Influences of initial water content and roughness on skin friction of piles using FBG technique

A series of pullout tests were conducted on a model pile in a soil with different initial water contents and different pile surface roughnesses to study their influences on pile skin friction. To measure axial strains and skin friction of the pile, fiber Bragg grating (FBG) strain sensors were used. Data were collected during the pullout tests and are analyzed in this paper. Test results indicate that the skin friction and axial strain of the model piles decrease with the initial water content of the soil but increase with the degree of surface roughness of the piles. The axial strain induced in the upper segment of the tested pile is considerably greater than that in the bottom segment of the pile. In addition, the skin friction is distributed nonlinearly along the length of the model piles.