Side load-transfer mechanisms in drilled shafts in soft argillaceous rock

Elastic-plastic axisymmetric finite-element analyses were performed to investigate the side load-transfer mechanism of drilled shafts socketed into cohesive intermediate geomaterials (very hard clays/very soft rocks). The roughness of the concrete-geomaterial interface was modeled explicitly by assuming sinusoidal undulations along a discontinuous surface. Smooth interfaces were also modeled. The results of the analyses indicated that the elastic response of rough sockets extends as the initial normal interface stress, sigma(n), increases. Value sigma(n) does not affect the maximum unit side resistance, f(max), of sinusoidal sockets significantly, as shearing of the geomaterial occurs by gouging through the geomaterial asperities emanating from locations between the roots and crowns soon after separation occurs at the backs of the asperities. However, sigma(n) is a principal factor affecting f(max) in smooth sockets. The sliding friction at the interface plays a major role in the development of load transfer, and internal friction of the geomaterial plays a less significant role. The behavior of smeared sockets was also investigated. A relatively Small thickness of residual remolded geomaterial along a rough interface was found to reduce load transfer significantly.