竖向加筋砂土直剪试验的颗粒流数值分析

发布时间：2018-05-07 07:56

本文选题：直剪试验 + 加筋　；参考：《浙江大学》2013年硕士论文

【摘要】：土工袋装砂石桩复合地基是一种新型的地基处理技术,目前关于该复合地基的剪切特性的研究很少。开展土工袋装砂石桩复合地基抗剪特性的研究,关键之一在于袋体与土体界面的剪切特性的研究,即竖向加筋土体剪切特性的研究。本文利用颗粒流软件PFC2D,从颗粒层面上对竖向加筋土体的直剪试验进行分析,揭示了其微观现象及机理,本文主要工作和研究成果如下： (1)利用颗粒流理论对直剪试验进行数值模拟,分析了颗粒级配、孔隙比、颗粒接触刚度、颗粒摩擦系数和颗粒形状等细观参数的变化对宏观抗剪强度的影响。 (2)对颗粒间摩擦系数取值为0.2～10,研究直剪试验中材料峰值内摩擦角和颗粒摩擦系数之间的关系,并对直剪试验中颗粒转动问题进行讨论,研究了其中的颗粒滑动和滚动破坏机理；讨论了直剪试验中颗粒尺寸效应；针对颗粒流中用圆形颗粒模拟实际不规则砂土的固有缺陷,提出了提高应力比的措施；对直剪试验中的临界加载速率进行了讨论。 (3)对竖向加筋的直剪试验进行了颗粒流模拟,宏观上,分析了加筋层数、密实度、筋材拉伸模量和筋材表观摩擦系数对剪应力—位移曲线的影响。微观上,从颗粒接触状态、颗粒分布状态、颗粒运动状态和主应力偏转等方面对剪切过程中的微观力学性质进行分析,并从宏观和微观上比较讨论了加筋的影响。本文的创新点在于利用颗粒流程序PFC~(2D)对砂土直剪试验模型进行了离散元分析,并对竖向加一层筋和加两层筋的情况进行数值研究,着重从颗粒层面上对加筋砂土剪切过程中的微观变化进行了细观机理分析。
[Abstract]:This paper studies the shear characteristics of soil - bagged sand - stone pile composite foundation , which is based on the study of shear characteristics of the soil interface . The key of this paper is to study the shear behavior of the soil interface , which is the study of shear behavior of the vertical stiffened soil .

( 1 ) The effects of particle size distribution , pore ratio , particle contact stiffness , particle friction coefficient and particle shape on the macroscopic shear strength were analyzed by using particle flow theory .

( 2 ) The relationship between the internal friction angle and the particle friction coefficient of the material in the direct shear test is studied . The particle sliding and rolling damage mechanism are studied in the direct shear test .
The particle size effect in direct shear test is discussed .
In order to simulate the inherent defects of the actual irregular sand by using circular particles in the particle flow , the measures to improve the stress ratio are put forward .
The critical loading rate in direct shear test is discussed .

( 3 ) The influence of reinforcement layer number , density , tensile modulus of rib and apparent friction coefficient on shear stress - displacement curve are analyzed . The micro - mechanical properties of shear process are analyzed from the aspects of particle contact state , particle distribution state , particle motion state and principal stress deflection , and the influence of reinforcement is discussed from the macroscopic and microscopic aspects .

In this paper , the discrete element analysis of the sand - soil direct shear test model is carried out by using the particle flow program PFC ~ ( 2D ) , and the numerical research is carried out on the case of vertical reinforcement and two - layer reinforcement , and the microscopic changes in the shearing process of the reinforced sandy soil are analyzed in detail from the particle level .

【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU411.7

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