门洞形断面衬砌混凝土温度裂缝机理及其发生发展过程

Analysis of mechanism and development of cracks in portal lining concrete

采用三维有限元法仿真计算,结合三峡、溪洛渡、白鹤滩、三板溪等近10个大型水工隧洞衬砌混凝土温度裂缝原因、控制措施研究和工程实践,对典型门洞形断面衬砌混凝土温度和温度应力的变化发展规律、温度裂缝的机理和发生发展过程进行了深入研究.结果表明：薄壁衬砌高强混凝土浇筑后,温度高,温升温降快,内表温差和温降差大,受到围岩等极强约束产生大的拉应力,在早期7~30d和冬季两个温降阶段极易产生温度裂缝,因此,施工期温度裂缝控制设计应该以这两个阶段温差控制为重点.

Combining with engineering practice,the evolution of temperature and thermal stress in lining concrete is studied based on the finite element method.The occurrence and development mechanisms of temperature cracks are studied in a systematic way,which shows a great consistence with those observed in engineering practice.The results show that lining concrete has high temperature,fast temperature drop,and large temperature difference after concrete pouring.Because of the great tensile stress caused by the strong constraint of surrounding rock,the concrete is easy to produce temperature cracks in the early 7-30 days and two winter temperature drop stages.Therefore,the temperature crack control in construction period should be focused in these two stages.