纳米级掺合料和粗合成纤维对湿喷混凝土回弹率的影响

降低喷射混凝土回弹率可提高支护效率、降低地下空间的坍塌及岩爆风险。为分析纳米级掺合料、粗合成纤维对喷射混凝土回弹率的影响，基于湿喷工艺对比了纳米级掺合料与同掺量硅灰在改善湿喷混凝土回弹率方面的差异；比较了不同纳米级掺合料掺量、细度条件下各湿喷混凝土的回弹率区别；研究了粗合成纤维掺量、长径比、混杂方式等对回弹率的影响。结果表明:应用纳米级掺合料有助于降低湿喷混凝土的回弹率；与同掺量硅灰相比，纳米级掺合料湿喷混凝土的回弹率降低了17%~25%，且回弹率随纳米级掺合料掺量提高、细度增加而降低。粗合成纤维可降低湿喷混凝土的回弹率，但受材质影响较小，存在较低回弹率的最佳长径比和掺量，分别为38和10 kg/m3。长径比76和长径比30的2种粗合成纤维混杂使用时，可进一步降低回弹率。

Effect of nanometer scale admixture and macro synthetic fiber on the rebound rate of wet mix shotcrete

Reducing the rebound rate of shotcrete can promote the efficiency of support and reduce the risks of collapse and rock burst for underground openings. To evaluate the effect of nanometer scale admixture (NSA) and macro synthetic fiber (MSF) on the rebound rate of wet-mix shotcrete (WMS), rebound rates were compared with each other based on wet sprayed technology among WMS with different cementing compositions such as introducing NSA or silica fume. The contents and fineness of NSA were also investigated when taking rebound rate as the main subject. Contents, aspect ratios and hybrid ways of MSF were discussed, too. The results indicated that NSA could reduce the rebound rate of shotcrete. The rebound rate of WMS could be reduced by about 17% to 25% when silica fume was replaced by NSA totally. Besides, the rebound rate of WMS would further decrease with the increment of contents or fineness of NSA. Macro synthetic fiber had a part in reducing rebound rate. Although fiber nature had little effect on rebound rate, the aspect ratio and content of MSF couldn't be ignored, and its best values were 38 and 10 kg/m3, respectively. In addition, the rebound rate could be further reduced when WMS was optimized with hybrid MSF consisting of two kinds of fibers, whose aspect ratios were 76 and 30.