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1.
Joanna Kozakiewicz 《Earth Science Informatics》2018,11(2):257-272
Image analysis methods are commonly employed to determine the size and shape of particles. Although commercial and non-commercial tools enable detection and measurement of grains from images, they do not provide good results in the case of images acquired during extensive in situ Martian investigations. Within the confines of the Mars Exploration Rover (MER) mission and the Mars Science Laboratory (MSL) mission thousands of images of sand grains were captured, and hitherto, they are the only source of ground-truth data on Martian sand particles. Therefore, a new approach is proposed to analyze such images. The semi-automatic algorithm allows fast detection and measurement of the size and shape of Martian grains from images obtained by the Microscopic Imager (MI) and the Mars Hand Lens Imager (MAHLI). The method was evaluated on 76 images of terrestrial and Martian deposits. The results for the terrestrial samples were compared to those from sieve analysis, as well as with ImageJ and Malvern Morphologi G3 systems. The method provides similar results to those from the other methods. It does not have any limitation on the size of grains, and permits separation of touching particles. 相似文献
2.
颗粒材料大多由不规则形状的颗粒组成,如砂土、谷物等,抵抗转动是不规则形状颗粒的固有特性。已有研究表明,颗粒抗转动特性对其宏观力学特性有显著影响。因此,在颗粒材料的细观数值模拟中或采用非圆颗粒,或在圆颗粒离散元模拟中采用考虑抗转动的接触模型。采用有限元-离散元耦合方法（FDEM）和离散元方法（DEM）分别对椭球形状颗粒和具有抗转动能力的圆球颗粒进行三轴剪切数值模拟,指出了采用抗转动接触模型考虑颗粒形状影响的局限性,并基于颗粒的局部排布结构揭示了形状影响的细观来源。峰值内摩擦角和剪胀均随着转动摩擦系数和形状偏离圆球程度而单调增加,但颗粒形状对它们的影响呈现出明显的收敛趋势。细观组构分析也表明,虽然颗粒形状和转动摩擦都能显著增强组构各向异性,但是组构各向异性的演化模式有明显的区别。造成以上结果的差异在于其抵抗转动的影响机制不同。转动摩擦是通过限制颗粒转动,增强了颗粒间的稳定承载能力,而非圆颗粒是通过咬合作用形成稳定的局部排列结构。由于椭球颗粒腹部比端部能够传递更大的接触力,颗粒受剪切后发生转动,颗粒长轴倾向于正交大主应力方向,呈现交错排列,颗粒间相互锁定。 相似文献
3.
基于颗粒流的堆石料三轴剪切试验研究 总被引：2，自引：0，他引：2
近年来频发的地质灾害使得深入研究大坝堆石体受力变形机制显得愈发迫切和重要。针对堆石颗粒具有形状极其不规则、咬合作用突出的特点,编写了一个简单易用的程序来随机生成形状不规则的数值颗粒。以正四面体为核,按照晶胞繁衍的方式,生成堆石的仿真颗粒集合体。模拟排水剪切条件下的大三轴试验,通过分析数值试验过程中细观参量的变化规律,探讨三轴剪切条件下堆石体变形的细观机制。分析表明,按照晶胞繁衍法生成的数值颗粒与圆颗粒相比能更好地模拟堆石,由颗粒簇形成的咬合力能形成更真实的力-变形关系;数值试验得到的应力-应变曲线和体变曲线与室内三轴试验结果基本一致;颗粒的破碎速率是联系堆石体宏、细观力学性质的重要纽带,通过分析堆石体颗粒破碎4个阶段细观参量的变化规律,深化了对堆石体变形机制的认识。 相似文献
4.
Andrew B. Vistelius 《Mathematical Geology》1970,2(1):1-14
An analysis of the results of investigation of the G- 1 and W- 1 samples are given and differ from F. Chayes’ point of view.
Results of the samples can be evaluated by comparison of frequency-distribution properties of determinations for chemical
elements from different laboratories with some standard distribution, which gives the idea of a statistical model. The comparative
results indicate that oxides from minerals of the same density have positive correlations and that oxides from minerals of
different density have negative correlations. The different results therefore are not from the precision of analysis, but
rather from differentiation of sample powder particles by density and shape in the course of preparation. 相似文献
5.
6.
A new approach to the three-dimensional quantification of angularity using image analysis of the size and form of coarse aggregates 总被引：1，自引：0，他引：1
This paper describes a system for the acquisition and analysis of 3D data from the surfaces of coarse aggregate particles. The technique uses laser triangulation to acquire data from the upper hemispheres of particles passing along a conveyor belt. Methods of determining particle size and form in three dimensions are described and a new approach to the quantification of angularity is presented. The algorithm uses mathematical morphology to provide a geometrically meaningful interpretation of particle shape. The relative advantages of 2D and 3D analysis of aggregate particles are discussed, and results are presented which demonstrate the validity of this approach. 相似文献
7.
This paper analyses the influence of grain shape and angularity on the behaviour of granular materials from a two‐dimensional analysis by means of a discrete element method (Contact Dynamics). Different shapes of grains have been studied (circular, isotropic polygonal and elongated polygonal shapes) as well as different initial states (density) and directions of loading with respect to the initial fabric. Simulations of biaxial tests clearly show that the behaviour of samples with isotropic particles can be dissociated from that of samples with anisotropic particles. Indeed, for isotropic particles, angularity just tends to strengthen the behaviour of samples and slow down either local or global phenomena. One of the main results concerns the existence of a critical state for isotropic grains characterized by an angle of friction at the critical state, a critical void ratio and also a critical anisotropy. This critical state seems meaningless for elongated grains and the behaviour of samples generated with such particles is highly dependent on the direction of loading with respect to the initial fabric. The study of local variables related to fabric and particle orientation gives more information. In particular, the coincidence of the principal axes of the fabric tensor with those of the stress tensor is sudden for isotropic particles. On the contrary, this process is gradually initiated for elongated particles. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
8.
河流搬运体系中,颗粒的形状属性可以反映其来源、搬运、沉积的过程。长期以来沉积学界缺乏相对统一的定量的、多维的颗粒形状参数。本研究以西藏雅鲁藏布江支流帕隆藏布为例,运用图像分析、软件分析等计算机辅助技术,对8个天然河流砂样品中的2276个颗粒开展碎屑成分鉴定和形状参数量化等工作。重点评估了11个颗粒形状参数,通过因子分析等统计方法提取并定义了3个形状信号,包括圆形度因子、规则度因子和平滑度因子。这些参数可用于表征颗粒宏观形状上接近圆形的程度、中观尺度上轮廓规则的程度及轮廓平滑的程度。挖掘天然河流砂的重要形状特征后,进一步探索了这些形状参数与颗粒成分、粒度的关系。本研究成果为解释河流系统中颗粒的形状信号、理解颗粒自身微观属性和外部物理过程等提供重要借鉴。 相似文献
9.
河流搬运体系中,颗粒的形状属性可以反映其来源、搬运、沉积的过程。长期以来沉积学界缺乏相对统一的定量的、多维的颗粒形状参数。本研究以西藏雅鲁藏布江支流帕隆藏布为例,运用图像分析、软件分析等计算机辅助技术,对8个天然河流砂样品中的2276个颗粒开展碎屑成分鉴定和形状参数量化等工作。重点评估了11个颗粒形状参数,通过因子分析等统计方法提取并定义了3个形状信号,包括圆形度因子、规则度因子和平滑度因子。这些参数可用于表征颗粒宏观形状上接近圆形的程度、中观尺度上轮廓规则的程度及轮廓平滑的程度。挖掘天然河流砂的重要形状特征后,进一步探索了这些形状参数与颗粒成分、粒度的关系。本研究成果为解释河流系统中颗粒的形状信号、理解颗粒自身微观属性和外部物理过程等提供重要借鉴。 相似文献
10.
To identify all desired shape parameters of granular particles with less computational cost, this study proposes a three-dimensional convolutional neural network (3D-CNN) based model. Datasets are made of 100 ballast and 100 Fujian sand particles, and the shape parameters (i.e., aspect ratio, roundness, sphericity, and convexity) obtained by conventional methods are used to label all particles. For the model training, by feeding the slice images of particles into the model, the contour of particles is automatically extracted, thereby the shape parameters can be learned by the model. Thereafter, the model is applied to predict shape parameters of new particles as model testing. All results indicate the model trained based on slice images cut from three orthogonal planes presents the highest prediction accuracy with an error of less than 10%. Meanwhile, the accuracy for concave and angular particles can be guaranteed. The rotation-equivariant of the model is confirmed, in which the predicted values of shape parameters are roughly independent of orientations of the particle when cutting slice images. Superior to conventional methods, all desirable shape parameters can be obtained by one unified 3D-CNN model and its prediction is independent of particle complexity and the number of triangular facets, thus saving computation cost. 相似文献
11.
G. H. Dury 《Australian Journal of Earth Sciences》2013,60(2):655-666
Mt Sturt is a duricrusted residual, from which particles of silcrete are discharged on to flanking slopes and surrounding pediments. Dimensional analysis of the particles yields log‐normal curves, bimodal on the crest but unimodal elsewhere, with an orderly downslope decrease in median dimensions. The rate of decrease appears insufficient to reduce the particles to sand size within conceivable limits of pediment length. Analysis of shape indices gives normal distributions with no significant down‐slope change of index, except for the roundness index which tends to assume distributions of the Poisson type and to increase in value downslope. The general correspondence between observed distributions and theoretical curves is close, although it seems likely that gilgai can disturb to some extent the distribution of dimensions in particular samples. 相似文献
12.
地震多属性拟合技术在粗粒扇体沉积相图编制中的应用--以玛131井区百口泉组二段为例 总被引：1，自引：1，他引：0
由于砾岩岩石类型复杂,储层非均质性强,难以建立地震属性与储层之间的一一对应关系,导致应用地震属性常常具有不确定性和多解性。为了克服单一属性反映粗粒沉积展布的片面性,同类属性间相关信息的彼此干扰性,地震相预测扇体分布的盲目性,针对性的提出了基于地震多属性拟合技术编制粗粒扇体沉积相图的方法:1）建立岩性识别图版;2）属性优化与线性逐步回归拟合含砂砾率;3）均方根振幅属性正态分布约束砂体边界;4）应用拟合含砂砾率等值线图,结合岩相和测井相编制粗粒扇体沉积相图。并将该方法用于玛131井区百口泉组二段的沉积研究中,为研究粗粒扇体沉积提供了新的思路,为玛湖滚动勘探及井位论证提供了可靠地质依据。 相似文献
13.
A large number of tests have recently been conducted with the Split Hopkinson pressure bar (SHPB) method to determine the characteristics of rock dynamics. However, it is still impossible to get test results at a perfect constant strain rate from this set-up owing to the rate dependency of rock materials. For instance in most cases, dynamic behavior of rock can only be described with an average strain rate. The results from these methods, including rich strain rate information, frequently tend to be inexplicable or self-contradictory. The obtained stress–strain curves can then never be directly treated as constitutive curves as in static tests. In this paper, the reasons behind the controversial stress–strain results with current methods are analyzed. In addition, the requirement for the rock specimen to deform at a constant strain rate is demonstrated after theoretical analysis of correlations among specimen, deforming stress, incident stress, reflected stress and transmitted stress. With test results from SHPB by pulse shaper and special shape striker methods, the requirement is verified. Finally, the method of 3D scattergram considering stress–strain–strain rate simultaneously is brought up to get constitutive relationships of rate-dependent rock. The new method gives reasonable predictions for constitutive relationships of rock at different strain rates. At the same time, the new method has fewer requirements and has a wider application scope for SHPB tests. 相似文献
14.
Frédérick Delay Hélène Housset-Resche Gilles Porel Ghislain de Marsily 《Mathematical Geology》1996,28(1):45-71
A new method for solving the transport equation based on the management of a large numbe of particles in a discretized 2-D domain is presented. The method uses numerical variables to represent the number of particles in a given mesh and is more complex than the 1-D problem. The first part of the paper focuses on the specific management of particles in a 2-D problem. The method also would be valid for three dimensions as long as the medium can be modeled similar to a layered system. As the particles are no longer tracked individually, the algorithm is fast and does not depend on the number of particles present. The numerical tests show that the method is nearly numerical dispersion free and permits accurate calculations even for simulations of low-concentration transport. Because each mesh is considered as a closed system between two successive time steps, it is easy to add adsorption phenomenon without any problem of numerical stability. The model is tested under conditions that are extremely demanding for its operating mode and gives a good fit to analytical solutions. The conditions in which it can be used to best advantage are discussed. 相似文献
15.
基于3D MAX的矿体三维立体形态研究 总被引：2，自引：0，他引：2
以小西南岔铜金矿北山矿段Ⅰ-Ⅱ号脉系金、铜矿体为例,提出按品位分级的研究方法,探讨其形态特征和空间赋存规律,进而将矿体细分为矿饼微元,由此建立北山矿段金、铜矿体的三维立体形态模型。从而得出如下结论：（1）使用3D MAX软件将矿体形态可视化,方法简单易行,便于指导矿山管理、设计和生产;（2）提出品位分级形态的概念,有利于人们更好地认识矿体在空间的展布形态和分布规律,为解决矿体随时间等因素变化提出了一种新的研究思路;（3）对分段富集规律有了新的认识,将其应用范围从平面域扩展到空间领域,进而更好地预测隐伏矿体。 相似文献
16.
Shape is a fundamental property of all objects, including sedimentary particles, but it remains one of the most difficult to characterize and quantify for all but the simplest of shapes. Despite a large literature on the subject, there remains widespread confusion regarding the meaning and relative value of different measures of particle shape. This paper re‐examines the basic concepts of particle shape and suggests a number of new and modified methods which are widely applicable to a range of sedimentological problems; it is shown that the most important aspects of particle form are represented by the I/L ratio (elongation ratio) and S/I ratio (flatness ratio). A combination of these two ratios can be used to classify particles in terms of 25 form classes. A method of obtaining a quantitative measure of particle roundness using simple image analysis software is described, and a new visual roundness comparator is presented. It is recommended that measurements of both roundness and circularity (a proxy measure of sphericity) are made on grain images in three orthogonal orientations and average values calculated for each particle. A further shape property, irregularity, is defined and a classification scheme proposed for use in describing and comparing irregular or branching sedimentary particles such as chert and coral. 相似文献
17.
悬浮颗粒形状对其在多孔介质中迁移和沉积特性的影响 总被引：1，自引：0，他引：1
悬浮颗粒在多孔介质中迁移的研究在地下水回灌、地下污染物扩散、核废料处置、石油开采等领域有重要的理论意义和应用价值。为了研究形状对颗粒迁移的影响,对1组球状颗粒（10 ?m中位粒径）和2组杆状颗粒（长径比为3:1和6:1）进行了三阶段室内土柱试验,得到了不同形状颗粒在多种溶液离子强度条件下的穿透曲线。结合DLVO理论分析了悬浮颗粒沉积和释放机制,阐释了形状对颗粒迁移行为的影响。试验结果表明,颗粒形状对迁移特性有重要影响,当离子强度较低时（6 mmol/L）,DLVO势能曲线展现较高能量壁垒,各种形状颗粒沉积主要为次级势阱沉积;当离子强度较高时（150 mmol/L）,球状颗粒因能量壁垒较高,其滞留机制仍以次级势阱沉积为主,但长径比为6:1的杆状颗粒在次级势阱和初级势阱都有沉积,这和杆状颗粒的静电性能和优先方向有关。对于杆状颗粒,边位沉积比端位沉积具有更深的次级势阱和更大的影响距离,边位沉积是更加稳定的沉积方式和沉积的优先方向。基于Derjaguin近似方法的DLVO理论计算显示,DLVO理论预测结果和土柱试验结果吻合较好。 相似文献
18.
考虑到颗粒形状对粗粒料的力学特性有重大影响,提出了一种新的表征颗粒形状的方法,即在椭圆上随机选取一系列点连接成多边形颗粒,表征狭长扁平的颗粒。新方法较圆上取点的方法能代表更多类型的颗粒形状,适用范围更广。提出了一种新的粗粒料投放算法,即先缩小颗粒,然采用随机算法将缩小的颗粒投放至给定区域,对颗粒划分好网格后,将颗粒放大到原来的大小,然后采用有限元-离散元(FEM/DEM)方法计算稳定后即生成了相应的试样。通过将上述颗粒生成及投放算法与FEM/DEM结合,应用于粗粒料的数值模拟。分析表明,FEM/DEM是研究粗粒料力学性质的较好方法,对复杂的颗粒形状也可简单建模,且因在颗粒内部划分了有限元网格,复杂的接触判断及接触力计算转化为标准统一的三角形和三角形之间的接触判断及接触力计算,所有的计算均可标准化、统一化。同时因为颗粒是可以变形的,依然保留了连续介质力学中应力和应变的概念,无须像PFC那样需通过测量圆来间接表示某点的应力、应变。最后,通过粗粒料的侧限压缩试验的数值模拟,展现了文中提出的一整套解决方案在模拟粗粒料方面的巨大潜力。 相似文献
19.
岩体结构要素分形几何研究 总被引：5，自引：1，他引：4
本文研究了岩体结构诸要素, 包括结构面形态、结构面厚度、结构面分布、产状分布、孔隙分布颗粒表面形态等的分形表征, 目的是提高岩体结构的定量描述程度, 为岩体工程的定量评价提供新的途径。 相似文献