A. INTRODUCTION
This case study focuses on the simulation of the pile-raft foundation of the 151-story high rise Incheon tower located at Songdo, Korea (figure 1a). The pile raft foundation consists of 172 concrete piles with a diameter of 2.5m meters supporting a pile cap of 5.5m thickness and approximate length and width equal to 90m and 70m respectively. The plan view of the pile cap is illustrated in figure 1b.
Figure 1: a) Incheon Tower [1] b) Incheon Tower Foundation Plan View
Regarding the geotechnical properties of the site, information on both the stratigraphy and strength properties are presented in [1,2]. The site lies entirely within an area of reclamation, which is understood to comprise of a thick layer of approximately 8 meters of loose sand and sandy silt, over approximately 20 meters of soft to firm marine silty clay, referred to as the Upper Marine Deposits (UMD). These deposits are underlain by approximately 2 m of medium dense to dense silty sand, referred to as the Lower Marine Deposits (LMD), which overlie residual soil and a profile of weathered rock. The rock materials found within about 50 meters have experienced weathering which is understood to have reduced their strength to a very weak rock or a soil-like material.
Figure 2: Diagrammatic Geological Model [1]
B. MODEL OF THE TOWER FOUNDATION IN DEEPFND
The presented pile-raft foundation is simulated in DeepFND with the P-Y analysis method. The analysis results are compared with the response published in [2] from several numerical software. A single combination of loads is applied according to [2] at the center of the Incheon Tower pile cap, as illustrated bellow:
Vertical Load = 6560.4MN
Torsion =1996MNm
Lateral Load (x-direction) = 149MN
Bending Moment (x-direction) = 21600MNm
Lateral Load (y-direction) = 114.6MN
Bending Moment (y-direction) = 12710MNm
The concrete piles of 2.5m diameter are simulated as Euler-Bernoulli beams with equivalent linear stiffness reduced to capture the cracking of the concrete sections. The P-Y spring properties for each individual layer (stiffness and strength) is based on the published tabulated data in [1,2] and additionally through further calibration of the single pile lateral tests included in [1] as illustrated in figure 3.
Figure 3: Single Pile a) model in DeepFND b) Lateral Deflection Measurements Comparison with Model Results
C. RESULTS COMPARISON
For the pile group model, interaction factors are automatically generated within the software. The DeepFND Model and the results of the analysis are illustrated in figures 4 to 7.
Figure 4: X-X’ Lateral Displacement of the Pile Cap
Figure 5: Y-Y’ Lateral Displacement of the Pile Cap
Figure 6: X-X axis Shear Force Fx(KN) at Section y=-30m
Figure 7: X-X Axis Moment Mxx(KNm) at Section y=-30m
The analysis results are compared to the pile group response data published in [2], in accordance with the numerical analysis of the pile group from numerous analysis software.
Table I: comparison results between [2] and DeepFND analysis
E. REFERENCES
[1] Abdelrazaq, A., Badelow, F., SungHo-Kim, and Poulos, H.G.(2011). “Foundation Design of the 151 Story Incheon Tower in a Reclamation Area”, Geotechnical Engineering Journal of the SEAGS & AGSSEA Vol. 42 No.2 September 2011, pp 85-93. ISSN 0046-5828
[2] Pirrello S. and Poulos, H.G.(2011). “COMPARISON OF FOUR PILE GROUP ANALYSIS PROGRAMS”, International Symposium on Advances in Foundation Engineering (ISAFE 2013)
