Research On The Characteristics Of Land Deformation And Its Relationship With Land Use Types In Lanzhou New District

The monitoring and analysis of land deformation is an important technical direction to master the law of deformation and evaluate structural health.With the proposal of "The Belt and Road" initiative,the construction and sustainable development of cities along the route have received widespread attention.As the first national new district in Northwest China,Lanzhou New District(LZND)is an important node city on Belt and Road Initiative.In recent years,LZND continues to carry out large-scale construction,and great changes have taken place in urban land use.Although some scholars have studied the spatio-temporal characteristics and mechanism of deformation in LZND at the beginning of construction,with the rapid development of the city,there are few new reports on the spatio-temporal characteristics of deformation in LZND,and there is a lack of comprehensive and systematic analysis of deformation mechanism.In addition,most of the existing literatures focus on applying a single time series InSAR(Interferometric Synthetic Aperture Radar)technique to extract the deformation measurement field of the test area,and few scholars combine a variety of time series InSAR techniques with radar data of different orbit modes to obtain the deformation characteristics of the test site.Based on the Sentinel-1A data from March 2017 to October 2019 and March 2017 to March 2020,this paper discusses the deformation characteristics of regional scale in the context of land use transfer and typical areas under the condition of no significant land transfer,and makes a detailed analysis of the mechanism.The main research contents and conclusions include:(1)The DS and PS points of LZND were extracted by SBASInSAR and PSInSAR techniques,and then the average deformation rate and time series deformation variables of LZND from March 2017 to October 2019 were obtained by inversion.The monitoring results obtained by two independent InSAR techniques showed high consistency,which proved the reliability of the experimental results.The deformation results showed that during the study period,most land of LZND was in a stable state and in the main deformation rate range from-10 to 10 mm/a,the deformation of Xicha Town was the most significant.The maximum annual deformation rates obtained by SBASInSAR and PSInSAR techniques were-52.48mm/a and-56.35 mm/a.The areas with significant deformation were the areas where the land use types were significantly transferred,including the construction area and the mountain-cutting area,and the subsidence area was mainly concentrated in the filled area.From the beginning of 2017 to the end of 2019,the scope of land deformation in LZND had been expanding and accelerating.Land creation,building construction,geological conditions and precipitation were the most important factors leading to serious land deformation in the region.(2)Based on 46 scene ascending orbit and 45 scene descending Sentinel-1A radar images,the land deformation rates and time series displacements of Zhongchuan International Airport(ZCIA)from March 27,2017 to March 23,2020 and March 20,2017 to March 28,2020 were obtained by employing SBASInSAR and PSInSAR techniques,and the four monitoring results were evaluated by means of internal and external inspection.At the same time,combined with the mean value of coherence coefficient,histogram statistics,deformation rate variance and its standard deviation,the most ideal deformation result was selected to discuss the deformation characteristics of land without significant transfer.The causes of land deformation of ZCIA were analyzed from human and natural factors.The results showed that four kinds of deformation results were generally consistent,and the variance and standard deviation of monitoring points obtained by using the same time series InSAR technique for different orbit mode data were close,and the deformation results of the same orbit mode data using different time series InSAR technique were slightly different,and the monitoring results of SBASInSAR were more robust than that of PSInSAR.There were scattered subsidence areas in ZCIA,and the deformation in the southwest corner of the airport was the most significant,with a maximum vertical subsidence rate of 11 mm/a.The land deformation of ZCIA was related to human factors such as road network and internal expansion,the stratigraphic boundary was not directly related to the internal deformation of the airport,and the land subsidence area was closely related to lithology.(3)The land use classification results of LZND on March 26,2017 and October 29,2019 gained by using two Gaofen satellite images and random forest algorithm were superimposed with the land deformation rate previously obtained by SBASInSAR technique from March 20,2017 to October 24,2019.The results showed that during the study period,the corresponding subsidence of different land use types was different,bare land and building land were the largest,the maximum subsidence could reach 23 mm and 10 mm respectively,followed by cultivated land and grassland,woodland and water body were the smallest and the subsidence fluctuation was significant.In the process of land transfer,the migration of bare land and building land had the highest correlation with subsidence.