湿喷混凝土回弹率影响因素

Influence factors rebound rate of wet shotcrete

为解决喷射混凝土回弹率过高的问题,根据碰撞能量守恒原理,对喷射混凝土回弹机理进行了分析,结合某隧道工程进行了具体的湿喷试验,针对湿喷角度、湿喷距离和速凝剂掺入质量分数三个影响因素对湿喷混凝土回弹率的影响进行了研究.结果表明:喷射混凝土施工中,应尽量保持喷射角大于70°,以获得良好的密实性和较低的回弹率;若喷射距离小,刚刚喷射的混凝土易被冲掉,喷射距离过大,混凝土又易脱落,喷射距离1 m左右时为最佳;速凝剂掺入质量分数过少时,混凝土凝结速度慢,易被冲掉,掺入质量分数过大,喷射面上的混凝土迅速凝结硬核,回弹率增加,掺入质量分数最佳为5%左右.

To solve the high rebound rate of shotcrete, basing on collision energy conservation principle and analyzing rebound mechanism of shotcrete, a concrete wet shot experiment was tested by tunnel construction, and the influences of wet shotcrete rebound rate were investigated by three factors, the wet shot angle, the wet shot distance and the rate of accelerator. The results show that in shotcrete construction, the angle should be kept more than 70 degrees to obtain good compactness and lower rebound rate; If the distance is too small, just shotcrete is easy to be washed, contrary concrete easy to drop, and the best shot distance is 1 m; When the dosage of accelerator is too low, concrete set speed is slow, contrary concrete is rapidly condensed into hardcore, which increased rebound rate, and the best rate of accelerator is about 5%.