针对松软低透煤层微差聚能爆破致裂增透问题，在分析微差聚能爆破作用过程及影响因素的基础上，利用流固耦合算法建立了微差聚能爆破数值模型，研究了煤体单元应力及裂隙发育特征，并通过煤层深孔微差聚能爆破现场试验探讨了微差聚能爆破致裂机理及对煤层增透的影响。结果表明:深孔微差聚能爆破的新自由面和应力波叠加效应是促进爆生裂隙扩展、衍生裂隙形成的关键因素，炮孔间煤体在短时间内经两次爆破作用使裂隙进一步发育和扩展。先爆炮孔为后爆炮孔提供了新的裂隙面，爆炸应力波经裂隙面绕射、反射并与入射波叠加，使裂隙面附近煤岩体处于拉伸应力状态并促进衍生裂隙的形成;后爆炮孔利用先爆炮孔形成的残余应力场使爆生裂隙密度增加，扩大了煤体致裂范围。微差时间与炮孔间距是影响爆生裂隙扩展特征的重要因素，在其他条件不变的情况下，两者共同作用决定了爆生裂隙的发育形态。当先爆炮孔产生的应力波在微差时间内传播距离小于炮孔间距时，爆炸应力波在两炮孔间煤体中相互叠加增强，随后在裂隙面之间发生反射形成拉伸应力波对煤岩体产生复杂的破坏作用，在原有爆生裂隙间形成新的裂隙。煤层实施深孔微差聚能爆破后增透效果显著，先爆炮孔附近煤体裂隙在后爆炮孔作用下进一步发育，炮孔间煤体裂隙随孔间距减小更易贯通。

This paper is concerned with the problem of cracking and permeability increasing in soft and low permeable coal seam.Based on the analysis of the process and influence factors of millisecond-delay cumulative blasting,the numerical models were established by using fluid-solid coupling algorithm to study the stress and crack development characteristics of coal.Combined with the field experiment in coal seam,the mechanism of millisecond-delay cumulative blasting and its influence on coal seam permeability enhancement were discussed.The results show that the new free surface effect and the superposition effect of stress wave are the key factors to promoting the expansion of blasting cracks and the formation of derived cracks.Millisecond-delay cumulative blasting promotes the further development and expansion of coal seam cracks between holes.The first blasting hole provides new crack surfaces for the later blasting hole.And the explosion stress wave diffracts and reflects through the crack surfaces and superimposes with the incident wave,which makes the coal mass near the cracks in a tensile state and promotes the formation of derived cracks.The residual stress field formed by the first blasting hole can increase the density of blasting cracks and expand the scope of coal cracks.In addition,the millisecond-delay time and the hole spacing are the important factors to affecting the propagation characteristics of blasting cracks,which determine the development form of blasting cracks jointly.When the propagation distance of the stress wave generated by the first blasting hole in millisecond-delay time is less than the hole spacing,the explosion stress waves will be superimposed between the blasting holes,and then reflect between the crack surfaces to form tensile stress waves,which have complex destructive effects on the coal mass and forms new cracks between the original blasting cracks.Moreover,the coal seam permeability is improved significantly after the application of deep-hole millisecond-delay cumulative blasting.The coal cracks near the first blasting hole are further developed under the action of the second blasting hole,and the coal cracks between the blasting holes are more easily connected with the decrease of hole spacing.

1 微差聚能爆破作用分析

   1.1 微差聚能爆破作用过程

   1.2 爆生裂隙面对微差聚能爆破裂隙发育的影响

   1.3 炮孔壁对微差聚能爆破裂隙发育的影响

   1.4 应力波叠加对微差聚能爆破裂隙发育的影响

2 微差聚能爆破数值分析

   2.1 微差聚能爆破数值分析模型

   2.2 微差聚能爆破煤体单元应力分析

   2.3 微差聚能爆破裂隙发育特征

3 微差聚能爆破作用机理讨论

4 深孔微差聚能爆破工程试验

   4.1 试验区瓦斯地质条件

   4.2 试验设计

   4.3 试验结果及效果

5 结论