Key Technologies Research On Heavy Hammer Compacting With Large Separated Layer Of Thick Riprap Foundation Under Deep Water

The riprap foundation is widely used in gravity wharf,breakwater and immersed tube tunnel.It has many advantages such as large load capacity,anti slip,economical and practical benefits.In order to solve the key technologies of compacting construction for the riprap foundation under deep water,this paper takes heavy hammer compacting the large separated layer of thick rap-rip foundation as the main target,and uses the research means such as theoretical analysis,numerical simulation,scaled model test and site verification to analyze the main problems of the effective ramming energy of the heavy hammer under water,the effective reinforcement depth analysis of the heavy hammer,the technology of heavy hammer compacting with large separated layer of thick riprap foundation and so on.(1)By using the explicit dynamic software ANSYS/LS-DYNA,the effective ramming energy numerical simulation model of heavy hammer's falling process under water is proposed by considering the effect of the floating force and the flow resistance according to the fluid solid coupling theory.(2)The dynamic process of heavy hammer ramming is analyzed by the discrete element particle flow simulation software PFC2D,and the numerical model of the full process analysis of heavy hammer ramming riprap is presented,and the influence of the thickness of riprap foundation,the drop distance,the weight of the hammer and the number of ramming on the effective reinforcement depth are discussed.(3)Based on the scale test results,the reasonableness of the theoretical calculation formula of the heavy hammer movement under water is verified and the range of the C_f value of the flow resistance coefficient is modified.The calculation formula of the average value and the peak value of the heavy hammer ramming process are established,and the Kogler empirical formula of the stress transfer in the riprap foundation of the heavy hammer ramming process is verified too.(4)According to the scale model test and the site test results,the numerical analysis model is amended and perfected,and the formula for calculating the ramming energy per unit area,the impact stress of heavy hammer and the additional stress at the bottom of the riprap are put forward.The model of the parameter derivation of the hammer ramming based on the stress control standard is established,and the complete set of technology for heavy hammer compacting with large separated layer of thick riprap foundation under deep water is brought forward.The results of this paper provide certain theoretical and technical bases for the high efficient compacting of thick riprap foundation under deep water,which can be an reference for the compaction construction of the similar projects.