Abstract
Retaining gob-side entryways and the stability of gas drainage boreholes are two essential techniques in the co-extraction of coal and gas without entry pillars (CECGWEP). However, retained entryways located in deep coal mines are hard to maintain, especially for constructing boreholes in confined spaces, owing to major deformations. Consequently, it is difficult to drill boreholes and maintain their stability, which therefore cannot guarantee the effectiveness of gas drainage. This paper presents three measures for conducting CECGWEP in deep mines on the basis of effective space in retained entryways for gas drainage. They are combinations of retaining roadways and face-lagging inclined boreholes, retaining roadways and face-advancing inclined boreholes, and retaining roadways and high return airway inclined boreholes. Several essential techniques are suggested to improve the maintenance of retained entryways and the stabilization of boreholes. For the particular cases considered in this study, two field trials have verified the latter two measures from the results obtained from the faces 1111(1) and 11112(1) in the Zhuji Mine. The results indicate that these models can effectively solve the problems in deep mines. The maximum gas drainage flow for a single hole can reach 8.1 m3/min and the effective drainage distance can be extended up to 150 m or more.
Highlights
As an associated product of coal production, gas is an innovative clean energy and high-class chemical material, it may cause major life threatening disasters in collieries and increase the greenhouse effect in the atmosphere (Zhang et al 2013; Xue et al 2014)
This paper presents three measures for conducting CECGWEP in deep mines on the basis of effective space in retained entryways for gas drainage
Several essential techniques are suggested to improve the maintenance of retained entryways and the stabilization of boreholes
Summary
As an associated product of coal production, gas is an innovative clean energy and high-class chemical material, it may cause major life threatening disasters in collieries and increase the greenhouse effect in the atmosphere (Zhang et al 2013; Xue et al 2014). A series of potential problems, such as gas outbursts, coal mining problems, high temperatures controlling, relief of high underground pressure, and support of surrounding rock, are considered in the technology and it has already been widely applied by the Huainan Mining Group, Shanxi Coking Coal Group, Huaibei Mining Group, and Jincheng Anthracite Group. This technology has several merits, it is difficult to adopt in every coal mine, especially deep buried soft rock coal mines, where the entryway convergence is extremely severe (Zhang et al 2012; Kong et al 2014). The purpose of this paper is to describe the implementation of CECGWEP in deep coal mines and present a systematic summary of the key techniques based on field trials in recent decades
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