无水砂卵石土体工程性质研究

发布时间：2019-01-18 10:21

【摘要】：随着国内外学者对岩土力学的进一步研究,人们逐渐意识到要想更深入的认识岩土力学性质,就要从其微观机理入手。离散元方法的出现,可以很好地运用到岩土力学的微观机理研究中。本文通过现在流行的颗粒流数值模拟方法,利用PFC来分析砂卵石的细观结构,并得出砂卵石细观性质和宏观性质之间的联系,来表述其力学特征。砂卵石地层是在地下工程施工中经常遇见的复杂地质之一,如在成都地铁施工过程中所遇见的砂卵石地层为典型的富水砂卵石,北京地铁施工过程中也遇见砂卵石地层。砂卵石地层的主要特点是离散性强、卵石自身强度相对其他细粒土强度高、其分布的几何规律性及个体形状可大体归类性。在这些特点共同影响下,砂卵石表现出复杂的力学特性,从而使地下隧道工程施工面临着巨大的难度。只有在清楚知道砂卵石微观机理的前提下,才能对这些问题和困难进行分析攻克。目前对于砂卵石的力学特性虽然有了大量的理论和试验基础,但多数基于有限元分析,有一定的局限性,所以本文通过离散元的方法首先建立基本的力学试验模型(三轴试验、堆积试验、活动门试验)。通过边界伺服控制来模拟室内试验的全部过程。通过这些基本的数值模拟试验,为文中室内试验提供基础参数。本文通过现有的理论基础,利用PFC软件,研究无水砂卵石的力学特征,并根据所取得的数据与室内试验、现场实例进行对比,为砂卵石地层隧道施工做一定的理论基础。其主要研究内容如下:(1)对砂卵石的个体表观特征和细观特征进行了系统的分类,如形状、粒径分配、自身摩擦系数、刚度强度等。(2)突破传统有限元的局限性,利用PFC程序,更加直接地模拟试验过程,并且利用程序的内置语言进行二次开发,建立不规则颗粒模型,证明PFC可以很好地模拟散体力学特性。系统的分析了不同形状及不同参数下的不同宏观力学表现。(3)通过室内试验和数值模拟,对不同宏细观参数下的散体颗粒进行多组试验对比,得出其内在规律性,揭示宏细观之间的相互影响。(4)根据上述结论与实际工程相印证,来进一步阐释砂卵石地层隧道施工时的影响和变化,为今后砂卵石施工提供有力的依据。
[Abstract]:With the further research of geotechnical mechanics at home and abroad, people gradually realize that in order to understand the properties of geotechnical mechanics more deeply, we must start with its microscopic mechanism. The emergence of discrete element method can be well applied to the study of microscopic mechanism of geotechnical mechanics. In this paper, PFC is used to analyze the meso-structure of sand and pebble by using the popular numerical simulation method of particle flow, and the relationship between the meso and macroscopic properties of sand pebble is obtained to express its mechanical characteristics. Sand pebble formation is one of the complex geology often encountered in underground engineering construction. For example, the sand pebble stratum encountered in the construction of Chengdu subway is typical rich in water sand and pebble stratum, and the sand and gravel stratum is also encountered in the construction process of Beijing subway. The main characteristics of sand and pebble strata are strong discreteness, high strength of pebbles compared with other fine grained soils, and their geometric regularity and individual shape can be roughly classified. Under the influence of these characteristics, sand pebbles exhibit complex mechanical properties, which make the construction of underground tunnel engineering face great difficulty. Only when the microcosmic mechanism of sand and pebble is well known can these problems and difficulties be analyzed and overcome. Although there are a lot of theoretical and experimental foundations for the mechanical properties of sand pebbles, most of them are based on finite element analysis and have some limitations. Therefore, in this paper, a basic mechanical test model (triaxial test) is established by discrete element method. Stacking test, movable door test) The whole process of indoor test is simulated by boundary servo control. These basic numerical simulation tests provide the basic parameters for the laboratory test in this paper. In this paper, the mechanical characteristics of anhydrous sand and pebble are studied by using PFC software and the existing theoretical foundation is compared with the data obtained in laboratory tests and field examples, which provides a theoretical basis for tunnel construction in sandy gravel strata. The main research contents are as follows: (1) the individual apparent and mesoscopic characteristics of sand pebbles are systematically classified, such as shape, particle size distribution, friction coefficient, stiffness strength, etc. (2) the limitation of traditional finite element method is broken through. The PFC program is used to simulate the test process more directly, and the program is redeveloped with the built-in language. The irregular particle model is established. It is proved that PFC can well simulate the mechanical properties of the bulk. The different macroscopic mechanical behaviors of different shapes and parameters are systematically analyzed. (3) through laboratory tests and numerical simulation, the experimental results of different macroscopical parameters of granular particles are compared, and the inherent regularity is obtained. (4) according to the above conclusion and actual engineering, the influence and change of tunnel construction in sand and gravel strata are further explained, which provides a strong basis for the construction of sand and gravel in the future.
【学位授予单位】：鲁东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U452.11

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