Abstract: In this paper, a triaxial experimental apparatus is developed to investigate the frictional sliding behavior of fissures in limestone. Slide-hold-slide (SHS) tests, velocity stepping (VS) tests and permeability tests are conducted on the limestone core samples under both dry and wet conditions. Time-dependence and sliding stability are firstly studied through SHS tests and VS tests, respectively, and then the effect of water on the frictional behavior of fissures is further analyzed. Meanwhile, the permeability of fissures is measured during the sliding process in permeability tests. SHS tests show that frictional strength of fissures exhibits significant time- and stress- dependent behavior. The decreasing magnitude of frictional strength at the controlled time and the healing magnitude after re-sliding are proportional to the controlled time intervals, but inversely proportional to the effective confining stress. In addition, the frictional behavior is obviously influenced by water. However, VS tests demonstrate that frictional strength of limestone increases with increasing sliding velocities, which indicates the velocity-strengthening behavior. Finally, it can be seen from a series of permeability tests under varied effective normal stresses from 1 to 3 MPa is carried out, the permeability declines sharply with the increase of effective confining stress, and even decreases gradually with sliding process at each level of effective confining stress.

Key words: split limestone core, frictional sliding behavior, frictional strength, time-dependent behavior, sliding stability, permeability