PILED RAFT - AN EFFECTIVE FOUNDATION DESIGN METHOD FOR HIGH-RISE BUILDINGS IN HO CHI MINH CITY, VIET NAM

Nowadays, the wave of construction of high-rise buildings, which usually use the concept of piled group foundation in their design, has increased in Ho Chi Minh City as well as other cities in Viet Nam. In this study, settlement, the load shared by the raft, and the behavior of the piled raft were considered via monitoring settlement and the Poulos-Davis-Randolph (PDR) method where the settlement of a varying number of piles, the pile length, and raft embedment were determined. The results of settlement monitoring of a high-rise building in Ho Chi Minh City showed that the foundation design of this building was conservative, with a ratio of allowable-to-actual settlement of 9.3. In the simplified method, the proportion of load share by raft was 2.8% (which was ignored in the piled foundation concept), with the settlement results being in good agreement with the measurement results. The parametric analysis indicated that the piled spacing/piled diameter was 5 - 7 times the recommended optimum value. Furthermore, increasing the pile length decreased settlement. The pile length was equal to 30 times the pile diameter, which was effective for the settlement ratio. In addition, the raft load share reached 30% of the applied load when the raft was put in the second layer of stiff-to-very-stiff clay. The study indicated the simplified method was effective for evaluating the preliminary conditions of the foundation, settlement, and that a piled raft was feasible for Ho Chi Minh City's subsoil geology.