Research on the bearing characteristics of confined stabilized soil

A confined stabilized soil pile is proposed in this paper as a new kind of foundation treatment method. It is constructed by filling a stabilized soil, which is made by mixing soil with a stabilizer containing a high content of expansive components, into a constraint pipe with enough tensile modulus and strength fixed in ground. Bearing characteristics of the confined stabilized soil are discussed in this paper. Core stabilized soil was made by mixing a soft plastic state clayey soil with stabilizer; stabilizer content are 10 and 15 percent. Confined stabilized soil cylinders, with 10 centimeters in diameter and 20 centimeter in height, were made by putting the core stabilized soil into polyvinyl chloride pipes with confinement stiffness of 3663.12 MPa. In order to eliminate vertical bearing function of the constraint pipe, its inner face was oiled and covered with plastic film. The hoop tensile strain of the constraint pipes was measured during the curing period and the bearing load period. Also the loaddisplacement curves and the failure mode of the cylinders were recorded. The conclusions are as follows: (1) the confined cylinder presents plastic failure mode, and its load-displacement curve shows three stages: linear stage 1 with large slope, approximately linear stage 2 with smaller slope and stage 3 with almost zero slope. Its deformation at the end of stage 1 is roughly equal to ultimate deformation of the unconfined soil; and its strain at ultimate load is about 10%. (2) With the same strength of the stabilized soil, the bearing capacity and the BPL of the confined stabilized soil cylinders are 2.72 ~ 3.39 and 1.70 ~ 2.00 times those of the unconfined ones respectively. The bearing capacity of the confined cylinders is 1.56 ~ 2.08 times that of its BPL. (3) In stage 1, the core stabilized soil maintains its structure integrity and is a cemented entirety to resist vertical load. In stage 2, as load increases, the hoop constraint force plays important role in resisting the load, as the stabilized soil structure disintegrates gradually and the load is transferred to the constraint pipe. In stage 3, the constraint pipe have yielded and produced plastic deformation until the pipe fails. (4) The BPL, the slope of stage 2, and the bearing capacity of the confined cylinder could be improved by choosing proper confinement stiffness and strength, optimizing the ratio of cementitious components to expensive components, and increasing the stabilizer content.