International Symposium on Urban Geotechnics / September 25～26, 2009 / Incheon / Korea
A Retrospection on Foundation Design of Taipei 101 Chung-Tien Chin1), Hsiao-Chou Chao2) , Der-Wen Chang3) 1)
Senior Vice President, Moh and Associates, Inc., Taiwan. Senior Engineer, Moh and Associates, Inc., Taiwan. 3) Professor, Department of Civil Engineering, Tamkang University, Taiwan. 2)
SYNOPSIS : Large diameter bored pile was selected as the foundation type for Taipei 101. The pile construction method and specific construction procedures were determined based on the results of trial installation and pile load tests. The baseline for foundation design was established using the friction versus depth characteristics of each ground layer obtained from the pile load tests. As the ground profile and depth to the top of rock formation varied significantly on this site, the pile length, bearing capacity and settlement for single pile were analyzed using the information interpreted from adjacent boreholes. The post grouting at pile tip was mandatory for pile construction. Nevertheless, it was treated as a measure reducing the influence of construction uncertainties and providing extra safety for the foundation system. Keywords : Taipei 101, bored pile, full casing method, reverse circulation method, pile load test, Taipei Fault.
1. Introduction Taipei International Finance Center, also known as Taipei 101, is located in Xinyi District, Taipei, Taiwan, and currently the world’s tallest completed skyscraper. The main tower of Taipei 101, soaring more than 508 meters above street-level, contains 101 floors above ground and five underground levels. A six-story L-shaped podium building is linked to the main tower on its north and east sides. Planning for the Taipei International Finance Center began in 1996. The construction started in 1999 and completed in 2004. Figure 1 shows the general plan and elevation of Taipei 101. Taipei International Finance Center was the first ever build-operating-transfer (BOT) project in Taipei. In 1997, the Taipei Finance Center (TFC) Corp. received a 70-year concession of the site from the Taipei Municipal Government. The TFC Corp as the project owner utilized the strategy hiring consultants to provide project management, designs, contract documents and construction management and contractors to implement detailed design and construction. As commissioned by the TFC, the partnership between the manager of project management Tuner Steiner International, the architect C.Y. Lee and Partners, the structural engineer Thornton Tomasetti and the Geotechnical consultants Sino Geotechnology Inc was formed. The contractor of the civil works was KTRT, a joint venture between Kumagai, Taiwan Kumagai, RSEA, and Ta-Yo-Wei Engineering Corps. Moh and Associates, Inc. (MAA) was commissioned by the project owner as a special consultant for supplemental geotechnical investigations, design optimization for foundation system and deep excavation. This paper is aimed at providing a review on some major design considerations of Taipei 101. As shown in Figure 1, the Taipei 101 complex, including the main tower and the podium building, is approximately 158m x 160m, within which the footprint of the main tower is 87m x 98m. The excavation depths for the main tower and podium building are 21.8m and 21.65m, respectively. The foundation mat and basement structures for the main tower and podium building are integrated with each other while the above ground structures are separated by expansion joints at grade. The structure of the main tower consists of 16 Super Steel Reinforced Concrete columns, 4 on each side.
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The loads transferred through each of the mega-columns to the foundation are greater than 100MN while the total loads applied on the foundation are greater than 4,000MN. Based on the consideration of geological characteristics of the site, experience and workmanship of local contractor, equipment availability, construction cost and demanding schedule, large diameter cast-in-place bored pile was selected as the foundation type (Chen, 2000). Retrospections of the decision making for foundation type selection, pile load tests, construction method selection, foundation design, and construction procedures modification for this project are presented in this paper.
Main Tower Podium Building
(a) Plan Figure 1. Plan and elevation profile of Taipei 101
2. Geological condition Taipei 101 is located on southeast boundary of Taipei basin that was formed by the settlement of nappies between thrusts in the foothill range of north Taiwan during Pliocene and Pleistocene. The ground strata of the Basin are composed of Quaternary sedimentary deposits overlying Tertiary bedrock formation. As revealed in literatures, the Taipei Fault, known as a reverse fault, runs down the region close to the site of Taipei 101. However, the exact location and activity of this fault remained uncertain prior to planning and design of Taipei 101. According to investigations conducted by various organizations or researchers (e.g. TCRI, 1995; Sinotech, 1998; Lin and Lee, 1998), the fault runs through two possible lines as shown in Figure 2. One crosses along the Xinyi Road adjacent to the site on its south side and the other crosses the region near the site in northeast-southwest direction. The Taipei Fault was listed as a suspected active fault in the 1998 published geological zoning map (Central Geological Survey, Ministry of Economic Affairs, MOEA 1998). Both the exact location and activity of the Taipei Fault were critical if the Taipei 101 was to be built on this site. To ensure whether the site was appropriate for super highrise building, data of earlier investigations were reviewed and supplemental investigations including borehole explorations, foraminifera fossil analyses and radiocarbon dating were conducted (Chen and Huang, 2000). Results of the these investigations showed the Taipei Fault runs down the region about 200m away from southeast corner of the site, and the Fault has not been active for a minimum of 45,000 year and thus can be considered non-activity (Chen, 2001). To obtain necessary information for foundation type selection, foundation design and construction, soil investigations utilizing borehole exploration and field and laboratory tests were conducted during the planning and design phases. A total of 155 boreholes with a total length of 11,172m were drilled in five stages within which the locations of boreholes drilled after the second stage are shown in Figure 3. The general soil and rock profiles referred from Chen (2000) are shown in Figures 4 and 5, respectively. Based on the results of soil investigations, the ground consists of the strata: (1) the lacustrine soft to stiff silty clay with average thickness of 30m in which the top 20m is much softer than the bottom 10m, (2) the colluvium/alluvial soil with thickness varied from 19m to 28m, and (3) the Pliocene Kuechulin Formation which is an older sedimentary formation mainly composed of interlayered sandstone and shale. The Kuechulin Formation layer, with the depths varying from 42m to 69m, was taken to be the bedrock of this site (Chen 2001). As
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