Method for weakening coal-rock mass by hydraulic blasting and fracturing

Abstract

The invention discloses a method for weakening coal-rock mass by hydraulic blasting and fracturing. The structure of coal-rock mass can be changed by adopting hydraulic blasting and fracturing. The method comprises the following steps: drilling a hole in a coal layer, and placing water-gel explosive in the hole; and then sealing the hole and injecting water into the hole to a set pressure; stopping water injection based on the standard that no hydraulic fracture is generated; detonating the explosive and carrying out hydraulic blasting to lead the wall rock of the drilling hole to burst; generating a great number of fractures on the periphery of the drilling hole; and then carrying out hydraulic fracturing; expanding along exploding fracture under the action of hydraulic pressure of the fracture, and forming a great number of hydraulic pressure fractures. The method of the invention not only can effectively weaken the strength of the coal-rock mass, can reduce wall rock stress of the weakening area, but also can improve ventilation property of the coal layer; is an effective technical way of improving the top coal caving, preventing impact mine pressure, preventing coal and gas burst, and improving efficiency of gas extraction in coal mine. The method has simple process, convenient construction, reliable safety, easy operation and good control.

Description

technical field [0001] The invention relates to a hydraulic fracturing weakening method, in particular to a hydraulic blasting fracturing weakening method for coal and rock mass. Background technique [0002] In the process of coal mining, if the top-coal caving mining method is adopted, it will be difficult to release the top-coal when encountering a hard top-coal, and measures must be taken to loosen the overlying coal to allow the top-coal to be released. One of the current treatment methods is Drilling directly, and then blasting with explosives to loosen the top-coal or roof, but this method is less effective for weakening the top-coal or roof, and if the amount of charge is not properly controlled, it will easily cause safety hazards; the second is to simply use hydraulic fracturing This method needs to inject a very large water pressure, it is difficult to control the expansion of cracks in the hole, and the number of large cracks caused by hydraulic fracturing is sma...

AI Technical Summary

Problems solved by technology

[0002] In the process of coal mining, if the top-coal caving mining method is adopted, it will be difficult to release the top-coal when encountering a hard top-coal, and measures must be taken to loosen the overlying coal to allow the top-coal to be released. One of the current treatment methods is Drilling directly, and then blasting with explosives to loosen the top-coal or roof, but this method is less effective for weakening the top-coal or roof, and if the amount of charge is not properly controlled, it will easily cause safety hazards; the second is to simply use hydraulic fracturing This method needs to inject a very large water pressure, it is difficult to control the expansion of cracks in the hole, and the number of large cracks caused by hydraulic fracturing is small, and the operation requirements are relatively high. If the control is not good, it will easily cause danger; In this case, it is necessary to master the direction and length of the crack propagation and its relationship with time in the three stages of initiation, propagation and instability propagation of the circular hole hydraulic fracture.

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