Study on the Effect of Filling on the Properties and Fracture Behavior of Gabbro with En-echelon Joints

En-echelon joints are common in rocky slopes and faults, and their instability seriously threatens the safety of geotechnical engineering. Filling and reinforcing en-echelon joints in slopes is highly important for maintaining the safety of engineering and human beings. In view of this, this study aims to investigate the fracture behavior of en-echelon joints after filling and reinforcing to provide a reference for the filling and reinforcing work of slopes In this study, en-echelon gabbro samples with different crack angles were filled with cement slurry, a compression test was subsequently conducted, and the loading process was monitored via acoustic emission technology. The results showed that the compressive strength of the specimens after cementing the joints is increased by more than 30%, the compressive strength of the specimens with a β of 15°increased by up to 59%, and the stability of the specimens significantly improved. The shear failure of the filled and unfilled samples was the main failure at the peak load. There were two failure modes for the samples with different crack angles. The small dip angle samples were lightly broken, and the main cracks were distributed at the corner points of the samples. The large dip angle samples were broken considerably, and multiple fracture zones were present. Under pressure, the filled cement slurry weakened the stress concentration, and bore the compressive stress and shear stress, and the interface friction with the sample prevented the cracking and expansion of the crack, which resulted in a reinforcement effect on the sample. Our findings might act as a reference for the filling engineering of rock slopes with en-echelon joints.