多年冻土区路基随机温度场及变形场分析模型研究

发布时间：2018-03-01 01:02

  本文关键词： 冻土路基 随机有限元 局部平均法 随机温度场 本构模型 随机应力场 随机变形场　出处：《中国矿业大学》2015年博士论文　论文类型：学位论文

【摘要】：多年冻土区公路及铁道工程路基热-力稳定性问题是一个亟待解决的工程难题,国内外学者对其进行了大量的研究,但考虑参数随机性的研究较少。与一般岩土工程中存在诸多不确定性因素类似,对于冻土工程,由于冰的存在,其工程性质复杂而特殊,表现出很强的离散性和随机性。为此,本文以多年冻土地区路基为研究对象,考虑冻土热力学参数的随机特性,采用理论分析与数值计算相结合的方式,建立典型路基随机温度场、随机变形场及随机应力场分析模型,为青藏高原多年冻土路基工程长期稳定性及可靠性评价提供依据。首先,引进随机场及其局部平均理论对冻土土性参数进行随机场描述与离散,提出实用性更广的三角形单元局部平均法。研究结果表明:随机场描述方法能合理考虑土性参数空间上的变异性;土性参数模拟为随机场和随机变量获得的均值结果相同,模拟为随机变量获得的变异性偏高;传统四边形单元局部平均法中,被包含的两个三角形单元数字特征不一定相同,且不等于包含的四边形随机场单元的数字特征,将其应用于三角形单元有限元法存在偏差;三角形单元局部平均法能与三角形单元有限元法完美结合,随机场单元与有限元单元对应关系清晰,操作方便,易于编程。其次,将多年冻土地区路基上边界条件模拟为随机过程,冻土热学参数模拟为随机场,基于三角形单元局部平均法及NSFEM方法,自行研制开发了多年冻土地区路基温度场随机有限元程序,计算获得了温度均值及温度标准差。研究结果表明:考虑参数随机性得到的温度场均值结果与传统确定性温度场结果相同;参数变异系数相同时,不同时刻较高的温度标准差位置不同,参数变异系数不同时,变异系数越大,温度变异性越强;地基中存在大量的高温冻土,由于区域内标准差的存在,高温冻土的热力学状态存在随机性;考虑气候变暖条件下,温度标准差总体随时间呈增加趋势。再次,基于修正剑桥模型及双屈服面理论,考虑冻土黏聚力及内摩擦角的影响,以整体变形特性εv-lnp曲线对试样的变形进行描述,采用应力路径相关因子对等向固结路径获得的屈服面硬化参数进行了修正,结合冻土临界状态参数得到了能够体现冻土固有临界特性的参考屈服面硬化参数,并由当前屈服面与参考屈服面间的关系定义了能够反映冻土当前状态的固结参数及潜在强度,得到了能够有效反应冻土剪缩、剪胀、硬化和软化特性的冻土模型。根据经典的弹塑性理论,推导了所得模型增量形式的应力-应变关系,结合变刚度弹塑性有限元算法,详细讨论了在有限元计算中开发模型计算程序的数值实现过程。最后,考虑随机温度对冻土区土体基本力学参数的强烈决定作用,将冻土力学参数模拟为随机场,基于三角形单元局部平均法及NSFEM方法,自行研制开发了多年冻土地区路基应力场与变形场随机有限元程序,计算获得了位移场与应力场的统计特征及其动态发展过程。研究结果表明:温度变化主要影响竖向位移均值及竖向位移标准差分布;路基断面特定位置沉降均值变化可分为沉降、冻胀、再沉降三个阶段,且距离路堤上表面越近,分段现象越明显;参数变异系数不同时,变异系数越大,位移标准差与应力标准差均越大,变异性越强;考虑气候变暖条件下,路基断面特定位置沉降标准差总体随时间呈增加趋势。
[Abstract]:Permafrost area of highway and railway subgrade thermal stability problem is an urgent need to solve the engineering problems, the domestic and foreign scholars have done a lot of research on it, but considering randomness less. And there are many uncertainties in general in geotechnical engineering for frozen soil engineering, due to the presence of ice. The engineering properties of complex and special, exhibit discrete and strong randomness. Therefore, based on the roadbed in the permafrost area as the research object, considering the random characteristics of thermodynamics parameters of frozen soil, using theoretical analysis and numerical calculation of the combined mode, set up a random temperature field of roadbed deformation, random field and stochastic stress field the analysis model for the long-term stability of permafrost subgrade engineering and provide the basis for the reliability evaluation. Firstly, with the introduction of the airport and the local average theory of frozen soil parameters with The airport is described and discrete, proposed triangular element local average method is wider in practicability. The research result shows that the method can describe the airport with reasonable consideration of variability of the soil parameter space; simulation of soil parameters as the mean random field and random variables obtained the same result, simulation of high variability for local random variables; the average traditional method of quadrilateral element, two triangular element digital features included are not necessarily the same, and is not equal to the quadrilateral with digital features include airport unit, applied to the triangular finite element method in deviation; local average method of triangular elements can be combined with triangular finite element method with perfect. The corresponding airport unit and finite element relationship clear, convenient operation, easy programming. Secondly, the boundary conditions of the permafrost subgrade simulated as stochastic process, soil thermal parameters model To be with the airport, the triangular element local average method and the NSFEM method was developed based on stochastic finite element program of temperature field of Subgrade in permafrost region, calculate the mean temperature and temperature standard deviation. The results show that: considering the mean temperature field results of random parameters obtained with the traditional deterministic temperature field results in the same parameter variation; at the same temperature coefficient, high standard of different time difference in different positions, the coefficient of variation is not at the same time, the coefficient of variation is larger, the temperature variability is strong; there are a lot of foundation in high temperature permafrost region, due to the existence of standard deviation, the thermodynamic state of permafrost are random; considered under the condition of climate warming, temperature standard the overall difference increased with the increase of time. Once again, the modified Cambridge model and double yield surface based on the theory, considering the soil cohesion and internal friction angle of the impact to the overall change The deformation of shape characteristic curve of specimen epsilon v-lnp described by stress path correlation factor to obtain equivalent consolidation path yield surface hardening parameter is modified, combined with the critical state parameters of frozen soil obtained can reflect the inherent characteristics of frozen soil critical reference yield surface hardening parameters, and the current yield surface and the relationship between the yield of reference the definition can reflect the current state of frozen soil consolidation parameters and potential strength, the frozen soil can reflect the effect of shear contraction dilatancy, hardening and softening characteristics of the frozen soil model. According to the classical elastic-plastic theory, deduced the model incremental stress-strain relationship with variable stiffness elastic plastic finite element the realization process of numerical algorithm, calculation program development model in finite element analysis are discussed in detail. Finally, considering the strong random temperature on the basic mechanical parameters of soil for permafrost area With the simulation of frozen soil mechanics parameters for random and triangular element local average method and the NSFEM method was developed based on the permafrost subgrade stress field and deformation field of stochastic finite element program, the displacement field calculation development and statistical characteristics of stress field and dynamic process. The results show that the effect of temperature the change of vertical displacement and vertical displacement of the mean standard deviation distribution; specific location of subgrade section settlement changes can be divided into settlement, frost, and settlement of three stages, and the distance between the upper surface of the embankment near the segmentation phenomenon is more obvious; the coefficient of variation is not at the same time, the coefficient of variation is larger, the standard deviation of displacement and stress standard deviation all the greater variability is considered strong; under the condition of climate warming, specific location of subgrade section settlement overall standard deviation over time showed an increasing trend.

【学位授予单位】：中国矿业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U213.1;U416.1
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本文编号：1549708