冲击荷载对无烟煤微纳观孔隙结构的影响

Effect of impact loads on the micro-nanopore structure of anthracite coal

为了研究冲击荷载对无烟煤微纳观孔隙结构的影响,自河南省焦作矿区赵固二矿矿井采煤工作面采集、制备煤样,利用分离式霍普金森压杆(SHPB)冲击加载系统模拟冲击波、应力波,通过开展冲击实验,并结合冲击前后煤样压汞及低温液氮实验的测试结果,探讨了冲击荷载对无烟煤微纳观孔隙结构的影响。研究结果表明:①冲击荷载作用后无烟煤的总孔容、孔比表面积、孔隙度及退汞效率都呈波动式增加,总体上孔隙数量增多,连通性得到较大改善;②不同方向冲击荷载对煤体孔隙的改造具有差异性,垂直层理方向上的冲击荷载主要使微孔和大孔数量增加,平行层理方向上的冲击荷载主要使微孔和小孔数量增加,而斜交层理方向上的冲击荷载则主要使中孔和大孔数量增加;③不同方向最佳冲击荷载大小不同,垂直层理方向最佳冲击荷载为42.10 MPa,平行层理方向最佳冲击荷载为20.45 MPa,斜交层理方向最佳冲击荷载为56.90 MPa。结论认为,冲击荷载对无烟煤孔隙的改造是全方位的,但由于与层理作用方向不同,不同方向冲击荷载改造孔隙的实际范围会产生差异。

To clarify the effect of impact loads on the micro-nanopore structure of anthracite coal,this paper acquired coal samples from the coal mining face of No.2 Zhaogu coal mine of the Jiaozuo Mining Field,Henan Province.After the samples were prepared,the shock wave and stress wave are simulated using the shock loading system of split Hopkinson pressure bar(SHPB).Then,the effect of impact load on the micro-nanopore structure of anthracite coal was discussed by carrying out impact tests,combined with the test results of mercury injection and low-temperature liquid nitrogen experiments on the coal samples before and after the impact.And the following research results were obtained.First,after impact loading,the total pore volume,specific surface area,porosity and mercury extrusion efficiency of anthracite coal increase in a fluctuating manner.On the whole,the number of pores is increased and the connectivity is improved significantly.Second,the impact loads in different directions have different transformation effects on the coal pores.The impact loads vertical to the bedding mainly increase the number of micropores and macropores,those parallel to the bedding mainly increase the number of micropores and transition pores,and those oblique to the bedding mainly increase the number of mesopores and macropores.Third,the optimal impact load is different in different directions.The optimal impact load which is vertical,parallel and oblique to the bedding is 42.10 MPa,20.45 MPa and 56.90 MPa,respectively.In conclusion,the transformation effects of the impact loads on the pores in anthracite coal are all around,but due to their different directions from the bedding,their actual pore transformation ranges in different directions are different.