Key Takeaways & Executive Findings
- •• Water immersion significantly degrades the mechanical properties of rectangular tunnel specimens, with average peak stress decreasing by up to 34% after 62 days. • Energy dissipation analysis reveals that water reduces both elastic and dissipated strain energy, weakening the rock's energy storage capacity. • AE monitoring shows that water immersion drastically reduces cumulative AE parameters, indicating suppressed microcracking activity. • The proposed energy damage model outperforms the AE damage model in fitting experimental data, enhancing rockburst prediction accuracy.
Abstract
To investigate groundwater influence on stability and rockburst mechanism of deep hard-rock rectangular tunnels, water-immersed treatment and uniaxial compressive acoustic emission (AE) experiments were conducted on rectangular tunnel specimens. Energy dissipation characteristics, AE evolution characteristics and damage evolution characteristics of rectangular tunnels were analysed under water-immersed condition. Under water-immersed condition, tunnel specimens were quite sensitive to water. Average peak stress and average peak strain energy exhibited negative exponential decay with water-immersed time. Among them, after 12 d of water immersion, average peak stress of specimens decreased by 28%. Average total strain energy decreased by 70%. Average elastic strain energy decreased by 71% and average dissipated strain energy decreased by 68%. After 62 d of water immersion, average peak stress of specimens decreased by 34%. Average total strain energy decreased by 78%. Average elastic strain energy decreased by 79% and average dissipated strain energy decreased by 75%. Water weakened bonding among mineral particles. Moreover, it undermined load-bearing capacity and diminished energy-storage properties. Under high stress, massive releasable elastic strain energy stored in natural specimens within pre-peak stage may abruptly release after peak stress. This caused rapid crack development and connection in specimens. During accumulation and release of elastic strain energy, initial failure typically occurred at sidewalls. This failure location was not affected by water. Compared with natural specimens, specimens immersed in water for 62 d had the lowest peak values of cumulative amplitude, cumulative AE energy and cumulative AE count. After 62 d of water immersion, peak values of cumulative amplitude, cumulative AE energy and cumulative AE count of specimens decreased by 84%, 97% and 99%. Compared with AE damage model, fitting degree of energy damage model was higher. For natural specimens, fitting degree of energy damage model was 0.96. For specimens immersed in water for 12 d, fitting degree of energy damage model was 0.96. For specimens immersed in water for 62 d, fitting degree of energy damage model was 0.72. Therefore, an energy damage model had more remarkable applicability and reliability. By establishing dynamic mapping relationship between energy and damage in the model, accuracy of rockburst early warning has been significantly improved. This provided scientific basis for support structure design of rectangular tunnels and regulation of high strain energy.
1. Introduction
Rockburst was a quite intractable engineering geological hazard in construction of deep hard-rock tunnels and building [1]. It was usually triggered by rock mass excavation under high stress. It posed a major challenge to deep hard-rock tunnel safety [2]. Essentially, rockburst was a phenomenon when high-stress rock masses fractured violently [3]. It was accompanied by rapid release of elastic strain energy and rock fragment ejection [4]. This was significantly different from brittle failure characterised by slow fractures and no fragment ejection (such as caving or spalling). It posed a great threat to construction equipment and operators’ safety [5].
Additionally, tunnels often crossed water-rich strata. However, for water-rich tunnels, evolution process and rockburst mechanism under water-rich condition remain unclear. This study aims to investigate the failure mechanism and damage constitutive model of rectangular tunnels under water-rich condition, providing scientific basis for support design and rockburst warning.
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ZENG Banquan, CHEN Jianhang, XU Wuyan, AN Xiaoyong, WANG Shiji, HU Songsong, WANG Kun, CHEN Yu (2025). Failure mechanism and damage constitutive model of rectangular tunnels under water-rich condition. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.10.011
Research & Educational Purpose Only:The translations, structured abstracts, analytical annotations, and data reports provided by SinoTechIntel are intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
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Frequently Asked Questions
How does water immersion affect the peak stress of rectangular tunnel specimens?
Water immersion significantly reduces the average peak stress of rectangular tunnel specimens. After 12 days of immersion, the peak stress decreased by 28%, and after 62 days, it decreased by 34%.
What is the role of energy dissipation in the failure mechanism of water-rich tunnels?
Energy dissipation analysis reveals that water weakens the bonding among mineral particles, reducing both elastic and dissipated strain energy. This diminishes the rock's energy storage capacity, making it more prone to violent failure under high stress.
How does water immersion affect acoustic emission (AE) signals?
Water immersion drastically reduces AE activity. After 62 days of immersion, the peak values of cumulative amplitude, cumulative AE energy, and cumulative AE count decreased by 84%, 97%, and 99%, respectively, indicating suppressed microcracking.
Which damage model is more suitable for predicting rockburst in water-rich tunnels?
The energy damage model shows higher fitting accuracy compared to the AE damage model. For natural specimens, the fitting degree was 0.96, and for specimens immersed for 12 days, it was also 0.96, while for 62 days, it was 0.72, demonstrating better applicability and reliability.
What are the practical implications of this study for tunnel engineering?
The study provides a scientific basis for support structure design of rectangular tunnels and regulation of high strain energy, significantly improving the accuracy of rockburst early warning in water-rich conditions.
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