Study On Microstructure And Mechanical Characteristics Of The Earth-rock Aggregate

Earth-rock aggregate is usually compose of gravel or cobble as its coarse grain and clay or sand as its granule, it is one kind of anisotropic and discontinuous substance formed in geological history, it behaves between earth mass and rock mass, which generally developed in loose accumulation horizon of the quaternary system, mainly formed by residual and slope deposit, alluvial deposit and collapse deposit. It is widely spread in the area of china as well as all over the world The earth-rock aggregate attracts more and more attention due to its important role played in china national economy, social production and people's living.Thesis uses modern nonlinear theory-Fractal theory, establishes layers and self-similarity of earth-rock aggregate, the microstructure component of earth-rock is put forward, each factor is coupling in the system which is an open system. Systemic property will occur remarkable diversification in different condition. Engineering property of earth-rock aggregate can be depicted by grain composition, way of permutation and combination, porosity and action between grains, in view of effect and importance of each factor, selecting granularity dimension, coarse distribution dimension, coarse grain boundary dimension and porosity distribution dimension as microstructure parameter index of earth-rock aggregate. These indexes are regarded as the basis of structure quantitative research of earth-rock aggregate.Through numerous screen grade testing, based on calculation, arrangement and induction, five typical granularity distribution curves of earth-rock aggregate are put forward, and their engineering properties can be qualitatively described according to different sort of curve. Fractal model of granularity of earth-rock aggregate is deduced, Research shows that gradating characteristic parameters of soil which conventionally define advantage and disadvantage of gradation are no longer applicable when gravel content beyond 50%, Analysis and comparison show that granularity fractal curve are able to describe gradation feature of earth-rock aggregate.Earth-rock aggregate commonly displays multi-fractal feature, there are very good parabola relationship between gravel content and granularity dimension for earth-rock aggregate of good gradation though their different origin ,mineral composition and granule properties. Number and magnitude of dimension deliver comparative content of coarse and granule grain and uniformity coefficient of size distribution of earth-rock aggregate, fitting shows that coarse grain granularity dimension average is more reasonable to deliver gravel content and homogeneity of earth-rock aggregate.Coarse grain distribution dimension of earth-rock aggregate holds a fractal feature, and its dimension ranges from 1.0 to 2.0. Coarse grain distribution dimension has definite physical meaning, it not only response centroid of coarse grain, but also express gravel content of earth-rock aggregate, coarse grain boundary dimension is determined by perimeter-area method to describe coarse geometric qualities with quantitative method.Deformation and strength properties are discussed through large-scale triaxial test, established relationship between grain dimension and strength, only one dimension has optical gradation is demonstrated, optical gradation dimension connects with grading range and maximum grain size, it provides basis for engineering application and scientific classification of earth-rock aggregate.