## 4 Discussion  
PS-InSAR technology was employed in this study to monitor the subsidence of the underground goaf in the Taibao lead-zinc mine, enabling acquisition of surface subsidence data for the mining area. Based on the findings, comprehensive analysis and discussion were conducted regarding the mechanism, laws, and influencing factors associated with goat-induced surface subsidence.  
From the perspective of spatio-temporal distribution characteristics, surface subsidence exhibits a gradual accumulation with the continuous expansion of goaf. Initially, the subsidence rate is rapid, and it subsequently stabilizes over time. This observation aligns with geomechanics theory and corroborates existing research findings, further validating the accuracy and reliability of monitoring methods [60; 61; 62; 63]. An in-depth analysis of surface subsidence mechanisms reveals that factors such as goaf span, stability of roof and pillars, and mining depth significantly influence subsidence patterns. Notably, the stable state of the roof and pillars in goaf exerts a particularly prominent impact on subsidence; variations in their stability lead to discernible differences in both distribution and rate of surface subsidence. Additionally, stope span and mining depth play crucial roles in surface subsidence dynamics; larger mining spans exacerbate surface subsidence when unstable pillars are present.  
According to the surface subsidence law of different goat treatment methods, the subsidence of an unstable pillar surface plays a decisive role in a closed goat. Achieving secondary stress balance in the rock mass solely through pillar support requires more time. In a partially filled goat, most pillars are stable while the filling body reinforces the unstable ones, resulting in obvious deceleration of surface subsidence. However, the stable pillars remain unreinforced and thus experience slower subsidence. As the filling body gradually compacts, surface subsidence gradually becomes gentler. For the goat with full-filling treatment, a significant portion of the roof and pillars exhibit instability. Before compacting the filling material, considerable settlement was observed on the surface of these unstable pillars and roof structures. However, once the filling material is compacted, controlled subsidence occurs on the surface and gradually ceases.  
Although this study has yielded certain results, there are still some limitations. By conducting a comparative analysis with previous studies, we have substantiated the universality and severity of the surface subsidence phenomenon and comprehensively examined various influencing factors to further elucidate its intricate mechanism. However, based on the monitoring data from the second year after completion of treatment, it is evident that certain areas exhibit slight elevation, which deviates from the anticipated movement pattern of overlying rock layers in surface subsidence. In reality, minor settlement exists, indicating that human activities significantly impact the overlying rock layers and surface movements. Therefore, in future endeavors, we will persistently enhance our monitoring efforts to improve data quality and furnish a scientific foundation for more effective prevention and mitigation strategies against surface subsidence problems.