Many industrial processes require the use of an hydraulic transport with macroscopic particles. Those methods are widely used in mining or food industries. However relatively few studies have been performed on the behavior on the transition between jamming and flowing states. Indeed, for that kind of flow, some intriguing effects are observable such as shear -thickenning or shear – thinning. It appears that fluid-particle interactions and hydrodynamic effects have an important impact on the suspension dynamic (especially for high packing volume fraction). For example, in oil industry, it is possible to observe interfaces problems for heavy oil extraction with sand or for hydrates crystals in off-shore pipe (in this case the hydrates are sedimenting leading to the jamming state). The jamming phenomenon is not systematic. This is why we have performed a lot of experiments in order to establish a statistical analysis. The experiments provided here intend to characterize the elements responsible for such a phenomenon (dense flow, fluid velocity, hydrodynamic forces…). We have performed a set of experiments with a rectangular pipe in 2D to investigate the jamming effect. We study the flow of non Brownian particles suspended in a liquid passing through a restriction. With image analysis we were able to count the total number of particles through the restriction between two jamming. We noticed that the total number of particles for different size (length) of restriction could be expressed as an exponential with only one fitting parameter.