# Research on an Index System for the Earthquake Disaster Resistance Capability of Highway Tunnels
## 4 Seismic Capability Index System of Highway Tunnels
### Analysis of the Evaluation Index
#### 4.1.1 Index Analysis of the Engineering Geological Factors  
Through the preliminary identification of the influencing factors of seismic damage in highway tunnels, it is concluded that the indicators of engineering geological factors include the surrounding rock characteristics, side slope characteristics, fault crushing belts and engineering environment. However, according to engineering experience [33; 34; 35; 36; 37; 38; 39; 40; 41; 42; 43; 44; 45; 46; 47; 48] and  
Figure 7: Fault tree of seismic damage scenes for highway tunnel sections passing through a fault crushing belt.  
relevant specifications, foundation conditions also have an important impact on the seismic capability of highway tunnels. Therefore, the foundation conditions are included in the impact indices of engineering geological factors.  
By consulting the relevant specifications and engineering experience (see Table 1 for details of the relevant regulations or experience), the surrounding rock indicators can be expressed by the surrounding rock grade, surrounding rock cavity, high ground stress, bias, burial depth, underground water and surrounding rock interface. The characteristic indicators of the side slopes include the side slope gradient, side slope height and weathering degree. The indicators of fault crushing belts can be expressed by the fault movement and fault width. The engineering environmental indicators are evaluated by the presence or absence of rockfall sites and adjacent engineering activities. The foundation condition indicators are evaluated by the bearing capacity of the foundation and the possibility of liquefaction of the foundation soil.  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Index of Engineering Geological Factors** & **Relevant Specifications and Engineering Experience** & **Speffic Indicators** \\ \hline \multirow{8}{*}{Characteristics of surrounding rock mass surrounding rock mass (ITG 3370.1-2018)} & (1) & The key monitoring objects in advanced geological prediction include surrounding rock cavities, which play an important role in tunnel safety. \\  & (2) & The detailed design requirements and checking calculation requirements for high ground stress and bias are made in the specification. \\  & (ITG/T 3660-2020) [49]. & (3) & Surrounding rock grade; surrounding rock of the tunnel should be comprehensively judged according to the buried depth and surrounding rock conditions. \\  & (ITG 3370.1-2018) [50]. & (4) & In general, the seismic resistance of tunnels in hard and complete rock mass is favorable, and the seismic resistance of tunnels in poor geological areas is unavoidable. \\  & (5) & The surrounding rock interface is divided into unfavorable sections, which should be avoided or strictly fortified when selecting the tunnel site. \\ \hline \multirow{8}{*}{Characteristics of side slope} & \multicolumn{1}{p{113.8 pt}}{\({}^{*}\)Specifications for Design of Highway Tunnels Section 1 Civil Engineering (ITG 3370.1-2018)} & The slope, slope height and weathering degree of the slope determine the stability of the slope. \\  & (1) & According to the analysis of disaster cases, the secondary disasters such as damage and blockage caused by the tunnel portal during the earthquake are caused by the high slope toe, large slope and high weathering degree of rock mass (soil). \\  & Related engineering experience & (2) & The characteristics of the slope are represented by the slope height, slope height and slope ratio as variables. \\  & (3) & The integrity and cohesion of the slope soil determine whether the landslide occurs, which can be judged by the degree of weathering. \\ \hline \hline \end{tabular}
\end{table}
Table 1: Index analysis of the engineering geological factors.