Study On Meso-simulation Of Vibration Rolling Process And Real-time Compaction Quality Control Of Roller-compacted Conctete Dam

The unique construction technology of successive thin layers lifting for roller compacted concrete(RCC)dam produces numbers of horizontal construction joints,which bring increasingly urgent construction quality problems,including the disqualification of RCC matrix compaction quality,and the cracks and leakages caused by the poor joints bonding quality between RCC lift layers.For a given RCC mixture,the vibrating compaction parameters adopted in the field are the important factors that affect the compaction quality of RCC matrix and the bonding quality between layers.At present,to determine the control standards of compaction parameters mainly depends on the existing specifications,previous construction practices and laboratory or field tests.The control standards by the above-mentioned means are usually applied for controlling each single construction parameter,which can not reveal the microscopic joints bonding mechanism and compaction mechanisms with considering the actual construction conditions,as well as lacks a certain control index and its corresponding control criteria which can reflect directly the interactions of different compaction parameters,thus leading to difficulties in real-time feedback and control of RCC dam compaction quality.Therefore,how to use the advanced technologies to study the macro and meso mechanisms of RCC vibration compaction process,how to build the relationship between rolling parameters and compaction quality of RCC,and how to timely adjust construction parameters according to the changing construction environment,become the key issues to assure RCC dam compaction quality.The macroscopic compaction experiments and mesoscopic numerical simulation method,i.e.,Particle Flow Code(PFC),were both taken to elaborate the influence mechanism of vibrating rolling process on compaction quality of RCC matrix and layer bonding interfaces.Meanwhile,the monitoring compaction quality index and its control standard were presented to reflect comprehensive interactions of compaction parameters.Furthermore,a real-time monitoring method for RCC compaction quality control was studied with considering multi-parameters influence,which would provide a new approach to timely quality assurance of RCC dam under complex construction conditions.The major research achievements of this thesis are as follows:(1)A mesoscopic discrete element modeling method of RCC dam vibration rolling process with PFC 3D software was proposed.A RCC dam material model that can reflect the geometric shape and the proportion of coarse aggregates was set up,and then the initial contact parameters of dam material model were determined based on the macro-micro relationships,thus resulting in realization of accurate simulation for RCC dam materials.The similarity ratio considering the size effect and the compaction capacity of different rollers were proposed to simulate the rolling process with vibration loads.Then,the PFC model of RCC matrix vibration rolling process was presented to analyze the meso-mechanism of vibration process.(2)Based on the adaptive differential evolution(ADE)algorithm,an inversion method of micro-parameters of RCC dam material was proposed.Taking the minimal difference of stress-strain characters of RCC dam material from uniaxial compressive test and PFC model as the optimized objective,the overall process of inversing meso-parameters of dam materials with ADE was given to obtain the contact parameters of RCC dam materials with different filling time.The proposed method could enhance efficiency of model contact parameters determination and overcome the inconvenience and time-consumption of conventional methods,thus provides precondition for studying RCC compaction characteristics with different filling time.(3)A method for analyzing RCC vibrating compaction characteristics based on PFC simulating was conducted.According to the vibration compaction mechanism of RCC dam materials,a process for analyzing the characteristics was proposed based on the PFC simulating.The indexes,such as porosity,settlement and velocity field,were selected to elaborate compaction effects of compaction passes,compaction capacity coefficient and layer lift thickness.The simulation results of material settlement and density were in high agreement with that of the macroscopic compaction test,which indicated that the PFC simulating was effective.The proposed method would provide a new perspective to reveal the relationship between compaction parameters and compaction quality of RCC material.(4)A real-time compaction quality control method of RCC dams was studied basing on the unit compaction energy(UCE)index.According to the different quality control requirements of the matrix and the interface of RCC dam,the unit volume compaction energy(UVCE)index and the unit area compaction energy(UACE)index were put forward.Moreover,the quantitative correlation models between the two indexes and compaction density and shear strength of dam material were established,respectively.Based on the established models,the control standards of UCE at job site and the implementation process of real-time monitoring for RCC compaction quality were presented,which would provide a new way for the timely and reasonable control of compaction quality of RCC dams.