Spatial Distribution And Trend Prediction Of Land Subsidence In Hohhot

Land subsidence is a geological phenomenon that changes the surface elevation value in a region due to geological conditions,groundwater exploitation or human activities,and is one of the manifestations of surface deformation.With the expansion of urban area and the increase of population,the use of underground reserve resources such as groundwater is also increasing,and geological disasters such as land subsidence occur in cities.The monitoring of ground subsidence can prevent the damage of urban infrastructure caused by geological disasters caused by subsidence and provide technical support and damage prevention schemes for the maintenance of urban infrastructure.In this paper,SBAS-InSAR method and PS-InSAR method were used to process C-band SAR images of 28 scenes sentry 1 covering Hohhot area from October 2018 to October 2020.The results of accumulated surface deformation variables and average surface deformation rate of Hohhot from 2018 to 2020 are obtained.The results of SBAS-InSAR show that:The surface deformation in the urban area of Hohhot is mainly caused by land subsidence.The shape of the subsidence area is funnel-shaped,and the amount of subsidence decreases from the center of the subsidence funnel to the outside of the subsidence funnel,and the subsidence funnel tends to expand with time.The three settlement centers are located in the Northern Part of Huimin District,Yuquan District and Taigemu Town respectively.The average settlement rate of most areas in the settlement area is 5.32-17.31mm/a during the study period,and the settlement rate of the settlement center is concentrated in 35-50mm/a,and the maximum settlement is 101.26mm during the study period.Located in Taigemu town settlement funnel center.The validation points were extracted from the surface deformation results obtained by SBAS-InSAR method and PSInSAR method.A total of 6 points were extracted.Pearson correlation of settlement time series data of 6 points was calculated,and the correlation coefficients were all greater than 8.5(P<0.01).The availability of InSAR method for ground subsidence monitoring is verified from the side.Use Theil-Sen Median trend analysis+Manna-Kendall test method to calculate the temporal and spatial trend of subsidence in the study area.As a result,and the edge area was slow subsidence,which was in line with the characteristics of the development of urban subsidence in funnel shape.The Hurst index is used to predict the future deformation trend of the study area.The results show that the west of the Settlement funnel of Taigemu Town will continue to settle in the future,and the east will have a rebound uplift in the future,that is,the settlement funnel of Taigemu Town will develop to the west in the future.Most of the settlement funnel in Hui area will have rebound uplift,and the north side of the settlement funnel will continue to settle,that is,the settlement funnel in Hui area will develop northward in the future.There will be rebound uplift on the west side of the settlement funnel in Yuquan area,and continuous change on the east side,that is,the settlement funnel in Yuquan area will develop to the east in the future.After field investigation,it is found that the main ground objects in the settlement of Yuquan district are residential areas,parks,construction sites and small farmland,the main ground objects in the settlement of Hui District are park residential areas,abandoned factories and warehouses,and the main ground objects in the settlement of Taigemu Town are new residential buildings,villages and industrial facilities in 8 years.The response of settlement on the ground can be found on the surface of the settlement area.According to the spatial distribution and composition data of soil texture in Hohhot city,the soil texture in Hohhot city is mainly sandy soil,accounting for 26%?73%.The content of silty sand soil is in the middle,accounting for 15%?45%.The content of clay is the lowest,accounting for 10%?29%,belonging to loose soil.It can be seen that one of the causes of land subsidence in Hohhot is the disturbance of loose soil caused by construction projects and industrial facilities.And land use data and Hohhot,groundwater area data superposition analysis found that the subsidence are mainly concentrated on the construction land,visible construction disturbance is one of the main factor of ground settlement in Hohhot,the subsidence distribution and Hohhot have good corresponding relation of groundwater distribution,the settlement also has close ties with the over-exploited groundwater.