Multi-Scale Detection Techniques for Local Scour Monitoring in River Bed: Case Study at Sutong Bridge

Local Scour is one of the key challenges for construction of Sutong Bridge- the first cable stayed bridge with main span over 1000m, located at downstream of Yangtze River. On the other side, though stability of riverbed is fundamental for design of riverbed protection, construction of temporary construction platform and pile group, the latter three might also effect on local scour evidently for strengthen/ disturbance on foundation soil and changing on nature flow condition. And the flow condition here is also complex due to tide influence and rugged topography. As for Sutong Bridge, Multi-beam Echo Sounder adopted to periodically measure and mapping riverbed topography, and Vibrating Wire Piezometers using to continually monitoring local scour happened within and around pile group. Then data fusion technology based on Wavelet Transformation and Geological Information System used at data processing and analysis. The result shows: 1) Multi-beam sounding system with water pressure sensors can record scour evolutionary process satisfactorily; 2) Riverbed protection does effect on riverbed and weaken the scour around pile group, but violent scour still happened near the worksite; 3) Different season, storm and tide fluctuation apply influence on siltation and scouring. And scouring/silting cause by bridge construction become stable progressively.