Research On Bearing Capability Of Double Direction Reinforced Composite Ground

Double direction reinforced composite ground (DDRCG), or both vertically and horizontally reinforced composite ground, which is a combination of horizontal reinforcement and vertical pile, has been applied in practice but has not been studied systemically. Thus, based on the existed researches at home and abroad and supported by the project of the Hunan Provincial Natural Science Foundation of China,"Research on Working Mechanism, Intelligent Design and Application of both vertically and horizontally reinforced composite ground", and the Hunan Provincial Communication Research Project,"Application of and Study on the soft ground treatment in Linxiang-Changsha Highway", the bearing capacity and stability of DDRCG under embankment load were analyzed.First analyzed were the bearing capacities of DDRCG constituted by horizontal reinforcement and gravel pile or horizontal reinforcement and rigid/semi rigid pile. By considering soil weight and the soil-pile interface friction, the formula for calculating the bearing capacity of DDRCG constituted by single layer of horizontal reinforcement and gravel pile were deduced. By assuming the deformation of horizontal reinforcement paraboloidal and with Winkler model considered, the equilibrium equations were established by examining the equilibrium of inter-pile cells of DDRCG constituted by single layer of horizontal reinforcement and rigid/semi rigid pile and formulas for calculating its bearing capability and the stress ratio between soil and pile were deduced on the basis that settlement controls designation.Based on the unified strength theory and by considering material softening, a new kind of unified strength criterion for such material was deduced. Besides, the unified solution of limit load for thick wall cylinder with different tensile and compression module, which was applied to calculating the limit load of gravel pile, was deduced together with the theory of expansion of cavities in infinite soil mass and was applied in calculating the bearing capacity of gravel pile composite ground.Limit analysis combined with the unified strength theory was applied to calculating the bearing capacity of DDRCG. By substituting the expressions of normal stress and shearing stress on a random plane for the principal stresses, a new expression of unified strength theory was obtained, based on which and the associated flowing rule, some basic questions in limit analysis with unified strength theory was...