# Application Study of the High-Strain Direct Dynamic Testing Method
## 3 High-Strain Direct Dynamic Test and Static Load Test  
### Engineering Background and Ground Investigation  
This paper uses a bridge project in Zhuhai City, Guangdong Province, China, as a case study. The proposed site for this project is located upstream of a river. Therefore, the pile foundation must penetrate through a thick layer of soft clay and embed into the moderately weathered rock layer to support the bridge's superstructure. There are four arch bases beneath the bridge. Arch bases 1 to 3 utilize nine straight bored piles with a diameter of 2.2 m and three inclined steel pipe piles with a diameter of 1.5 m (inclined at 7 degrees). While arch base #4 employs twenty-four straight bored piles with a diameter of 2.2 m and fourteen inclined steel pipe piles with a diameter of 1.5 m (inclined at 7 degrees). The foundation piles are designed as rock-socked piles, requiring an embedment into the moderately weathered granite of no less than 2D. The reinforcement for the piles uses HRB400\(\varphi\)32 main bars, and the concrete used is C30 underwater concrete. The design parameters of the foundation piles are shown in Table 1.  
In routine traditional high-strain testing for pile quality, random sampling is typically employed at the project site. In this study, 15 straight test piles were randomly selected for hammer impact testing. Initial data collected from on-site testing equipment revealed that some test piles did not yield complete or valid data. This issue was primarily due to the loosening or damage of the Fiber Bragg Grating (FBG) sensors during concrete pouring in certain piles. Additionally, some test piles experienced eccentric hammer impacts, resulting in significant deviations and invalid data.  
To address this, the most complete and valid test pile from each of the four arch bases was selected for detailed analysis and to conduct static load tests. The analysis focuses on  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Material** & **Diameter (m)** & **Elastic Modulus GPa** & **Poisson’s Ratio** & **Bulk Density kN/m\({}^{3}\)** \\ \hline C30 & 2.2 & 34 & 0.2 & 24 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Pile design parameters.  
these four test piles, identified as #1-5, #2-7, #3-9, and #4-17. Basic information about these four test piles is presented in Table 2.  
It is worth noting that the region features of Zhuhai City, Guangdong Province, extensive coastal plains with alluvial soils. These areas are typically characterized by soft, silty, and clayey soils deposited by rivers and tidal actions, which can pose challenges for construction because of their compressibility and potential for settlement. Therefore, accurate assessment of soil parameters often requires a comprehensive approach to drilling sampling and in situ testing. Based on the geological age, origin, and physical-mechanical properties of the foundation soil, along with the results from geotechnical tests and in situ test indicators, and integrating regional experience, the recommended geotechnical parameters for each rock and soil layer are provided in Table 3. The soil profiles revealed by site drilling beneath the four arch bases are illustrated in Figure 4.