Experimental investigation of failure characteristics of deep surrounding rock containing an inclined joint under true triaxial compression

Abstract

The distance between a structural plane and a tunnel opening can influence the failure of deep surrounding rock, but experimental evidence under a general three-dimensional stress state remains limited. This study presents a specimen-scale comparison of three cubic sandstone specimens containing a circular opening and one structural plane at different distances. One specimen was tested at each distance under the same true triaxial stress path, while acoustic emission (AE) monitoring recorded hit count, ringing count, and RA-AF parameters. The maximum loading-direction stresses of three specimens were 50.0, 49.0, and 47.9 MPa, respectively. The experimental results indicated a progression from local sidewall cracking at low vertical distance to more extensive peeling and a V-shaped groove at middle vertical distance, followed by broader damage and sliding at high vertical distance. The shear-classified AE fractions of three specimens were 14.9%, 18.9%, and 31.3%, respectively, and the corresponding turning-point stress ratios were 0.84, 0.76, and 0.76. S30, which showed the longest low-activity period followed by the most abrupt increase in ringing count.