In the last decade, use of suction caissons (suction piles) has increased in offshore arena. Suction caissons have the appearance of inverted buckets with sealed tops and are installed by pumping water out of them. Pumping creates a differential pressure across the top pushing the caisson into place, and thus eliminating the need for driving. Suction can be used also to resist axial tensile loads. Suction caissons realize economical advantages over traditional driven piles due to the speed of installation, elimination of the pile driving process, and reduction in material costs. There are a number of uncertainties in the design of suction caissons. The state of stress and soil conditions adjacent to a suction caisson may be different from those surrounding driven or bored piles; thus experience-based design methods may not work well with suction caissons. The tensile load capacity of suction caissons depends primarily on the hydraulic conductivity and the shearing strength properties of the foundation material, drainage length, and rate of loading. The relationship between the various parameters affecting the tensile capacity is not clearly understood. Furthermore, during pullout, volume change characteristics of the surrounding soils may change the theoretical suction pressures. A review of the existing knowledge relating to the design and construction of suction caissons is presented in this paper. Experimental results from a number of laboratory studies in sand and clay are also presented along with case histories.
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