Piling in Shanghai Soils: Historical Sketch and Growth of Capacity with Time
SourceThe first part of this paper is a historical sketch of piling in Shanghai: (1) Different kinds of piles used, including the “Foochow poles” a few metres long, prevalent in early days, followed by imported Oregon pine (OP) piles some 30 m long, during the 1930s and 1940s; pre-cast and cast in-situ concrete piles, which took the place of timber piles in the 1950s; and finally the steel tubular piles up to 60 or 70 m long, which came into use in the late 1970s. (2) Reasons for piling: Piles or no piles? Short or long piles? (3) Development of empirical rules for skin friction and end bearing. (4) Settlement of pile foundations. (5) Outlook for future development in connection with more efficient use of short piles (L ≤ 10 m, for example), avoiding overconservatism in design of extra-long piles (L ≥ 60 m, for example), and pre-boring as a preventive measure when driving piles in built up areas.
The second part is a collection of test data, showing that bearing capacity of piles in soft clay, including Shanghai soils, grows considerably with the elapse of time. Such data may hope to be of use in developing more rational and economical design methods, including consideration for reduced capacity caused by pre-boring.