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 variations of discharges and
sand beds on scouring depth at a groin using an experimental flume having a 180
degree bend. The laboratory experimental program used three sands with different
median grain sizes, i.e, 0.41, 0.95, 1.6 mm, and three discharge values of 20, 24, and
30 l/s. Whereas, the groin was aligned at 90 degree position, with width of 8 cm.
The results pertaining to the effects of discharge and sand median grain size on
maximum scour depth were analyzed in the light of previous published data. The
results further substantiated that an increase in discharge or decrease in sand median
grain size causes an increase in the dimensions of scouring hole around the groin. It
is also observed that increasing the discharge or decreasing the sand median grain
size leads to increase in the extent and thickness of sedimentation downstream of the
groin. This paper shows that, maximum scour depth shows an increasing trend with
increasing Froude number.The results are represented by curves and equations to
facilitate determination of the maximum scour depth for various discharge and sand
bed conditions. |
