Abstract

Utilization of coal reserves in the protection area of the coal mine gives the possibility of unusual mining methods. Just use methods room pillar in lignite coal mining is quite unusual opportunity. Application of the room pillar method can become very beneficial to the place where it can be somehow limited extraction using longwall face. This method is respectful of the overburden and excavated areas stay stable. The paper deals with the issue of stability and stabilization of coal pillars by using rockbolt support. The problem with this method is currently designing pillars so as to sufficiently handle pass the load.

1. Introduction

Coal mining under the end slopes of surface lignite mines is becoming quite an important topic especially in areas where coal mining is slowly finishing up. The first experience with the method of pillar mining was acquired in the North Bohemian ČSA Mine, where this method was tested for mining in protected zones. This method is based on the room-and pillar mining method, where the principle is driving parallel galleries, while pillars that ensure stability are left between galleries. Therefore, it is not the case of caving mining, but the pillars remain stable even after the excavation. This brings a number of problems that must be solved. These include the size of galleries, which is partly influenced by mining mechanisms (milling machines), as well as the stability of the pillars, which depends on the strength of coal, thickness and the properties of the overlying rocks, but also the dimensions of the pillars. The advantage of this method is continuous extraction while the stability of the extracted space is ensured.

To ensure the long-term stability of the mine excavations, they must be secured (stabilized) by means of supports. Due to the right-angled profile of the working and the applied technology of driving using road headers, separate roof bolting in combination with welded meshes is used to ensure the stability.

The applied methods of dimensioning separate roof bolting as well as the methods of calculating the stable pillars between the mining galleries are mostly based on empirical and empirical-analytic procedures based on knowledge and in-situ measurements. The method of pillar mining and separate roof bolting has not been applied yet in the conditions of this lignite deposit, therefore, the results of in situ measurements are not available, either. For that reason, we adjusted the results of general analytical and empirical methods for determining the minimum parameters of roof bolting to the results of mathematical modelling [1, 2].

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