Design Charts of Piled Raft Foundations on Soft Clay
Young-Kyo Seo and Kyung-sik Choi
Div. of Ocean Development Engineering, Korea Maritime University
Department of Civil Engineering, Dong-A University
For the structure foundation under the soft clay layer conditions, the
design charts are first presented for the evaluation of both bearing
capacity and total settlement in the raft alone foundation system. Load-
settlement relationship curves are used to evaluate the ultimate soil-
bearing capacity. The total settlement is evaluated by applying various
traditional safety factors of the uniformly distributed loads. Then, the
parametric studies are carried out for the piled raft foundation system.
In the numerical analyses, elasto-plastic finite elements models are used
to present the foundation response and the design charts, which enable
the determination of the raft size and pile length and spacing if piles are
KEY WORDS: Piles; rafts; foundations; design; numerical modeling.
As Korean government has proposed a plan of new land development
in the Nakdong river deltaic plane near the Busan, second largest city in
Korea, infrastructures such as industrial and commercial facilities have
being constructed since the early 1990’s. In this area, the soft clay layer
about 20 to 30m thickness have been deposited over the sandy soil or
directly on the undulated bedrock surface. On the top of the soft clay
layer, typically about 5 to 10m’s of sand layer is placed. Figure 1 shows
the typical results of laboratory tests on samples of Busan clay. The in-
situ groundwater table is around 0.5 to 0.8m below the ground surface.
For the structure foundation under the soft clay condition in this area,
piles are costumery used to transmit the structural loads to the bedrock.
So far, the designer of the raft or the piled raft foundations in this area
has very little information available for the e