A numerical study on mechanical behavior of jointed rock masses after tunnel excavation

Zhang, Wanzhi; Xu, Bin; Mei, Jie; Yue, Guangyao; Shi, Weihang

doi:10.1007/s12517-020-05358-y

Cited by 10 publications

(1 citation statement)

References 22 publications

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“…Figure 9near here] 2.4.2 Separating, rotating and sliding down of unstable rock blocks Affected by the cross cutting of beddings and joints and tunnel contour line, unstable rock blocks are formed in the arch of tunnel after excavation(Wu and Chen 2001;Zhang et al 2012). In our previous work, the failure modes of the unstable rock blocks formed by the intersection of horizontal beddings and one or two sets of joints and the tunnel contour line were studied in detail by using the ubiquitous joint model embedded in FLAC3D(Zhang et al 2020). Fig.10shows the numerical model of tunnel.…”

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Experimental Study of Blasting Excavation for Large Cross-Section Tunnel in Horizontal Layered Rock Mass

Mei

Zhang

et al. 2021

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The drilling and blasting method is still the main method in mountain tunnel excavation. For large cross-section tunnel in horizontal layered rock mass, tunnel blasting often causes serious overbreak and underbreak. In this study, blasting excavation tests of tunnel upper face were conducted and failure mechanisms of surrounding rocks with weak beddings and joints were analyzed based on the Panlongshan tunnel. Then, the blasthole pattern, the cut mode, a variety of peripheral holes, the charge structure and the maximum single-hole charge were optimized. Compared with the failure characteristics, overbreak and underbreak, and deformations of surrounding rocks before and after optimization, the latter was better in tunnel contour forming and surrounding rock stability. The results show that after optimization, the large-area separation of vault rock mass is solved, the step-like overbreak of spandrel rock mass is reduced and the large-size rock blocks and underbreak are avoided. The maximum linear overbreak of vault, spandrel, and haunch surrounding rocks is decreased by 42.3%, 53.7% and 45.1%, respectively. The underbreak at the bottom of the upper face is reduced from -111.5 to - 16.5 cm. The average overbreak area is decreased by 61.1%. In addition, the displacements after optimization finally converge to the smaller values. The arch crown settlement and the horizontal convergence of haunch are reduced by about 21.6% and 18.3%, respectively. Furthermore, from the completion of blasting excavation to the stabilization of surrounding rock, it takes less time by using the optimized blasting scheme.

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confidence: 99%