EVALUATION OF VERTICAL BEARING CHARACTERISTICS FOR SOIL-CEMENT COMPOSITE PILES

: There are several pile construction methods with relatively small construction machinery that are suitable for construction in narrow urban spaces and areas with low overhead clearance. The Top-drive Boring Hole (TBH) method, which has a machine height of 4.5m, is often used. The Boring Hole (BH) pile method can handle narrow spaces and low overhead clearances better than the TBH method. However, because the BH pile method is a direct circulation method, mud cakes easily form on the hole walls, and slime tends to accumulate at the pile tip. Such challenges related to the construction method, bearing capacity and settlement need to be resolved for pile construction in narrow urban spaces. Pile construction in narrow urban spaces and for existing structures to strengthen the seismic resistance is subjected to constraints on the construction site and process. Therefore, a method for soil-cement composite pile construction was developed that uses a compact mechanical agitator for pile foundations of lightweight structures. In this study, static compression load tests on soil-cement composite piles that were constructed with the developed ground improvement construction method were carried out to evaluate the vertical bearing characteristics. Furthermore, it was evaluated the performance of vertical bearing characteristics on the soil-cement composite piles to compare the evaluation method as shown in the design specifications in Japan.