Research On The Development Characteristics And Disaster Simulation Of Shawandagou Landslide-type Debris Flow Based On Time Series InSA

Influenced by the uplift of the Qinghai-Tibet Plateau,the geological conditions in the mountainous areas of southwest China are extremely complex,with frequent tectonic activities and frequent occurrence of various natural disasters such as landslides,mudflows and avalanches,of which landslide-type mudflows occupy a considerable amount.Landslide debris flow is provided by the destabilization and disintegration of landslides,and the transport,impact and destruction capabilities during the movement are extremely strong,which seriously threaten the safety of roads,houses and other infrastructure as well as people’s lives and properties.Therefore,the research on the deformation mechanism and disaster generation mode of landslide-type debris flow is an important prerequisite to ensure the safe development of mountainous areas and the smooth implementation of disaster prevention and mitigation research.Interferometric Synthetic Aperture Radar(In SAR)technology,as an emerging means of surface deformation monitoring,breaks through the limitations of traditional monitoring technology and has the advantages of all-day,all-weather,wide monitoring range and high spatial resolution,which can play an important role in landslide-type debris flow deformation monitoring.Therefore,in this paper,we use the Shawan Dagou to monitor the landslides.Therefore,this paper takes Shawan Dagou watershed as the study area and conducts a study on the surface deformation monitoring and landslidetype debris flow development characteristics based on time-series In SAR technology,and analyzes the degree and extent of landslide-type debris flow hazard under different rainfall frequencies.The main results obtained in this paper are as follows:(1)Based on the Small Baseline Subset In SAR(SBAS-In SAR)technique,the surface deformation monitoring of the Shawan Dagou watershed was carried out using the lift-track Sentinel-1A data covering the study area,and the surface deformation results of the study area from 2020 to 2022 were obtained,and the surface deformation characteristics of the Shawan Dagou were analyzed.The surface deformation in the study area from 2020 to 2022 was obtained and analyzed.The monitoring results show that the Nuole landslide in the upstream source area has the most obvious deformation,while other areas in the Shawan Dagou are generally stable.Further study of the Nuole landslide reveals that the difference in the geometry of the lifting and lowering satellite observation causes the leading edge of the slope to move away from the satellite direction with a maximum subsidence rate of-190 mm/a in the lowering monitoring results,and to move closer to the satellite direction with a maximum uplift rate of 93mm/a in the raising monitoring results.(2)For the most seriously deformed Nuole landslide in Shawan Dagou basin,the two-dimensional deformation information of the slope body along the slope direction and vertical direction is solved by combining the LOS deformation results of the lift rail,and the two-dimensional deformation characteristics of the landslide body are analyzed in depth.The results show that the deformation of the back edge of the slope is stronger than that of the front edge in the vertical direction,and the deformation rate ranges from-60mm/a to-89mm/a.The deformation of the front edge of the slope is stronger than that of the back edge in the slope direction,and the deformation rate ranges from 177mm/a to 324mm/a.On this basis,the spatial deformation law of the landslide body is further studied by combining the information of the rock stratum of Nuole landslide,and the results show that the back edge of the slope body is mainly the vertical downward displacement and the displacement along the slope direction together,while the front edge of the slope body is mainly the displacement along the slope direction.By comparing the rainfall data with the two-dimensional time-series deformation curve of the slope body,the relationship between the deformation of the slope body and rainfall is further investigated.The results show that the slope body undergoes seasonal movement with rainfall,and the strong rainfall in the rainy season accelerates the displacement of the slope body,while the gradual infiltration of rainwater over time causes a two-month lag in the acceleration of the deformation of the slope body in the vertical direction compared with that in the slope direction.(3)Based on numerical simulation,the movement process and hazard degree of landslide-type debris flow under different rainfall frequencies were studied.The results show that the mudflows under 20-year,50-year and 100-year rainfall frequencies will cause different degrees of inundation to the downstream houses and farmlands,and the degree of hazard increases with the increase of rainfall.The analysis of debris flow movement characteristics further reveals that the high solids source volume and high fluid concentration of landslide-type debris flow lead to the final accumulation of debris flow mostly in the gully,and the range of accumulation area decreases,but the average mud depth of the gully and accumulation area increases,which increases the hazard degree of debris flow and will continue to affect the surrounding area under the subsequent rainfall.This study confirms the high feasibility of the time-series In SAR technology in the exploration of landslide-type debris flow,and the results can provide reliable scientific support for the engineering management,monitoring and early warning,and disaster prevention and mitigation of landslide-type debris flow disasters,and also provide a reference for the research of such landslide-type debris flow.