Because of simplicity and easiness, dynamic pile driving formulae have long been used by most of the field engineers for pile quality control purposes. Yet their reliability have been repeatedly reported unsuitable and the results can lead to significant errors. According to the research results by the authors, the two most important sources of unreliability of dynamic pile driving formulae are uncertainty in the estimation of hammer efficiency and time dependent characteristics of pile bearing capacity. Based on this finding a new method is proposed. By using the actual value of hammer efficiency the pile bearing capacity at the time of driving could be reasonably estimated. By performing restrike test sometime after pile installation, time effect coefficient could be determined. The effectiveness of the proposed method was proven in the actual construction project.

Europe and US which have more restrictive regulations than Korea about the noise and vibration during construction are using Auger-cast Pile to reduce the problem relating with noise and vibration. However Auger-cast Pile has problems like difficult quality control and low bearing capacity. In Europe, Displacement in-situ concrete Pile has been used to sove that problems since 1990s, and Korea has performed the test construction in 1997 and it has been used as the real structural foundation since 1998. Test and real construction results verified that the allowable capacity of the pile(diameter = 410mm) is between 70 and 100ton. Though De Beer & Van Imps design method utilizing CPT result is used to calculate the bearing capacity of the Displacement in-situ Pile, Korea is dependant upon the SPT as the sounding test, so design method utilizing SPT result is necessary to promote the application of the pile. To find out reasonable design method using SPT result, rearing capacity of the pile constructed in sand and clay in Korea was calculated using Meyerhof, SPT-CPT translation method, Nordlund, Douglas and DM-7 method, and the calculation results were compared to the load test result. Analysis result shows that SPT-CPT translation method is more reliable than others and economical design can be possible because it considers efficiently the friction capacity of Displacement in-situ Pile.

The load distribution and deformation of drilled shafts subjected to axial loads were evaluated by a load transfer approach. The emphasis was on quantifying the load transfer mechanism at the interface between the shafts and surrounding highly weathered rocks based on a numerical analysis and small-scale tension load tests performed on nine instrumented piles. An analytical method that takes into account the soil coupling effect was developed using a modified Mindlin's point load solution. Based on the analysis, a single-modified hyperbolic model is proposed for the shear transfer function of drilled shafts in highly weathered rocks. Through comparisons with field case studies, it is found that the prediction by the present approach is in good agreement with the general trend observed by in-situ measurements.

Large diameter piles can be defined as piles with diameter of at least 0.76 m (2.5 ft). In bridge foundation, large diameter piles have been used as pier foundations and their use has been increased greatly. In this study, static pile load tests for large diameter piles peformed in Kwangan Grande Bridge construction site were introduced. Also, various sensor installation methods for several types of piles (that is, open-ended steel pipe pile, drilled shafts and socketed pipe piles), pipe axial load measuring method, load transfer analysis method and pile load test results (pile-head load - settlement curve, and pile axial load distribution curve along the pile depth) were introduced.