A rigid true triaxial apparatus for analyses of deformation and failure features of deep weak rock under excavation stress paths

• Published in: Journal of Rock Mechanics and Geotechnical Engineering Vol. 15; no. 5; pp. 1065 - 1075
• Main Authors: Feng, Xia-Ting, Yu, Xiaojun, Zhou, Yangyi, Yang, Chengxiang, Wang, Feiyan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2023; Key Laboratory of Liaoning Province on Deep Engineering and Intelligent Technology,Northeastern University,Shenyang,110819,China; Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines,School of Resources and Civil Engineering,Northeastern University,Shenyang,110819,China; Elsevier
• Subjects: Deep weak rock; Excavation stress path; Instantaneous unloading; Large deformation; True triaxial apparatus (TTA); True triaxial apparatus (TTA); Deep weak rock; Excavation stress path; Instantaneous unloading; Large deformation; True triaxial apparatus(TTA)
• ISSN: 1674-7755
• DOI: 10.1016/j.jrmge.2022.08.009

The squeezing scenario in deep weak rock tunnels can hinder underground construction. However, due to the limitations of test technologies at hand, the real excavation stress path cannot be mimicked in the laboratory. Thus, the large deformation mechanism of deep weak rocks still remains unclear. For this, a true triaxial apparatus (TTA) to investigate the mechanical responses of deep weak rock under excavation stress paths in field and reveal the squeezing mechanism of deep tunnels is assembled and developed at Northeastern University, China. The apparatus can perform instantaneous unloading in σ3 direction based on electromagnetism technology. In addition, uniform loading and deformation measurements can be carried out based on the proposed linked interlocking clamp and antifriction device, even if the sample has a strong dilatation deformation performance. Next, a bore trepanning is designed to capture noiseless acoustic emission (AE) signals for deep weak rock at a low threshold. Finally, two tests were are conducted using this instrument to preliminarily understand the failure and deformation features of deep weak rock based on fractured marble. The results show that the complete stress–strain curves of fractured marble have the characteristics of low strengths and large deformations, and the larger deformation and the more serious failure occur when the fractured marble enters the post-peak state after excavation. The results show that the developed apparatus is likely to be applicable for deep weak rock engineering. •A novel rigid true triaxial apparatus was developed to investigate the large deformation mechanism of deep weak rock.•Deep engineering excavation was reproduced based on a developed electromagnetic instantaneous unloading mechanism.•Uniform loading and deformation measurements can be carried out consistently even if the sample has a severe dilatation.•The deep fractured marble in Jinchuan nickel mine has large postpeak deformation and low strength under true triaxial compression.