聚丙烯纤维喷射混凝土抗渗性能试验研究及机理分析

Test Study and Mechanism Analysis on Impermeability of Polypropylene Fiber Shotcrete

在非(少)降水或止水施工的地下与隧道工程建设中,喷射混凝土的抗渗性能已引起广泛关注。以不同纤维长度、水泥用量、砂率和水灰比为因素水平,利用正交试验方法,得出了聚丙烯纤维喷射混凝土(PP/SC)最佳配合比。通过灰色关联系数分析及方差分析,得出各因素水平与抗渗性能之间的关联程度和影响顺序;利用MATLAB数据拟合的方法,拟合出砂率与纤维长度抗渗性能目标函数;借助扫描电镜,对PP/SC的微观结构及抗渗机理做了分析。研究结果表明:各因素对PP/SC抗渗性能的影响顺序为:砂率>纤维长度>水灰比>水泥用量;砂率取49.12%,纤维长度为21 mm时,PP/SC抗渗性能最优;聚丙烯纤维的掺入,抑制了PP/SC微裂纹的产生与发展,优化了基体界面过渡区,使其体现出了高阻裂和高阻渗的特性。

In the underground and tunnel projects with a no(less)dewatering or water sealing construction,the impermeability of the shotcrete was widely noted.With the different fiber length,cement consumption,sand ratio and water cement ratio as the factor level,an orthogonal experiment method was applied and the optimum proportion ratio of the polypropylene fiber shotcrete(PP/SC)was obtained.With the analysis on the grey correlation coefficient and the variance analysis,the correlation degree and influence sequence between each factor level and impermeability were obtained.The MATLAB data fitting method was applied to fit the impermeability objective functions of the sand ratio and fiber length.With the aid of the scanning electron microscope,an analysis was conducted on the micro-structure and the impermeability mechanism of the PP/SC.The study results showed that the influence sequence of each factor to the PP/SC impermeability:sand ratio>fiber length>water cement ratio>cement consumption.When the sand ratio was 49.12%and the fiber length was 21 mm,the PP/SC impermeability would be optimal.The mixing of the polypropylene fibers could restrain the occurrence and development of the PP/SC micro-cracks,could optimize the transition zone of the matrix interface and could show the features of the high crack resistance and high impermeability.