火灾是隧道结构面临的重大灾害之一，通常会导致混凝土管片的高温爆裂和力学性能退化，降低其安全性。混杂使用钢纤维与PP纤维可以改善管片的高温爆裂行为与力学性能，但管片密集且复杂的配筋使混杂纤维混凝土管片存在制备上的难题，而配制混杂纤维自密实混凝土（HyFRSCC）是解决上述问题的有效途径。但是，目前对于HyFRSCC管片的火灾高温爆裂机制与力学性能退化规律尚不明确，成为制约HyFRSCC管片应用的瓶颈。本项目拟针对HyFRSCC管片的火灾高温爆裂和力学性能退化问题，通过试验与理论方法研究混杂纤维的影响规律和作用机制。具体包括：HyFRSCC的配合比、材料高温力学性能、管片高温爆裂行为以及管片高温力学性能研究。拟完成HyFRSCC的配合比设计、建立材料的高温力学本构模型、管片的火灾高温爆裂行为预测模型以及承载力、裂缝和变形性能的计算模型。研究成果可为隧道混凝土材料与结构的抗火研究提供参考。

Fire is one of the major disasters to tunnel structures, which usually leads to spalling and degradation of mechanical performance of concrete tunnel segment, thus reduces the safety of structures. Hybrid use of steel fiber and PP fiber can improve the spalling resistance and mechanical performance of tunnel segment. But the reinforcement of tunnel segment is dense and complex, which leads to a big difficulty in the preparation of tunnel segment by using hybrid fiber reinforced concrete. The use of hybrid fiber reinforced self-consolidating concrete (HyFRSCC) is an effective way to settle the above problem. However, the mechanism of fire spalling and mechanical performance degradation of HyFRSCC segment is not clearly understood now, which becomes the bottleneck restricting the application of HyFRSCC tunnel segment. In this project, the effect mechanism of hybrid fibers on the spalling and mechanical behaviors of HyFRSCC segment will be studied experimentally and theoretically. The contents include the design of mix proportion for HyFRSCC, the mechanical properties of HyFRSCC at elevated temperature, the spalling behavior of HyFRSCC segment and the mechanical performance of HyFRSCC segment during fire exposure. It aims at setting up the design method of mix proportion for HyFRSCC, the mechanical constitutive models of HyFRSCC during elevated temperature, the spalling prediction model, bearing capacity model, cracking and deformation model of HyFRSCC segment during exposing to fire. This project will serve as a reference for the study of fire resistance of tunnel concrete materials and structures.