Research On Regional Subsidence Monitoring Along High-Speed Railway Using MT-InSAR Technique

The differential InSAR data processing flow is established suited for regional subsidence monitoring of High-Speed Railway (HSR) using multi-temporal InSAR (MT-InSAR) technique. Some key problems of MT-InSAR are solved to monitor the regional land subsidence along the railway in the low coherent regions when the quantity of SAR images is limited. The accuracy and precision of subsidence value from the improved method of MT-InSAR are higher. The results along Jingjin high-speed railway based on C-band ASAR data explain the characteristics and laws of subsidence along HSR in business, which provides the scientific basis for the stability evaluation of HSR. The investigations and conclusions performed in the paper are outlined as follows.(1) The principles, merits and demerits of different methods of baseline parameters estimation are contrasted and discussed. The procedures, which achieve the algorithm of baseline parameters estimation based on five-point method and TCN method, are compiled by C++language. The effectiveness of the procedure and the reliability of the method are certified by the test of experimental data.(2) The traditional method of identifying high coherent targets is improved. A dual-thresholding algorithm is proposed to increase the quantity and improve the quality of coherence target points (CTs) detection. Amplitude dispersion index (amplitude difference dispersion index, alternatively) threshold and whole phase correlation-coefficient threshold are used for the amplitude stability analysis and phase stability analysis, respectively. The testing results show that the probability of reliable CTs can be increased through the improved method when the quantity of SAR images is limited.(3) The combined of deformation evolution model based on PS-InSAR and SB-InSAR is raised, which integrates whole phase correlation-coefficient maximization with singular value decomposition (SVD). The method of calculating the repeating CTs’ phases is studied and the data processing flow is improved. The testing results show that the model can increase the CTs’distribution density, improve the reliability of phase unwrapping and acquire the subsidence values along the railway in low coherent regions more objectively and effectively.(4) ENVISAT ASAR data from Feb.,2007to Jul.,2010in the study area are acquired and applied to monitor the subsidence using the method proposed in the paper. Regional average subsidence velocity varying with time along the Jingjin HSR (Yongle-Tianjin segment) is extracted as well as the average subsidence velocity profile maps. The distribution and magnitude characteristics of subsidence are studied from point, line and surface ways for the first time. The results indicate that the subsidence difference value affects on the railway stability. The regional subsidence classification and assessment along Jingjin HSR, which is significant to maintain the route, are obtained by analyzing the effect on line gradient, construction stability and track regularity. By comparing the features of different monitoring modes, the frame of HSR subsidence monitoring comprehensive system, combining ground surveying and InSAR technique, is put forward.