关键词: 穿湖隧道, 超大尺度混凝土, 温度效应, 入模温度, 环境温度, 模板

Abstract: A tunnel constructed through a lake has high requirements for the anti-seepage properties of the concrete used, and the temperature effects of the concrete are closely related to concrete cracking. A high-performance dual-grating temperature-strain sensor was used to monitor the temperature and strain of the concrete during the concrete pouring process, and the variation law of concrete temperature and strain were analyzed. The site conditions following concrete pouring were investigated. It was found that cracks appeared in the side walls and caused leakage. Based on on-site constructions conditions, the finite element method was used to simulate the poured concrete, where the results of a numerical simulation were compared with on-site monitoring data to verify the accuracy of the numerical simulation results. In addition, the parameters that affected the temperature difference between the inner and outer walls of the concrete were analyzed. Results showed that the higher the temperature of the concrete when first introduced into the mold, the greater was the temperature difference between the completed inner and outer concrete walls. The temperature of the mold when the concrete was introduced increased by 10 ◦C, and the temperature difference between the completed inner and outer concrete walls increased by 1.46 ◦C. During construction in summer, the concrete raw materials should be cooled to ensure that the temperature of the concrete when introduced into the mold was less than 30 ◦C. The greater the decrease in ambient temperature, the greater was the temperature difference between the inner and outer concrete walls. When the ambient temperature decreased by 20 ◦C, the temperature difference between the inner and outer walls increased by 6.38 ◦C. When the ambient temperature decreased, thermal insulation measures must be taken. Specifically, wooden formwork was recommended for maintenance when thermal insulation was required. However, the demolding time should not be less than 6 d; otherwise, the temperature of the concrete surface would drop rapidly, and the temperature difference between the inner and outer walls would increase sharply.

Key words: tunnel through a lake, super-large concrete, temperature e?ect, mold temperature, ambient temperature, template