Abstract: The combined bearing structure of crescent-rib bifurcated pipe, backfill concrete and surrounding rock is simulated using 3D finite element method. The important roles including the plastic characteristics of backfill concrete, the gap between crescent-rib bifurcated pipe and backfill concrete, and the mechanical properties of surrounding rock are analyzed. Results showed that the sharing ratio of surrounding rock decreased with the plastic properties of backfill concrete into consideration; when the gap width exceeded a certain value, the constraint of backfill concrete and surrounding rock to crescent-rib bifurcated pipe plummeted, and the sharing ratio of surrounding rock was close to zero; the better the mechanical properties of surrounding rock, the higher the sharing ratio of surrounding rock. In the presence of combined bearing, the crescent-rib bifurcated pipe may not be able to bear 1.25 times of the design pressure in hydraulic test. Therefore, the allowable stress of crescent-rib bifurcated pipe must be considered in hydrostatic test. The research findings provide reference for design of embeded crescent-rib bifurcated pipe with surrounding rock sharing the internal pressure.

Key words: crescent-rib bifurcated pipe, backfill concrete, elastic-plastic, gap, elastic modulus of surrounding rock, mechanical property of bifurcated pipe, sharing ratio of surrounding rock