Risk Assessment and Control Strategy of Residual Coal Pillar in Room Mining: Case Study in Ecologically Fragile Mining Areas, China

Hengfeng Liu,Qiang Sun,Nan Zhou,Zhongya Wu

doi:10.3390/su13052712

Abstract

Gradual instability of coal pillars left behind underground with room mining is one of the main reasons for sudden roof caving in the gob, surface subsidence, and other significant hazards. Moreover, room mining implies great losses of coal resources. In this paper, the main failure mode and room mining coal pillar process were analyzed according to the coalfield regional engineering geological and hydrogeological conditions. A numerical model was adopted to study the effect of different sizes of coal mining pillars and progressive instability failure of coal pillar on the plastic zone’s evolution characteristics and stress field of coal pillars in the stope. The proposed technologies of cemented paste backfilling and reinforcement of residual coal pillars are applied, and a numerical simulation model is established to study the strata movement characteristics and analyze the stability degree of residual coal pillar and key aquiclude strata in the Pliocene series of Neogene. Consequently, the performance and application prospect were evaluated. The results obtained substantiate a new method for the long-term stability control of coal pillars in room mining and protecting the ecological environment in China’s western eco-environmental frangible area.

Highlights

The water resources of mining areas in western China are extremely short [1]
At the end of the 20th century, the room and pillar (R&P) mining method was widely used in the western coal resources, and many coal pillars remained in the goaf [3,4]
Given the roof dynamic disaster and environmental damage hazards caused by the instability of coal pillars in room mining in the western ecological fragile mining area, the

Summary

Introduction

The water resources of mining areas in western China are extremely short [1]. The degree of land desertification is high, the surface is covered with thick aeolian sand, the ecological environment system is very fragile, and soil erosion is very serious [2]. It is easy to cause the mining fractures of overburden rock to expand from the bottom to the top and directly communicate with the surface, resulting in the leakage of shallow water and groundwater [5]. This would destroy the vegetation on the surface and imply land desertification and other environmental hazards, deteriorating the originally fragile ecological environment system [6,7,8] (Figure 1). TheCoal caseMine study is Study performed for the coal mine located in the Dongsheng Coalfield, InnerThe Mongolia Autonomous

Methods

Results

Conclusion