Study On The Inspection Technology Of Highway Slopes Based On InSAR

Due to the mountainous and hilly landforms in Chongqing,there are many artificial slopes formed in the process of expressway construction.At present,the highway company will take manual inspection every year to make a qualitative evaluation of the current stability of the slope,which requires a lot of manpower and material resources,and lacks quantitative slope rating standards.In this paper,the Yufu Expressway in Chongqing was taken as the research area.Based on the slope deformation data obtained by InSAR technology,the quantitative highway slope inspection technology was studied.The main research contents and results are as follows:(1)According to the topographic and geomorphic characteristics of the study area,the spaceborne SAR image data of ALOS-2 with 7 scenes of L-band was selected as the data source of this experiment.Through the analysis of the backscattering coefficient of the experimental SAR data,it is proved that the L-band radar sensor has a better imaging effect on the study area with large relief and dense vegetation.According to the influence factors of the backscattering coefficient in the study area,the backscattering coefficient of the SAR data in the study area can be further improved by adjusting the incidence Angle of the radar,so as to improve the relative coherence of the interference.(2)The selected 7-scene SAR data were divided into six groups for D-InSAR processing,and the interference relative with high coherence coefficient was obtained,which indicated that the deformation data obtained in the study area was highly reliable.Through the comparative analysis of the six interference relative coherence coefficients,it is found that the time baseline between the data is the main factor affecting the coherence,and the smaller the time baseline,the higher the coherence.(3)According to the development process of slope instability,a quantitative classification standard of slope disease degree was established.The annual deformation value of slope in the study area was obtained by using InSAR technology,and the slope conditions in the study area in 2016,2017,2019 and 2020 were inspected by using the quantitative classification method.By comparing the inspection results based on InSAR with the corresponding manual inspection results,the following conclusions are obtained:1)The matching degree of the two methods ranged from 36.1% to 64.3%.When the second group of test data was used to carry out the slope inspection in 2017 in the study area,the matching degree was 36.1%,and the low matching degree was due to the large deformation value obtained from the second group of data.When the fourth group of test data was used for the slope inspection in 2019 in the study area,the obtained deformation value was closest to the actual deformation value of the slope in 2018 in the study area,and the matching degree reached 64.3%.The error of the results mainly comes from: the error caused by the measurement accuracy of InSAR technology,the error caused by the classification standard,and the error caused by the limitation of InSAR technology.2)The matching degree of the inspection results for the less stable slope is 48.6%-79.1%,which indicates that the slope inspection method based on InSAR has a certain recognition rate for the slope with changes in stability,and can achieve a certain inspection purpose.3)Through the inspection results of the study area for four years,it is found that the accuracy of the inspection results is high for the slope whose coherence coefficient is greater than 0.4.(4)Through this study,it can be known that the limitation of highway slope inspection technology based on InSAR is that it cannot identify dangerous rock,aging of protective structure and other slope diseases.However,InSAR has the advantage of large-scale allweather deformation monitoring,which can make the inspection of deformation related diseases of highway slope more efficient.The slope quantitative classification method based on InSAR deformation data also makes up for the deficiency of the existing highway slope inspection due to the lack of quantitative classification.