Abstract
To study the characteristics of rock fracture in deep underground under blast loads, some numerical models were established in AUTODYN code. Weibull distribution was used to characterize the inhomogeneity of rock, and a linear equation of state was applied to describe the relation of pressure and volume of granite elements. A new stress initialization method based on explicit dynamic calculation was developed to get an accurate stress distribution near the borehole. Two types of in situ stress conditions were considered. The effect of heterogeneous characteristics of material on blast-induced granite fracture was investigated. The difference between 2D models and 3D models was discussed. Based on the numerical results, it can be concluded that the increase of the magnitude of initial pressure can change the mechanism of shear failure near the borehole and suppress radial cracks propagation. When initial lateral pressure is invariable, with initial vertical pressure rising, radial cracks along the acting direction of vertical pressure will be promoted, and radial cracks in other directions will be prevented. Heterogeneous characteristics of material have an obvious influence on the shear failure zones around the borehole.
Highlights
Chinese Sichuan-Tibet railway, which will cross Sichuan Basin, Yunnan-Guizhou Plateau, and Qinghai-Tibet Plateau, is one of the most challenging railway lines to build in the world [1, 2], along with more than 90% of its length running on bridges or in tunnels [3]
Fewer radial cracks can be observed around the borehole. is is because that higher initial pressure leads to higher inner pressure, which suppresses radial cracks growing and propagating. ese phenomena can be seen clearly in the plots at 116.0 μs and 132.0 μs. ere are more radial cracks that propagate faster in numerical models under lower initial pressure
E numerical fracture plots are shown in Figure 16. ere are some clear differences for the models under the different ratios of initial lateral pressure and initial vertical pressure. e shape of pure shear failure tends to change into an ellipse with initial vertical pressure increasing. e radial cracks are not uniformly distributed along the borehole anymore
Summary
Chinese Sichuan-Tibet railway, which will cross Sichuan Basin, Yunnan-Guizhou Plateau, and Qinghai-Tibet Plateau, is one of the most challenging railway lines to build in the world [1, 2], along with more than 90% of its length running on bridges or in tunnels [3]. Lu et al [7] investigated dynamic rock response around the tunnel induced by the release of in situ stress by finite element method in ABAQUS code; Yang et al [8,9,10,11] and Yan et al [12] studied the rock damage near the tunnel under blast loads, and dynamic stress redistribution by plenty of numerical simulations, and the results show that the redistribution of dynamic contributes a lot to the rock damage. Xiao et al [13] conducted numerical research for dynamic rock stress unloading near the tunnel by dynamic implicit and explicit methods in LS-DYNA code.
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