Crack-Proof Technique By Temperature Control Of Tunnel Concrete Lining In Construction Period

As for tunnel lining concrete, thermal stress is one of the important factors which causing concrete cracks, due to the heat of hydration of cement, the surroundings temperature variation, and the strong constraint of the surroundings rock in the construction period. Thermal crack, especially cutting through concrete lining, are very harmful to tunnel concrete lining structure.In china and overseas, deeper research has been done and increasing attention has be paid to massive concrete engineering, On the other hand, research on lining concrete engineering under the earth is carried out simply and rather insufficiently, requirements from temperature control of it are rare, regulations involved are not strict, and practical examples are few as well. Therefore, making a particular research for the design of temperature control of the under earth tunnel concrete lining is very critical.This paper take the concrete communication tunnel of LAXIWA Hydropower Station in upper YELLOW RIVER as example, worked out the temperature field in concrete lining section under different construction seasons, different lining length, different concrete placement temperature, different surrounding rock elastic module, and the heat of hydration of cement, and also worked out elastic creeping thermal stress. According to the study, finding out that the length of the tunnel lining and the elastic module of the surrounding rock take few affection on lining thermal stress, which can be neglected in engineering. But, concrete placement temperature, surrounding temperature and the heat of hydration of cement, they take a more affection on lining thermal stress. In matured period, cracks cutting through linings can be caused easily in concrete linings placed in Summer and Autumn. Rare cracks cutting through linings can be found in concrete linings placed in Winter, if thermal insulation during until next year middle Spring. Concrete lining placed in Spring can not cause cutting through cracks. According to the analysis, this paper found that thermal stress is the primary factor which caused concrete lining cracking, and also this paper provide some corresponding thermal control measures. Found out the contribution of self constraint thermal stress and out constraint thermal stress to the total thermal stress in concrete lining, they are both not...