering geological data,the stability evaluation is carried out by means of numerical simulation.On the basis of remote sensing monitoring and numerical simulation,scientific and effective suggestions are put forward for the engineering management of landslides.The research results have reference significance for the investigation,monitoring and early warning of other landslides in the fault zones in the region,and can further improve the understanding of the evolution of landslides in the fault zone in Zhouqu region,and play an active role in disaster prevention and mitigation in the region.This study has achieved the following four main research results:(1)The early spatiotemporal deformation characteristics of Yahuokou landslide were obtained by SBAS-In SAR technology.The results show that the landslide was in the stable creep stage from October 2014 to April 2017,the landslide was in the fluctuating creep stage from April to September 2017 and April to September 2018,and the landslide was in the accelerated instability stage after July 2019.And through field investigation,the reliability of the deformation results of Yahuokou landslide was verified.Based on field investigation and hydrological analysis,it is determined that the main factors causing the spatial difference of landslide deformation are lithology,topography and precipitation.It is found that the reason for the large fluctuation of the deformation rate of the landslide from April to September is the concentration of regional precipitation in this time period.(2)Using the COSI-COrr technique,the sliding characteristics of the Yahuokou landslide were obtained.The two-dimensional displacement field of the landslide revived and slipped in July 2019 was extracted,and the results showed that the landslide started from the upper part and slipped to the Minjiang River on August 15,with the sliding direction concentrated between 45-135°.It was determined that the landslide was in an accelerating slip state before August 3,2019,and in a decelerating slip state after August 10,2019;and the accuracy of the COSI-COrr results was verified using GNSS data.(3)Combining the results of SBAS-In SAR and COSI-COrr,the failure mode of the landslide in this fault zone was determined.The overall sliding mode of the Yahuokou landslide is a progressive failure mode of pushing and sliding from the back to the front.The middle and lower parts of the landslide are pushed and squeezed by the upper part to slide.Combined with remote sensing observation and field investigation,the upper part of the landslide is a small traction landslide.Under the action of precipitation and other factors,the upper part of the landslide first revives,and then conducts downward step by step,forming positive feedback on the landslide body,and finally reviving the entire landslide.(4)Based on FLACSLOPE,the strength reduction method is used to analyze the stability of the Yahuokou landslide,and the safety factor of the landslide at failure is0.91.The simulation results under rainstorm and earthquake conditions show that rainstorm can significantly reduce the stability of the landslide,and the earthquake can accelerate landslide instability.By setting up anti-sliding piles,it is found that the antisliding piles can significantly improve the stability of the landslide in the fault zone. |
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