High Capacity Steel H-Piles in Franciscan Rock

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by Demetrious C. Koutsoftas, Principal; Dames & Moore, 221 Main Street, Suite 600, San Francisco, CA 94105.,

Document Type: Proceeding Paper

Part of: New Technological and Design Developments in Deep Foundations:

Abstract: For many years prestressed concrete piles have been the most popular pile type in the San Francisco Bay Area because of their relative economy and good performance. However, prestressed concrete piles displace considerable volume of soil and can cause significant heave, lateral deformations, and subsequent settlements when driven through thick deposits of soft soils. The ground deformations caused by pile driving can have significant impacts on adjacent structures and must be controlled within relatively small values. Predrilling is often used to minimize the soil deformations caused by pile driving. However, in certain areas along San Francisco's waterfront, where very thick deposits of soft soils are present, predrilling through the full depth of the soft soils is both impractical and uneconomical. Steel H-piles offer an economic alternative under conditions where capacities in the range of 1.8 MN to 2.7 MN can be safely mobilized. The paper describes two case histories involving high capacity H-piles driven into Franciscan Rock. Extensive indicator driving programs, dynamic tests with the Pile Driving Analyzer (PDA) and static load tests were used to verify the design loads. The results of the tests together with the results of production pile driving are reviewed and evaluated in terms of: (1) driving criteria, (2) penetrations in rock, (3) safe design loads, and (4) potential for pile damage. Statistical summaries of the results of production pile driving are presented to provide guidance for future projects for estimating pile lengths, formulating practical driving criteria, and for anticipating potential problems during driving.

Subject Headings: Load tests | Concrete piles | Pile tests | Soil deformation | Rocks | Piles | Pile driving | Soft soils | Soil settlement | Dynamic loads | North America | United States | Minnesota | California | San Francisco Bay Area

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