Behavior of laterally loaded cast-in-place (CIP) piles with double steel casings embedded in bare hard rock in deep water areas

Difficulties can be encountered during the installation of a cast-in-place (CIP) pile in bare hard rock located in deep water areas, including the installment of the steel casing and mud leakage during drilling. We proposed a novel CIP pile consisting of inner and outer steel casings, a steel reinforced concrete (RC) shaft embedded in the rock, and a hollow concrete cylinder between the two steel casings. A numerical study was conducted on the novel CIP pile with double steel casings (CIPDSC) and a CIP pile with one steel casing (CIPASC). The results showed that the load could be transferred from the CIPDSC to the rock mass by two methods: from the steel casing to the RC shaft and the rock mass, and from the outer steel casing and the hollow concrete cylinder to the rock mass. The load–displacement curves of the CIPDSC were characterized by five points: debonding at the interface of the inner steel casing and RC, tensile yielding of the inner steel casing, tensile yielding of the outer steel casing, compressive yielding of the outer steel casing, and compressive yielding of the inner steel casing.