高寒区混凝土坝越冬面的水平开裂机理研究

Study on the horizontal cracking mechanism of concrete dams overwintering surface in high cold regions

摘要

越冬面层间结合与防裂是高寒区混凝土坝施工建设的重点、难点。基于监测资料及观测结果，通过三维有限元数值仿真分析，探索不同因素对越冬后新老混凝土结合面法向应力的影响，通过仿真结果阐明上下层温差、自生体积变形、层间结合强度等不同因素状态下的层间应力状态。分析结果表明，高寒区越冬层的张开、闭合、黏结状态取决于施工过程中新老混凝土温差、自生体积变形和层间结合强度3项关键因素。其中新老混凝土温差和自生体积变形将导致较大的法向应力作为阻止层间结合的驱动力，而层间结合强度作为阻止层间开裂的抵抗力。根据分析结果可知高寒区越冬后新浇混凝土重点控制指标就是新老混凝土温差及通过层间特殊施工工艺增强层间结合，上下层温差叠加自生体积变形差异引起的层间面应力较大，尤其是在端部约束等作用时，因此在保障温控措施的同时增大层间结合强度也是越冬后新浇混凝土的施工重点。

Abstract

The combination of winter surface layers and crack prevention is a key and difficult point in the construction of concrete dams in high cold areas. Based on the monitoring data and observation result, through three-dimensional finite element numerical simulation analysis, the influence of different factors on the normal stress of the interface between new and old concrete after overwintering is explored. Through simulation result, the interlayer stress state under different factors such as temperature difference between upper and lower layers, self generated volume deformation, and interlayer bonding strength is elucidated. The analysis result indicate that the opening, closing, and bonding state of the winter layer in high-altitude cold regions depend on three key factors: temperature difference between new and old concrete, self generated volume deformation, and interlayer bonding strength during construction. The temperature difference between new and old concrete and the self generated volume deformation will result in a larger normal stress as the driving force to prevent interlayer bonding, while the interlayer bonding strength will serve as the resistance force to prevent interlayer cracking. According to the analysis result, it can be concluded that the key control indicators for newly poured concrete in high cold areas after overwintering are the temperature difference between new and old concrete, as well as the strengthening of interlayer bonding through special interlayer construction techniques. The interlayer surface stress caused by the difference in self generated volume deformation caused by the temperature difference between upper and lower layers is relatively large, especially under the effect of end constraints. Therefore, increasing interlayer bonding strength while ensuring temperature control measures is also a key construction focus for newly poured concrete after overwintering.

关键词

高寒区 / 越冬面 / 层间应力 / 新老混凝土

Key words

high cold areas / overwintering surfaces / interlayer stress / new and old concrete

Author summay

张晓光(1977—), 男, 高级工程师, 学士, 主要从事水电站建设管理。E-mail: [e-mail]

基金资助

国家重点研发计划(2021YFC3090102)

陕西省东庄水利枢纽工程大坝建设期温控科研项目[DZ-JSFW-KY-203-028(DBWKKY)

巴基斯坦巴沙项目(土建标)及唐吉尔水电项目温度控制标准及温控措施研究(DBDP-DC-CHN-004)