# Numerical Simulation of Rock Mass Structure Effect on Tunnel Smooth Blasting Quality: A Case Study
###### Abstract  
Taking the Zigaojian tunnel, Hangzhou-Huangshan high-speed railway, China, as background, the rock mass structure effect on smooth blasting quality was studied. Four rock mass structures were determined on the basis of the information collected on the tunnel site. Smooth blasting finite element models were established using LS-DYNA. The accuracy of the numerical calculation model was verified by comparing the overbreak and underbreak between the numerical simulation and monitoring. Orthogonal numerical test was used to study the rock mass structure effect through single factor and main effect analysis methods. With the decrease in rock mass integrity, the smooth blasting overbreak of tunnels with massive integrity structure, massive structure, layered structure, and cataclastic structure increased. For massive integrity structure and cataclastic structure, the peripheral hole spacing should be emphatically considered. Meanwhile, in massive structure and layered structure, the included angle and spacing of structural planes had a great influence on the smooth blasting quality. The research results could provide a reference to improve the quality of similar tunnel smooth blasting. t  
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Many factors affect the quality of tunnel smooth blasting, which is difficult to control. How to correctly and reasonably control the quality of tunnel smooth blasting has attracted the attention of researchers, and fruitful studies have been carried out. During the construction of the Fuling highway long tunnel, [PERSON] et al. [9] conducted 18 field smooth blasting tests and studied the influence of rock-saturated uniaxial compressive strength, peripheral hole spacing, pressure relief hole spacing, the minimum charge amount of peripheral holes, and linear charge concentration on the quality of tunnel smooth blasting. On the basis of the three-dimensional blasting model of LS-DYNA, [PERSON] et al. [10] simulated tunnel smooth blasting. Meanwhile, the orthogonal test design method was used to study the effects of seven factors on the over- and under-excavation of the tunnel, including peripheral hole spacing, least resistance line, charge density, charge form, rock mass type, detonation speed, and borehole inclination. The study revealed that the rock mass type has the greatest effect on the blasting quality, while the charge density and detonation velocity could be regarded as secondary factors under specific site conditions. On the basis of model tests and field investigation, [PERSON] et al. [11; 12] evaluated the joint direction and rock mass quality affecting tunnel overbreak and considered that blasting quality was related to the average rock mass size, depth, and geometric dimensions of the cross-sectional profile. [PERSON] et al. [13] used the horizontal layered rock mass large-section tunnel as the research object and proposed the cutting methods of \"center holes and four-wedge cutting holes\", \"empty holes, long holes, short holes, and additional relief holes\", and the fine excavation mode of the maximum single hole charging scheme. [PERSON] et al. [14] improved smooth blasting parameters and construction technology in large dip tunnels in accordance with the actual construction situation on site, the rock, and the explosive properties. In smooth blasting, [PERSON] et al. [15] proposed a controlled blasting method using pilot holes to smooth the smooth fracture surface and reduce the blasting damage zone. [PERSON] et al. [16] studied the blasting method of slotted tube charging structure in fault stratum through a field test. The research showed that the circumferential hole with a slotted tube charging structure significantly improved the overbreak phenomenon in the fault stratum. [PERSON] et al.