Analysis of installation of suction caissons in multilayered sand and silt using a classical bearing capacity method

There have been few analytical research studies to elucidate the effect of a low-permeability soil layer on the suction-induced seepage flow in the sand layer during the installation of suction caissons in multilayered soils. In this study, the influence of silt on penetration into the sand layer during suction caisson installation in multilayered sand and silt was investigated using a classical bearing capacity method. Since sand liquefaction tends to occur during suction installation, the relationship between suction and penetration was revealed in both preliquefaction and postliquefaction. The experimental results so far indicated that the unit shaft and base resistances of piles do not necessarily increase with depth, but instead reach maximum values at a certain critical depth. Thus, the friction reduction factors along the caisson skirt and the bearing capacity reduction factors at the caisson tip were presented for installation with both hardening and softening. Furthermore, an analytical procedure for punching shear failure in the silt layer overlying a sand layer during installation was proposed. For the relationships between suction and penetration during installation in multilayered sand and silt, a comparison between the results obtained from field and centrifuge tests and those predicted by the proposed method was carried out.