Skin Friction Behavior of Prebored and Precast Piles in Weathered Rocks

The prebored and precast piles (PPP) are frequently used in urban areas where the noise and vibration are caused by the pile driving. In PPP design, skin friction is the most critical factor affecting the bearing capacity and the settlement behavior. In this study, the behavior and loaddistribution of PPP were investigated by pile load tests and an analytical study. A series of pile load tests were performed in the field (14 test piles). In addition, the condition of the shaft along the test pile was investigated through the borehole image profile system (BIPS). The BIPS images actually show that the cement milk injected in the borehole has penetrated into the surrounding ground. Based on this, it is found that the piles show two different load transfer behaviors, such as ductile and brittle shapes, and tz curves according to two shapes are proposed for a hyperbolic-and sawtooth-shape, respectively. It is also found that the prediction by the proposed load-Transfer curve is in good agreement with the general trends observed by in situ measurements.