Dynamic Behavior of Straining in Randomly Packed Beads: Experimental Study

Abstract

Straining depicts the geometrical retention of fine particles within materials’ pore network. Whether or not fines can be retained depends on (1) the structure of materials’ pore network as well as (2) fines’ size distribution, manner of deposition, and retained amount. In this paper, the main results of straining tests are presented for randomly packed beads filters. The experimental program included a series of tests performed in both dry and water-saturated filters. The tests provided information on the dynamics of fines in the filters’ pore network and changes of filters’ efficiency. For instance, data supported the existence of four distinct stages: the filling of accessible cavities, the formation then clogging of the preferential pathways, the transfer of fines toward the lateral unobstructed capillaries, and eventual formation of a surface cake. The postulated mechanisms inherent to every single stage are discussed in terms of retention rate, straining length, lateral transfer, and progressive obstruction of constrictions. Additionally, the straining mechanisms were also probed in hydrodynamic conditions at increasing water flows.