| This paper chooses the area centered on Lanzhou as the research area.This area is a transitional area between the Qinghai-Tibet Plateau and the Loess Plateau.Lanzhou City in its center is a typical river valley basin city,with mountains facing each other in the north and south.The urban area is distributed in east-west strips along the banks of the Yellow River.Due to the unique geological environment such as the type of landforms and stratigraphic structure in the area,as well as the frequent human activities such as land excavation,unreasonable artificial irrigation and mining in recent years,natural disasters such as landslides often occur in the area.Interferometric Synthetic Aperture Radar(InSAR)technology is an emerging remote sensing technology.Because of its high observation accuracy,wide monitoring range and short period,it has been widely used in landslide deformation,mining,seismic monitoring and other fields.The application of SBAS-InSAR technology to monitor landslides,collapses,unstable slopes and other geological hazards has become a research hotspot in the field of geological hazards in recent years.Due to the application requirements of geological disaster monitoring and control in the research area,and the strong support of synthetic aperture radar technology.In this paper,using the Sentinel-1 lifting rail data,based on the SBAS-InSAR technology,the value of the surface deformation rate of the lifting rail in the study area from 2017 to 2020 is obtained.The east-west and vertical deformation rates of the surface displacement are further obtained,and the temporal and spatial characteristics of the surface deformation in the study area are analyzed and classified based on the vertical rate.On this basis,the impact factors of geological disasters were screened.Based on these influencing factors,the deterministic coefficient model and logistic regression model are used to evaluate the susceptibility of regional geological disasters,and the evaluation results of disaster-prone zones are obtained.And use the ground deformation data obtained by SBAS-InSAR technology to correct the evaluation results,and finally get the revised susceptibility zoning results.The main contents are as follows:(1)Obtain the results of time series surface deformation in the east-west and vertical directions in the study area.Using the Sentinel-1 lifting rail data,the SBAS-InSAR technology was used to obtain the LOS surface deformation rate value of the lifting rail in Lanzhou from 2017 to 2020.The quasi-three-dimensional surface deformation field was further constructed to obtain the east-west and vertical deformation rates of the surface displacement The range of the annual average deformation rate of the study area is-94?55mm/a,the range of the annual average deformation rate of the descending orbit is-100?37mm/a,and the range of the annual average vertical deformation rate is-107?45mm/a.The range of the horizontal east-west average annual velocity value is between-103?67mm/a.After comparing the results of lifting orbiting and field investigation and verification,the ground deformation results obtained based on SBAS-InSAR are more reliable.(2)The spatial distribution characteristics in the east-west direction and the vertical space-time distribution characteristics of the study area are analyzed.It is found that the area with large surface deformation in the east-west direction is mainly located in the Xiguoyuan area in the southwest of the study area.It is speculated that the deformation is controlled by the active fault along Guanshan-Xinglongshan.The vertical deformation of most areas in the study area is relatively small,and the deformation value is between-5 and +5mm/a.The deformation rate of the region with larger deformation is mainly concentrated between-25 and-5 mm/a,and its distribution pattern is two patterns of sheet distribution and linear distribution.The flaky deformation areas are mainly distributed in several development areas such as Yanchi,Jiuzhou and Qingbaishi where the study area is excavated.The linear distribution areas with large deformations are mainly in the areas of Diaoling,Xiguoyuan,Huangyu and Bali Town.The water system and roads have linear distribution characteristics.Using time series statistical analysis tools,different types of curve fitting analysis were carried out on the points with vertical deformation less than-15mm/a in the study area.It was found that there are fewer linear deformation points,more nonlinear deformation points,and non-linear deformation points.The quadratic and catastrophic curves are mostly distributed in the construction area of human activities.Among them,the quadratic curves are more and generally distributed,and the catastrophic curves are mainly distributed in the slope position of the engineering construction area.(3)The study area is divided based on the types of surface deformation.The surface deformation is divided into the types of surface deformation dominated by natural factors and those dominated by human factors.The natural factors include rainfall and soil water erosion.The surface deformation caused by the resurrection of new landslides,unstable slopes,and old landslides is found to have a good correspondence with rainfall.It is believed that rainfall is the cause of new landslides,unstable slopes,and The main reason for the resurrection of the old landslide.The surface deformation caused by soil hydraulic erosion is mainly distributed along the Wanchuan River.Affected by the accumulation of soil erosion,the surface on both sides of the river presents a seasonal erosion accumulation process.Human factors mainly include three types: digging for land,mining in mining areas,and road construction in mountainous areas.The surface deformation caused by mountain excavation shows a funnel shape with an increase in the deformation from the surrounding to the center.Compared with the adjacent building area,the deformation of the slope is larger and mostly abrupt,reflecting the slope of the new development area.The risk of regional geological disasters is greater.The surface deformation caused by mining in the mining area also presents a funnel shape that increases from the surrounding to the center.The deformation area is horizontally deformed in the east-west direction into a symmetrical distribution,which conforms to the distribution law of surface deformation caused by underground mining in the mining area.The surface deformation caused by road construction in mountainous areas presents a cyclical trend of "sinking-stable",and the sinking period is mainly the rainy season.(4)By analyzing the relationship between impact factors and disaster events,the impact factors of disaster events were screened.Based on these impact factors,the deterministic coefficient model and logistic regression model were used to evaluate the susceptibility of regional geological disasters,and the results of disaster-prone zoning were obtained.It finally shows that: 1)The degree of contribution of each influencing factor to the disaster in the area is in order of slope,distance from fault,aspect,distance from road,elevation,vegetation coverage,lithology,land use type,and distance to water system.At a slope of 9?25°,within2 kilometers from the fault,the slope direction is northeast and southwest,within 1.6kilometers from the road,the elevation is between 1400 and 1700 meters,and the NDVI is between-0.18 and-0.15.,The stratum is Quaternary loess,the land use type is bare land,and the distribution area within 3.6 kilometers of the water system is the most prone to geological disasters.2)The disasters in the area are divided into very low-prone areas,low-prone areas,medium-prone areas,high-prone areas and extremely high-prone areas according to their proneness.The high-prone and extremely high-prone areas of geological disasters in the discovery area are mainly distributed on the slopes of the north and south mountains,railway roads,river valleys,and major new development areas such as Yanchi,Kyushu,Qingbaishi,Heping and Dingyuan.The overall distribution pattern of susceptibility is highly consistent with the spatial distribution characteristics of surface deformation obtained by SBAS-InSAR.(5)The accurate surface deformation rate value obtained by SBAS-InSAR is used.The evaluation results of the geological hazard susceptibility based on the model's static influencing factors are revised,and the revised regional geohazard susceptibility evaluation results are obtained.Compared with the evaluation results based on the model's static influencing factors,The revised evaluation results show that the area of extremely low-prone areas increased by 43.13 km 2,the area of extremely high-prone areas increased by 34.50 km 2,the area of low-prone areas decreased by 46.20 km2,the area of medium-prone areas decreased by 15.93 km2,and the area of high-prone areas decreased by 15.50 km 2.Combining the two methods can achieve complementary advantages and obtain more accurate susceptibility evaluation results. |
PDF Full Text Request