松碎煤层造穴增透技术抽采特性动态响应规律研究OA

Cavity-making technology in coal seams is one of the main technologies for controlling gas in loose,low-permeability,and difficult-to-drain coal seams.Due to the limitations of equipment and process technology,the on-site construction parameters of cavity-making are mostly determined based on equipment feasibility.To achieve uniform and refined gas drainage,the design para-meters of mechanical cavity-making need to comprehensively consider the drilling results of cavity-making boreholes and the evolu-tion law of the effective influence range.In order to clarify the influencing factors of borehole formation and the spatio-temporal evolution law of drainage characteristics of mechanical cavity-making in high-gas loose coal seams,and to provide a basis for the reasonable design of construction parameters,a study on the dynamic response law of drainage characteristics of cavity-making per-meability enhancement technology in high-gas loose coal seams was carried out through numerical calculation and on-site experi-ments.The results show that during the drainage process,the effective influence range of mechanical cavity-making boreholes in high-gas loose coal seams presents a geometrically non-uniform distribution in space.On the spatial plane where the section normal is parallel to the borehole axis,the evolution of the effective influence range of drainage boreholes presents a concentric circle distri-bution with the diameter gradually increasing from the inside to the outside.On the spatial plane where the section normal is perpen-dicular to the borehole axis,the evolution of the effective influence range of drainage boreholes presents a spindle-shaped distribu-tion.The effective influence range of drainage boreholes in three-dimensional space presents a frustum-shaped dynamic evolution.During the cavity-making operation,the coal pillars between cavities are mainly shear instability under cyclic loading,and the scope of the instability zone is mainly affected by the cavity diameter and the length of coal pillars between cavities.Based on the above results,a cavity-making parameter design model coupled with factors such as plastic zone change,cavity diameter,and coal pillar length between cavities was established,and on-site experiments were carried out based on the parameters designed by the model.The on-site experimental results show that the mechanical cavity-making technology has a significant promoting effect on gas con-trol in high-gas loose coal seams.Compared with conventional drainage methods,the overall gas drainage effect is improved by 4 to 6 times.