隧道湿喷混凝土回弹率影响因素及施作工艺研究

喷射混凝土在应用过程中不可避免产生回弹,降低了初支的强度,造成了材料的浪费。本文通过对喷射混凝土回弹现象的理论分析,并依托浩吉铁路崤山隧道,采用现场喷射试验的方式发现:提高砂率有助于降低混凝土的回弹率;同时粉煤灰加入量的提升,需水量也随之逐步提升,回弹率有所下降;考虑到坍落度经时损失,190 mm坍落度可作为最优坍落度;速凝剂掺量偏大或偏小都会增加混凝土的回弹率。同时,在现场喷射试验中发现,一次喷层厚度选择4 cm厚较为合适,喷头与受喷面的最佳距离为0.6~1.2 m。通过喷射混凝土配合比试验和现场喷射试验,可为湿喷工艺降低回弹率提供参考。

Study on Influence Factors and Construction Technology of Wet-mix Shotcrete Rebound Rate in Tunnel

The rebound of shotcrete is inevitable in the application process,which reduces the strength of initial support and causes the waste of materials.Based on the theoretical analysis of the rebound phenomenon of shotcrete and relying on the Xiaoshan Tunnel of Haolebaoji-Ji’an Raiway,it is found that the increase of sand ratio is helpful to reduce the rebound rate of concrete.At the same time,with the increase of fly ash content,the water demand will gradually increase,and the rebound rate will decrease.Considering the time-dependent loss of slump,190 mm slump can be regarded as the optimal slump.The higher or lower dosage of accelerator will increase the rebound rate of concrete.Meanwhile,it is found in the field spray test that the appropriate thickness of primary spraying layer is 4 cm,and the optimal distance between nozzle and spraying surface is 0.6~1.2 m.Through the shotcrete mix proportion test and field spray test,it can provide reference for wet spraying technology to reduce the rebound rate.