Study on Dynamic Characteristics of Diorite Under Dry–Wet Cycle

During the construction of tunnels in the central and western regions of China, diorite is frequently affected by vibration, blasting and water which will lead to the questions of the quality and operational safety of project. However, there are few studies on the dynamic characteristics of diorite under the action of dry–wet cycles. Therefore, this paper selected the gray–green altered diorite from Ning shan County, Shaanxi Province, China, mainly composed of plagioclase, and used the Slit Hopkinson pressure bar (SHPB) to study the effect of dry–wet cycle on the dynamic characteristics of Diorite. The test results show that the strength decay rate of the peak strength of diorite is the maximum under 1–3 dry–wet cycles, then decreases gradually. The dynamic elastic modulus of diorite dropped by 35.02% after three dry–wet cycles, accounting for 98.45% of the total attenuation. Compared the test result of three dry–wet cycles, the decrease volumes of the stress growth rate of diorite are the largest after six dry–wet cycles. Because of the actions of the dry–wet cycles, the growth rate of the rapid growth stage of the reflected energy–time history curve reduces and the growth rate of the rapid growth stage of the transmitted energy–time history curve improves. Under the action of the dry–wet cycles, the dissipation energy ratio gradually decreases, and the decrease of energy consumption density follows a negative exponential function relationship. Under the action of multiple dry–wet cycles, the tension and compression stress frequently change between the particles of rock, resulting in a significant increase of micro-cracks and an obvious degradation effect on the dynamical properties of diorite.