Experimental study on failure characteristics of single-sided unloading rock under different intermediate principal stress conditions

• Published in: 矿业科学技术学报（英文版） Vol. 33; no. 3; pp. 275 - 287
• Main Authors: Chongyan Liu, Guangming Zhao, Wensong Xu, Xiangrui Meng, Zhixi Liu, Xiang Cheng, Gang Lin
• Format: Journal Article
• Language: English
• Published: Key Laboratory of Safe and Effective Coal Mining,Ministry of Education,Anhui University of Science and Technology,Huainan 232001,China%State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines,Anhui University of Science and Technology,Huainan 232001,China 2023; Post-Doctoral Research Station,Huaibei Mining Corporation Limited,Huaibei 235006,China%Laboratoire de Géologie,Ecole Normale Supérieure,Paris 75005,France; State Key Laboratory of Mining Response and Disaster Prevention and Control in Deep Coal Mines,Anhui University of Science and Technology,Huainan 232001,China
• Subjects: Stress intensity factor; True triaxial; Single-sided unloading; Acoustic emission; Intermediate principal stress
• ISSN: 2095-2686
• DOI: 10.3969/j.issn.2095-2686.2023.03.002

Investigation of unloading rock failure under different σ2 facilitates the control mechanism of excavation surrounding rock.This study focused on single-sided unloading tests of granite specimens under true tri-axial conditions.The strength and failure characteristics were studied with micro-camera and acoustic emission(AE)monitoring.Furthermore,the choice of test path and the effect of σ2 on fracture of unload-ing rock were discussed.Results show that the increased σ2 can strengthen the stability of single-sided unloading rock.After unloading,the rock's free surface underwent five phases,namely,inoculation,par-ticle ejection,buckling rupture,stable failure,and unstable rockburst phases.Moreover,at σ2≤30 MPa,the b value shows the following variation tendency:rising,dropping,significant fluctuation,and drop-ping,with dispersed damages signal.At σ2≥40 MPa,the tendency shows:a rise,a decrease,a slight fluc-tuation,and final drop,with concentrated damages signal.After unloading,AE energy is mainly concentrated in the micro-energy range.With the increased σ2,the micro-energy ratio rises.In contrast,low,medium and large energy ratios drop gradually.The increased tensile fractures and decreased shear fractures indicate that the failure mode of the unloading rock gradually changes from tensile-shear mode to tensile-split one.The fractional dimension of the rock fragments first increases and then decreases with an inflection point at 20 MPa.The distribution of SIF on the planes changes as σ2 increases,resulting in strengthening and then weakening of the rock bearing capacity.