Technology Research Of T-shaped Cement Mixing Pile Reinforcement Soft Ground

As a new type of a technology to reinforcement soft ground, T-shaped bidirectional cement-soil deepmixing column (T-shaped column) has a broad prospect of application. Based on previous studiesfoundation, the settlement model and deformation characteristics of T-shaped column compositefoundation under embankment loads were analyzed through field tests and3D numerical simulation.Settlement calculation methods for T-shaped column composite foundation under embankment loadswere developed, especially with the penetration of pile tops, the amount of compression of reinforcementarea and the settlement of underlying layer. Main contents are as follow:(1). The test sites were established in field to research and analysis the effect of T-shapedbidirectional cement-soil deep mixing column to soft ground. The result of test indicate that the strengthof columns adopted bidirectional mixing technique was better than the pile which made by the normaltechnology, and the effect of T-shaped bidirectional cement-soil deep mixing column to soft ground muchbetter than ordinary column; the area replacement ratio of pile in composite foundation has a big affecton Pile foundation load sharing ratio and Stress ratio between Pile and soil; the cap height H andcolumn space S values of T-shaped bidirectional cement-soil deep mixing column have a big affect oncomposite foundation.(2). T-shaped column composite foundation under embankment loads were studied through the3-Dnumerical simulation and the influence of cap height H, cap diameter D, column space S, columnlength L, column modulusE Pwere analyzed. Simulation results indicated that the Pile foundationload sharing ratio and Stress ratio between Pile and soil were influenced main by the area replacementratio of pile; if the area replacement ratio has a big value, than the Pile foundation load sharing ratiowould change bigger and Stress ratio between Pile and soil would change smaller; the pile volumereplacement rate and column modulusE Phave a big influence to the amount of compression ofreinforcement area and the settlement of underlying layer: when the value ofE Pand pile volumereplacement rate much bigger, than the amount of compression of reinforcement area would becomesmaller and the settlement of underlying layer would become bigger than before.(3). Based on some simplifications, the settlement calculation formula for T-shaped columncomposite foundation under embankment loads were developed which considering the penetration of piletops the amount of compression of reinforcement area and the settlement of underlying layer and theformula only has two unknown quantity: embankment height h and equal settlement sectionhe.