Monitoring and analysis of surface subsidence after separation grouting based on SBAS-InSARR technology

In order to reveal the long-term evolution characteristics and causes of surface subsidence in the mining area after grouting, the small baseline synthetic aperture radar interferometry technology was used to process the time series of 45 Sentinel-1 A ascending image data from October 2, 2023 to May 12, 2025, and the surface subsidence information in the study area was inverted. The results show that the annual average subsidence rate in the working face area after grouting is mainly distributed in the range of 10-40 mm/a, accounting for more than 84% of the monitoring points, indicating that surface deformation in the area is generally controlled, although obvious subsidence still occurs in some local areas; surface subsidence increases continuously with time while the subsidence rate gradually slows down, exhibiting typical residual subsidence characteristics, which can be well described by the Kelvin creep model. By comparing and analyzing the characteristics of surface subsidence after grouting and non-grouting conditions, it is found that after the implementation of separation grouting, the surface subsidence decays faster, and the final residual subsidence value is relatively small. Further analysis combined with the volume conservation model shows that, it can be seen that the grouting volume is an important factor affecting residual surface subsidence after grouting, areas with larger grouting volumes are more fully filled with separations and fractures, the residual compressible space of the overburden system is smaller, and the corresponding residual surface subsidence is lower than that in areas with smaller grouting volumes. Through comparison and validation with leveling measurement data, the surface subsidence results retrieved by the SBAS-InSARR technique are consistent with the measured subsidence trends, with a root mean square error of 7.4 mm and an average difference of 5.3 mm, indicating that this technique has high reliability for monitoring surface subsidence after the completion of grouting.