Dynamic Testing System For Rocks Under In Situ Stresses

Rocks may be subjected to dynamic disturbances while under high in situ stresses. When disturbed by dynamic loads from blasting, seismicity or rockbursts, the underground structures would be vulnerable to failure. Depending on the distance from the underground opening, the in situ stress states change from hydrostatic in the far-field, to triaxial in the intermediate distance, and to the pre-tension nearby the opening. Thus, SHPB testing system is further adjusted with confining pressure system into dynamic testing system of rocks under different in situ states. In the experiment with this dynamic testing system, the Brazilian disc rock specimens are first subjected to pre-stresses simulating in-situ stresses underground (including pre-tension, hydrostatic confinement, and triaxial confinement) and then loaded dynamically using the modified SHPB system. The dependence of dynamic tensile strength of the rock material on the static pre-stress and loading rate is investigated. These experimental results will be of great importance in the design and safety of underground rock engineering projects.