Experimental study on the strength characteristics of coal specimens under static and dynamic loadings

摘要

An advanced SHPB system was used to test the second-1 coal seam in Yima mine area under one and three dimensional coupled static-dynamic loading conditions for the analysis of the dynamic mechanical properties of the coal. The results indicate that the dynamic strength of the coal is higher under the three-dimensional coupled static-dynamic loading condition for the static axial load in the range of 8 MPa~36 MPa than under the one-dimensional loading condition. The dynamic strength of the coal increases with the increase in the static axial pressure until it exceeds the elastic stress limit of the specimen. Beyond the elastic limit, the internal fractures in the coal specimen dramatically increase and lead to a decrease in the strength of the specimen. However, the dynamic strength of the coal increases with the confining pressure when the confining pressure varies in the range of 0-8 MPa but the static axial stress remains constant,. The result shows that the axial stress can restrain or expand the fracture propagation, while the confining pressure will inhibit the occurrence and propagation of fractures, and enhance the dynamic strength of the coal. It lays a principle for preventing rockburst in coal mines.