NOMINAL CAPACITY OF BORED PHC NODULAR PILSES BASED ONLOADING TEST DATA CONSIDERING LOGNORMAL DISTRIBUTION(AIJ1999)
M.B.karkee（Akita prefectural University）・H.Ogura（GEOTOP）・T.Horiguchi（GEOTOP）・H.Kishida（Science University of Tokyo）
The correlation formulations for vertical capacity ofpiies based on the loading test data are often based on the analysis assuming normal distribution of data (e. g. Horiguchi & Karkee, 1995). Recent investigation on a database of 51 Ioading tests on fully instrumented bored PHC nodular piles, covering different ground conditions throughout Japan, indicate that lognormal distribution is better suited for such analysis. The database consists of siow maintained tests with the incremental loads maintained for 30 minutes, and the loading cycled back to zero incrementally. The pi]e top applied load Po, top movement So and toe movement Sp were measured directly. Axial distribution of Po Was obtained by strain gage measurements. Load Po Was increased until So reached at least I Oo/o of pile nodule diameter (D), except when creep defbrmations were excessive to make maintaining the load difficult.
The measured resistance (R~) from loading tests was defined as Po at S0=0.1D following the Japanese Geotechnical Society standard. In few cases where maximum So couid not reach 0.1D, R was estimated by extrapolation based on the hyperbolic curve fitted to the measured data. The details are given in Karkee et al. (1 998). The unit shaft resistance in different gagoe interva]s was obtained from axial distribution of R. Standard penetration test N-va]ues and classification of soi] type constitute the basic information avai]able for foundation design in practice, particularly in small to medium size construction projects where the PHC nodular piles are mostly used. Accordingly, correlation formulations for the vertical resistance are given in terms ofN-va]ues and simple soil type c]assification.