洞室和围岩温度对泄洪洞衬砌混凝土温度和温度应力影响研究

Influence of temperature in tunnel and surrounding rock on temperature and thermal stress of lining concrete of flood discharge tunnel

以溪洛渡无压泄洪洞为研究对象,采用三维有限单元方法对不同洞室环境温度和围岩温度情况下的施工过程进行仿真模拟,通过比较底板、边墙和顶拱不同衬砌部位的最高温度、最大内表温差、最低温度、早期和冬季最大拉应力等,对洞室环境温度和围岩温度的变化对泄洪洞衬砌混凝土温度和温度应力,以及温度裂缝发生、发展与控制的影响进行分析。结果表明,洞室气温和围岩温度对衬砌混凝土的温度场和应力场均有明显的影响。在冬季施工衬砌混凝土更容易产生早期裂缝,夏季施工时既要防止早期裂缝,也要注意防止冬季裂缝。围岩温度低时,衬砌围岩侧混凝土拉应力明显增大,但对表面和中心的应力影响很小,因而对温度裂缝的发生影响很小。研究成果为隧洞工程衬砌混凝土的设计和施工提供有价值的参考。

Temperature in tunnel and temperature of surrounding rock which distribute in distinct regions and mountains are always different, and even have great differences sometimes. Accordingly, although under the same pouring materials and operating conditions, the temperature and the thermal stress of the lining concrete which will affect the occurrence and control of the temperature cracks to a great extent are also different. Taking Xiluodu free-flow tunnel as a research object, a 3-D finite element method is applied to simulate the construction process under conditions of different air temperatures in tunnel and temperature of surrounding rock. Through comparing the maximum temperature, maximum temperature difference between inner and surface, minimum temperature, maximum tensile stress in early period and winter, the effects of the change of temperature in tunnel and surrounding rock on the temperature and thermal stress of the lining concrete as well as occurrence, development and control of the temperature cracks are analyzed. The results show that both the temperature in tunnel and the temperature of surrounding rock have significant influences on the temperature field and stress field of the lining concrete. The lower the air temperature in tunnel is, the easier the early cracks will occur in winter; and it is necessary to prevent both early cracks in summer and winter cracks. The tensile stress of the lining concrete increases obviously when the temperature of the surrounding rock is low, however, the effect on the stress of the surface and inner is small; so the temperature of the surrounding rock has little effect on the temperature cracks. The research results provide valuable references for the design and construction of tunnel engineering.