Xufeng Wang

Mechanism of mining-induced slope movement for gullies overlaying shallow coal seams

This paper provides an improved understanding of the movement mechanisms of both bed-rock gully and sandy soil gully when underground mining occurs underneath, followed by systematic analysis of the contributing factors such as mining advance direction, gully slope angle, gully erosion coefficient and mining height. This paper presents the results from monitoring, theoretical analyses and up to date modeling based on the geological features in the gully affected area, and the implications of these results to the success of roof support trial. It was observed that when mining occurred towards the gully, sliding of slope block along the fracture surface occurred, which resulted in unstable roof condition; when mining progressed away from the gully, polygon blocks developed in the gully slope and rotated in reversed direction forming hinged structure; within the bed-rock slope, the hinged structure was unstable due to shear failure of the polygon block; however, within the sandy soil slope, the structure was relatively stable due to the gradual rotating and subsiding of the polygon block. The increase of the value of slope angle and mining height lead to a faster and more intensive fracture development within the gully slope, which had a pronounced effect on gully slope stability and underground pressure. Various remediation approaches are hence proposed in this paper including introducing more powerful support and reasonable mining height, setting up working face along or away from gullies, using room and pillar, strip mining and backfill instead of longwall mining.

Analysis of Mathematical Model for Migration Law of Radon in Underground Multilayer Strata

This paper summarized the separation process of radon based on its geophysical-chemical properties. Taking into account the geological conditions of mining, the mathematical model of radon migration in underground multilayer strata (UMS) was established to investigate the distribution law of radon concentration in UMS. It was found that the distribution of radon concentration in UMS is affected by both the properties of the strata and the depth of cover and the radon concentration law varies at different depths even in the same layer stratum. At last, in order to validate the derivation result of the mathematical model of radon migration in UMS, the actual measured values (AMV) and the calculated values (CV) were compared further. As a result, the CV was found to be approximately equal to the AMV with deviation values (DV) less than 5%, which indicates that the derivation result of the mathematical model of radon migration in UMS is correct.

Surface subsidence control during bag filling mining of super high-water content material in the Handan mining area

This paper focuses on the analysis of the overburden strata control mechanisms in stopes utilising bag filling mining super high-water content material. The factors affecting the mining-induced surface subsidence were determined, and control methods were applied to improve the filling rates of the working faces. The effects of filling rate changes on overburden failure and surface subsidence were investigated quantitatively using the field data. The results indicate that high filling rates and small changes could improve surface subsidence control. When the filling rate exceeded 86%, a 1% increase in the filling rate could decrease the average surface subsidence speed and distance by 5% and 7%, respectively. According to the current geological conditions of the Handan mining area, surface subsidence was observed as 260 mm at a 92% filling rate. Thus, these surface movements and damage indicators could be used to meet the requirements of I-level building codes and adequately control surface subsidence. [Received: July 28, 2015; Accepted: January 14, 2016]