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measures For the rest of the paper, please use Times Roman (Times New Roman) 12 A bstract. During the concrete pouring process, the long downtime would weaken the bonding strength between old and new concrete layers. The bonding parts would like to form horizontal cracks, especially winter intermittent surface in the severe cold region, of which cracks would easily propagates from surface to i nside, even through the concrete, seriously affects the security of dam. This paper takes the sediment storage da m of the down reservoir of Hohhot pumped storage power station as a case, the heat preservation and crack control measures of overwintering area have been analyzed. To avoid the occurrence of cracks of overwintering layer during winter and according to the site or local material, this paper draws up two schemes. Scheme I: taking the water storage to preserve heat; Scheme II: 5cm thick polystyrene insulation (which can be used as temporary heat preservation measures normally) and 15cm thick straw and 30cm thick corn straw +2 layer water proof cloth. According to the simulation of the two schemes, the results shows that: scheme I exist "chilling effect" and the local stress is too high, while both the temperature and stress conditions of scheme II meet the requirements for overwintering. After overwintering period, the construction of the dam continues. To ensure the quality of concrete near the overwintering layer, the upper and lower temperature difference and the highest temperature should be controlled and the crack prevention of concrete should be took. According to the construction conditions, the similar experience in project site and relevant requirements of crack prevention, this paper makes three schemes. Scheme I: control the upper pouring new concrete pouring layer thickness, pouring temperature, intermittent, water and temporary insulation and return to construction in late-April; Scheme II: Taking all measures of Scheme I and heating the old concrete layer; Scheme III: Taking all measures of Scheme II and return to construction in mid-May. The simulation results show that Scheme I occurs upper and lower temperature difference and the existence of tensile stresses exceed the standard phenomenon, while Scheme II and III are feasible. After two consecutive 2011~2013 ov erwinters test, the implementation of heat preservation and crack control measures of overwintering layer c oncrete of the sediment storage dam of the down reservoir of Hohhot pumped storage power station works well, which can provide a reference for the similar problems in other engineering.

Study and application of heat preservation and crack control measures for gravity dam in severe cold regions