## 2 Materials and Methods  
### Materials  
The Taibao lead-zinc mining area is in Shilong Town, Guiping City, Guigang City, Guangxi Zhuang Autonomous Region. The terrain of the mining area is gentle, with ground elevations ranging from 39.8 m to 42.5 m. The stratum distribution is relatively uncomplicated. The surface is covered by a quaternary soil layer measuring approximately 1 to 2 m in thickness. Surrounding the mining area are agricultural lands and scattered residential areas. Figure 1 illustrates the geographical location and geomorphic characteristics of the mining area. Within this mining area, the ore body primarily occurs in dolomite formations that constitute the goat's roof and floor. Since 2015, comprehensive mining methods have been employed to extract ore bodies while leaving irregular pillarsfor goaf support. This study focuses on three goaves: goaf No. 2 is located between depths of 42 m and 57 m below the surface, and the pillar height is 7.2 m\(\sim\)8.5 m; goaf No. 3 is distributed at depths ranging from 11 m to 33 m below the surface, and the pillar height is 5.7 m\(\sim\)13.2 m; and goaf No. 6 is found beneath depths of 22 m\(\sim\)35 m below the surface, and the pillar height is 5.1 m\(\sim\)11.6 m. The pertinent information regarding goaf is depicted in Figure 1, The goaf sectional view can be found in Section 3 Results and Analysis. In rder to ensure subsequent mining safety, in September 2017 the Taibao Company commissioned Changsha Mining Research Institute to analyze the goaf stability using theoretical formulas and numerical simulations [51]. The analysis revealed that the No. 3 and No. 6 goaves exhibited the poorest stability conditions: goaf No. 3 had four unstable pillars and an entirely unstable roof, while goaf No. 6 had a stable roof, but nearly half of its pillars were unstable; on the other hand, goaf No. 2 had a generally stable roof with only a few unstable pillars. Based on these findings, the Taibao Company designed two treatment schemes in January 2018, considering the instability of each goaf, conducted further numerical simulation analyses, and ultimately selected a cost-effective and superior treatment scheme as depicted in Figure 1: complete filling of waste rock mortar for goaf No. 3; partial filling and reinforcement of pillars for goaf No. 6; and closure and isolation measures for goaf No. 2, respectively. The implementation of the goaf treatment project was completed by March 2019.  
The PS-InSAR monitoring area is the Taibao mining area, with geographical coordinates of 109\({}^{\circ}\)50\({}^{\prime}\)30\({}^{\prime\prime}\)-109\({}^{\circ}\)51\({}^{\prime}\)5\({}^{\prime\prime}\) east longitude and 23\({}^{\circ}\)16\({}^{\prime}\)00\({}^{\prime\prime}\)-23\({}^{\circ}\)16\({}^{\prime}\)45\({}^{\prime\prime}\) north latitude. The data utilized in this study consisted of Sentinel-1A radar data images with descending VV polarization obtained from the European Space Agency (ESA). The image acquisition timeline was as follows:  
Figure 1: The geographical location of the study area and the characteristics of the goaf.  
1. 21 images prior to goat treatment (June 2015-January 2018);
2. 15 images during goat treatment (January 2018-March 2019);
3. 13 images within the first year after goat treatment (March 2019-March 2020);
4. 13 images within the second year after goat treatment (March 2020-March 2021).  
To ensure monitoring accuracy, precision orbit information for the same period and NASA STRM1_V3 DEM data with a resolution of 30 m were simultaneously employed to rectify terrain residuals. Appendix A Table A1 provides details on the image acquisition timeline.