Taiyuan Ligong Daxue xuebao (Jul 2023)
Mine Pressure Characteristics in Fully Mechanized Working Face while Mining Under Residual Coal Pillar and Hydraulic Fracturing Roof Cutting Control
Abstract
Purposes In order to study the characteristics of strong mine pressure under the influence of concentrated stress in fully mechanized mining face under residual pillar, the 31106 working face of Huoluowan Mine passing through the overlying concentrated coal pillar is taken as the engineering background. Methods The mine pressure characteristics and support adaptability during passing through the coal pillar are analyzed through the measured support resistance of the working face. The similar material simulation experiment is carried out to reveal the strong dynamic pressure mechanism of the working face passing through the coal pillar, and the hydraulic fracturing roof cutting control technology passing through the coal pillar is proposed. Findings The results showed that during the period of coal pillar extraction in the working face, the overall support resistance is middle, lower, upper. The periodic weighting step distance of the working face is 10.85 m, the average continuous length is 4.27 m, accounting for 40% of the periodic weighting time, and the average dynamic load coefficient reaches 1.4. The proportions of the support load exceeding the normal working resistance (35 MPa) during the coal pillar are 32.14%, 63.83%, and 87.94%. The working face is subjected to the dynamic load of roof fracture and long-term high static load. Similar material simulation shows that when the coal pillar is pulled out, the overlying ‘T-type structure’ is unstable and the overall rotary sinking occurs, causing the main roof of the lower working face to break synchronously, resulting in an increase in the support resistance of the working face in a large range. The opening rate of the safety valve of the hydraulic support reaches 31.2%, and there is a risk of support crushing. Conclusions On the basis of above findings, the hydraulic fracturing roof cutting technology for working face crossing coal pillar is put forward. Field test shows that the hydraulic fracturing roof cutting in the coal pillar area can effectively destroy the roof integrity. There is no strong mine pressure within 10 m after the working face is out of the coal pillar, which reduces the dynamic load and high static load of the support, and no strong dynamic load crushing occurs.
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