Key Takeaways & Executive Findings
- •• Shear strength of drilled rock decreases linearly with increasing borehole diameter. • Cohesion first increases then decreases with higher pre-static load and dynamic load amplitude, while internal friction angle consistently decreases. • Shear failure surface transitions from rough to smooth due to static load enhancing tooth cutting and dynamic load causing repeated crack friction. • Borehole pressure relief enlarges the plastic zone radius of surrounding rock following a quadratic function, informing support design.
Abstract
Borehole pressure relief helps prevent rock bursts. However, this may change the physical and mechanical properties of the surrounding rock, affect the variation of the plastic zone of the roadway, and lead to the failure of roadway support, thus threatening the safety of the roadway. In this paper, the variable angle shear test of drilled specimens under the action of static and dynamic loads is used to study the evolution of mechanical parameters of the specimens and their influence on the plastic zone of the surrounding rock. The shear strength decreases linearly with the increase of drilling diameter. With the increase of pre-static load level and dynamic load amplitude, the cohesion first increases and then decreases, and the internal friction angle decreases. Moreover, the shear failure surface changes from rough to smooth. The reasons include that the static load enhances the tooth cutting effect and the repeated friction of cracks caused by the dynamic load. Borehole pressure relief leads to an increase in the radius of the plastic zone of the surrounding rock following a quadratic function. The research results of this paper provide a theoretical basis for designing drilling unloading parameters and supporting parameters for rock burst roadways.
1. Introduction
In rock burst roadways, although drill unloading can prevent impact ground pressures, it can also cause damage to the surrounding rock, expansion of the plastic zone, and failure of the anchor support [1,2]. One of the important reasons for this problem is that the mechanical properties of the surrounding rock would change under the combined effect of drilling decompression and static and dynamic loads [3,4]. Therefore, it is of great significance to study the mechanical properties and damage characteristics of the surrounding rock under the combined action of drilling dynamic and static loads and its influence on the plastic zone of the roadway through the variable angle shear test. This study can provide guidance for optimizing drilling parameters and designing anchor support in impact ground pressure roadways.
Many scholars have studied the mechanical properties and impact ground pressure characteristics of preset borehole specimens. Zhang [5] focused on the impact range of unpressurized drilling through experimental and theoretical studies. In addition, Gong et al. [6] and He et al. [7] measured the impact propensity index of coal and rock bodies from preset drill holes, and showed that unloading of drill holes can effectively reduce the impact propensity. Lu et al. [8] and Huang et al. [9] found that the larger the diameter of the drill holes, the lower the peak strength and modulus of elasticity of the specimens, and the main form of damage was splitting, and the damage was mainly in the form of splitting. Moreover, the main damage form of the specimen was splitting, and local shear damage existed. In order to simulate a more realistic rock stress situation, many scholars have studied the damage characteristics of rocks under dynamic and static loads. Cai et al. [4] and Li et al. [10] proposed the theory of shock ground pressure induced by the combination of dynamic and static loads, and investigated the damage mode of coal under the joint action of dynamic and static loads. Li et al. [11] proposed two coupled loading modes: 'critical static st...'
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Yujiang Zhang, Bingyuan Cui, Guorui Feng, Chunwang Zhang, Yuxia Guo, Shuai Zhang, Zhengjun Zhang (2025). Shear mechanical properties of loaded rock under drilling and dynamic load and its influence on the plastic zone of roadway. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.06.009
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Frequently Asked Questions
What is the effect of drilling diameter on shear strength of rock?
The shear strength of drilled rock decreases linearly with increasing drilling diameter, as found in the study.
How do pre-static load and dynamic load amplitude affect cohesion and internal friction angle?
With increasing pre-static load level and dynamic load amplitude, cohesion first increases then decreases, while the internal friction angle consistently decreases.
What happens to the shear failure surface under combined static and dynamic loads?
The shear failure surface changes from rough to smooth due to static load enhancing the tooth cutting effect and dynamic load causing repeated friction of cracks.
How does borehole pressure relief influence the plastic zone of roadway?
Borehole pressure relief leads to an increase in the radius of the plastic zone of the surrounding rock following a quadratic function, which is critical for support design.
What is the practical significance of this research?
The research provides a theoretical basis for designing drilling unloading parameters and supporting parameters for rock burst roadways, helping to optimize safety and stability.
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