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.