Measurement of sea bed scour around a pile - Simplified instrumentation

This paper outlines a simplified experimental technique for the measurement of scour around pile foundation in laboratories. There are certain difficulties in predicting the scour depth as the particulate movement of sediments due to scour is time dependent. Considering the complexity of the problem, a suitable instrumentation system has been developed and adopted for measuring scour depth with time till the equilibrium profile of the soil bed is attained. Based on the measurements, a relationship for the scour depth in terms of properties of soil, model characteristics and fluid parameters has been suggested. A detailed laboratory testing programme on model piles of diameters 50mm to 110mm was carried out in a wave cum current flume of 30m length, 2.0m width. Currents (velocities are beween 0.19 and 0.32 m/sec) are generated by the circulation of water through inlet and outlet arrangements for the operating water depths ranging between 30cm and 60cm over the test section. The time development of scour process around a single vertical pile is studied due to steady currrent, combined action of waves and current. To highlight the usefulness of the instrumentation and understanding the principle of measuring scour around pile, the studies are discussed in the case of only currents.