Study and Application of High-Level Directional Extraction Borehole Based on Mining Fracture Evolution Law of Overburden Strata

Abstract

The technical principle of gas drainage using high-level directional extraction boreholes was analyzed. A range of overburden strata was stimulated for pressure relief during mining, the effects of different borehole parameters on gas flow in the goaf and gas concentration in the upper corner were compared, and a field test was conducted to analyze the effect and peculiarities of gas drainage. With the mining of the work plane, overburden mining fissures gradually develop forward and upward, showing a “saddle” shape along the coal seam. The fissures in the middle zone of the goaf are gradually compacted, and a gas accumulation zone is formed around the goaf. High-level directional extraction boreholes arranged in an ellipsoidal belt at the side of the air return can achieve efficient gas extraction in the roof fissure belt. Numerical simulation results showed that the height of the fully depressurized area was 65 m from the roof of the coal seam. In addition, three high-level directional extraction boreholes were drilled in the roof of the coal seam. The gas extraction concentration and gas extraction pure volume of these three boreholes first increased, then decreased, and finally tended to be stable. The sequence of their average values was borehole No.2 > No.3 (twice as much) and > No.1 (2.7 times as much), which are closely related to the evolution law of overburden mining fissures. The research results can provide a reference for the further study of gas extraction technology using high-level directional extraction boreholes in coal and gas outburst seams.

Thickness and Strength Analysis of Prestressed Anchor (Cable) Compression Arch Based on Safe Co-Mining of Deep Coal and Gas

“…The elastic modulus (E) and Poisson's ratio (v) of coal rock were measured with a rock triaxial shear composite testing machine, and the bulk modulus and shear modulus of surrounding rock were calculated by Formulas (3) and (4).…”

“…Deep coal seams have a large amount of gas [1]. Through the excavation of gas extraction roadways [2], arranging coal seam drilling and gas extraction devices in the roadway for gas extraction is widely used in engineering [3][4][5]. However, due to the complex and changeable deep geological conditions and significant ground stress, it is difficult for conventional support to maintain the stability of the roadway [6][7][8][9][10].…”

A hierarchical roof control and pressure relief method for Gob-side Entry Retaining with Compound Roof

“…Notably, the lateral bearing stress from adjacent goafs and the advanced bearing stress from caving faces exacerbate the di culty in maintaining the structural integrity of these roadways, thus posing a signi cant hindrance to the effective mining of deep coal resources. Addressing the predicaments associated with RNGs stability requires a thorough understanding of the dynamics of surrounding rock deformation and the exploration of innovative support technologies [6][7][8].Efforts to understand the physical properties and mining response characteristics of deep-buried coal and rock formations have provided insights into the challenges and potential strategies for surrounding rock control in deep mines [9,10]. The derivation of a boundary equation for a plastic zone of surrounding rock and the evolution of plastic zone morphology [11,12] are among the notable advancements towards understanding the behavior of deepburied roadways.…”

Study on the Pseudo-Slope Length Effect of Buried Pipe Extraction in Fully Mechanized Caving Area on Gas Migration Law in Goaf

“…The location of the gas aggregation zone varies with the ventilation parameters, which can be used as an evaluation index to study the degree of air leakage in the mining area. Zhang et al [19] analyzed the development height of fracture zone in an inclined coal seam by using FLAC and used Fluent simulation to optimize the arrangement parameters of a high-level directional long borehole, instead of a high extraction lane, for efficient extraction. Brigida et al [20] processed the dynamic data of gas concentration by using an optimization algorithm to obtain the cyclic nonlinear distribution of mine gas subject to perturbation.…”