# Creep Behavior of Rocks and Its Application to the Long-Term Stability of Deep Rock Tunnels
## 5 Potential Factors Influencing Rock Creep
### Hydraulic Pressure, Stress Level, Water Content, and Temperature
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Study (Year)** & **Rock Type** & **Specimen Conditions** & **Testing Type** & \begin{tabular}{c} **Duration of Tests** \\ **(Days)** \\ \end{tabular} & **Effect of Water on Rock Creep** \\ \hline [PERSON] et al., (2010) [90] & Tage tuff & Waterlogged & Uniaxial compression creep tests & 912.5-4380 & \begin{tabular}{c} Creep behavior of \\ water-saturated Tage tuff \\ is shortened. \\ \end{tabular} \\ \hline [PERSON] et al., (2014) [91] & Green-schist & Immersed in clean water & \begin{tabular}{c} Biaxial compression \\ creep tests \\ \end{tabular} & 32.5–46.6 & \begin{tabular}{c} The increase in instantaneous \\ axial and lateral strains is \\ caused by the increase of \\ water content. \\ \end{tabular} \\ \hline [PERSON] et al., (2015) [83] & Limestone & \begin{tabular}{c} Saturated and \\ immersed in water \\ \end{tabular} & \begin{tabular}{c} Tiaxial compression \\ creep tests \\ \end{tabular} & 8–40 & \begin{tabular}{c} The increase in water and \\ hydraulic pressure results in an \\ increase in creep strain rate. \\ \end{tabular} \\ \hline [PERSON] and [PERSON] (2017) [92] & Mudstone & \begin{tabular}{c} Saturated in \\ purified water \\ \end{tabular} & \
\begin{tabular}{c} Uniaxial compression \\ tests and multistage \\ creep tests \\ \end{tabular} & 1.90–2.30 &
\begin{tabular}{c} The reduction in short-term \\ mechanical properties and the \\ increase in both creep strain \\ and creep strain rate are \\ provided by the presence \\ of water. \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of the effects of water on the creep behavior of rocks (adapted from [89]). These data are taken into account given that the rock samples were mainly collected from deep rock tunnels, and also because of the available relevant studies. The maximum duration or duration range of the tests is provided to better understand the results. Temperature is another key concern significantly affecting the creep behavior of rocks. Variation in the microstructure of rocks can be caused by changes in temperature [96]. This induces serious impacts on rock properties. Specifically, high temperatures usually deteriorate rock properties by debilitating the rock system, diminishing effective stress, and enhancing pore pressure [86]. Both short-term and long-term creep behaviors of rocks are influenced by increasing temperature. Tertiary creep as well as the breakage of rock can prematurely occur at high temperature [97]. This is generally due to the propagation of cracks which is favored by the increase in temperature. It is therefore important to take into account the range of temperatures to which the rocks are exposed. It is observed that nowadays, tunnels and mines are being built deeper and deeper and their surrounding rocks are experiencing complex conditions where temperatures are high [98]. Consequently, the effects of temperature fluctuations must be seriously considered in any study of rock creep aimed at effectively predicting the long-term stability of such structures. A summary of relevant temperature effects on the creep behavior of different rock types is presented in Table 2.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Study (Year)** & **Rock Type** & **Specimen Conditions** & **Testing Type** & \ \begin{tabular}{c} **Duration of Tests** \\ **(Days)** \\ \end{tabular}  &
\begin{tabular}{c} **Effect of Temperature on Rock Creep** \\ **Effect of Water on Rock Creep** \\ **Effect