Key Takeaways & Executive Findings
- •• Increasing disturbance directions reduce shear strength but increase structural plane roughness and anisotropy. • Shear crack proportion on structural planes rises with increasing shear stress. • Disturbance strain rate before failure exhibits a U-shaped trend. • Precursory signals include high-energy acoustic emissions, b-value drop below 1, and lgN/b ratio above 3.
Abstract
After the excavation of deep mining tunnels and underground caverns, the stability of surrounding rock controlled by structural planes is prone to structural damage and even engineering disasters due to three-dimensional stress redistribution and multi-directional dynamic construction interference. However, the shear mechanical behavior, fracture evolution mechanism and precursor characteristics of rockmass under true triaxial stress and multi-directional coupling disturbance are not unclear. Therefore, this study carried out true triaxial shear tests on limestone intermittent structural planes under uni-, bi- and tri-directional coupling disturbances to analyze its mechanical behavior, fracture evolution mechanism and precursor characteristics. The results show that as the disturbance direction increase, the shear strength of limestone generally decreases, while the roughness of structural planes and the degree of anisotropy generally exhibit an increasing trend. The proportion of shear cracks on the structural plane increases with the increase of shear stress. The disturbance strain rate before failure shows a U-shaped trend. Near to disturbance failure, there were more high-energy and high-amplitude acoustic emission events near the structural plane, and b-value drops rapidly below 1, while lgN/b ratio increased to above 3. These findings provide experimental recognition and theoretical support for assessing the stability of rockmass under blasting excavation.
1. Introduction
In recent years, the phenomenon of surrounding rock disasters triggered by the dynamic disturbance during the excavation of underground engineering has become increasingly significant, which poses a major challenge to the construction of underground engineering and the development of resources and energy, while it has also become a research hotspot in the field of rock mechanics and engineering at home and abroad [1,2]. Deeply buried rockmass with intermittent structural planes are subjected to complex true triaxial stress (TTS) states during excavation, which leads to stress path changes and internal damage.
Subsequent excavation of the tunnel face and cyclic advancement continually impose dynamic excavation disturbances on the damaged rockmass, further deteriorating the surrounding rock. These disturbances originate from blast-induced shock waves and mechanical drilling impacts, which attenuate rapidly as they propagate through surrounding rock, transforming into low-amplitude, low-frequency stress waves [3,4]. The disturbance direction of the structural plane is d...
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Zhi Zheng, Zhanpeng Ma, Jinghua Qi, Guoshao Su, Gaoming Lu, Shufeng Pei, Quan Jiang (2025). Multi-directional disturbance effect of shear mechanical behaviors and fracturing mechanisms of rockmass intermittent structural plane under true triaxial shear test. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.04.008
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Frequently Asked Questions
What is the effect of multi-directional disturbances on shear strength of rockmass?
As the number of disturbance directions increases, the shear strength of limestone generally decreases, while the roughness and anisotropy of structural planes tend to increase.
How does shear stress affect crack types on structural planes?
The proportion of shear cracks on the structural plane increases with the increase of shear stress.
What are the precursor characteristics before shear failure under disturbance?
Before failure, there are more high-energy and high-amplitude acoustic emission events near the structural plane, the b-value drops rapidly below 1, and the lgN/b ratio increases above 3.
What is the significance of this study for engineering practice?
The findings provide experimental recognition and theoretical support for assessing the stability of rockmass under blasting excavation in deep mining and underground engineering.
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