## 2 Materials and Methods
### Field Test Details  
The pull-out test scheme of rock bolts was conducted at the construction site for the Suseo-Pyeongtaek high-speed railway in the South Korean capital, Seoul. This site features the weathered gneiss rock, soft gneiss rock, and moderate gneiss rock assessed on three rock-mass classification systems (RQD, RMR, and Q systems), as shown in Table 1. Owing to the stress-strain relationship at the tunnel face [17], the rock-mass quality at the tunnel face during construction was comparatively lower than that predicted during the design. At the tunnel face, soft filling materials were observed in the dense joints. The groundwater leakage rate was 0-3.78 L/min from the soft rock and weathered rock, as shown in Figure 1a. The tunnel in this construction site was 12.6 m wide and 9.7 m high, with an average depth of 50 m at the location where pull-out tests were conducted. The conventional method was used during tunnel construction and was supported with fiber-reinforced shotcrete and rock bolts (25 mm in diameter). The thickness of shotcrete is 200, 150, and 100 mm for weathered, soft, and moderate rock mass, respectively. The 4 m long rock bolts were used in the moderate and soft rock masses, and the 5 m long rock bolts were used in the weathered rock mass. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Rock-Mass** & \multicolumn{3}{c}{**Rock-Mass Class**} \\
**Classification System** & & **Weathered Rock Mass** & **Soft Rock Mass** \\ \hline RQD & \textless{}25 & 25–50 & 50–75 \\ RMR & \textless{}20 & 21–40 & 41–60 \\ Q & \textless{}0.1 & 0.1–1 & 1–10 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Ground condition at site, based on rock-mass classification systems. Figure 1: (**a**) Groundwater in flow-through drilled hole, (**b**) pull-out test machine, and (**c**) the points of pull-out test. Pull-out tests were conducted to examine the behavior of rock bolts under ASTM standards [18] for 3, 4, and 5 m rock bolts in the three different rock-mass classes of Table 1. The tests were executed on fully grouted rock bolts, D25, installed in a 38 mm diameter drilled hole and with a water-cement ratio of up to 40%. Instead of the water-cement grout, resin is used as grout material in a few tests, as well. The influence of the mortar's curing time on the rock-bolt pull-out behavior was studied for the weathered and moderate rock mass. For the purpose of comparison, the inflated steel-tube rock bolts were also tested via the pull-out test methods in the wet ground condition. The details of 142 field tests, whose results are included in this manuscript, are shown in Table 2. During the expansion and installation of this type of rock bolt, the water pressure was increased up to 30 MPa. During the tests, the pull-out force was incremented by 10 kN per minute, and the load displacement was measured at each step. The pull-out failure was defined when either the total displacement reached 12.7 mm or the maximum load remained constant with displacement. Based on dry and wet conditions, the wet condition is further divided into small and large inflow sections, taking 1.0 L per minute as a reference. Figure 1b, c shows the machine and the parts used during the test, and the points of the pull-out test, respectively. The main components of the rock-bolt pull-out test machine are the hand pump with a dial gauge, flexible hose pipe, and face plate for the measurement of the working and ultimate capacities of the rock bolt. This manually operated piece of equipment has a pull-out capacity of 300 kN and was operated adequately during the field tests, following ASTM standards. Different points were selected due to the ground grade/type, water inflow, and length of the rock bolt installed, as per the construction design of the project. Data from previous studies regarding the factors affecting the performance of fully grouted rock bolts (conducted either in the field, laboratory, or through modeling) are combined.