干湿循环作用下非饱和粉土路基的工程特性研究

发布时间：2018-04-23 16:16

本文选题：非饱和粉土 + 路基　；参考：《郑州大学》2014年硕士论文

【摘要】：河南部分地区为黄河冲击平原，粉土作为路基填筑材料应用较为广泛。由于道路交通流量的日益增长以及重载超载车辆比例的不断增大，粉土不良的工程性质易导致路基发生不均匀沉降等病害，增加了道路养护和维修费用。本文针对粉土路基的变形沉降问题，在综合分析现有国内外研究成果的基础上，利用室内试验对粉土的力学特性进行了较为系统的研究。通过干湿循环试验与土水特征曲线进一步探讨了干湿循环作用对非饱和粉土变形特性的影响，分析了影响饱和与非饱和粉土力学特性的主要因素。本文的主要研究成果为：（1）通过GCTS试验，得出了典型粉土在3种压实度下的土水特征曲线。采用不同的模型进行拟合，结果表明，Fredlund-Xing模型对试验结果拟合效果较好，，能够反映典型粉土土水特征曲线过渡段的陡降特性。随着压实度的增大，其土水特征曲线过渡段曲线的斜率略微变缓，表明增加压实度有利于粉土路基的稳定。（2）基于不同干湿循环次数作用下非饱和粉土的力学特性试验结果，粉土试样在经历1次干湿循环后，其强度和压缩模量均明显降低；经历多次干湿循环后，土样的强度和变形特性基本趋于稳定。在进行粉土路基设计时，采用多次干湿循环后粉土的强度与变形参数更为合理。（3）基质吸力对粉土的破坏形式和峰值强度都具有一定的影响。在低吸力情况下，粉土的应力应变曲线呈应变硬化型，而在高吸力情况下则表现为应变软化型。由此表明，随着基质吸力的增加，粉土的“脆性”性质更加明显。关于基质吸力对粉土剪切强度的影响，在不大于200kPa基质吸力范围内，粉土峰值强度随基质吸力的增大而单调增大。（4）与饱和粉土相比较，非饱和粉土的粘聚力随着基质吸力的增大有明显的提高，而内摩擦角近似等于饱和试样的内摩擦角，表明基质吸力对非饱和土粉土强度参数的影响主要体现在粘聚力c。（5）利用ABAQUS软件建立了考虑粉土路基沥青路面结构的非线性有限元计算模型，主要分析了不同的干湿循环次数对路面结构变形的影响，对粉土路基的路面结构设计具有一定的参考价值。
[Abstract]:Part of Henan is the Yellow River impact plain, silt is widely used as subgrade filling material. Due to the increasing traffic flow and the increasing proportion of overloaded vehicles, the poor engineering properties of silt easily lead to uneven settlement of roadbed, which increases the maintenance and maintenance costs of roads. Aiming at the problem of deformation and settlement of silt subgrade, based on the comprehensive analysis of existing research results at home and abroad, the mechanical properties of silt are studied systematically by laboratory tests. The effects of dry and wet cycling on the deformation characteristics of unsaturated silt were further discussed through dry and wet cycling tests and the characteristic curves of soil-water. The main factors affecting the mechanical properties of saturated and unsaturated silt were analyzed. The main research results of this paper are as follows: 1) through GCTS test, the soil water characteristic curves of typical silt under three kinds of compaction are obtained. The results show that Fredlund-Xing model can fit the experimental results well and can reflect the steep drop of the transition section of typical silt soil water characteristic curve. With the increase of compaction degree, the slope of the transition curve of soil-water characteristic curve becomes slightly slower, which indicates that increasing compaction degree is beneficial to the stability of silty soil subgrade. 2) based on the experimental results of mechanical properties of unsaturated silt under different times of dry and wet cycles, the strength and compression modulus of silt samples decreased obviously after one dry and wet cycle, and after several dry and wet cycles, The strength and deformation characteristics of soil samples tend to be stable. In the design of silt subgrade, the strength and deformation parameters of silt are more reasonable after several dry and wet cycles. 3) the matrix suction has certain influence on the failure form and peak strength of silt. In the case of low suction, the stress-strain curve of silt shows strain hardening type, while in the case of high suction, it shows strain softening type. The results show that the brittleness of silt is more obvious with the increase of matrix suction. As to the influence of matrix suction on the shear strength of silt, the peak strength of silt increases monotonously with the increase of matrix suction in the range of no more than 200kPa matrix suction. Compared with saturated silt, the cohesive force of unsaturated silt increases obviously with the increase of matrix suction, and the internal friction angle is approximately equal to the internal friction angle of saturated silt. The results show that the influence of matrix suction on the strength parameters of unsaturated silt is mainly reflected in the cohesive force c. The nonlinear finite element calculation model of asphalt pavement structure considering silt subgrade is established by using ABAQUS software. The influence of different times of dry-wet cycle on the deformation of pavement structure is mainly analyzed. It has certain reference value to the pavement structure design of silt subgrade.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U416.1

【参考文献】