| The report of the 19 th Party Congress points out that we should adhere to the harmonious coexistence of man and nature,and establish and practice the concept of green water and green mountains is the silver mountain.There are a large number of red layer mudstone soils widely distributed in Sichuan,and it is inevitable that the railroad will pass through the red layer development area when it is built.If the sand and pebble discarded material is used as filler to treat the red layer mudstone landfill by column hammer punching and expanding pile method,it can reduce the environmental pressure brought by the red layer mudstone discarded soil.However,the research on the reinforcement mechanism of the column hammer pile method is relatively late,the scope of reinforcement influence is still unclear,and there is little specific research information,so it is necessary to do further research on the reinforcement mechanism of the column hammer pile method to provide reference for the theoretical research and design of the column hammer pile.In this paper,we take the pile formation process of column hammer pile expanding method as the research object,carry out the indoor model test of column hammer pile expanding method,and study the soil force and deformation law during the pile formation process by combining numerical simulation and theoretical analysis,explore and summarize the influence law of the foundation state and construction parameters on the effective reinforcement influence range during the pile formation process,and propose the depth of the effective reinforcement area of column hammer pile expanding method.The calculation formula of the effective reinforcement area of column hammer pile is proposed.The main research contents and results are as follows.(1)The energy dissipation law within the foundation soil and the change law of the surrounding soil before and after pile formation are analyzed and summarized from the acceleration propagation law,impact ramming sinkage,strain gauge distribution law and pore ratio change through indoor model tests,and the numerical simulation results are verified with each other.(2)Adopting the discrete-continuous coupling calculation method to analyze the pile formation process of column hammer pile,the soil displacement and stress change law in the pile formation process is studied,and the reinforcement mechanism of column hammer pile in the pile formation process is clearly divided into the strong ramming effect in the hole and the lateral crowding effect of the filler.(3)Based on the numerical model of the actual project,the influence of the foundation state and different construction parameters on the effective reinforcement range is analyzed,in which the reinforcement effect of the foundation is enhanced with the increase of the falling distance and the number of impacts of the column hammer,and the reinforcement effect of the foundation is weakened when the soil is dense.On the basis of the influence law of each parameter,the formula for calculating the depth of the effective reinforcement area below the pile base is proposed when the red-layered mudstone fill foundation is reinforced by the column hammer punching and expanding pile method. |
