## 3 Laboratory Experiment
### Grotated Surrounding Rock Strength  
The mechanical behavior of rock and soil conformed to the Mohr-Coulomb failure criterion, and the main grouting and solid strength parameters were the friction angle \(\varphi\) and the cohesive force c. The grouted surrounding rock strength has a great relationship with the strength of the rock mass before grouting, the strength of the grout stone body, grouting pressure, and time. When the grouting pressure and time met the specification requirements, the strength of rock and soil before grouting was the main influencing factor. The UCS of rock and soil before grouting, water-cement ratio, and strength of rock and  
Figure 6: Bleeding rate of cement slurry with different water-cement ratios. Figure 7: Compressive strength of cement sample with different water-cement ratios. soil after grouting reinforcement were obtained from references [34; 35; 36; 37; 38; 39; 40; 41], combined with the relationship between rock mass UCS parameters and shear strength parameters (3) and (4), the friction angle \(\varphi\) and cohesion c increase rate of grouted surrounding rock were obtained. Table 1 shows the statistical results. \[\zeta_{coh}\ =\ 0.95\zeta_{c}, \tag{3}\]  
\[\xi_{f}\ =\ 0.05\zeta_{c}, \tag{4}\]  
where \(\xi_{coh}\), \(\xi_{f}\) and \(\xi_{c}\) are the increase rate of cohesive force \(c\) (%), friction angle \(\varphi\) (%) and UCS (%), respectively. The data in Table 1 are plotted in Figures 8 and 9. The relationship between the UCS of rock and soil before grouting and the shear strength parameter increase rate of rock and soil after grouting were obtained by curve fitting when the water-cement ratio \(\eta\) of the grout was 0.75 and 1.0. The distribution of the data has certain regularity. The cubic polynomial was used to fit the limited data corresponding to the slurry water-cement ratio \(\eta\) = 0.75 and \(\eta\) = 1.0, and the fitting correlation coefficients R\({}^{2}\) were 0.9738 and 0.8349, respectively, indicating that the model fitting effect was good. The UCS, internal friction angle, and cohesion of the rock and soil before grouting in the construction area were determined according to geological survey data or laboratory experiments. The shear strength parameters of rock mass under different grouting reinforcement were calculated. According to the detailed survey report of Haicang Tunnel, the UCS of the surrounding rock before grouting within the tunnel excavation range was 0.108 MPa, the internal friction angle \(\varphi\) = 20\({}^{\circ}\), and the cohesive force \(c\) = 0.06 MPa. Substituting the unconfined compressive strength into the fitting curve formulas of Figures 8 and 9, the shear strength increase rates of the rock and soil mass were obtained as \(\xi_{coh(\eta\ =\ 0.75)}\ =\ 596.5\), \(\xi_{f(\eta\ =\ 0.75)}\ =\ 31.4\), \(\xi_{coh(\eta\ =\ 1.00)}\ =\ 236.5\), and \(\xi_{f(\eta\ =\ 1.00)}\ =\ 12.4\). According to the shear strength increase rate, the internal friction angle \(\varphi\) = 20.28\({}^{\circ}\) and the cohesion force \(c\) = 0.4179 MPa when the water-cement ratio \(\eta\) = 0.75. Similarly, the internal friction angle \(\varphi\) = 22.49\({}^{\circ}\) and cohesion force \(c\) = 0.2019 MPa when the water-cement ratio \(\eta\) = 1. Figure 8: Relationship between the UCS of rock and soil before grouting and the shear strength parameter increase rate of rock and soil after grouting when water–cement ratio \(\eta\) = 0.75: (**a**) Relation between the increase rate of \(\varphi\) and the UCS of rock and soil before grouting; (**b**) relation between the increase rate of \(c\) and the UCS of rock and soil before grouting.