ABSTRACT:

Based on the phenomenon of the rock burst caused by suddenly releasing of highly concentrated elastic energy in the steeply inclined coal seam, the distribution of elastic energy before and after extraction is studied by the numerical simulations. Two key areas of energy releasing in the main roof are recognized. The energy bifurcation in a form of herringbone after elastic energy releasing is elaborated. The left branch of the energy bifurcation is a principal source of disaster after pressure relief in the steep seam roof. The directional releasing method of elastic energy for control of rock burst is put forward accordingly. The monitoring data shows that the directional releasing method is significance in the reduction of roof pressure, the weighting interval, as well as the probability of secondary disaster.

1 INTRODUCTION

The particular sedimentary structure of the steeply inclined seam usually leads to the occurrence of rock burst, and hence, the behavior of rock burst and control methods have been paid much attention. Wu et al. (2010, 2011) indicated that the position of strata movement begins in the middle of working face first, and consequently develops towards the top and finally to the bottom along the seam inclination, and the movement of roof strata shows more active in the middle region. It is known that the long hole blasting method can reduce the periodic weighting interval in the main roof as well as the roof pressure in steeply inclined seam preferably. Yu et al. (2011) proposed 3-Dl stress control method to effectively prevent the coal bumping. Some other control methods has been put forward, include the intensity weakening theory by Dou et al. (2005), stress gradient moderation method by Qi et al. (2013). However, most of rock burst control methods for steeply inclined seam follows the pattern used for horizontal seams. It is noticed that some methods did not produce the expected results, but might cause secondary disaster. The main reasons are lack of understanding of the distribution characteristics of elastic energy in steeply inclined seam.

In this paper, the distribution of elastic energy in steeply inclined seam is analyzed by numerical simulation, and the directional releasing methods of elastic energy are proposed. The effect of method has been verified through monitoring data.

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