Design a Reasonable Width of Coal Pillar Using a Numerical Model. A case study of Khe Cham basin, Vietnam

Phuc Le Quang,Thang Pham Duc,Vladimir Zubov,S Vöth,M Straka,D Nuray,Y Tan,M Cehlár,J Janocko,A Abay,D Szurgacz,M Petrova

doi:10.1051/e3sconf/202017401043

Abstract

Problems in surrounding rock displacement, roadway deformation and complex support are the hallmarks of the long wall mining system. Such problems seriously affect the safety and efficient production of coal mines. To control the deformation of the rocks around the roadway next to the goaf, to reduce the support pressure, in Vietnamese underground mines often leave supporting coal pillars. Identification of a reasonable design for roadway supporting pillars by a numerical simulation study was conducted under the geological and technical foundation of I-10- 2 working faces at the Khe Cham coal mine, Vietnam . The characteristics of stress and pressure distribution of roof layers on coal pillars are modeled under different pillar widths. The results show a great linear increase of the vertical stress on the narrow coal pillar and as the width of the coal pillar increases, the area of the elastic core area also increases and the level of stress increase tends to be stable without any apparent uptrend. Coal pillar deformation decreases with increasing coal pillar width, but it leads to large coal loss and waste of resources. Therefore, with the current supporting solutions to increase the stability of the coal pillar, the size range of a coal pillar is determined to be 6-8 m through numerical simulation. The conclusions obtained may provide a certain reference number to choose the logical location of the furnace lines under similar geological conditions.

Highlights

In underground coal mining, an increase in coal recovery rate can be achieved by not leaving supporting coal pillars in the mining space or reducing its size to the minimum limit [1]
When the pillar width is less than 8 m, the maximum vertical stress of the coal pillar is smaller than the coal seam, so the coal seam will bear the main force from the pressure of the roof rock layers
The present study has deduced the relational effects that arise between the width of the coal pillars and the stresses exerted on the coal seams

Summary

Introduction

An increase in coal recovery rate can be achieved by not leaving supporting coal pillars in the mining space or reducing its size to the minimum limit [1]. Sheorey [4] proposed three methods for pillar analysis and design: (i) select the strength of the pillar from the formula, determine the average load (depending on one-sided or two-sided goaf, caving or stowing) and the width of pillar with a suitable safety factor; (ii) choose the width of the pillar so that the roadway is not much affected by the previous mining panel; and (iii) perform a numerical model to analyze stresses with different coal pillar sizes according to coal seam conditions. The pillar of coal in a coal mining panel with gently sloping coal seam and average thickness was analyzed using a 2D model. In this model, stress distribution and failure regions are analyzed in detail. Eight different coal pillar widths were considered: 4, 6, 8, 10, 12, 14, 16 and 20 m

Research method

Formatting Vertical stress distribution on coal pillars

Findings

Conclusions and Discussion