Abstract

Groins are commonly used at the river bends for controlling erosion along the banks and protecting the adjacent infrastructure. Groins are designed to divert river flows towards its axis, thus reducing stream pressures leading to enhanced protection of river banks. The new flow pattern, however, entails the inherent risk of disturbing the established river regime leading to scouring around the groin. This research was undertaken to investigate the effect of groin geometry, represented in its length and angle of inclination, on scouring of sand bed using an experimental flume having a 180° bend. The laboratory experimental program modeled groins of four different lengths, that is, 2, 4, 6, and 8 cm, with angles of inclinations of 30, 60, 90, and 120°. Whereas, aggregation of natural sand with a median grain size, d50 = 1.6 mm was used as material of the flume bed, with discharge of 30 lit/s. The results pertaining to the effects of groin geometry on maximum scour depth were analyzed in the light of previous published data. The results further substantiated that an increase in length or inclination of groin causes a corresponding increase in the dimensions of scouring hole around it. It is also observed that increasing the groin length or its inclination leads to increase in the extent and thickness of sedimentation downstream of the groin. The results are represented by curves and equations to facilitate determination of the maximum scour depth for various groin geometry conditions.

Key words: Groin, river erosion, scour depth, groin geometry, groin length, groin inclination.