Experimental investigation of dry granular flow impact via both normal and tangential force measurements

The study of granular flow is important for natural hazards such as avalanche and debris flow. In this context, granular flow impact against a retaining wall was investigated through the measurement of both normal and tangential sub-forces. The tangential sub-forces change from positive to negative with respect to the wall in the impact process, which can be classified into two impact states according to the development of the stagnant zone. In the process, interface friction between the granular material and the wall is calculated according to normal and tangential forces and defined as the equivalent interface friction angle, which is observed to vary, and is smaller than the value measured in interface friction tests. The absolute value of the equivalent interface friction angle decreases with slope angle. It was also observed that a reduction in the interface friction angle of the wall has a negligible influence on the impact force calculation, while a reduction in the interface friction angle of the flume base leads to a significant overestimation of the force. These findings should significantly aid the study of granular flow and its applications.