# Research on the Self-Drilling Anchor Pull-Out Test Model and the Stability of an Anchored Slope
## 2 Experimental Analysis of the Key Performance of Hollow Self-Drilling Anchor Bolts
### Analysis of the Experimental Results  
Through systematic uplift tests, a total of 24 sets of valid experimental data were obtained. When the anchor bolt models were RS4, RS6, RS8, and RS10, the measured values of their  
Figure 4: Field test diagram. Figure 3: Qf100-100t hollow hydraulic jack. ultimate uplift capacity ranged from 178 to 208 kN, 257 to 383 kN, 289 to 367 kN, and 368 to 411 kN, respectively. The bond strength, which describes the bonding performance between the self-drilling anchor bolt anchorage body and the soil layer, is defined as the average bond stress at the interface between the anchorage body and the rock-soil mass within the anchoring section of the anchor bolt. It is calculated according to Equation (1). \[\tau=\frac{P_{a}}{\tau d\Omega} \tag{1}\]  
In Equation (1), \(P_{a}\) represents the ultimate uplift strength of the anchor bolt (kN); \(\Omega\) is the anchorage length (m); \(d\) is the diameter of the anchorage body (mm); and \(\tau\) is the bond strength between the anchorage body and the surrounding soil (MPa). According to Table 1, the range and average values for each group of anchor bolts were obtained, from which the coefficient of variation for each group of anchor bolts was calculated as 22%, 14%, 23%, and 11%, respectively. The corresponding coefficient of the variation curve is shown in Figure 5a (blue curve). According to the criteria for data dispersion outlined in the \"Technical Code for Foundation Pit Support\" (GJ120--2012) [11], which specifies that the range should not exceed 30% of the average value, the characteristic values of the ultimate uplift capacity for the four groups of anchor bolts can be taken as the average ultimate uplift capacity for each group, as recommended in the standard. These values are 187 kN, 274 kN, 341 kN, and 391 kN, respectively. Based on this, the relationship curve between anchorage length and average ultimate uplift capacity is plotted as the red curve in Figure 5a. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Group** & **Number** & **Anchorage Length/m** & **Ultimate Uplift Capacity/kN** & **Bond Strength/MPa** \\ \hline \multirow{8}{*}{RS4} & RS4-01 & 3.66 & 178 & 0.155 \\  & RS4-02 & 3.41 & 184 & 0.172 \\  & RS4-03 & 3.89 & 197 & 0.161 \\  & RS4-04 & 3.21 & 189 & 0.188 \\  & RS4-05 & 3.93 & 208 & 0.169 \\  & RS4-06 & 3.76 & 166 & 0.141 \\ \cline{2-5}  & Average & 3.64 & 187 & 0.163 \\ \hline \multirow{8}{*}{RS6} & RS6-01 & 5.75 & 272 & 0.151 \\  & RS6-02 & 5.53 & 257 & 0.148 \\  & RS6-03 & 5.77 & 296 & 0.163 \\  & RS6-04 & 5.84 & 269 & 0.147 \\  & RS6-05 & 5.64 & 283 & 0.160 \\  & RS6-06 & 5.57 & 269 & 0.154 \\ \cline{2-5}  & Average & 5.68 & 274 & 0.154 \\ \hline \multirow{8}{*}{RS8} & RS8-01 & 7.12 & 289 & 0.129 \\  & RS8-02 & 7.76 & 351 & 0.144 \\  & RS8-03 & 7.66 & 333 & 0.138 \\  & RS8-04 & 7.84 & 367 & 0.149 \\  & RS8-05 & 7.54 & 347 & 0.147 \\  & RS8-06 & 7.79 & 356 & 0.146 \\ \cline{2-5}  & Average & 7.62 & 341 & 0.142 \\ \hline \multirow{8}{*}{RS10} & RS10-01 & 9.34 & 377 & 0.129 \\  & RS10-02 & 9.68 & 389 & 0.128 \\ \cline{1-1}  & RS10-03 & 9.59 & 411 & 0.136 \\ \cline{1-1}  & RS10-04 & 9.83 & 368 & 0.119 \\ \cline{1-1}  & RS10-05 & 9.66 & 399 & 0.132 \\ \cline{1-1}  & RS10-06 & 9.79 & 403 & 0.131 \\ \cline{1-1} \cline{2-5}  & Average & 9.65 & 391 & 0.129 \\ \hline \hline \end{tabular}  
* The explanation of the meaning of the numbers in the table is the following (take RS4-01 as an example): RS stands for the self-drilling bolt model (taken from the bolt model RS388 in this test), the number 4 represents the length specification of the self-drilling bolt, and -01 represents the specific bolt number. The anchor solid diameter (hole size) of all bolts is uniformly 100 mm.  
\end{table} 
Table 1: Self-drilling anchor bolt test results. For the average bond strength of each group of anchor bolts, it is calculated using Equation (1) and the average ultimate uplift capacity values (187 kN, 274 kN, 341 kN, and 391 kN) determined according to the specifications mentioned earlier.