Application of D-InSAR in monitoring the impacts of shaft grouting on surface and building deformations

Objective In coal mining engineering, damaged well walls pose a threat to the safety of production facilities and mines. Comprehensively monitoring the impacts of shaft grouting on the deformations of mine surface plants and surface buildings is critical for ensuring the safe production of mines. Methods This study investigated a coal mine in the mining area within northern Anhui Province. Using the 15 scenes of Sentinel-1A image data covering the coal mine and the differential interferometric synthetic aperture radar (D-InSAR) technology, this study comprehensively monitored the subsidence of mine surface plants and surface buildings before and after shaft grouting, obtaining information on the dynamic deformations of surface and buildings. Accordingly, this study analyzed the impacts of grouting on the surface and buildings. Results and Conclusions The results indicate that compared to leveling measurements, the D-InSAR-based land subsidence monitoring yielded an average error of 1.70 mm and a maximum error of 2.70 mm. These results demonstrate the reliable accuracy of D-InSAR in monitoring minor land subsidence, thus meeting the requirements for land subsidence monitoring in mine surface plants. Before shaft grouting, the surface and buildings were in a continuous subsidence state, with a maximum subsidence of 21.12 mm recorded during the monitoring period. After shaft grouting, their subsidence slowed down and then gradually stabilized. The analysis of shaft strain monitoring results and changes in land subsidence reveals that the grouting engineering exhibited remarkable remediation effects by forming an impermeable curtain around the shaft. The monitoring results show that the surface underwent four deformation stages, i.e., continuous subsidence, slight uplift, minor subsidence, and stabilization, before and after grouting. Specifically, initial grouting demonstrated a pronounced effect in curbing land subsidence. As the grouting progressed, the surface was slightly uplifted, followed by minor subsidence until stabilization after grouting completion. During the monitoring period, the deformations of major buildings remained within the safety threshold according to the Class I damage criterion specified in the Regulations for Coal Pillar Retention and Coal Mining thereunder for Buildings, Water bodies, Railways, and Main Shafts (2017 Edition). Therefore, grouting engineering can ensure the safety of buildings by further mitigating their deformations.