Abstract
Overstress in the surrounding rock of the roadway is a key reason that causes failures of deep roadways. Destressing blasting is one of the promising techniques that could improve the supporting quality. If the depth of the pressure relief blast hole is too shallow, the surrounding rock of the roadway will be broken or even collapsed. If the pressure relief blast hole is too deep, the pressure relief area will be located in the deep part of the surrounding rock of the roadway, which cannot achieve the purpose of releasing the stress in the shallow part of the surrounding rock and cause waste of the blast hole. The width or range of the pressure relief area should just fall in the high stress area of the surrounding rock of the roadway, so the pressure relief blast hole should have a reasonable depth. In order to quantitatively describe the relationship between borehole depth and the width of the stress relief zone, numerical simulations were carried out in ANSYS according to different borehole depths. The results show that the optimal destressing effect is achieved when borehole depth is 4 m. Peak stress of and is significantly reduced by 30.51% and 49.07% after blasting. Meanwhile, the high-stress area shifts about 4.8 m from the roadside to the depth of surrounding rock, thus a 3.8 m wide stress relief zone is formed around the roadside, thus, the aim of quantizing the effects of destress blasting is achieved.
Highlights
In order to quantitatively describe the relationship between borehole depth and the width of the stress relief zone, numerical simulations were carried out in ANSYS according to different borehole depths
The results show that the optimal destressing effect is achieved when borehole depth is 4 m
The main method widely used for the control and prevention of pressure bump, is an active approach to lower the frequency of rock burst [2]-[13]
Summary
In order to reduce the difficulties of deep roadway supporting and enhance the quality of supporting, this paper adopts destress blasting to improve the stress state of shallow surrounding rock and lower its stress level. Regarding research on deep roadway supporting, theoretical analysis, numerical modeling, and field monitoring methods have been utilized to study the effect of destress blasting. [M] is determined according to the following equation of modified yield criterion which considering the effect of mean stress σ m. This modified yield criterion can be used to determine whether the rock is in an elastic state or a plastic state.
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