# Field Pull-Out Tests of Percussion Driven Earth Anchors (PDEAs)
## 6 Discussion  
Load variations among different anchors were attributed to the type of soil encountered at the anchor depth. It was observed that during installation, the rate at which the anchors were driven was associated with the ultimate pull-out capacity measured during field tests. Anchors 1 and 2 were driven at a relatively faster rate than anchor 3; hence, the associated field pull-out test showed a higher load for anchor 3 than for anchors 1 and 2. Additionally, compared to anchor 3, anchors 1 and 2 might be installed close to or within the moist zone since the two anchors' locations are near the middle of the slope. Moreover, it can be inferred and confirmed from the ERI resistivity images that anchors 1 and 2 were installed in the highly moist zone. In contrast, anchor 3 was installed in a dry, stiff, granular soil pocket area. During the installation of the anchors, the contract went through different equipment trials to determine the most efficient way to install these anchors. It was observed that the most effective way to install this type of PDEA anchor was by using mini-excavators with hollow hammer attachments and malleable steel hammering rods, along with experienced equipment operators that have performed similar work.  
The load-locking method used by the contractor utilized a mini-excavator along with a load reader to pull the anchor tendons until the desired locking load. After achieving the desired loading, the contractor locked the top termination using a manual button crimping tool. This method has limitations in that it does tend to leave some slack during crimping, and the slack causes the final locking load to be lower than the expected value. One obvious limitation of the PDEA anchors observed in this study's site work was that the PDEA system is a great candidate where there is no high variability of soil stiffness and  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Anchor ID** & \begin{tabular}{c} **Max. Field Pull-Out** \\ **Load (kN)** \\ \end{tabular} & \
\begin{tabular}{c} **Pull-Out Load Estimated** \\ **from Lab Data (kN)** \\ \end{tabular} & **Error (\%)** &
\begin{tabular}{c} **Pull-Out Load Estimated** \\ **from TCP Data (kN)** \\ \end{tabular} & **Error (\%)** \\ \hline Anchor 1 & 13.2 & & 30.1 & & 4.5 \\ \hline Anchor 2 & 14.0 & 9.23 & 34.1 & 13.8 & 1.4 \\ \hline Anchor 3 & 17.0 & & 45.7 & & 18.8 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Summary of maximum field pull-out load and pull-out capacity estimated from laboratory and TCP data.  
the existence of high gravel, rocks, and limestone layers. Therefore, this system is ideal for medium-stiffness clay materials.  
The prediction equation's limitation is that it does not consider the high variability in soil stiffness and the existence of gravel, rock, and sand seams in real-time conditions. However, this is a global challenge, as most geotechnical theories assume idealized conditions. It is recommended to use the in situ TCP values, especially for cut conditions, to minimize the limitations of this empirical equation and improve the accuracy of predicting PEDAs' ultimate pull-out load.