隧道敞开段底板大体积混凝土温度应力控制技术

摘要

港珠澳大桥东人工岛敞开段隧道底板最大宽度超过55 m,轴向长度为15～30 m,厚度最大超过3 m,属于典型的板式大体积混凝土结构,温度和裂缝控制难度较高.针对底板的结构特点,采用有限元对混凝土温度场进行了模拟计算分析,提出了冷却水管布设方案和一系列的温控技术措施,并对底板的温度和应变进行了监测.结果表明,混凝土芯部最高温度降低至69.7℃,端头冷却水管加密区最高温度降低至65.8 ℃,最大芯表温差为11.1℃;横向应变不超过160×10-6,轴向应变不超过250×10-6,端头应变小于中心应变.因此,采用的温控技术措施,有效地控制了底板大体积混凝土的温升,降低了混凝土内应力和开裂风险.%The maximum width over 55 m,the maximum thickness over 3 m and the axial length is 15 to 30 m of open section of tunnel floor in east artificial island of Hongkong-Zhuhai-Macao Bridge,which is the typical plate-type mass concrete structure,so,there are higher technical difficulties for temperature and crack controlling.According to the structure characteristics of the floor,we used the finite element to carried out the simulation analysis on the temperature field of concrete,put forward the lay scheme of cooling water pipe and a series of technical measures for temperature control,and monitored the temperature and strain of the floor.The results show that the maximum tenperature of concrete center was reduced to 69.7℃,the tip of the cooling water pipe encryption area was reduced to 65.8 C,and the maximum center-surface temperature difference was 11.1 ℃.The transverse and axial strain under 160×10-6 and 250×10-6 respectively,and the strain of tip is less than center.So,the temperature control measures was adopted to effectively control the temperature rise of the floor mass concrete,and reduce the strain and the cracking risk of the concrete.