## 2 Tunnel Description and Geological Conditions
### Effectiveness Analysis of Grouting Treatment  
An evaluation of the grouting effect is an important part of the grouting reinforcement technique. The drilling acoustic wave, borehole TV, geological radar exploration, convergence monitoring, and numerical simulation were adopted to comprehensively examine the grouting effect and to accurately understand the actual situation of the grouting effect so as to ensure the reliability of the grouting effect and to prevent the recurrence of water inrush disasters due to insufficient grouting reinforcement. As depicted in Figure 11, the average values of wave velocity after grouting reinforcement were larger, which identified an excellent grouting effect. Meanwhile, the borehole TV was used for videotaping rock masses in the inspection holes to visually assess the integrity of the strata, the cementation of the grouting reinforced rock bodies, and the location of the water inrush. The results of the borehole TV showed that the integrity of grouting reinforced rock bodies improved significantly and that the rock mass had the self-stabilization ability. No collapsed holes were observed, and the grouting reinforcement effect of the rock mass was remarkable. Portable geological radar was employed to detect the grouted rock mass and to identify the weak areas of grouting. The elliptical circled area was the water-bearing zone. The rectangular area was the artificial interpretation zone, whose signals were abnormal, and the information of this area was ignored for interpretation. The reflected wave groups in the radar images before grouting were few and horizontally distributed, while those after grouting were more energetic and exhib  
Figure 10: Grouting hole arrangement and grouting site. ited a chaotic pattern with no regularity in the vertical and horizontal directions. This phenomenon demonstrated the change in the structure of the soil layer after grouting, which led to the destruction of the original soil layer after the slurry penetrated the soil layer. Horizontally and vertically distributed grouting areas or the staggered distribution of ungrouted areas formed a reflective surface between grouted and ungrouted areas. Due to the unevenness of this distribution, the above phenomenon reflected by radar images demonstrated the reinforcement effectiveness of the grouting. A convergence monitoring deformation analysis was carried out on section DLIBK0+840 of the tunnel. Since the upper bench was under excavation when the monitoring was conducted, the convergence monitoring points were arranged in the upper bench. Monitoring points A, B, and C were placed in the vault, left abutment, and right abutment, respectively. The convergence deformation of tunnel rock mass after grouting was controlled within 8.00 mm, which could ensure the safe construction of the tunnel. According to the laboratory mechanical test results of the core samples from the inspection holes, the comparison of the mechanical properties of the rock mass before and after the grouting of the 2# adit of Xianglushan tunnel was presented in Figure 12. The deformation modulus of the rock mass after grouting was increased by 37-53%. The rock mass possessed better elastic deformation capacity to external loads, which slowed down the deformation process of the rock mass. The shear strength parameters (cohesion c and friction coefficient tan\(\varphi\)) were increased by 10-14%, which enhanced the overall adhesion and improved the shear and sliding resistance of the rock mass. Figure 11: Results of borehole acoustic, borehole TV, geo-radar detection, convergence monitoring. The analysis on the comprehensive geological investigation and evolution of the water inrush of the water-resistant rock mass at the face showed that the rock mass reinforced by the proposed grouting scheme experienced less deformation and had a high self-stabilization capacity.