季冻土力学特性及试验技术研究

发布时间：2018-02-21 02:41

本文关键词： 季冻土季冻土制样新标准冻融循环修正系数抗剪强度指标计算公式残余应变振陷参数　出处：《中国地震局工程力学研究所》2017年博士论文　论文类型：学位论文

【摘要】：我国季冻土分布广泛,跨越了我国一半以上的省份,随着经济的发展及国家“一带一路”战略的提出,季冻区的交通基础设施建设规模也越来越大。经调查统计,季冻土路基常常会出现冻胀、融沉、沉陷、翻浆、边坡滑塌等一系列的路基病害,威胁行车安全,造成严重的经济损失。因此从季冻土覆盖范围、经济发展、国家战略布局和季冻土路基灾害的角度上,研究季冻土的强度变形特性都显得尤为重要。季冻土的相关研究很不成熟,截至目前,连基本的冻融循环下抗剪强度指标的变化模式都存在很大争议。造成争议的根源就在于季冻土试验技术的不成熟,这种不成熟表现在多个方面,缺乏季冻土试验标准以及试验仪器限制等等。因此注重试验的研究才能合理揭示季冻土的强度变形特性。本文对冻融循环土试验技术、季冻土静力学本构理论、冻融循环土强度理论和季冻土残余应变理论中的几个关键问题开展研究,提出季冻土制样新标准,得到了冻融循环下土应力应变关系变化规律与抗剪强度指标变化模式,给出了抗剪强度指标计算公式,得到了更符合实际的季冻土残余应变发展模式与更符合实际的振陷参数。主要工作和成果如下:(1)发现了常规土制样标准对季冻土试验的不适用性,指出了冻结融化使试样密度离散性放大是目前季冻土试验缺乏稳定性的原因,提出了减少土试样密度离散性的思想,建立了季冻土制样的新标准,并通过三轴试验验证了该标准的可靠性。(2)按照季冻土制样新标准,提出了冻融循环下三种典型土类应力应变变化模式及静强度变化模式,得到了围压、冻融循环次数和土类对季冻土静力特性的影响规律。(3)提出了冻融循环修正系数的概念,给出了冻融循环下典型土类抗剪强度指标变化模式,提出了粘聚力和内摩擦角冻融循环修正曲线和计算公式,阐明了其工程应用方法。(4)基于新型低温动三轴仪及改进的试验条件,以更符合实际的季冻土埋藏条件、动应力水平和冻结固结过程,提出了季冻土冻结期的残余变形发展规律和振陷计算参数。
[Abstract]:The seasonal frozen soil is widely distributed in China, spanning more than half of the provinces in our country. With the development of economy and the strategy of "Belt and Road", the scale of transportation infrastructure construction in the seasonal frozen area is becoming larger and larger. A series of roadbed diseases such as frost heaving, thawing, subsidence, mudding, slope collapse and so on often occur in the seasonal frozen soil subgrade, threatening the safety of driving and causing serious economic losses. Therefore, from the seasonal frozen soil coverage, economic development, From the perspective of national strategic layout and seasonal permafrost subgrade disaster, it is particularly important to study the strength and deformation characteristics of seasonal frozen soil. Even the basic model of variation of shear strength index under freeze-thaw cycle is very controversial. The root cause of the controversy lies in the immature test technology of seasonal frozen soil, which is manifested in many aspects. Therefore, the strength and deformation characteristics of seasonal frozen soil can be reasonably revealed by focusing on the experimental research. In this paper, the test technology of frozen and thawed soil, the constitutive theory of statics of seasonal frozen soil, and so on are discussed. Several key problems in the theory of frozen and thawed cyclic soil strength and the theory of residual strain of seasonal frozen soil are studied, and a new standard for the preparation of seasonal frozen soil is put forward. The variation law of stress-strain relationship and shear strength index of frozen and thawed soil under freeze-thaw cycle are obtained. The calculation formula of shear strength index is given. A more practical model of residual strain development in seasonal frozen soil and a more practical vibration subsidence parameter are obtained. The main work and results are as follows: 1) the inapplicability of the standard of conventional soil sample to seasonal frozen soil test is found. It is pointed out that the dispersion of sample density caused by freezing melting is the reason for the lack of stability in the present seasonal frozen soil test. The idea of reducing the density dispersion of soil sample is put forward, and a new standard for sample preparation of seasonal frozen soil is established. The reliability of the standard is verified by triaxial test. (2) according to the new standard of sample preparation for seasonal frozen soil, the stress strain and static strength variation modes of three typical soils under freeze-thaw cycle are put forward, and the confining pressure is obtained. The influence of freezing and thawing cycle times and soil on the static characteristics of seasonal frozen soil is studied. (3) the concept of freezing and thawing cycle correction coefficient is put forward, and the variation mode of shear strength index of typical soil under freeze-thaw cycle is given. A modified curve and calculation formula for freezing and thawing cycle of cohesive force and internal friction angle are put forward, and its engineering application method is expounded. Based on the new low temperature dynamic triaxial apparatus and the improved test conditions, it is more suitable for the buried conditions of seasonal frozen soil. The dynamic stress level and freezing consolidation process are studied. The residual deformation development and vibration settlement parameters of the frozen soil during the frozen season are presented.
【学位授予单位】：中国地震局工程力学研究所
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TU445

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