Development and applications of the quasi-dynamic triaxial apparatus for deep rocks

The mechanical behaviors of deep rocks have always posed a challenge for the implementation and safe operation of major underground engineering projects. To this end, this study modified the existing mainstream rock mechanics instruments equipped with a dynamic disturbance loading system and developed a second-generation TFD-2000/D triaxial instrument. The first-generation device is equipped with an independent disturbance system and an advanced EDC-580 all-digital servo controller, which can apply disturbing load independently, implement the function of cyclic disturbance, and combine dynamic and static disturbances. The instrument was found to be reliable for use in analyzing the damage process of rocks in the disturbance test of marbles. The second-generation instrument tackles three limitations of the first-generation instrument: (i) it upgrades the strain measurement system and uses extensometers with linear variable differential transformers to accurately measure deformation; (ii) it uses the self-balanced chamber to replace the Hoek–Franklin triaxial cell and auto-balancing triaxial pressure chamber; and (iii) the loading rod is independently equipped with an EDC-580 all-digital servo controller, which measures precise loads. The experimental findings confirmed that the second-generation instrument can be used for rock mechanics testing under cyclic disturbance loading, the disturbance–stress relaxation cycle, and the creep–fatigue cycle. In this sense, the second-generation instrument can be a useful addition to deep rock mechanical instruments and provide a valuable reference.