# Application Study of the High-Strain Direct Dynamic Testing Method
The key to applying the high-strain method for testing the load-bearing capacity of foundation piles lies in determining the soil resistance model and its corresponding parameters. [PERSON] and [PERSON] [28] highlighted the need to restrict fitting parameter ranges to address the uniqueness problem in common soil resistance models. In addition, the actual accuracy and application scope of high-strain dynamic pile testing, noting discrepancies, uncertainties in CAPWAP signal matching, negligible effects of soil properties on results, and potential misinterpretations, were discussed, as clearly explained in [29; 30]. [PERSON] et al. [31] found that for multi-layer soils with many parameters, fitting often relies heavily on the analyst's subjective judgment, introducing significant subjectivity. To address these issues, [PERSON] and [PERSON] [32] proposed a new method for dynamic testing of pile load-bearing capacity under high-strain conditions. Unlike traditional methods, this approach involves placing more strain sensors at various depths along the pile shaft. After a heavy hammer impacts the pile, these sensors accurately capture strain data at each measurement point. Based on these empirical data, the ultimate load-bearing capacity of the entire pile can be determined. This calculation model is straightforward and intuitive, avoiding the need for complex soil resistance models and allowing for direct calculation of the pile's ultimate load-bearing capacity. Thus, it is termed the \"high-strain direct dynamic testing method.\"  
Currently, research on this method is limited to theoretical analysis [33] and laboratory experiments [34]. Its effectiveness and reliability in actual projects have yet to be validated. Additionally, the sources and ranges of errors in using this method to test the load-bearing capacity of individual piles in engineering practice are not yet clear. Given that this method requires numerous strain sensors to be installed along the pile shaft, efficient sensor placement remains a technical challenge in practical applications. In previous studies, researchers mainly evaluated the accuracy of the high-strain method by comparing dynamic and static load test results [35; 36; 37; 38]. Although the high-strain direct dynamic method has improved computational principles over traditional methods, making bearing capacity predictions more direct, static load test results remain the benchmark for evaluating the reliability of dynamic testing results. The objective of this paper concerns the ability to use the high-strain direct dynamic method in engineering practice. The first part of this research focuses on explaining the basic principles of the arrangement of measurement instruments. The second part calculates the ultimate bearing capacity of a single pile using measured data. In the current research, the bridge project founded in Guangdong Province, China, was taken as a case study to apply the methods of the high-strain direct dynamic method under field conditions. To verify the method's reliability in detecting single pile-bearing capacity, static load tests were designed and implemented on selected test piles, using the results as a base for evaluating the accuracy of the dynamic test results. The error range and possible sources of error between the high-strain direct dynamic method and the static load test were compared and analyzed.