| With the continuous increase of energy demand in China's economic development,the hydroelectric energy plays an increasingly important role in the process of China's economic development as a clean and renewable energy.The earth and rockfill dam,which shows good performance,strong adaptability and excellent seismic resistance,is widely constructed in the engineering practice.Rockfill is the main filling material for large-scale infrastructures such as earth and rockfill dam.But the rockfill material must be scaled by a certain percentage so that it can be used to carry out laboratorial triaxial test due to its large size.However,the particle shape of rockfill may be different before and after scaling.Therefore,it is important to evaluate the effect of particle shape on the deformation behavior of rockfill material.At present,the research on the basic theory of macro and micro mechanical properties and deformation control of rockfill material is not enough,which is one of the important reasons that lead to the theory and method of deformation calculation for earth and rockfill dam still far behind the engineering practice.In addition,the rockfill particles will be broken even though the confining pressure is low and the particle breakage will cause the change of gradation,which will have a significant influence on the mechanical properties of rockfill.A plenty of research work of particle breakage test and numerical analysis have been carried out by researchers around the world.But the current research on the quantification of rockfill particle shape and its quantitative effect on particle breakage index is unusual.The study on the accurate description and calculation of gradation curves of rockfill materials is also not enough.In this paper,the macro and micro mechanical properties of rockfill material were considered,and the size effect on the particle shape of rockfill was systematically studied.The macro particle breakage characteristics of rockfill material were analyzed from the viewpoint of micro particle shape and strength.The variation rule of gradation curve caused by particle crushing was studied.Under the support of the national science fund project(51678113,51379028,51608095)and the national key research and development program of China(2017YFC0404900),the main research works in this thesis are listed as following:(1)The particle shape of the rockfill materrial with the size of 10 ~ 20 mm,20 ~ 40 mm and 40 ~ 60 mm before and after triaxial test was tested and statistically analyzed.The shape parameter changes with particle size were systematically studied and the change rule of the shape index of the rockfill particles before and after the test was compared.(2)A high-precision 3D laser scanning technology was introduced to analyze the spatial shape of the rockfill particles with the size of 2.5~5mm,5~10mm and 10~20mm of Zipingpu CFRD.And the size effect of single particle strength was analyzed.Further,triaxial tests were carried out to study the correlation between particle shape index and particle breakage.The results provide a reference basis for revealing the size effect mechanism of granular group from the perspective of fine particles.(3)The gradation curve of Zipingpu rockfill after particle breakage was analyzed and the fractal characteristics was studied.A method for ascertaining the gradation curve of rockfill triaxial test was presented based on the Weibull distribution function and the validity of this method was verified. |
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