The bearing mechanism of the timber pile has not been clarified in many ways. In this paper, vertical loading analysis of tapered timber piles is carried out by using two-dimensional distinct element method (DEM). It is considered that DEM is the most appropriate analysis method that simulates large displacement caused by pile driving. The parameters of DEM are determined by one dimensional consolidation test. The taper angle and the number of the driving pile are conditioned by taken into considerations practical situations. The displacement of ground particles and the contact force are investigated. Results show, that the bearing capacity of the tapered pile is developed as the taper angle increases. The tapered pile has significant effect on the horizontal contact force of the ground particles. The effect confining the surrounding ground is caused by the increase of the contact force due to the taper.
In Kyoto Protocol, the Japanese government has decided to reduce our overall emissions of greenhouse gases by at least 5 per cent below 1990 levels in the committed period 2008 to 2012. Emission of greenhouse gases in Japan does not decrease but increase after 1990. The Environment Ministry stated in 2008 that the emission did not decrease in fiscal 2006 either, and the amount of increase was 6.2% compared to the total emission in 1990. According to IPCC Technical Paper VI, additional effort is essential to curb the emissions of greenhouse gases across the globe in the long run, and a high curb ratio is required in Japan. As presented above, a reduction of 6% is not an easy objective to achieve. In the long run, there are concerns that a higher rate of emission will be resulted instead. Recognizing this as a problem requiring imminent resolutions, Numata et al. (2008) suggest that natural materials, such as soil, stone, and trees, should be used in an efficient manner to help promote a sustainable construction and reduce global warming.