[This article belongs to Volume - 51, Issue - 01]
Gongcheng Kexue Yu Jishu/Advanced Engineering Science
Journal ID : AES-16-10-2021-23

Title : Effects of the High In-situ Stress Level on the Acoustic Detection and the Damage Degree Evaluation of the Excavation Damage Zone
LIU Xiao, YAN Peng, LU Wenbo, CHEN Ming, WANG Gaohui, NING Jinhua, NI Shaohu, LIU Jun,

Abstract :

With the increasing depth of underground engineering, the accurate evaluation of the depth and the degree of excavation damage zone (EDZ) in deep rock engineering is gradually influenced by the high geostress field and it is important to assess the impact reasonably. Relying on the excavation of a deep diversion tunnel, the drilling plan of distressing the in-situ stress step by step was adopted. At the outer zone of sampling area, conventional sampling holes were drilled in the form of a circular closed boundary. And boreholes and low stress coring were also carried out at the centre of the sampling area. The acoustic detection results of the depth and the degree of the damage area under different in-situ stress levels were obtained at the same location by acoustic detection device, and laboratory tests were carried out based on the core samples from the holes above. The uniaxial compressive strength of rock mass under different in-situ stress levels were given from acoustic wave velocity results by Hoek-Brown strength empirical formula to represent rock mechanics properties. These above contributed to judge the influence of the different in-situ stress levels on acoustic detection and damage degree evaluation in blasting EDZ. Researches showed that the conventional acoustic detection of excavation damage zone in high stress area would underestimate the depth of surrounding rock and the damage degree, which would be underestimated about 10% to 30% when the initial stress was 45 MPa. When the local stress level was reduced from 45 MPa to 30 MPa, the uniaxial compressive strength of rock mass would be seriously overestimated about 30% to 100%. Therefore, the high in-situ stress level had a significant impact on the results of acoustic detection and damage zone evaluation of surrounding rock. The effect of in-situ stress level on acoustic detection must be taken into account and corrected properly by reducing and increasing in evaluating rock mass quality by using wave velocity index in engineering.