## 5 Relevant Measures Guaranteeing Tunnel Long-Term Stability
In harsh rock environments, traditional monitoring techniques cannot provide real-time alerts on the health status of deep soft rock tunnels. In this sense, it is of great significance to opt for reliable monitoring methods, as relayed by [PERSON] et al. [68] and [PERSON] et al. [69]. Indeed, the primary support and the secondary support must be properly monitored thanks to high-performance monitoring systems capable of providing effective information in real time on the state of health of the tunnel. Long-term monitoring using appropriate remote sensors is of utmost consideration to prevent any unexpected or unwanted event in the tunnel. For instance, the stability limit can be overtaken unexpectedly at any time when the supports are heavily stressed and the convergence deformation becomes very strong [60], and this can happen during the sudden triggering of dynamic situations. Additionally, over time, structural deficiencies can seriously disrupt the overall health and functionality of the tunnel. It is indeed worth \begin{table}
\begin{tabular}{c c c} \hline \hline
**Support Scheme Component** & **Characteristics** & **Remarks** \\ \hline Pressure aid & 300 mm \(\times\) 300 mm groove & Diminish any extent of floor heave. \\ Deep grouting & Pressure 0.5–3.0 MPa; flow rate 50 L/min & Penetrate sufficiently at 10 m into the surrounding rocks. \\ Rock bolts & \(\Phi\)42 \(\times\) 7000 mm; spacing: 200 mm (roof) & They are longer in the floor than in the sidewalls. \\ Cable bolts & \(\Phi\)42 \(\times\) 6000 mm; spacing: 200 mm (sidewalls) & the sidewalls. \\ Cable bolts & \(\Phi\)35 \(\times\) 10,000 mm; spacing: 300 mm (roof) & They are longer in the floor than in the sidewalls. \\ Steel arch & 36 U-shaped steel arches; row spacing: 250 mm & They are the same anywhere in the tunnel alignment. \\ Secondary lining & Reinforced concrete with minimum & \\ Secondary lining & compressive strength of 50 MPa, tensile & Correct the final structure of the tunnel. \\  & strength of 8 MPa, thickness 400 mm & \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Details related to the proposed robust support scheme. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Support Scheme Component** & **Type** & **Main Functions** & **Main Characteristics** \\ \hline \multirow{4}{*}{Pressure aid} & \multirow{4}{*}{Groove} & Combat stress concentration at the corners of the surrounding rocks, mainly applied in the tunnel roof to decrease the floor heave risk. & Sufficient wide with adequate equipment. \\ \hline \multirow{2}{*}{Deep grouting} & \multirow{2}{*}{High performance} & Reinforce the mechanical properties of the surrounding rocks, act as anti-leakage. & High pressure and high flow, penetrate until 10 m deep into the surrounding rocks. \\ \hline \multirow{4}{*}{Rock bolts} & \multirow{4}{*}{Fully grouted} & Consolidate and help the surrounding rocks to maintain their stability. & Ribbed steel shank, optimal diameter, sufficient length exceeding the host rock plastic zones, strong elongation, able to bear strong static and dynamic loads. \\ \hline \multirow{2}{*}{Cable bolts} & \multirow{2}{*}{Fully grouted} & Strengthen the functions of rock bolts, and also control local deformations. & Strong flexibility, extreme length, able to bear strong static and dynamic loads. \\ \hline Steel arch & U-shaped & Control local deformations. & High performance. \\ \hline \multirow{2}{*}{Secondary lining} & \multirow{2}{*}{Reinforced concrete} & Reinforce the primary support, act as waterproof structure, and act as structural corrector. & High performance reinforced concrete, sufficient depth. \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Components of the proposed robust support scheme. remembering, as pointed out by [PERSON] et al. [70], the deterioration of tunnel surrounding rocks by creep is considered to be a continuous process. Appropriate remote sensors can provide suitable real-time alerts at any time regarding the overall structural health conditions of the tunnel. The proposed long-term monitoring is comprehensive.