Bearing Capacity Determination of Jointed-Timber Piles in the Saga Lowland

Abstract

The pile load tests were conducted in the soft clay with high compressibility and lower shear strength with depths until 10–30 m in the Saga lowland, Japan. Generally, single-timber piles (STP) were used as the pile foundation of the small-scale buildings in this area. However, differential settlements were experienced in these buildings. To overcome the problems, the tip of the timber piles was required to reach supporting stratum at greater depth. In order to reach the stratum, the timber piles were connected with several joints. Until then, there were methods to calculate the bearing capacity of STP. However, there was no detailed study to describe the bearing capacity and its mechanism of the jointed-timber piles (JTP). Based on the several pile load test results, the bearing capacity evaluation method has been proposed for the JTP in terms of bearing capacity coefficients α and β. It was confirmed that the second limit resistance forces were higher than the bearing capacity evaluated with the proposed method, including the reduction effect of joints, length/diameter ratio.