## 10 Conclusions  
The propensity for plugging based on basic pile properties such as pile diameter, length, and L/D ratio was investigated using a database of load tests on 74 open-ended pipe piles. The closeness between the capacity interpreted from a load test and that computed for three plugging conditions was used to identify plugging for each design method, then a voting system was employed to decide the overall plugging condition of a pile. Four commonly used designed methods were used to compute the calculated capacity including: (1) FHWA, (2) USACE, (3) Revised Lambda, and (4) API. The results  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Method** & **Average** & **Std. Dev.** \\  & \(Q_{c}/Q_{m}\) & \(Q_{c}/Q_{m}\) \\ \hline FHWA & 1.54 & 1.01 \\ \hline USACE & 1.28 & 0.82 \\ \hline Revised Lambda & 1.15 & 0.53 \\ \hline API & 1.2 & 0.62 \\ \hline NGI-04 & 0.99 & 0.35 \\ \hline ICP-05 & 1.18 & 0.84 \\ \hline FUGRO-04 & 1.13 & 0.80 \\ \hline UWA-05 & 1.15 & 0.82 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Average performance statistics of all design methods employed in this study.  
were checked using 23 load tests where CPT soundings were available and a similar voting methodology was employed but using four CPT-based pile design methods including (i) NGI-04, (ii) UWA-05, (iii) FUGRO-04 and (iv) UWA-05 methods. Finally, the results were validated using 24 case histories were plugging records have been reported. A summary of the findings is presented below:  
Most of the piles in the database of 74 piles used in this study appear to be unplugged, evidenced by that condition providing the closest capacity to the one interpreted from the load test. This was also the case for the test dataset of 24 case histories where plugging records have been reported;  
No plugging pattern was found based on a diameter-length relationship or a length-L/D ratio relationship, or soil condition, as data was largely scattered;  
Piles larger than 0.9 m (36 inches) in diameter have higher likelihood of being unplugged, while piles smaller than 0.5 m (20 inches) tend to be plugged. These dimensions are proposed as a diameter criterion for preliminary determination of the plugging condition of a pile with an average accuracy of 70 \(\pm\) 10%.  
Both authors contributed to the study conception and design. The specific roles are: data manipulation, software development, investigation, formal analysis, methodology, visualization, writing original draft, A.K.; conceptualization, supervision, validation, project administration, writing review and editing, M.I. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
All data used during the study appears in the submitted article.  
This study employed data from FHWA DFLTD v2 as well as [PERSON] piling database. The authors are grateful to [PERSON] and FHWA for providing the data. The databases were ported from their original sources to a relational database by [PERSON], now Data and Analytics Leader at Haley and Aldrich, as part of his doctoral dissertation at NYU. [PERSON], PE, now Associate Principal/Vice President GZA Geoenvironmental, reviewed the geotechnical data of all load tests as part of his master's thesis at NYU. The authors gratefully acknowledge these previous efforts, without which this work would not have been possible.  
The authors declare no conflict of interest and certify that they have no affiliations with or involvement in any entity with any financial, or non-financial, interest in the subject matter or materials discussed in this manuscript.