【作者】 岑成贤；

【导师】 贾艳敏；

【作者基本信息】 东北林业大学 ， 道路与铁道工程， 2005， 硕士

【摘要】 我国是多年冻土大国,冻土热力学方面的不稳定性,使多年冻土地区修筑的建筑物稳定性受到了很大的影响,工程冻害现象较为普遍,严重影响到了正常的交通,因此研究冻土冻胀引起的冻害对多年冻地区建筑物的影响有着很重要的意义。对于冻胀的计算,目前还没有一个完整的理论体系,实际工程当中往往是通过做实验的方法来研究冻胀对工程的影响。本文主要是对钻孔灌注桩灌注完混凝土后桩的回冻过程的研究,也就是对冻土与钻孔灌注桩的温度场的研究。本文首先介绍了目前国内外对冻胀的研究现状及发展趋势,然后根据所查阅的参考文献总结了多年冻土地区常用的桩基础形式、冻土的工程特性、力学性质及冻土温度场计算方法,还介绍了冻胀的机理和冻胀力的一些基本理论,同时对ANSYS热分析模块的基本功能作了简单介绍。在研究桩基础回冻时,本文借鉴了当前桩-土相互作用问题的研究方法和成果及热力学计算的基本理论,考虑到了多年冻土特殊的热学性质,如冻土的相变特性等,另外还考虑到了混凝土桩灌注完后混凝土水化热对桩周冻土的影响,采用目前流行的大型有限元分析软件ANSYS的热分析模块,建立了不同的桩长、桩径及不同的入模温度的桩与冻土的有限元模型,求得在考虑时间因素的情况下(瞬态热分析)多年冻土与钻孔灌注桩之间温度场的分布情况,并且通过昆仑山多年冻土桩基试验场的实验桩的数据与有限元模型的计算结果进行对比分析,验证有限元分析的准确性。在此基础上,根据有限元模型的计算结果本文作了以下几方面的工作:第一,对不同的桩径时钻孔灌注桩回冻进行了比较分析,得出在不同的桩径条件下,钻孔灌注桩的温度变化曲线;第二,对不同的桩长二钻孔灌注桩回冻进行了分析,得出在不同桩长条件下,钻孔灌注桩的温度变化曲线;第三,分析了不同的入模温度时钻孔灌注桩的回冻,得出一个合理的入模温度;第四,混凝土水化热对钻孔灌注桩周围冻土的影响是随着距离的增加而减小,根据有限元模型的计算结果,本文得出了混凝土水化热对桩周围冻土的影响范围。更多还原

【Abstract】 China is a country with large permafrost. The structures which are constructed in permafrost region are influenced by the instability of frozen soil on thermodynamics. It is universal that the structures are destroyed in permafrost region for the frost heave and it is serious influenced the normal traffic of our country. It is important for people to study frost heave of frozen soil. There are no more perfectly system of theory for the study of frost heave. People usually study the frost heave by doing experiment during the real engineering. The thesis mainly study course of freezing soil when the bored pile has cast the concrete, that is, studying the temperature file between frozen soil and bored pile. In the thesis, firstly, the author introduces the actuality and the development of study frost heave of our country and oversea. Secondly, the author sum up forms of piles in the permafrost, characteristic of frozen soil in engineering, property of mechanics and the way of calculate temperature of frozen soil. The author also introduces some basic theory of frost heave and frost heave force and then introduces basic functions of ANSYS in thermal model. In the thesis, the author uses for reference the way which people use to study the problem between soil and pile, uses for reference the basic theory of thermodynamics during the study. The author also consider the special character of frozen soil, for example, enthalpy of frozen soil and consider the effect of hydrate of concrete after casting the concrete, building the finite element model of different length and radius of pile and different temperature of casting concrete by ANSYS software in thermal model, finding out distributing of temperature field between the permafrost and bored pile on the condition of considering factor of time(transient). The result of finite element model created by ANSYS is verified by the single pile experiment in KunLunShan permafrost zone , lately. On the basis of the finite element model, this thesis mainly consummate four aspects of works following. Firstly, the author analyses the effect of bored pile during refrozen by different length of pile and find out different curve of temperature of bored pile. Secondly, the author analyses the effect of bored pile during refrozen by different radius of pile and find out different curve of temperature of bored pile Thirdly, the author analyses the effect of bored pile during refrozen by different temperature of casting concrete and find out different curve of temperature of bored pile. Lately, the function of hydration of concrete is reduced with the distance from pile increasing. The author find out the incidence which hydration of concrete effect on permafrost on the bases of the result of finite element model that created by ANSYS.更多还原