碾压混凝土重力坝施工期温控措施及温度应力优化研究

发布时间：2018-01-04 18:20

本文关键词：碾压混凝土重力坝施工期温控措施及温度应力优化研究　出处：《西北农林科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：混凝土有别于普通混凝土,具有干硬性且没有坍落度,在施工过程中采用通仓浇筑,薄层铺料,震动碾压的方法,因此具有施工快、用料省的优点。经过我国广大科研工作者的不懈努力,碾压混凝土坝施工已具备了相当成熟的技术,并在拥有高粉煤灰掺量、少水泥用量的特点。由于碾压混凝土坝中掺入了大量的粉煤灰,水化热速率要明显降低,同时,坝体的上升速度较快,致使仓面与空气接触时间较短,散热不足,容易在坝体内部形成温度集中,导致很大的温度应力,使坝体更容易产生裂缝,影响大坝安全。论文利用有限元分析软件ANSYS对碾压混凝土重力坝施工期的温度场和应力场进行仿真分析,综合考虑了外界气温变化、水泥水化热随龄期变化、不同的浇筑温度及分层的实际影响,以及混凝土弹性模量、徐变度随龄期变化等特性,提出了仿真实现过程。在模拟施工过程中,通过改变水管通水冷却方案、浇筑仓面保温、改变混凝土浇筑温度等温控措施对坝体温度应力进行分析,从而对施工期的施工方案进行优化,对不同方案下坝体的温度应力进行对比,并在最后提出碾压混凝土施工期温度控制的最佳方案。经分析可得到以下结论:(1)水管冷却能够在一定程度上降低坝体温度,应根据实际需要选取水管冷却方案,可适当增大水管间距和提高通水温度以节约成本。(2)坝体浇筑尽量减少间歇时间,特别是高气温时段,浇筑时可选择去掉间歇时间,从而使混凝土的预冷措施得到最大利用。(3)坝体表面保温措施可以防止表面裂缝产生,但对整个大坝温度场的影响较小。
[Abstract]:Concrete is different from ordinary concrete. It is dry and hard and has no slump. In the process of construction, it adopts the methods of storehouse pouring, thin layer laying and vibration rolling, so it has fast construction. Through the unremitting efforts of the vast number of scientific research workers in our country, the RCC dam construction has already possessed quite mature technology, and has the high fly ash content. Because a large amount of fly ash is added into the RCC dam, the hydration heat rate will be obviously reduced, and the rising speed of the dam body will be faster, resulting in a shorter contact time between the silo surface and the air. Because of insufficient heat dissipation, it is easy to form temperature concentration inside the dam body, which leads to great temperature stress and makes the dam body easier to produce cracks. The finite element analysis software ANSYS is used to simulate the temperature field and stress field of RCC gravity dam during the construction period. The cement hydration heat varies with age, the actual influence of different pouring temperature and delamination, as well as the characteristics of concrete elastic modulus and creep with age, etc. The temperature stress of the dam body is analyzed by changing the water cooling scheme of the water pipe, the heat preservation of the pouring silo surface and changing the pouring temperature of the concrete, so as to optimize the construction plan during the construction period. The temperature stress of dam body under different schemes is compared. Finally, the optimal scheme of temperature control during the construction period of RCC is put forward. The following conclusion can be obtained by analysis) the cooling of water pipe can reduce the temperature of dam to a certain extent. The cooling scheme of water pipe should be selected according to the actual needs, which can increase the spacing of water pipes and increase the water temperature to save cost. 2) the intermittent time, especially the period of high temperature, can be reduced as much as possible. When pouring, the intermittent time can be removed, so that the precooling measures of concrete can be used to the maximum extent. The surface heat preservation measures of dam body can prevent surface cracks, but have little effect on the temperature field of the whole dam.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TV642;TV544

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