高频振捣对混凝土抗冻性的影响机理及在寒区隧道施工中的应用

为探讨寒区隧道二衬施工新工艺新方法,以兰新铁路二线甘青段LXS-8标铁路隧道为工程依托,针对高频振捣系统在隧道二衬施工中结构可靠性和性能稳定性开展试验研究。在系统分析高频振捣对混凝土抗冻性影响机理的基础上,从设备选型、安装调试、振捣时间控制以及混凝土抗冻性能试验等方面入手,制定高频振捣施工工艺,总结施工注意事项和寒区隧道二衬施工的保温措施。试验对坍落度为16.8 cm,水胶比为0.37的C35混凝土进行多次振捣试振,最终确定持续振动为25~40 s的情况下,可以取得理想的表观质量和混凝土强度;同时抗冻性试验表明,冻融循环300次后,混凝土质量损失率均保持在3%以下,相对动弹性模量在80%~90%,达到F300抗冻等级。试振试验和检测结果表明,高频振捣技术可以推广应用于寒区冻土隧道的二衬施工。

INFULENCE MECHANISM OF HIGH-FREQUENCY VIBRATION ON CONCRETE ANTIFREEZE AND APPLICATION IN CONSTRUCTION OF TUNNELS IN COLD REGIONS

To explore new technology and new methods in tunnel secondary lining construction in cold region, according to the second double of the Lanzhou-Xinjiang Railway,it was carried out experimental study of the structural reliability and the performance stability of frequency vibration system for tunnel secondary lining construction,the construction technology was determined and the matters needing atteation as well as the insulation measures were also summarized. By field trials study,it was found that 20 ~ 40 s of continuous vibration of C35 concrete whose slump was 16. 8 cm and water-binder ratio was 0. 37,could achieve the desired surface quality and strength of the concrete. Meanwhile frost resistance test showed that the concrete mass loss rates were maintained at 3% or less,the relative dynamic elastic modulus in the range of 80% to 90%,after 300 cycles of freeze-thaw,thus reaching the frost resistance grade of F300. The vibration test and the detection results showed that the high frequency vibrator technology could be used for tunnel secondary lining construction in cold region.