Abstract: The siltation of foundation trench has severe impact on the smoothness of immersed tube tunnel and threatens its waterproof performance.The silt characteristics of immersed tunnel foundation trench at the intersection of two rivers are researched by establishing a numerical calculation model.The simulation result is compared with actual monitoring value to verify the applicability of the model,and furthermore to reveal the siltation characteristics of immersed tunnel foundation trench at inland river intersection.Results display small error between the simulated flow velocity and the actual monitored value,verifying that the model is applicable.The silt depth is large in the middle and small in two ends,and large in the upstream while small in the downstream.The siltation varies largely in space,distributing apparently at the trench foot and remarkably on slope crest than at slope toe.The sensitivity of siltation attenuates gradually over time.After the excavation of foundation trench,the silt depth reached 10 cm,which would affect the application of the immersed tunnel.Dredging measures on site are required.

Key words: intersection of inland rivers, immersed tunnel, back-silting of foundation trench, numerical simulation, law of back-silting