An experimental investigation for the determination of the optimum ratio of nano clay for reducing local scour around a cylindrical bridge pier

Local scour is one of the main causes of the bridge collapse. It occurs when the flow erodes the sediments surrounding the bridge's piers. This experimental study aims to find an innovative approach for armoring the bed using nano clay to mitigate the erodibility of non-uniform sand beds. Additionally, the study investigates the nano clay-sand bed under various hydraulic conditions, with different pier diameters to determine the optimal nano clay ratio for minimizing local scour around a cylindrical bridge pier. This study indicates that the nano clay could be used effectively to reduce the local scour depth, with an optimum ratio of 0.25% when the flow shallowness is less than 1.4 and an optimum ratio of 0.5% for the flow shallowness between 1.4 and 2. Notably, a significant reduction of up to 68% in local scour depth is observed out of all experiments. Furthermore, the study demonstrates the influence of nano clay on other factors related to local scour depth. It presents a predictive equation that can be used to estimate the depth of local scour in a bed composed of nano clay and non-uniform sand. This equation is derived from the obtained data from this experimental investigation.