Limiting force profile for laterally loaded piles in clay

Response of a laterally loaded pile is normally dominated by limiting force mobilised along the pile. The limiting force profile (LFP) varies from pile to pile at different sites. In order to provide guidelines for constructing the LFP, in this paper, an extensive back-estimation has been made against measured responses of 32 piles tested in situ. It was done using a spreadsheet program called GASLFP, which in turn was based on closed-form solutions. The solutions and GASLFP were developed by the first author in 2001 and 2002 respectively. Parameters obtained through the backestimation are presented herein for each pile. They indicate remarkably lower resistance than that derived from the conventional Matlock LFP for 18 piles; provide an average (slip) depth of 7.2d (d = pile diameter); offer an average ratio of modulus of subgrade reaction over shear modulus of 3.0 and an average ratio of the shear modulus over undrained shear strength of 92.3. These values may be directly used to design laterally loaded free-head piles and only the soil within the slip depth may need to be carefully investigated or improved.