Quantitative Morphological Characteristics Of Particle Population And Its Effect On Shear Characteristics Of Abandoned Agglomerates

Abandoned ballast pile masonry is an artificially constructed rock and soil body formed during the construction of a tunnel in a mountain area,with rock blocks as the mainstay.As a temporary system composed of a large number of irregular hard particles,the value of its mechanical parameters has always been a research difficulty in particle mechanics.Previous researches mostly focused on random particle generation.With the development of image recognition and 3D modeling technology,the fine description of particles has become a reality.In this paper,the limestone spoils deposits on the right side of the dumping site of the Xinwan to Dacun line of the newly built local railway Xuyong to Dacun line in Luzhou City,Sichuan Province are used as the research object.The evaluation index is based on the quantification of the morphological characteristics of the abandoned ballast particles,combined with the large indoor triaxial compression test and the discrete element numerical simulation test to analyze the influence of the particle group morphology on the shear characteristics of the abandoned ballast accumulations.In this study,we conducted a study on the influence of particle group morphology on the physical and mechanical properties of abandoned ballast deposits.For the selection of rock and soil parameters of abandoned ballast piles stability evaluation,enrich the design theory of abandoned ballast slopes,and promote the construction of railway projects in mountainous areas Sustainable development and avoiding soil erosion are of great significance.The main research work of this article is as follows:?1?With the help of CT scanning technology and graphic processing technology,the three-dimensional morphological information about the abandoned ballast particles is obtained.The spherical harmonic function is used to realize the accurate reconstruction of the three-dimensional shape of the particles,and the comparison and analysis of the volume of the reconstructed particles and the solid particles verify the rationality and effectiveness of the spherical spherical harmonic reconstruction method.The concept and calculation formula of particle similar rotational inertia ellipsoid are proposed,and the calculation formula suitable for calculating the quantitative index of each particle shape by the spherical harmonic function is re-derived and improved.?2?Calculate the shape index of each sample particle according to the improved formula,including 6 shape indexes such as particle sphericity,edge angle,elongation,flatness,maximum projected sphericity,and shape factor.Among them,the five shape indicators such as prism angle,elongation,flatness,maximum projected sphericity,and shape factor has two values due to the calculation method of the two equivalent ellipsoids.Use these 11 parameters to carry out shape characteristic evaluation research on the particles of the sample set.The principal component analysis method is used to reduce the dimensionality of the shape index,and the correlation between each shape index is calculated and analyzed.The first principal component in the principal component analysis results is used as the single particle shape quantification index F1*,and its value is positively correlated with the sphericity,elongation,and flatness of the particles,and negatively correlated with the angle of the edges.Calculate the F1*of each sample particle,and make a cumulative distribution curve of shape parameters,and use the curve to describe and quantify the morphological characteristics of the particle group.And the spherical harmonic function is used to reconstruct the morphological characteristics of the granule group.?3?A large-scale triaxial compression test was carried out in the abandoned ballast accumulation body.Three different confining pressures of 0.1 MPa,0.2 MPa and 0.3MPa were designed into the test,and the stress-strain full-process curves and resistances under three different confining pressures were obtained The shear strength index provides a basis for the selection of miso-parameters in discrete element numerical simulation tests.?4?PFC^3d was used to establish a numerical simulation test with the same conditions as the indoor test.The mesoparameters of the discrete element model were calibrated by comparing the stress-strain curves of the numerical simulation test and the indoor test.After the meso-parameters were determined,the triaxial compression test was conducted under the confining pressures of 0.1 MPa,0.2 MPa,and 0.3 MPa for different groups of morphological characteristics.Ring strain monitoring.Using the monitoring data,the stress-strain curves of different grain groups were drawn,and the influence of the morphological characteristics of the grain group on the physical and mechanical properties of the abandoned ballast accumulation was analyzed and compared.?5?On the basis of conducting indoor tests and numerical simulation tests.A three-dimensional generalized discrete element model of the slope of the abandoned ballast field was established,and the instability process of the slope of the abandoned ballast field was analyzed through the simulation of the displacement cloud map and the displacement data of the monitoring points;After the grain group,the instability simulation was conducted to study the influence of the group morphological characteristics of the grain group on the stability of the abandoned ballast field and the process of instability.