【作者】 杨杰；

【导师】 李英民； 甘永辉；

【作者基本信息】 重庆大学 ， 建筑与土木工程， 2007， 硕士

【摘要】 随着我国基础建设的快速发展,高层建筑底板厚度越来越厚,大体积混凝土施工越来越广泛,成为建筑施工技术领域新的热点之一。在施工和使用过程中,底板由于温度应力产生裂缝的情况在工程实践中屡见不鲜,混凝土裂缝成了混凝土结构的一种主要病害。大量的工程实践和理论分析表明,大部分裂缝在使用荷载或外界物理、化学因素的作用下,不断产生和扩展,引起混凝土碳化、保护层剥落、钢筋锈蚀,使混凝土的强度和刚度受到削弱、耐久性降低,严重时甚至发生结构破坏事故,危害结构的正常使用,必须加以控制。因此对高层建筑底板大体积混凝土施工技术进行研究,有着十分重要的工程意义。本文以高层建筑底板大体积混凝土施工中的温度和温差控制为主要研究对象,围绕高层建筑大体积混凝土底板产生裂缝的主要原因是温度应力和温度变形这一特点,针对大体积混凝土温度裂缝产生的主要影响因素,探讨防止底板大体积混凝土出现裂缝的施工技术,在此基础上提出采用提高混凝土外部环境温度来控制大体积混凝土温差的施工方法,并应用于具体工程中进行实践和总结,为同类工程施工提供切实可行的实践经验。本文的主要工作有:(1)阐述了大体积混凝土及混凝土裂缝的基本概念、裂缝控制的实际意义,并对国内外在这个领域里的研究现状作了简要叙述。(2)阐述了大体积混凝土温度裂缝产生的主要影响因素及温度计算理论。(3)阐述了防止大体积混凝土温度裂缝的主要技术措施。(4)运用前面阐述的计算方法、步骤及技术措施,以昆明第二长途电信枢纽工程(该工程基础底板砼等级为C40P8,基础底板厚2400mm,其中1/1-A轴~1/1-C轴厚度为3400mm、5个集水井总深3400mm,2个电梯井总深6100mm,基础底板总长度59.4m,宽43.8m,属典型的大体积混凝土)为工程对象,计算和分析施工期间的混凝土温度和温差,进行防裂工程分析,在采取控制集料温度、出机温度、入模温度和混凝土绝热温升的基础上,进一步提出采用环境升温法控制混凝土温差的技术措施,并应用于实际施工中,最终混凝土温度、温差和裂缝均得到有效控制,达到预期效果。同时,该工程的研究应用,对其他类似工程也具有很好的借鉴意义。更多还原

【Abstract】 With the rapid development of basic construction in our country, the thickness of the foundation slab in high-rise buildings is getting thicker and thicker, and the application of mass concrete is increased extensively, becoming one of the new hot in the zone of construction technology. During the construction, it is so often to find cracks due to temperature stress in the slab that the cracks in concrete have become the main hazard to the structure. A large number of project practice and theoretical analysis has shown that most of the cracks would develop with the load or the physical and chemical factors, causing many problems, such as the carbonation of concrete, the spalling of cover and the rusty of reinforcing steel, impairing the strength and stiffness of concrete, and reducing the durability, even resulting in the collapse and affecting the normal use,thus it must be paid attention. Therefore, it is meaningful to study the construction technology for the mass concrete of the foundation slab in high-rise building.In this paper, we would focus on the temperature and the controlling of the temperature difference during the mass concrete construction. According to the factor that the temperature stress and the temperature deformation are the primary reasons to make the mass concrete crack, combining with other factors, the construction technology to prevent the mass concrete from cracking would be discussed, and then the method to achieve this aim through rising the environment temperature would be tested in practice, providing the practical experience for the similar projects.The major work of this paper: (1)To explain the basic concepts of the mass concrete and the cracks in concrete, and the practical significance of controlling cracks, briefly describing the present situation of this field at home and abroad.(2)To give the chief reasons that result in the temperature cracks, and the theoretical calculation formula for the temperature.(3)To raise the primary technology method that prevents the mass concrete from cracking due to the temperature difference.(4)By the calculation procedure and technical measures above, taking the 2nd long-distance telecommunication project, Kunming for an example (the foundation slab, where the concrete grade is C40P8, is 2400mm in depth, while the distance between axis1/1-A and 1/1-C is 3400mm. The total depth of 5 tapping wells is 3400mm, and 6100mm for 2 elevator raises. The dimension of the foundation slab, which is 59.4m in length, and 43.8m in width, is the typical mass concrete.), we will compute and analyze the temperature of concrete during construction, and take the corresponding measures on this issue. Furthermore, the method of raising environment temperature would be put forward, and make it be practiced. Finally, the concrete temperature, the temperature difference and the crack would be in control effectively, achieving the expected purpose. In the meantime, valuable experience from this project could be offered to the colleagues.更多还原