Abstract
It is very important to accurately determine the depth of excavation damaged zone for underground engineering excavation and surrounding rock stability evaluation, and it can be measured by acoustic test, but there is no quantitative method for analysis of the results, and it relies heavily on the experience of engineers, which leads to the low reliability of the results and also limits the application of the acoustic method. According to substantial field test data and the feedback of surrounding rock support parameters, the boundary method is proposed to determine the depth of excavation damaged zone in surrounding rock based on the relation between the ultrasonic velocity of measured point and the background wave velocity of rock mass. When the method is applied to the columnar jointed rock mass of Baihetan and the deep-buried hard rock of Jinping, the excavation damaged zone was well judged. The results in the Baihetan project show that the proposed method of determining excavation damage zone by the acoustic test can well demonstrate the anisotropy characteristics of the columnar jointed rock mass, and the damage evolution characteristics of jointed rock mass at the same position can also be obtained accurately. Moreover, the method also can accurately reveal the damage evolution process of the deep-buried hard rock under the condition of high ground stress, which proved the applicability of this method in jointed or nonjointed rock masses.
Highlights
With the intensification of energy utilization activities such as mining, geothermal development, and hydropower station construction, the stability of rock engineering is a common challenge faced by engineers and researchers
Scholars have studied the relationship between the depth of excavation damaged zone and its influencing factors, such as the buried depth, the section shape of caverns, the excavation and blasting method, the initial stress state, the mechanical properties of the rock mass, and the supporting state of the surrounding rock [2,3,4,5,6]. e depth of EDZ and damage degree of surrounding rock are the basis of support parameter design and can play an early warning role in engineering disasters such as rock burst and spalling [7, 8]
Acoustic testing is to excite the ultrasonic wave to propagate in the rock mass medium, and the propagation speed of the wave depends on the integrity of the rock mass. e wave velocity of intact rock mass is generally high, but it decreases relatively in the loose zone where the stress drops and the fracture expands
Summary
With the intensification of energy utilization activities such as mining, geothermal development, and hydropower station construction, the stability of rock engineering is a common challenge faced by engineers and researchers. By applying panoramic digital borehole televiewers, Li et al [15] investigated the evolution of the EDZ in rock masses in deeply buried tunnels at the Jinping II Hydropower Station (Sichuan Province, China) during construction using tunnel boring machines (TBMs). On this basis, the changing characteristics of new cracks, primary fractures, and lithology during the excavation and support process of surrounding rocks were revealed. In order to increase the operability of the acoustic testing method in the field and improve the reliability of the EDZ test results, the boundary method, based on a large number of field measured data and the feedback of surrounding rock support parameters, is proposed to determine the depth of EDZ in surrounding rock, and the applicability of the proposed method is verified by comparing with the digital borehole televiewers test results
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
