Experimental study on the effect of loading rate on the strain energy accumulation and release during the weakening process of circular-tunnel

• Published in: Geomechanics and geophysics for geo-energy and geo-resources. Vol. 10; no. 1; pp. 1 - 15
• Main Authors: You, Xun, Wang, Yunmin, Liu, Xiangxin, Zhao, Kui, Zhang, Zhengnan
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.12.2024; Springer Nature B.V; Springer
• Subjects: Accumulation; Circular-tunnel; Correspondence; Dredging; Energy; Engineering; Environmental Science and Engineering; Excavation; Flakes; Foundations; Geoengineering; Geomechanical challenges in the process of comprehensive utilization of closed/abandoned mines; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Hydraulics; Hydrostatic pressure; Instability; Load distribution; Loading rate; Phases; Probability theory; Rocks; Strain energy; Strain energy accumulation; Strain energy release; Tunnel construction; Tunnel supports; Tunnels; Vertical loads; Weakening process; Circular-tunnel; Strain energy release; Strain energy accumulation; Weakening process; Loading rate
• ISSN: 2363-8419; 2363-8427
• DOI: 10.1007/s40948-024-00785-7

The weakening of circular tunnels is a global problem that has not been resolved satisfactorily. In the tunnelling process, surrounding rock of circular-tunnel performs a process of “excavating → weakening → continuous excavating → weakening strengthens”. Different rates of excavation affect the stress adjustment of the surrounding rock, and also have an impact on the weakening of a circular-tunnel. An instability failure test was conducted on a circular-tunnel with varying vertical loading rates. The loading rate was utilized as a representative measure for the excavation rate on the site . The results showed that the weakening process of a circular-tunnel can be divided into four distinct phases, hydrostatic pressure ( E1 ), particle ejection ( E2 ), flake stripping ( E3 ), and instability ( E4 ). The ordering of these phases is E3  >  E4  >  E1  >  E2 . In the weakening process of a circular-tunnel, the root cause is the original stress level, while the essential factor is the engineering disturbance. A faster vertical loading rate leads to greater stress adjustment, higher strain energy accumulation, and an increased probability of circular-tunnel instability. The presence of a quiet period of AE events in the middle and later phases of flake stripping is a precursory characteristic of circular-tunnel instability. This study has both theoretical and practical significance in terms of revealing the mechanism of circular-tunnel instability and achieving a reasonable arrangement of the circular-tunnel support process. Article Highlights The intensity of circular tunnel fracturing is found to increase with higher vertical loading rates and greater strain energy migration. Specifically, the hydrostatic pressure phase is identified as the phase associated with the largest amount of strain energy. Strain energy migration is identified as a useful indicator of the weakening process in a circular tunnel. It provides valuable information about the redistribution and accumulation of energy within the tunnel structure, which can help in understanding the progression of tunnel instability.