Method for pre-cracking and softening of igneous rock hard roof

Abstract

The invention discloses a method for pre-cracking and softening of an igneous rock hard roof. While an upper coal seam is exploited, on the premises that the distance between upper and lower coal seams, rock stratum characteristics between the coal seams and the invasion condition of an igneous rock hard rock stratum are mastered, during exploitation of the upper coal seam, by reasonably forming drilling holes in a bottom plate of an upper working face and injecting a high-pressure acid solution, a fracture acidizing unit is used for controlling the pressure of injected acid solution, on one hand, the hard igneous rock stratum are cracked through pressure, and on the other hand, the igneous rock stratum is furthered softened through the chemical reaction function of the acid solution, so that the effect of safely and efficiently cracking and softening the hard igneous rock roof of the lower coal seam is achieved finally. According to the method, acid is injected while the upper coal seam is exploited, the structure of the hard roof of the lower coal seam is broken, and the strength of the hard roof is lowered; and possible hazards of the igneous rock hard roof to normal exploitation of the working face, staff and equipment can be reduced or even avoided during exploitation of the lower coal seam.

Description

technical field [0001] The invention relates to a method for pre-cracking and softening the hard roof of igneous rock to ensure safe and efficient passage of the working face through the intrusion area of ​​igneous rock, in particular to a method for drilling in advance, injecting high-pressure acid solution to rupture and softening the hard roof of igneous rock, which belongs to the coal mining technology field. Background technique [0002] With the reduction of Jurassic coal resources, the mining of Carboniferous Permian coal seams has been gradually carried out and has become the current main coal seam. However, the geological conditions of the coal-measure strata are complex and changeable, and the rock bed formed after the intrusion of igneous rocks and its damage to the properties of the coal strata have become the most important factors restricting the safe and efficient mining of coal seams. The intrusion of igneous rocks, on the one hand, makes the coal seam silic...

AI Technical Summary

Problems solved by technology

The management of blasting pre-splitting is complicated, involving the management and transportation of explosives and detonators. The "one shot, three inspections" and "three-person chain firing system" must be strictly implemented for blasting; a large amount of harmful gases such as CO produced instantaneously by blasting are used to ventilate the mine safely. Management has a huge impact, forming a safety hazard; and the economic cost of blasting is relatively high

Due to the limitations of existing technology and equipment, high-pressure water injection conditions require high equipment conditions and there are certain safety hazards, so the control effect of hydraulic fracturing weakening technology under hard roof conditions is not significant

In addition, the above two types of methods are all implemented in the mining project of the coal seam, which has a great impact on the mining efficiency of the coal seam, and the process of roof treatment is very likely to cause the roof to be uncontrollable, which has a great impact on the safety of the working face. threaten

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