Surface Dynamic Damage Prediction Model of Horizontal Coal Seam Based on the Idea of Wave Lossless Propagation

Abstract

According to traditional concepts, the movement of overlying strata and surface damage caused by coal mining in horizontal coal seams are symmetrical in terms of spatial distribution. However, in a lot of engineering practices, this symmetry has not been discovered. We often use the symmetry function to establish the profile prediction function of the surface damage, which results in a large difference between the prediction result and the actual situation. To solve this problem, this paper takes subsidence velocity as an example. Firstly, the spatial distribution functions of subsidence velocity on both sides were deduced theoretically. Through comparison, it is found that the change rate of the spatial distribution curve of the coal pillar side subsidence velocity is smoother than that of the goaf side and the subsidence velocity curves are skewed to the left. Secondly, based on the idea of lossless propagation of harmonic waves and idealizing the propagation environment, the spatial propagation relationship of surface subsidence velocity in the time domain is established. Then, the Box–Cox transform function is introduced to improve the normal distribution probability density function, and a new dynamic subsidence prediction model based on the Box–Cox transformation is obtained, which is suitable for the full mining stage. The model is tested by practical cases, the prediction accuracy is better than 7%, and the prediction results can meet the needs of engineering prediction accuracy (10%). The results of this research can enrich the existing subsidence prediction theory and provide theoretical and technical support for the prediction of dynamic surface damage caused by similar mining.

A Novel Surface Subsidence Prediction Model Based on Stochastic Medium Theory for Inclined Coal Seam Mining

“…Coal resources play a key role in the primary energy structure, accounting for 60% of the energy produced. Large-scale mining of coal resources has resulted in large-scale overburden movement and surface disturbance [1][2][3]. In accordance with relevant statistics, the coal subsidence area in China is approximately 1.4-2.0 × 10 6 hm 2 , and it is increasing at a rate of 2.0 × 10 4 hm 2 /year.…”

Development of a Dynamic Prediction Model for Underground Coal-Mining-Induced Ground Subsidence Based on the Hook Function

“…This typical variation pattern of subsidence cannot be described by the Knothe model, as evidenced in Figure 3, which shows an example of a subsidence time series calculated using three typical models when the maximum ground subsidence is 4000 mm. The studies in [28,29] reveal that, before the ground subsidence velocity reaches its maximum, the acceleration of subsidence (second-order derivative of the subsidence time series or first-order derivative of the subsidence velocity time series) increases with respect to time; then, the acceleration of subsidence reaches its maximum at the time when the subsidence velocity equals 1/2 of the maximum subsidence velocity. Finally, the subsidence acceleration decreases to zero at the time corresponding to the maximum subsidence velocity.…”

“…Many field measurements show that the underground coal-mining-induced gro subsidence velocity increases sharply with the increase in time; after the velocity rea its maximum, the velocity gradually decreases to zero [28]. In addition, the increa…”

“…Many field measurements show that the underground coal-mining-induced ground subsidence velocity increases sharply with the increase in time; after the velocity reaches its maximum, the velocity gradually decreases to zero [28]. In addition, the increasing pattern of the velocity is much different from the decreasing pattern of the velocity, due to the mechanism difference between underground rock collapse and compaction; specifically, the increasing rate of subsidence velocity is greater than the decreasing rate in general [29].…”

“…As indicated in many previous studies, once the ground point begins to be affected by the underground coal mining, the subsidence velocity increases sharply to reach its maximum, which can also be termed as the velocity increasing period (VIP). Then, the velocity decreases gradually to zero, which may take more than several years in general (or velocity decreasing period, VDP) [28]. Basically, the variation pattern of subsidence velocity can be very different for the two periods at a given ground point.…”