Research On Application Of Cement Fcy-ash Gravel Pile In High-grade Highway Soft Foundation Treatment

It is a new reinforcement method for cement fcy-ash gravel pile to consolidate foundation. It has remarkable characters, such as pile body, crush and close, concentration of stress, diffusion influence, capacity of foundation improvement, small deformation, rapidness settlement stability, etc. It can efficient improve pile body stress and exert soil capacity between pile and pile. Although cement fcy-ash gravel pile composite foundation basic theory and practice are got rapid development, the perfect theory about it is not formed. Especially, the important parameter for stress ratio between pile and soil as well as the rule of settlement deformation are not systemic researched. From deformation of composite foundation, determining cushion technology, design method, test in situ and technology economy, cement fcy-ash gravel pile is systemic researched in application in high-grade highway. Main contents and conclusion include:(1) Based on deformation conforming condition and static mechanics balance condition, the foundation, pile body composite foundation and vertical deformation of underlayer are researched. The deformation mode of pile body composite foundation is systemic studied. The solution of stress and displacement of two-layer elastic continuous body is built under vertical load of axisymmetric, elastic upper space body and circle axisymmetric. Compress deformation of underlayer of cement fcy-ash gravel pile composite foundation is analyzed.(2) From determining cushion influence of cement fcy-ash gravel pile composite foundation, determining cushion technology, proper thickness of determining cushion and proper space between pile, the core content and theory of application of cement fcy-ash gravel pile in high-grade highway are analyzed. At the same time, the engineering character of title reinforcement cement fcy-ash gravel pile composite foundation, constitute, action mechanism and action mechanics of cement fcy-ash gravel pile - net composite foundation are researched. Under determining cushion thickness more than failure face depth, determining cushion thickness less than failure face depth and the space between pile is small etc, the calculation equation of proper determining cushion is got. The proper determining cushion thickness and proper pile space are analyzed theoretically. By analyzing the engineering characters of title reinforcement cement fcy-ash gravel pile composite foundation, the best cement fcy-ash gravel pile - net composite foundation is put forward during soft foundation consolidation in high-grade highway. The basic character of its action is researched. And the calculation equations are put forward.(3) A series of tests in situ are achieved in soft foundation consolidation for Bengning highway. The quality control methods are put forward. It ensures pile capacity and intact in highway soft foundation consolidation. The pile quality and capacity are prior to tradition DJM (dry jet mixing) pile. The accumulative total settlement less than tradition soft foundation consolidation method.