Abstract: During the construction and maintenance period of road projects in flood detention areas, low roadbed and extremely shallow covering soil conditions often result in insufficient culvert burial depth. Traditional culvert structures, due to repeated exposure to heavy loads and prolonged submersion, have concerning durability. To assess the applicability of double-row glass fiber reinforced plastic (FRP) sand-filled pipe culverts under this special shallow burial condition, indoor fatigue tests and field vehicle load tests were conducted to study their mechanical response and fatigue performance under long-term vehicle loads. The results indicate that under low roadbed conditions, shallow burial environments are unfavorable for culverts to resist traffic loads. After 2 million cycles under a strain rate of 1%D to 3%D and low-frequency alternating loads, the maximum reduction in the ring stiffness of the FRP sand-filled pipe under extreme stress conditions was only about 20%, demonstrating excellent deformation resistance and fatigue performance. In double-row pipe culvert arrangements, the top of the loaded pipe and the inner sides between pipes are stress-concentrated weak areas. However, under shallow covering soil and heavy load conditions, the double-row pipe solution can meet structural requirements, and reducing the pipe diameter can resolve elevation conflicts between the low roadbed and drainage structures. Finally, the study evaluates the significant technical advantages of replacing large-diameter single-row pipe culverts with small-diameter double-row pipes in terms of drainage efficiency, stress and deformation characteristics, and construction convenience.

Key words: flood retention and detention area, double-row FRP sand-core pipe, fatigue test, load test, deformation characteristic