Study On The Microfabric Of Coarse Aggregate

Coarse aggregate is the main material of high soil and rock dam. And its mechanical property is an important research problem in civil engineering and water power project. While the mechanical property of coarse aggregate is different from normal soil and sand's as coarse aggregate's big size and discrete property. It is very difficult to explain its mechanical property with continuum mechanics theory. In this paper it is tried to explain the mechanism of coarse aggregate bye the microfabric rule of coarse aggregate. The constitutive model of coarse aggregate based on microfabric was to be constructed.A series of coarse aggregate research results including grading similarity, rheology, slaking deformation and shear dilation are summarized in this paper. A series of triaxial shear tests are practiced with two kinds of typical coarse aggregates. And their similar and different mechanical characteristics are compared.In order to verify that the mechanical characteristics of coarse aggregate are influenced by microfabric elements, a special triaxial shear test was practiced with spherical particle coarse aggregate. It is shown that the relationship between stress and strain is theoretic elastic-plastic. The axial strain and volumetric strain curve is linear. The properties of spherical particle coarse aggregate are closely related to the way of particle adjusting. It is proved that different of initial microfabric elements of coarse aggregate affect its mechanical property. And the feasibility that numerical simulation research coarse aggregate with pellet is denied.The inner structure of coarse aggregate sample can be seen by Nuclear Magnetic Resonance. And the fabric elements of coarse aggregate can be obtained by Digital Image Processing. The statistical comparison can be obtained. Some conclusions can be drawn from the statistical comparison. Shear dilating is the main property of coarse aggregate under lower pressure. The shear dilating property of coarse aggregate is closely related to the way of particle adjusting and is caused by horizontal displacement. The horizontal displacement and vertical displacement of the aggregate are symmetrical in the axis of the sample. And in the transect, there are relative horizontal displacement and vertical displacement between the particles. There are not only horizontal displacement and vertical displacement but also angle ariety. The longer axis of the particles leans to the vertical orientation of bigger main stress during the testing. The longer axis of the particles leans to shear belt orientation with the sample failure.