# Numerical Simulation of Rock Mass Structure Effect on Tunnel Smooth Blasting Quality: A Case Study
## 2 Material and Methods
### Rock Mass Structure Analysis and Mechanical Information  
Information on the structural surface of the tunnel face was collected using manual collection, three-dimensional scanners, and infrared thermal imaging cameras onsite. The occurrence and spacing of structural planes, which were easy to identify, were directly measured by geological compass. The infrared thermal imager was used for auxiliary discrimination of discontinuities that were difficult to identify because of dust cover and weathering zone. For the structural planes beyond the manual measurement range, the three-dimensional scanner was used for omnidirectional scanning, and the results were imported into the computer for three-dimensional data reorganization. Geomagic Studio Software was used for post-processing of the scanning results. After virtual imaging was conducted, the occurrence was measured. The uniaxial compressive and tensile strength of  
Figure 1: Geological longitudinal section of Zigaojian tunnel (unit: m). rocks were measured by point load test. Through field measurement of rock mass structure information and structural plane statistics, the monitoring section DK 149 + 928-DK 149 + 957 was found to have a set of controllable structural planes of 157\({}^{\circ}\)/62\({}^{\circ}\), with an average spacing of 3 m, which is marked with a red line in Figure 2a. The rock mass structure type was a massive integrity structure. The three-dimensional scanning pictures and geometric model diagrams are shown in Figure 2b,c. The average tensile strength and compressive strength of rocks were 2.37 and 44.57 MPa, respectively, as measured by point load test. Many and staggering structural planes were found in DK 150 + 876-DK 150 + 895. The rock mass was very broken, no control structural plane was observed, and the rock mass was a cataclastic structure. The structural plane information is shown in Figure 3a,b. The average tensile strength of the rock was 1.53 MPa, and the average compressive strength was 32.17 MPa. Due to the extremely developed structural planes in the fragmented structure, it could be considered as a continuous medium in the numerical simulation. The strength of the rock mass was reduced based on the rock strength. The geometric model was the same as the complete rock mass structure, as shown in Figure 3c. Starting from the 1970s, many scholars have proposed some treatment methods for reducing rock mass strength when jointed rock mass was considered as an equivalent continuous medium. In 1993, [PERSON] [24] proposed using elastic longitudinal wave velocity to estimate the uniaxial compressive strength of weak rock masses. In 1995, [PERSON] [25] et al. proposed a formula for estimating the uniaxial compressive strength of rock mass by using its longitudinal wave velocity. In 2005, [PERSON] and [PERSON] [26] proposed an empirical method for estimating rock mass strength on the basis of deformation modulus. The strength reduction coefficient of the above empirical determination method of the equivalent strength of jointed rock mass was based on wave velocity or elastic modulus, but it was not satisfactory from the perspective of engineering application, and the dispersion of the estimation results was large. The reason may be that these evaluation standards were not fully considered, and the evaluation factors were greatly affected by the occurrence of environmental conditions of the tested rock mass. Thus, in recent years, some scholars proposed a method to determine the equivalent continuum strength on the basis of rock mass classification index, and they achieved good results. In 1997, [PERSON] and [PERSON] [27] proposed the uniaxial compressive strength formula of rock mass that was based on the study of a large number of complete rock brittle failure test data and many jointed rock mass characteristic models. In 1995, [PERSON] and [PERSON] [28] proposed an estimation formula of rock mass equivalent strength that was based on the RMR rock mass classification index.