Monitoring And Modeling Of InSAR Mining Area Subsidence

Since the rise of InSAR technology in the early 1990 s,InSAR has played an important role in many fields.Compared with traditional measurement technologies,InSAR has unique advantages in monitoring ground subsidence due to underground mining.With the rapid development of InSAR technology,the difficulties faced by InSAR technology have also surfaced.For example: signal recovery,image registration,phase unwrapping,etc.Among them,phase unwrapping is an important step to restore the subsidence phase.It has been at the forefront of research in recent years.However,when the subsidence gradient of the subsidence trough exceeds the maximum measurable gradient of InSAR technology,the interference fringes will be too dense,causing phase aliasing.As the result,it is impossible to obtain the correct phase unwrapping result.Compared with the traditional direct unwrapping phase,this paper proposes a new unwrapping strategy to solve the problem that DInSAR cannot correctly unwrap the large gradient subsidence in the mining area.The main objectives of this study are two folded.First is to develop an unwrapping strategy to deal with the unwrapping problem caused by large subsidence gradient at the mine subsidence trough.The main idea of this strategy is to estimate most of the subsidence phase by multiple model inversions based on iterative approach.Then,combine the inversion phase from the multiple models with the final residual unwrapping phase.Another objective of this study is to evaluate the feasibility of the three common deformation models,i.e.Mogi,PIM and Okada,in solving the phase unwrapping problem.Their advantages and disadvantages are outlined.Both simulated data and real data are used for this experiment.The result shows that the problem of large subsidence gradient in DInSAR results can be solved by multiple model inversions.Overall,amongst the three models,the accuracy of the results is highest with the use of Okada model.In this paper,the main research work of large gradient subsidence in mining area is as follows:(1)Through the inversion of the unwrapping phase,the phase inverted by multiple models and the original interferogram are conjugate multiplied to eliminate the subsidence phase,and then the model phase and the final unwrapping phase are added to obtain the final true phase.(2)In this paper,the feasibility of Mogi,Okada and PIM models to solve the problem of large gradient subsidence in mining area and the advantages and disadvantages of different models are verified by simulation data and real data.The results show that multiple model inversions can solve the problem of large subsidence gradients in InSAR mining areas that cannot be unwrapped correctly,and the Okada model is more stable among the three models.(3)Using the model iteration method proposed in this paper,the DInSAR results of Kouzi East Mine in Fuyang,Panyi Coal Mine,Pansan Coal Mine,Guqiao Coal Mine in Huainan,and West Cliff Coal Mine in Australia are recovered.(4)Using the method proposed in this paper,the time series subsidence trough information of the West Cliff mine area in Australia is recovered.and the time series analysis is carried out.The results are quite consistent with the GPS survey data.The root mean square error is 19 mm,and the absolute average error is 13 mm.The result meets the accuracy requirements of the subsidence monitoring in the mining area.(5)Using the method proposed in this paper,the time series subsidence trough information of Panyi Mine in Huainan,Anhui Province,China was recovered,and the time series analysis was performed.