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Minerals 2015, 5(4), 707-722;

Soft Roof Failure Mechanism and Supporting Method for Gob-Side Entry Retaining

1,2,* , 1,2
State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
College of Resources and Environmental Science, Chongqing University, Chongqing 400044, China
School of Computer Science and Control Engineering, North University of China, Taiyuan 030051, China
National Key Laboratory of Gas Disaster Detecting, Preventing and Emergency Controlling, China Coal Technology Engineering Group Chongqing Research Institute, Chongqing 400037, China
Author to whom correspondence should be addressed.
Academic Editor: Saiied Aminossadati
Received: 12 May 2015 / Revised: 16 October 2015 / Accepted: 20 October 2015 / Published: 28 October 2015
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To study the soft roof failure mechanism and the supporting method for a gateway in a gently inclined coal seam with a dip angle of 16° kept for gob-side entry retaining, and through the methodology of field investigation and numerical and analytical modeling, this paper analyzed the stress evolution law of roof strata at the working face end and determined that the sharp horizontal stress unloading phenomenon along the coal wall side did not appear after the working face advanced. Conversely, the horizontal stress along the gob side instantly decreased and the tensile stress produced, and the vertical stress in the central part of the roof had a higher reduction magnitude as well. An in-depth study indicates that the soft roof of the working face end subsided and seriously separated due to the effect of the front abutment pressure and the roof hanging length above the gob line, as well as certain other factors, including the rapid unloading of the lateral stress, tension and shear on the lower roof rock layer and dynamic disturbance. Those influencing factors also led to rapid crack propagation on a large scale and serious fracturing in the soft roof of the working face end. However, in the gob stress stabilized zone, the soft roof in the gob-side entry retaining has a shearing failure along the filling wall inside affected by the overburden pressure, rock bulking pressure, and roof gravity. To maintain the roof integrity, decrease the roof deformation, and enable the control of the working face end soft roof and the stabilization of the gob-side entry retaining roof, this study suggests that the preferred bolt installation angle for the soft roof situation is 70° based on the rock bolt extrusion strengthening theory. View Full-Text
Keywords: gob-side entry retaining; unloading loose; bolt installation angle; extrusion strengthening gob-side entry retaining; unloading loose; bolt installation angle; extrusion strengthening

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Yang, H.; Cao, S.; Li, Y.; Sun, C.; Guo, P. Soft Roof Failure Mechanism and Supporting Method for Gob-Side Entry Retaining. Minerals 2015, 5, 707-722.

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