【作者】 毛然；

【导师】 王翠英；

【作者基本信息】 湖北工业大学 ， 岩土工程， 2011， 硕士

【摘要】 2008年初,我国大部分地区遭受了百年一遇的冰雪灾害,这次冰雪灾害对于常年不受冰雪灾害影响的中南地区电网设施造成了很大程度的破坏,输变电塔地基也发生了各种形式的破坏。论文以地基承载力相关理论为基础,以冻土的温度、含水量、冻融循环次数三个变量为研究主线,输变电塔的地基承载力为研究核心,在阐述了冻土物理性质的基础上,分析了中南地区典型土体(粉质粘土)抗剪强度与温度、含水量、冻融循环次数三个变量之间的关系,即在0°～-12°温度范围内,含水量相同的土体,温度越低,其内聚力C和内摩擦角φ愈大,土体的抗剪强度也逐渐增大;含水量为17%～35%范围内,同一温度下,土体含水量越高,其内聚力C和内摩擦角φ愈小,土体的抗剪强度也逐渐减小;在冻融循环次数(8次)以内,温度和含水量都不变的情况下,土体随冻融循环次数的增加,其内聚力C减小。论文分析了温度、含水量、冻融循环次数三个因素对地基承载力的影响,得出含水量为对地基土承载力影响最为敏感;温度是对地基土承载力影响较为敏感的因素。论文分别提出了温度、含水量、冻融循环次数与地基承载力之间的关系,提出了冻融土地基承载力的确定方法。采用极限平衡理论的太沙基极限承载力公式,建立了不同温度下含水量与地基土承载力之间的线性关系。分析了冻结-解冻温度下,《建筑地基基础设计规范》中的地基承载力系数的确定方法,依据修正后的《建筑地基基础设计规范》中的地基承载力公式,总结出不同冻结温度下的地基土承载力与0℃时的地基土承载力之间的比例关系表,不同解冻温度下的地基土承载力与-12℃时的地基土承载力之间的比例关系表,以此可求出任意温度下的地基土承载力。论文采用ANSYS7.0,对冰雪环境下输电塔基在不同工况下剪力、位移、总应变进行了数值模拟分析,模拟塔基在冰雪环境下内力的变化,并得出相应的结论:覆冰荷载对塔基的变形具有一定的影响,地表温度对塔基的影响较大;随着地表温度的降低,塔基最大位移量、XY平面最大剪应力和塔基在热-结构耦合条件下最大应变均呈逐渐增加趋势,并逐渐趋于某一稳定值;在塔基荷载和风荷载联合作用下,塔基与基础接触点出现明显的应力集中;本论文的研究成果对中南地区在极端冰雪灾害时期,准确确定输电塔基的地基承载力具有一定的实际意义。更多还原

【Abstract】 In early 2008, most regions of China suffered a big of snow disaster. The power grid in central south district which is not affected by ice and snow disaster perennial was destroyed by the big of snow disaster. And transmission tower foundation also changed all forms of destruction. Based on the base tilt factor related theory basis, the temperature, moisture content, freeze-thaw cyclic number of frozen soil are the research main, the base tilt factor of transmission tower is the core research. On the basis of the physical properties of frozen soil analyzed the relationship between the silty clay of central south district and three variables that are shearing strength, temperature, moisture content and freeze-thawcyclic number, namely at 0°~ 12°temperature range, the soil mass have the same moisture content, temperature is lower, the cohesion C and internal friction Angle phi is larger, the shearing strength of soil mass also gradually increased. When the moisture content was at 17% ~ 35% temperature range, the soil mass have the same temperature, moisture content is taller, its cohesion C and internal friction Angle phi are smaller, the shearing strength of soil mass also gradually decreased. When freeze-thaw cyclic number are less than 8, temperature and moisture content aer invariable, soil mass with the increase of number of freeze-thaw cyclic number, the cohesion C decreases. This paper analyzes the relationship between three factors which are temperature, moisture content and freeze-thaw cyclic number and the base tilt factor, it is concluded that a method to determine the base tilt factor of frozen-thaw soil. Using Terzaghi’s formula of the limit equilibrium theory,the linear relationship between soil moisture at different temperatures and base tilt factor is established. Analysis the freeze and thaw temperatures, a method to determine the <the code for design of building foundation> of base tilt factor. Based on the amended <the code for design of building foundation> of base tilt factor formula, summarize that the proportional relation on the base tilt factor at different freezing temperatures and the base tilt factor at 0℃while the proportion relation on the base tilt factor at different thawing temperatures and the base tilt factor at - 12℃, which can give the base tilt factor at arbitrary temperatures. The paper use ANSYS7.0, under the environment of transmission Kentucky on snow and ice in different conditions shear and displacement, total strain was simulated analysis, simulation under the environment of internal force in ice and snow Kentucky changes, and corresponding conclusion drawn: Cladding ice load on the deformation of Kentucky has certain effect, and the surface temperature on the influences of Kentucky. As surface temperature decrease, the Kentucky maximum of displacement, the shear stress ratio of XY plane and Kentucky in hot - structural coupling conditions under the maximum stress ratio are tending to gradually increasing trend, and gradually become a steady value; In Kentucky load and wind load combination, Kentucky and basic contact point appears obvious stress concentration.This paper researches on the central south district in extreme snow disaster period, to properly determine the transmission of Kentucky foundation bearing capacity has certain practical significance.更多还原