InSAR Monitoring Of 3D Surface Deformation Of Tailings Pond

In this paper,the Niuwangtian Tailings Pond of Sichuan Longmang Mining and Metallurgy Co.,Ltd.(hereinafter referred to as "Niuwangtian Tailings Pond")is selected as the research area.The construction type of tailings pond is valley type,and a large proportion of tailings ponds in China belong to this type.At the same time,this tailings pond belongs to a second-class pond,and its construction type and scale are representative,so it has certain universality as a research area.Tailings pond is an essential engineering facility for mining enterprises in mineral processing work.After a long time of discharge and accumulation,it forms a hazard source of artificial debris flow with high potential energy.Long-term and large-scale human engineering activities inevitably lead to surface deformation of tailings ponds.Therefore,it is necessary to monitor the surface deformation in the tailings pond area.Interferometric Synthetic Aperture Radar(In SAR),as a new geodetic technology,has the advantages of low cost and wide monitoring range,and can realize all-day monitoring.After discussion,it is found that there are few monitoring stations of the Global Navigation Satellite System(GNSS)in the research area,and there is no deformation feature of large gradient,so it is more suitable to use multi-track line-of-sight deformation to obtain a threedimensional deformation field.In this paper,the multi-track Sentinel-1A data is selected,the deformation results are obtained by temporal In SAR technology,the three-dimensional decomposition model of the temporal In SAR is established,and the deformation rate and deformation variables of the tailings pond are indirectly solved by using the least squares iterative method combined with prior conditions,and the deformation law of the study area is analyzed.(1)By performing time series In SAR analysis and processing on Sentinel-1A data,the deformation value along the line of sight(LOS)of radar was obtained.Firstly,the Sentinel-1A data of the three tracks were processed by Persistent Scatterer Interferometric Aperture Radar(PS-In SAR)technology,and a total of 44 points with an average annual deformation rate of 0 in each track were screened.In the small baseline set technique(SBAS-In SAR)processing,the screened points with a deformation rate of 0 are used as the GCP points of each track.(2)According to the experimental results of SBAS-In SAR,the spatiotemporal variation law of the overall and dam surface deformation of the tailings reservoir was studied and analyzed by extracting contour lines and obtaining the values of feature points.The overall surface deformation law of tailings pond is as follows: the deformation mainly occurs in the dry beach area of the accumulation dam and tailings reservoir,the settlement area is scattered in the ascending mode,and the settlement area is more concentrated in the downorbit mode.The time series analysis of the cumulative deformation variables at two-month intervals shows that the settlement area gradually increases over time.The surface deformation law of the tailings reservoir dam body was as follows: the experimental results of ascending and descending were very different,and four settlement areas A,B,C and D were obtained in each track.At the same time,the feature points are selected for the deformation center area,the north and south areas,and the east and west areas of the dam body,and the deformation values of the feature points are extracted to obtain the temporal characteristics of the dam shape variables.(3)Establish a three-dimensional decomposition model for time-series In SAR,and indirectly solve the annual average deformation rates and cumulative deformation variables in the vertical,east-west,and north-south directions using the least squares iteration method combined with prior conditions.By setting a priori condition,the redundant observation equation is constructed and solved using the least square iterative method.The distribution of deformation regions in the solution results is basically the same as the SBAS-In SAR processing results of the descent orbit 62 and 135 satellites.Divide the research time into 6time periods and analyze the temporal variation characteristics.Finally,the threedimensional deformation characteristics of the surface of the tailings dam are analyzed separately.(4)Through trend analysis and coherence analysis,the relationship between the threedimensional shape variables of the tailings dam surface and the changes in precipitation is discussed.It is found that precipitation has higher coherence with east-west deformation variables.From August to December of each year,precipitation has the greatest impact on deformation in the east-west direction;In May and August,precipitation has no effect on the deformation in the east-west direction;From January to April,precipitation has a relatively low impact on east-west deformation.(5)By comparing GNSS measured data with experimental results,it is found that the trend of change is consistent,which proves that the least square iterative method combined with prior conditions is reliable.