BF分散效应对喷射混凝土韧性影响机制

Influence Mechanism of Basalt Fiber Dispersion Effect on Shotcrete Toughness

玄武岩纤维(BF)喷射混凝土因其良好的韧性被广泛应用于地下工程,BF良好的分散性是其充分发挥增强增韧作用的关键。结合人工合成透明土技术与劈拉/抗弯强度试验,研究BF分散效应对喷射混凝土韧性的影响。定义了纤维平均贡献值αj和贡献增长系数γj评价不同掺量比的分散效果,分析最优掺量下的受拉破坏应力-应变曲线并建立本构方程,利用SEM技术观察纤维束在混凝土基体内的微观形态。结果表明:掺量为3 kg/m3时纤维在透明材料模型内部分散均匀无结团现象,掺量超过4.5 kg/m3后,纤维结团现象明显,试件韧性下降。由SEM结果可知,BF掺量过大会导致纤维无法均匀分散,降低对喷射混凝土的增益效果甚至起到劣化作用。

Basalt fiber(BF) shotcrete is widely used in underground engineering because of its good toughness. The good dispersion of BF is the key to give full play to the role of strengthening and toughening. The effect of BF dispersion on the toughness of shotcrete was studied by combining the synthetic transparent soil technology and splitting tensile/bending strength test. The average fiber contribution value αj and contribution growth coefficient γj are defined to evaluate the dispersion effect of different dosage ratio. The tensile failure stress-strain curve under the optimal dosage is analyzed and the constitutive equation is established. The micro morphology of fiber bundles in concrete matrix is observed by SEM technology. The results show that: when the basalt fiber content is 3 kg/m3 the fiber is evenly dispersed in the transparent material model without agglomeration phenomenon. When the basalt fiber content exceeds 4.5 kg/m3, the fiber agglomeration phenomenon is obvious, and the toughness of the specimen decreases. From the SEM results, it can be seen that too much BF will lead to the fiber can not be evenly dispersed, reduce the gain effect of shotcrete, and even play a deterioration role.