Coal pillar failure method for weakening potential failure surface of remaining coal pillar

Abstract

The invention belongs to the field of coal mines, and particularly relates to a coal pillar failure method for weakening a potential failure surface of a remaining coal pillar. The coal pillar failuremethod comprises the following steps that core drilling is performed on the remaining coal pillar of an upper layer to process a core into a test piece with the same height to diameter ratio as the remaining coal pillar for a uniaxial compression test to confirm whether the failure form conforms to the shear failure form or not, and if yes, a next step is performed; a variable angle shear test isperformed on the test piece to measure an internal friction angle phi, and an angle alpha between the failure surface of the test piece and the supporting pressure is calculated; the position and length of a weakened borehole are calculated according to the measurement results of the test piece and parameters of the remaining coal pillar and a lower coal seam roadway; a starting point of the weakened borehole is located on the side wall of the side, near the coal pillar, of the lower coal seam roadway, and the weakened borehole passes through the center of form of the remaining coal pillar; and according to the calculation result, the weakened borehole is drilled, so that the remaining coal pillar is destroyed under the action of the mine ground pressure. According to the coal pillar failure method for weakening the potential failure surface of the remaining coal pillar, the critical strength required for destroying the coal pillar can be reduced and the technical difficulty is reduced.

Description

Technical field [0001] The invention belongs to the field of coal mines, and in particular relates to a coal pillar destruction method for weakening the potential failure surface of the remaining coal pillars. By weakening the potential failure surface of the upper remaining coal pillars, the coal pillars are destroyed under the action of supporting pressure. Background technique [0002] Due to the limitation of mining level, equipment conditions, geological factors and other factors, a large number of coal pillars of various types are left in the coal mining process to support the roof, protect the upper coal roadway, and ensure safe production. These coal pillars will remain underground permanently and cannot be mined, resulting in a lot of waste of resources. More importantly, the existence of coal pillars will lead to stress concentration, causing abnormal pressure in the mining of the lower coal seam, and accidents such as pressure support, roof fall, and rock burst are pro...

AI Technical Summary

Problems solved by technology

[0004] (1) High cost

The existing method does not make full use of the force of the top and bottom plates on the coal pillar, and only increases the amount of explosives, fracturing fluid, and low-temperature liquid nitrogen to achieve the overall crushing of the coal pillar, resulting in an excessive amount of materials required for coal pillar destruction and increased costs.

[0005] (2) High technical difficulty

The existing technical method is to destroy the integrity of the coal pillar through external force, so a large external force is needed to destroy the coal pillar, which increases the technical difficulty

[0006] (3) Low safety and poor effect

The prior art does not take the above factors into consideration, resulting in gas explosion in gobs that are prone to blasting, and there are great safety hazards; while in the process of hydraulic fracturing, fracturing fluid easily flows into gobs through coal pillar fissures, and the damage effect is very poor.

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