兰州大学机构库 >物理科学与技术学院
颗粒介质的传力特性研究
Alternative TitleOn Force Transmission in Granular Media
缪馥星
Thesis Advisor苗天德
2005-05-31
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword应力链 拱效应 拱结构 滑移线
Abstract本文对块状颗粒和圆形颗粒二维堆积体中的应力传递规律(力的传递上呈现“应力链”现象)进行了实验研究和模型分析。对块状颗粒的无缝隙和有缝隙两种堆积情形,实验研究了其在不同基底上受集中荷载作用时内部的应力传递和分布。发现块状颗粒无缝隙排列的堆积体内的应力传递范围具有抛物线型边界,而有缝隙情形下则具有带尖头的曲线传力边界。整体上看,有缝隙情形的应力传递范围要小于无缝隙情形。对无缝隙排列的情形,当基底不同时,传力范围不同。对圆形颗粒的二维堆积体,内部的应力传递规律与块状颗粒的相比,存在明显的“拱效应”。发现在自重作用下,颗粒堆积体底层个数为偶数时出现“六角形或梅花形”的稳定的“拱结构”;为奇数时,出现“类抛物线形”的稳定“拱结构”。在集中力作用下,当着力处的颗粒发生约三分之一颗粒直径的位移时,颗粒堆中出现沿正三角形两边传力的现象,此正三角形内的颗粒并不发生移动;在均布力作用下,对堆积体左右边无约束情形,当施加均布力的一边发生约三分之二颗粒直径的位移时,随堆积形式的不同,颗粒堆自组织排列成“N”形、“双菱形”、“倒正三角形”、“M”形或“W”形等不同形状的“滑移线”;在重力和均布力共同作用下,对梯形排列的颗粒堆,当侧边自由时,出现双重的倒正三角形的“滑移线”。理论分析方面,对块状堆积体的传力进行了量纲分析,同时构造了若干简单理想模型并进行了分析研究,提出和验证了散体颗粒堆传力规律的若干观点。所得实验结果不仅弥补了已有结果的不足,还对揭示颗粒物质的“应力链”现象的机理和解决涉及颗粒物质的现实工程技术问题,都具有重要指导意义。
Other Abstract"In this thesis, we experimentally study the force transmission in granular material, and we conduct the model analysis to the response of granular packings to various applied forces as well. We use 2D granular arrays consisting of particles: either aluminium disks or plexiglass squares. There are two kinds of arrays for square particles. One is that the grains fit together, without gaps, to fill the space. The other is that the grains cover the container with a certain gap. The experiments are carried out on the square particle arrays on different substrates under concentrated force. Static arrays show inhomogeneous spatial stress profiles called stress (or force) chains. For packings without gaps, the outer envelope of the response is a parabolic, but for packings with gaps, the stress profile is a curve with a sharp angle. A major finding is that spatial ordering of the particles is a key factor in the stress response, and the packings with gaps have a smaller transmissive scope than the packings without gaps do. Compared with square particle packings, there is an obvious “arching effects” of stress transmission in disk particle packings. The key findings are as follows: (1) Under gravitational force, the stable “arching structure” is a “hexagon or quincunx” if the bottom layer has even particles, and the “arching structure” is a quasi-parabola if the bottom layer has odd particles. (2) Under a concentrated force, when the displacement at the contact point reaches up to 1/3 of the particle diameter, the stress profile is an equilateral triangle. Within this triangle, the particles keep unchanged. (3) Under a uniform force, the stress profile varies with the packing form, if the displacement at the contact point reaches up to 2/3 of the particle diameter, there are five kinds of stress profiles: N-type, M-type, W-type, double-diamond type and inverse equilateral triangle type. (4) Under both gravitational and uniform forces, there is a dual inverse equilateral triangle stress profile in the trapezoid packing geometry when the lateral sides are free from applied forces. II In addition, we do some dimensional analyses on the stress transmission for the square particle packings, and develop a simple theoretical model applied to predict the stress distribution in granular materials. To conclude, we have measured the force response of 2D granular packings to local forces and modeled the stress transmission in granular media, the results of this th...
URL查看原文
Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/229650
Collection物理科学与技术学院
Recommended Citation
GB/T 7714
缪馥星. 颗粒介质的传力特性研究[D]. 兰州. 兰州大学,2005.
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