Abstract: FRPM pipe, as a kind of flexible non-metallic composite materials, has excellent mechanical properties and good economic efficiency, which has broad application prospect in highway culvert engineering. Due to the long term heavy load of the vehicle, the strength of the buried culvert is more demanding, and the quality of FRPM pipe sand layer is very important. But, there are some problems existing in the FRPM pipe sand layer produced by many enterprises. The strength of the sand layer were optimized by making different graded samples, and fracture surface morphology of the samples was analyzed by stereomicroscope. The results show that the optimum mechanical properties of fourth groups of gradation sample, the better the quartz sand and resin binder, resin filling, which provides scientific basis for the quality control of FRPM pipe production in highway culvert engineering application.

Key words: FRPM pipe, sand layer, strength optimization, cross section characteristic