| The high strain dynamic testing method is widely used around the world. As a effective testing method for single-pile vertical bearing capacity, it has many unparalleled advantages. The waveform fitting method which bases on wave motion theory is the most advanced and strict one to achieve an accurate outcome. It uses the iterative method by comparing the value from actual measurement and the calculated one. The current empirical calculating model which was put forward by Smith in 1960 would give rise to inaccuracy because the determination of the parameters is quite subjective. In addition, the application on the large diameter and over length cast-in-place pile is very difficult, thus the improvement and research have a high prospect.The Smith model and its improved model are introduced first in this paper, following the analysis of the impact caused by the elastic limits of soil in the waveform fitting method, then picked out the disadvantages of this method. The author designed a new testing method to kick these disadvantages and researched on how to gain the measured value. Based on the high strain dynamic testing measured value, the author defined the analysis method model and compared the results with the reliable measured value from static load test of pile. The project example has proved that this method is very effective and useful.For the large diameter and over length cast-in-place pile, the author started from soil friction. Based on the testing measured value of the soil friction, hypothesis test method is used on the data analysis of the high strain dynamic test. As to some huge error data, the author proposed improved method.Finally, in the research on the application of the high strain dynamic testing method, the author proposed some method to decrease the error and analyzed the factors of the error. In the end, the author compared the conditions of dynamic and static testing.
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