Development and application of multifunctional shear test apparatus for rock discontinuity under dynamic disturbance loading

Dynamic disturbance is an important influence factor that causes the sliding instability of rock discontinuity and then triggers strong dynamic geological disasters, such as earthquake and rock burst. In order to study the mechanical response and disaster-causing mechanism of rock discontinuity under dynamic disturbance loading, a multifunctional shear test apparatus for rock discontinuity under dynamic disturbance loading (DDST-1800) is independently developed. The test apparatus is composed of normal and shear loading units with quasi-static loading, varied normal boundary conditions, dynamic disturbance loading with complex and wide-frequency waveform (0.5-50 Hz), and wide-range shear velocity loading (0.000 1-10 mm/s) functions, pendulum impact system, cyclic shear box unit, data acquisition and control units. The servo-controlled apparatus DDST-1800 can conduct the following typical tests by programmed operations: monotonic or cyclic direct shear test of rock discontinuity under constant normal load (CNL), constant normal stiffness (CNS), unloading normal load (UNL), variable normal stiffness (VNS), and dynamic normal load (DNL) boundary conditions with different shear velocities, superimposed dynamic disturbance shear test, velocity and stress step tests, and pendulum hammer-driven impact test of rock discontinuity under pre-set normal and shear stress conditions. Preliminary experimental studies were carried out and the results verified the stability and accuracy of the new apparatus. The research and development of the new apparatus has important scientific significance and engineering value for clarifying the dynamic response characteristics of rock discontinuity under dynamic disturbance, and deeply understanding the triggering effect of activation instability of rock discontinuity and disaster-causing mechanism of geological disasters such as earthquake and rock burst.