Low-temperature cracking and caving method of hard roof in coal mine goaf

Abstract

The invention discloses a low-temperature cracking and caving method of a hard roof in a coal mine goaf. The low-temperature cracking and caving method is suitable for the technical field of strengthening cracking of roofs in the coal mine roaf, and comprises the steps that a digital display thermograph, temperature sensors, a water injection pipe, a low-temperature fluid freezing pipe, a capsulehole sealer, a high-pressure water injection system and a low-temperature fluid tank car are utilized to form a plurality of cracking drill holes and an empty hole in the hard roof in the goaf sequentially; the spiral low-temperature fluid pipe, the water injection pipe and the capsule hole sealer are connected and sent into the multiple cracking drill holes, the capsule hole sealer is adopted forhigh-pressure hole sealing, cylindrical expanding sections of hole openings of the cracking drill holes are frozen to form a self-hole-sealing structure, then the multiple cracking drill holes are frozen, and the coal seam roof is cracked by water-ice phase transformation; and when the temperature sensors all rise above 3 DEG C, freezing is conducted repeatedly, and the cycle of cracking of frostheaving, melting and frost heaving is formed. The water-ice phase transformation is conducted by the low-temperature fluid to generate an expansion rate of 9.1 % to crack the coal seam hard roof, themethod is simple, operation is convenient, the cost is low, operation is easy, and the cracking effect is good.

Description

technical field [0001] The invention relates to a method for low-temperature fracturing and caving of hard roofs in goafs of coal mines, and is especially suitable for the roofs of goafs in coal seams that are dense and hard, difficult to collapse naturally, and must be artificially strengthened for fracturing. Background technique [0002] With the continuous advancement of the coal mining face in the coal mine, the length of the left roof and the area of ​​the overhanging roof in the goaf are getting larger and larger, and the strength of the coal pillars used to support the roof of the goaf is getting smaller and smaller, and it is easy to form stress concentration, which will last for a long time It is easy to cause accidents such as roof collapse, injury and mine impact accidents. For high-gas mines, it is easy to form local accumulation of gas at the roof of the goaf, causing gas accidents. Therefore, it is necessary to pre-crack the roof of the goaf, artificially col...

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Problems solved by technology

[0003] However, the traditional fracturing method has certain defects. For example, the deep hole blasting method requires a large amount of high explosives. The stress wave during the blasting process produces strong stress disturbances on the original rock, changing the stress distribution of the original rock, and easily inducing rock burst accidents. In addition, when explosives explode, a large amount of smoke is produced, which pollutes the underground environment; in addition, gas is easy to accumulate in goafs in underground coal mines, and it is easy to induce gas explosions by using explosives to blast and crack.

High-pressure hydraulic fracturing equipment is bulky and poorly adaptable to small underground spaces. Due to relatively high water pressure, drilling and sealing are difficult and the probability of failure is high

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