A method for predicting the rock strata subsidence boundary at deep-buried mining areas with thin bedrock and Thick soil layer

Surface subsidence resulting from underground coal mining is a significant geological hazard. Researching the features of surface subsidence and rock strata subsidence boundaries (RSSB) is crucial for protecting surface structures. Traditional methods, such as the angle of draw, can predict the RSSB reasonably well. However, these methods overlook the influence of rock strata movement processes (RSMP) on subsidence. In this study, based on the combination principle, a new RSSB prediction method is developed considering the deformation relationships for ‘roof, RSMP, and thick soil layer’, applicable to deep-buried mining areas with thin bedrock and thick soil layers. The results indicate that RSMP primarily involves four leading distinct stages in the evolution of rock strata subsidence and RSSB. The subsidence coefficient of Zhaogu No. 2 coal mine is 0.97, and the angle of draw is 61.79°. The main key layer controls the bedrock subsidence boundary, making the slope of the curve low; the increase in tensile deformation caused an increase in the slope of the curve as the burial depth of the thick soil layer decreased. The RSSB exhibits an overall upward concave power function pattern. Validation demonstrates that the average error of the new method is 7.3% for predicting the RSSB under the influence of different RSMP. The proposed method offers an effective method for assessing surface subsidence hazards.