STUDY OF SCOUR AROUND PERMEABLE SPURS

Abstract

Increasing economic costs of river protection works in India have led to the adoption of permeable spurs in practice. However, research on different types of permeable spurs is not developed to the same extent as that on solid spurs, bridge piers and abutments. Different types of permeable spurs have come into existence. However, permeable pile spurs are being favoured in north and north-eastern region of India. To use these pile spurs in field, one needs to know the development of scour as well as equilibrium scour. The present study basically fills this gap. It examines various types of permeable spurs to assess the merits associated with the pile permeable spur. It is observed that these spurs experience minimum scour. Based on the study of bed condition in certain experiments, the variables influencing scour have been identified and used to model the equilibrium scour depth in case of pile permeable spurs. Use of different scaling parameters is also examined in the model development. Based on lab experiments, a model is calibrated for scour depth estimation. Subsequently, the use of the model is tested against field data. The predictions are satisfactory in certain cases only and are found dependant on the type of calibrated model. An approach for the estimation of scour in transient condition is suggested and an insight into the future work is also provided.