## 4 Engineering Application of the ASRB Parameter Design Method
### Scheme Design and Effect Evaluation of ASRBs
#### 4.2.4 Determination of Test Scheme Indicators  
According to the description in Section 3.3.4, the average stress release rate and the average volume release energy were used in this study as the evaluation indexes of the stress release and energy dissipation effects of ASRBs under different scenarios. In the monitoring location, for the stress and energy distribution pattern after the deployment of ASRBs, the monitoring area as shown in Figures 12 and 13 was used in this study for the calculation of test indexes, respectively.  
(1) Stress aspect  
From the viewpoint of stress, the stress release effect was examined within the range of one tunnel diameter fore and one aft of the current tunneling head this study. Therefore, the face of the current tunneling head and the cross-section at both 0.5 diameters and one diameter fore and one aft of the current tunneling head were selected as the monitoring sections (Figure 12a). In addition, the stress release area was mainly concentrated between adjacent boreholes on one side of the tunnel cross-section, so the midpoint position on the arc connecting two adjacent boreholes on one side of each monitoring section was selected as the monitoring point, as shown in Figure 12b.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Factors**} & \multicolumn{4}{c}{**Factor Level**} \\ \cline{2-5}  & **1** & **2** & **3** & **4** \\ \hline Inclination (\({}^{\circ}\)) & 13.00 & 14.30 & 15.60 & 16.90 \\ Length (m) & 30.00 & 33.00 & 36.00 & 39.00 \\ Included angle (\({}^{\circ}\)) & 10.00 & 11.00 & 12.00 & 13.00 \\ Aperture (m) & 0.20 & 0.22 & 0.24 & 0.26 \\ Spacing (m) & 2.00 & 2.20 & 2.40 & 2.60 \\ \hline \hline \end{tabular}
\end{table}
Table 7: The level of each factor in the orthogonal test.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Experiment Number** & **Inclination (\({}^{\circ}\))** & **Length (m)** & **Included Angle (\({}^{\circ}\))** & **Aperture (m)** & **Spacing (m)** \\ \hline
1 & 13.00 & 30.00 & 10.00 & 0.20 & 2.00 \\
2 & 13.00 & 33.00 & 11.00 & 0.22 & 2.20 \\
3 & 13.00 & 36.00 & 12.00 & 0.24 & 2.40 \\
4 & 13.00 & 39.00 & 13.00 & 0.26 & 2.60 \\
5 & 14.30 & 30.00 & 11.00 & 0.24 &Energy aspect  
From the perspective of energy, the energy calculation area was arranged as shown in Figure 13 in combination with the distribution of the stress release area mentioned above. Along the TBM tunneling direction, the area encompassing one tunnel diameter fore and one aft of the current tunneling head was divided into four energy monitoring areas, each one half the tunnel diameter in length. Each monitoring area extended along the axis of the ASRB. At the cross-section of the tunnel, to reduce the interference of stress and energy concentrations on the results in the monitoring area, it was only extended to the location of one diameter of the borehole wall, and the inner diameter and outer diameter of the monitoring area were constrained by the axial position of the inner and outer ASRBs to plan the regional distribution of energy calculation.  
Figure 12: Schematic diagram of monitoring points for average stress release rate: (**a**) top view of the model; (**b**) left view of the model.