论文部分内容阅读
大体积混凝土的裂缝已是混凝土坝施工中的重大质量问题之一。在混凝土中出现的裂缝绝大多数为表面裂缝,浅层的表面裂缝不会对坝体带来危害,通常不必对所有的表面裂缝进行处理,但是也应注意到一些表面裂缝会发展成深层裂缝或贯穿性裂缝。据一些工程资料分析,大多数的贯穿性裂缝也是由于表面裂缝的不断扩展而形成的。发生在重要部位的贯穿性裂缝和深层裂缝,如在坝体的基础部位或迎水面等处,就会影响到结构物的耐久性、防渗性和整体性,造成较为严重的后果,这就需要采取工程措施来进行补强或防渗处理。这种事例在国内外的工程中都曾有发生。因此,目前人们对表面裂缝的扩展所带来的危害有了进一步的认识。同时,还认为表面裂缝产生的主要原因是气温骤降(俗称冷空气入侵或寒潮)。在气温骤降期间,通常还伴随着大风,更加速了空气与混凝土表面的热交换,促使表层混凝土的温度急骤下降。而表层混凝土的降温收缩受到内部混凝土的约束,会在混凝土表层生产过大的拉应力,使得混凝土开裂或使已有裂缝进一步地扩展。 众所周知,我国是受气温骤降影响较大的国家。每当秋末或冬、春季节,冷空气经常不
Cracking of mass concrete is one of the major quality problems in concrete dam construction. Most of the cracks in concrete are surface cracks. The superficial surface cracks will not cause any damage to the dam, and it is not usually necessary to treat all the surface cracks. However, it should be noted that some surface cracks can develop into deep cracks Or through the cracks. According to some engineering data analysis, most of the through cracks are also due to the continuous expansion of surface cracks formed. Through cracks and deep cracks that occur in important parts, such as in the foundation of the dam or facing the water, will affect the durability, impermeability and integrity of the structure, resulting in more serious consequences, which Engineering measures need to be taken for reinforcement or seepage control. Such cases have occurred in both domestic and foreign projects. Therefore, people now have a further understanding of the harm caused by the expansion of surface cracks. At the same time, it is also believed that the main cause of surface cracks is the sudden drop in temperature (commonly known as cold air intrusion or cold wave). During the sudden drop in temperature, wind often accompanied by strong winds accelerated the heat exchange between the air and the concrete surface, causing the temperature of the concrete surface to drop abruptly. The shrinkage of surface concrete is restrained by the internal concrete, which will produce excessive tensile stress on the surface of concrete, causing the concrete to crack or further expanding the existing cracks. As we all know, our country is greatly affected by the sudden drop in temperature. Whenever autumn or winter, spring, cold air often do not