Mining-Induced Seismicity during Development Works in Coalbeds in the Context of Forecasts of Geomechanical Conditions

Dariusz Chlebowski,Zbigniew Burtan

doi:10.3390/en14206675

Abstract

Mining-induced seismicity in the area of development works and proper mining operations is one of the major determinants of the rockburst hazard level in underground mines. Rockburst hazard assessment in Polish collieries is performed by a variety of mining and geophysical methods, including seismic and seismoacoustic techniques, borehole surveys, small diameter drilling, rock strata profiling and analyses of geomechanical properties of rocks, geological structure and geological mining conditions. In the case of zones particularly exposed to potential hazards, it is recommended that analytical or numerical forecasts of the state of stress in the vicinity of workings should be used already at the stage of planning of mining operations. This study summarises the comparative analysis of seismic test data and analytical forecasts of the state of stress in five selected headings in one of the burst-prone collieries within the Upper Silesia Coal Basin in Poland (USCB). As regards the seismic data, duly defined quantitative indicators and energy criteria of the registered seismic activity are recalled in the assessment of rockburst hazard level during the roadheading operations. Analytical simulations utilise a developed geomechanical model and stress–strain relationships stemming from the principles of elastic media mechanics. From the standpoint of mining engineering practice, interpretation of results obtained by the two methods reveals how effective analytical models will be in prognosticating or verification of rockburst hazard conditions.

Highlights

The rock strata remain in natural stable mechanical equilibrium conditions [1,2,3]
From the standpoint of geomechanics, rockbursts are regarded as the rock strata response to variations of stress and elastic energy distribution in the vicinity of mine excavations
Calculation parameters, duly summated and averaged, alongside the mapped foci positions, were benchmarked against the analytical forecasts obtained at the stage of design of mining operations

Summary

Introduction

Underground mining operations will disturb this equilibrium, triggering the rockburst occurrence (seismic events generating energy in excess of 10 J and producing vibrations with frequency below 100 Hz [4]). From the standpoint of geomechanics, rockbursts are regarded as the rock strata response to variations of stress and elastic energy distribution in the vicinity of mine excavations. On account of its direct association with rockburst hazard, induced seismicity has received a great deal of attention from rock engineering practitioners at geophysical stations in mines, mine supervision authorities as well as research institutes [5]. A forecast or a rational prognosis of future processes/phenomena consists in predicting the magnitude (scale) of an upcoming event, as well as where and when it is to be anticipated. A fully accurate prediction of when the outburst will occur still remains a distant goal [6,7,8,9]

Objectives

Methods

Results

Discussion

Conclusion