ABSTRACT This paper introduces the PDT (Pulse Discharge Technology) piling method. The PDT piling method is to install in-situ a pile using electrical power so called Pulse power. Since this piling technique can make not only a bore hole to be expanded but also the ground to be improved by compaction, the pile installed by PDT appears to be able to develop shaft and end bearing capacity efficiently. In this study, we introduce a coefficient of expansion. In order for quantitative evaluation of the relation between pulse power and ground expansion a series of in-situ tests were conducted. In the tests, we divided soil conditions into several groups by constituents and the number of blows in the standard penetration test, N. The tests were carried out on various numbers of pulse discharge. As a result, it was concluded that the coefficient of expansion appeared to increase with an increase of the number of discharge and with a decrease of the number of blows, N. In addition, the coefficient of expansion appeared to differ from one position to another even though having the same N value.
INTRODUCTION Since 1990s the piling technique, in which a precast pile is installed in the ground after boring, has been widely used in Korea especially in urban area(Lee et al, 2003). Even though this technique induces much less vibration and noise than pile driving, it has several disadvantages as following. First, the ground disturbance is inevitable during boring and it gives rise to the reduction of shaft resistance. In general, it has been known that the bearing capacity of a bored pile is taken by shaft resistance up to 60%. Such a shaft resistance is, however, far smaller than that of a driven pile due to the ground disturbance and stress release (Van Weele, 1988; DeBeer, 1988).