Abstract
For the problem that the hard roof causes wider end‐mining coal pillar, and the roadway is greatly affected by mining, this paper took Shanxi Luning Coal Mine as the engineering background; based on the stress distribution characteristics of the coal pillar, the calculation method of the limit end‐mining coal pillar size was given; considering the formation conditions and transmission forms of the advanced abutment stress, a method combining presplitting and deep hole blasting was proposed to weaken the advanced abutment stress. The numerical simulation was used to analyze the stress distribution of coal pillars, which was verified by on‐site industrial tests. The results showed that the presplitting can achieve the blocking of stress. The closer it is to the peak of the abutment stress, the better the blocking effect. Deep hole blasting can weaken the source of the advanced abutment stress and reduce the peak of abutment stress. With the combination of the two blasting methods, the end‐mining coal pillar size of Luning Coal Mine can be reduced to 60 m. The method combining presplitting and deep hole blasting can effectively reduce the end‐mining coal pillar size and reduce the impact of mining on the deformation of the dip roadway.
Highlights
Blasting pressure relief has a lot of research in theory and practical application; Xia et al [6] used shallow hole blasting to reduce the roof pressure in front of the mining panel and combine grouting reinforcement technology to improve the stability of roadway surrounding rock; Zuo et al [7] used theory, and the method of numerical simulation was used to study the evolution behavior of the stress field induced by deep hole blasting
Yang et al [13, 14] respectively adopted directional hydraulic fracturing technology and directional energy gathering blasting technology to presplit the front roof of the mining panel, thereby shortening the cyclic pressure step to reduce the energy accumulated in front of the coal wall
It can be seen from previous studies that hydraulic pressure has been applied in the field as an emerging technology to control the advanced abutment stress, the fracturing process is not easy to control and is seriously affected by the original cracks in the rock mass. e development of physical blasting technology has been very mature, but it mostly stays in the application research of a single method and fails to combine the advantages of multiple blasting methods to achieve efficient control of the pressure field
Summary
Erefore, the width of the limit end-mining coal pillar is the sum of the range I and II of the surrounding rock stress area of the roadway and the area I, II, and III of the advanced abutment stress zone. E radius Rb of the limit equilibrium zone of the surrounding rock of the roadway can be obtained by the following equation:. E harder the main roof, the more the weight of the overlying strata will be transferred to the surrounding rock mass, resulting in an increase in the range of the advanced abutment stress field. Rough this combination of “prevention and treatment,” the size of coal pillars and the effect of the advanced abutment stress on the stability of the surrounding rock are reduced After the mining panel has been mined, the broken roof will collapse directly under the pressure of the overlying rock layer and will not produce a suspended roof structure, weakening the advanced abutment stress from the source. rough this combination of “prevention and treatment,” the size of coal pillars and the effect of the advanced abutment stress on the stability of the surrounding rock are reduced
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