The Study Of Interaction Mechanism And Simulation Of Hammer-pile-soil In High Strain Dynamic Testing

On the basis of that reason that there are no effective methods to estimate the interaction among pile, soil and hammer, and simulation of driving process with forecast of bearing capacity of PHC pile in high strain dynamic testing at present. The theory of pile-soil-hammer impulse response had been studied and the methods of simulation of driving process with forecast of bearing capacity of PHC pile has been developed.Based on a lot of international and our country's papers, research level of high strain dynamic testing has been proposed and discussed. By the method such as theory study, field test and numerical value simulation, main research work and achievements of this dissertation can be summarized as follows:First, in the consideration of the analysis of the pile driving process and some published testing results using dynamic elastic theory, this paper summarize affection factors of high strain dynamic testing results, then pile, soil and hammer should be analyzed as one system was advanced.Second, the hammer of high strain dynamic testing is comprehensively researched in this paper, and hitting effect is simulated based on analytical solution of impulse. For drilling piles, this paper presents the concept of knockdown hammer, describing the hammer force model and the hammer-pile-soil impulse response model and its arithmetic. The research of the utility and safety of the hammer was performed. Based on analytical and thermodynamic solution the behavior of diesel hammer has been researched, and the optimized thermodynamic simulation arithmetic is put forward then.Third, a numerical model and its software for analyzing the hammer-pile-soil impulse response in high strain dynamic testing especially for drilling piles are developed based on the theory of one-dimensional wave. In order to confirm all factors that affecting bearing capacity, by using numerical analysis, the influence of the hammer weight on the simulated resistance of the surrounding and the bottom soils of the pile is quantitatively evaluated. In the same manner, the influences of the drop elevation, the stiffness of pile cushion, the pile length and diameter, and the soil quality etc are also studied. Forth, a numerical model and its software for analyzing the simulation of driving process with forecast of bearing capacity of PHC pile in high strain dynamic testing which combined the improved continuous pole and optimized scattered mass-spring models. The optimized design method for PHC pile is put forward in this paper. The interaction among pile, soil and hammer during the driving process and rationality for selected pile and driving system are simulated to determine the initial design plan firstly. Then driving and monitoring tested pile are carried through to validate or adjust the parameters of pile, soil and diesel hammer system in the initial design plan. Such design idea of PHC pile is closely link to driving process. That makes the design much more accord with practical mechanical behavior in the pile and soil and breaks through the current design principle with major static analysis.The successful applications of the achievements to model pile and engineering showed that the numerical model and its software for analyzing the hammer-pile-soil impulse response, a numerical model and its software for analyzing the simulation of driving process with forecast of bearing capacity of PHC pile, and the optimized design method for PHC pile put forward in this paper are science rational which are of great significance in both theory and practice.