寒冷地区坝内垫层管运行期温度效应及保温措施研究

Study on Temperature Effect and Thermal Insulation of Dam-embedded Steel Penstock Encircled by Cushion Layer During Operation Period in Cold Region

为研究寒冷地区温度变化及保温措施对坝内垫层管外包混凝土开裂状况的影响,基于混凝土塑性损伤模型,考虑运行期的温度作用,对某水电站坝内垫层管进行非线性有限元分析。结果表明:由于垫层的铺设,正常运行工况下管道混凝土几乎无损伤,管道表面不会出现宏观裂缝;但在温降工况下管道顶部混凝土损伤较严重,而在温升工况下管道底部混凝土损伤更明显,相应损伤区域的钢筋应力也明显增加;坝面保温板的铺设能够有效降低结构所承担的温度荷载,改善混凝土损伤状况,降低钢筋应力,且随着保温板厚度的增加其作用效果逐渐显著,但当增加到一定程度后,其作用效果趋于稳定,同时考虑投资等工程实际情况,不宜过度增加保温板厚度,建议保温板厚度由裂缝宽度控制。

To study the influences of temperature variation and thermal insulation on the cracking state of dam-embedded steel penstock encircled by cushion layer at runtime in cold region,the concrete damage and bearing characteristics of one penstock under temperature action were analyzed by nonlinear finite element method based on the concrete plastic-damage model. The results indicated that due to the cushion layer there was little damage on the concrete and no macro-cracks would appear on the concrete surface under normal operation condition. Temperature drop led to serious damage at the top of pipe,and temperature rise caused to damage at the bottom of the pipe and the apparent increase of the stresses of reinforcement within damage zone. Thermal insulation slab could help reduce temperature load,concrete damage and reinforcement stress efficiently,and the thicker the better,but after the thickness of the slab increased to a certain extent,its effect would tend to be stable. In different engineering the thickness of thermal insulation slab could be controlled by the width of the cracks.