The multiple flawed rock mass is a common feature and is of fundamental interest for rock engineers. Several underground excavation and mining work is carried out in these rock masses. The correct understanding of the mechanical characteristics of the flawed rock mass, especially under a true triaxial state of stress, is required for the safe design of various engineering structures. These flaws are a source of new cracks, which ultimately can coalesce under the action of external load to cause failure. But, predicting the mechanical response of multi-flawed rock mass by field investigation is difficult. The mechanical behaviour of rock mass, especially under a true triaxial state of stress, can be estimated based on the experimental test data. In this research work, the multiple flawed rock mass specimens with an angle of 45ᵒ were prepared using a mould by casting method. The true triaxial tests were performed on these simulated rock-like specimens by varying the value of intermediate principal stress after fixing the minimum principal stress. The direction of intermediate principal stress is such that it remains parallel to the direction of penetration of flaws in the rock-like specimens. The failure mechanism of rock-like specimens with multiple parallel penetrating flaws subjected to true triaxial compression is investigated. The variation in peak compressive strength with the intermediate principal stress and varying confining pressure were obtained. The results show that the peak compressive strength increases with the increase in the intermediate principal stress for a constant minimum principal stress. However, under the same minimum principal stress, the peak strength shows an increasing trend. Furthermore, the typical failure pattern of multiple flawed rock mass specimens under true triaxial compression and crack coalescence are shown based on the experiments conducted. The macrocracks in the multi-flawed rock-like specimens in true triaxial confinement develop mostly from the crack coalescence occurring due to oblique shear cracks. Moreover, the complete stress-strain curve and the peak strength are reported.

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