The Densification Mechanism Of Underwater Rubble-mound Foundation By High-frequency Vibratory Hammers

At present,explosive compact and heavy hammer compaction method are brought into the current specification,which are frequently-used densification methods of underwater rubble-mound foundation bed.For the port construction project with the construction characteristics of variable depth and high precision,the traditional underwater rubble-mound foundation bed densification methods cannot meet the needs of the construction and reach the engineering demand.Therefore,in order to obtain a better compaction for the underwater rubble-mound foundation,the new technology of vibratory compaction by high-frequency hydraulic vibratory hammer is become a new trend of densification technology development of underwater rubble-mound foundation bed.However,the project case about the underwater rubble-mound foundation densification is deficient and the researches related to the high-frequency vibratory compaction of foundation bed under exciting force which is produced by the hydraulic hammer are much rarer.Therefore,the research of densification mechanism of underwater rubble-mound foundation bed under the action of high-frequency vibration has very high scientific and practical application values.The two-dimensional granular discrete element analysis method is adopted to study the mechanism of the vibratory compaction for the underwater rubble-mound foundation under the action caused by the high-frequency vibration hammer accounting for the issues above in this paper.The main original works are as following:1.According to the existing site construction experience,two-dimensional riprap particles that the apparent shape and size resemble the down-to earth riprap are generated by conducting the second development with the built-in fish language in the PFC2D simulation platform and the numerical simulation model of underwater rubble-mound foundation bed based on meso-characteristics analysis is established.2.The process of high-frequency vibration and compaction of underwater rubble-mound foundation are analyzed by numerical simulation in detail,especially the changing circumstance of regional porosity.Meanwhile,the vibration response and the mechanism of densification by high-frequency vibratory compaction of underwater rubble-mound foundation is discussed.The compaction effect is checked through monitoring the final settlement of underwater rubble-mound foundation and it confirms the feasibility of using high-frequency hydraulic vibration hammer for compacting the underwater rubble-mound foundation bed.3.A few sensitivity parameters of high-frequency vibratory compaction of the underwater rubble-mound foundation are analyzed in detail,which include vibration frequency,vibration duration,exciting force,riprap grain size and depth of water,and preliminarily obtained the optimum vibration frequency,exciting force,vibration duration and the approximate range of grain size distribution that applied to high vibratory compaction.The results of numerical simulation confirm the reliability by contrasting the existing engineering test results and provide reference for similar engineering construction.