Objective Substantial measured data indicate that the along-strike horizontal displacement of the surface tends to be nonzero in the central part of the mining-affected zone. This phenomenon deviates from traditional understanding, leading to systematic deviations in the predicted results of the traditional prediction model for horizontal displacement.

Methods This study investigated mining face 1414 of the Guqiao Coal Mine in the Huainan mining area, Anhui Province. Using measured data and numerical simulation methods, this study explored the spatiotemporal evolution of the horizontal displacement within the mining overburden and of the surface. Then, it analyzed the sources, patterns, and distribution characteristics of both horizontal displacement along the goaf boundary and inertial horizontal displacement in the center of the mining area. Accordingly, this study constructed a new surface prediction model considering inertial horizontal displacement. Finally, this model was verified in mining face 1117 of the Guqiao coal mine.

Results and Conclusions  In the case of along-strike supercritical mining, the symmetrical along-strike horizontal displacement of the surface was observed on both flanks of the boundary inflection points of the mining zone. Additionally, along-strike inertial horizontal displacement also occurred in the central part of the mining zone. Consequently, the superimposed along-strike horizontal displacement of the surface was not proportional to the surface deformations in the inclination direction, failing to match traditional models. Inertial horizontal displacement arose from the underground mining process. In the simulation process, a smaller progressive step distance corresponded to more pronounced inertial horizontal displacement, which showed a distinct directly proportional relationship with the mining height. Inertial horizontal displacement peaked in the center of the surface mining zone and measured zero along the boundary of the mining-affected zone, generally resembling the distribution of surface subsidence. The new surface prediction model performed well in predicting the horizontal displacement of the surface in mining face 1117. Specifically, it yielded accurate predicted results of the difference in the horizontal displacement of the boundaries on both sides of the goaf and the horizontal displacement in the central part of the mining zone, with a fitting error of 7.0%. The results of this study hold significant implications for revealing the mechanisms underlying the horizontal displacement of the surface and improving the fundamental theory of mining subsidence.