Research On The Meso-structural Mechanics And Scale Effect Of Soil-rock Mixture

Soil rock mixture(S-RM)is common in a variety of shallow geological disasters,hydraulicengineering,road engineering,building construction,mining and other fields.The soil and rock block are very different both in particle size and strength,resulting in strong heterogeneity.The meso-structural characteristics of soil-rock mixture has a significant impact on the macroscopic physical and mechanical properties,and is closely related to the research scale.In this paper,a systematic study of the meso-structural mechanics and scale effect of soil rock mixture is carried out by physical experiments and numerical simulation.Combined with real-time X-ray Computerized Tomgraphy(CT),a series oftriaxial testswere carried out.The influence of rock block content,particle size distribution and sample size on the macroscopic strength and deformation properties of soil-rock mixture were studied.This also enables real time information acquisition of the sample meso-structure and its evolution.With the application of digital image processing technology,database management technology and 3D visualization technology,a three dimensionalMeso-Structure Reconstruction and Analysis System(MSRAS3D)forsoil-rock mixture was developed.MSRAS3 D can reconstruct the meso-structure model of soil-rock mixture sample.It also can be used for statistical analysis of sample’s meso-structural characteristicsquantitatively,which provides a powerful means to reveal the meso-structure evolutionduring the whole triaxial test.Thusthe spatial movement regularity and typical break forms of internal rock block,the deformation localization in the soil-rock mixture under external load are revealed.The DEM numerial simulation of a series of triaxial tests for the soil rock mixture’s reconstruction model were carried out.On this basis,the inversion meso-mechanical parameters of the soil and rock block were obtained according to the laboratory test results.With this set of inversion parameters,more numerical triaxial tests for the random model of soil rock mixture were carried out.Through these numerical tests,some impact factors,such as the shape and fracture properties of rock block,the sample size were studied in depth.The evolution of meso-structural characteristics of soil-rock mixture in the shear failure process,such as the space motion and coordinate number of internal particles,the normal and shear force between particles,the meso volumetric strain were analyzed quantitatively.The influence mechanism of particle size distribution,shape and fracture property of rock block,the sample size on the macroscopic strength and deformation characteristics of the soil-rock mixture are revealed from the meso level.Through the research of the thesis,it is an effective means to reveal the macro-meso mechanical properties of soil-rock mixture by using the reconstruction model in the laboratory experiments and the stochastic model in the numerical simulation to analyze the evolution of meso-structure.The meso-structural characteristics of soil rock mixture and the inherant natures of soil and rock block affectits mechanical behavior jointly.During the deformation and failure process,the internal rock blocks’ s movement and breakage lead to different adjustments of the meso structur,thus affecting the macroscopic strength and deformation properties of soil-rock mixture.The research scale and particle size distribution determine the role of rock block played in the response to load directly.The Angularity rock blocks can improve strength of the soil-rock mixture by occlusion when they are not broken.The facture nature of rock blocks has an important impact on both the strength and deformation of the soil-rock mixture,which is controlled by rock blocks’ own strength and the stress level.