Abstract: The high normal stress and constant normal stiffness are the general boundary constraint features of deep rock joints. Advanced rock joint shear servo test system with high normal load, large shear area, multi-shear mode and long shear distance is the premise for understanding the shearing deformation and failure of rock joints in deep stress condition. Thus, a new shear servo testing system, with large-scale, multi-functional and high-pressure, is invented. The system consists of normal and shear loading and unloading subsystems, servo control subsystems, data acquisition and software subsystems, and hydraulic oil source auxiliary subsystems. The functional parameters of the testing system include the maximum normal load of 1 500 kN, the maximum shear load of 2 000 kN. This testing system is available for the rock joint shearing test on the sample with standard sizes of 20 cm×10 cm×20 cm, 30 cm×20 cm×30 cm and 50 cm×30 cm×30 cm (length×width×height). The testing system can finish complex loading and unloading, constant normal loading (CNL), constant normal stiffness (CNS), fast/slow shearing, reciprocating shearing and other loading modes, assisting with shear observation window and acoustic emission positioning monitoring. Based on the test specimens of cement material and rock specimens, the experimental results show that this servo testing system can achieve high-frequency feedback control and data acquisition due to the excellent hardware structure and efficient software control, which can give out stable and reliable experimental data, support the stability study and engineering application analysis for deep rock engineering.

Key words: rock joint, shear test, servo control, constant normal stiffness, shear system