Scaling effects of g-level and fluid viscosity on flow velocity through transverse cracks in embankments

Flow through transverse cracks in embankments is a potential failure mode that can lead to concentrated leak erosion (CLE) and embankment failure. Current practice to assess whether CLE will initiate compares the hydraulic shear stress imparted by the fluid on the crack walls to the critical shear stress of the soil. Hydraulic shear stress, and by relation, fluid velocity through the crack, depends on factors including crack geometry, change in head, and fluid viscosity. An experimental parametric study was conducted to evaluate the scaling factors associated with g-level and fluid viscosity on flow velocity through a known crack geometry. Centrifuge models comprising homogenous embankments with 1.5H:1V slopes were constructed using low plasticity clay compacted to 95% standard Proctor maximum dry density. Tests were performed at 1 g, 20 g, and 40 g, using 1 cPs, 7 cPs, and 40 cPs fluid. For each test, a 4.7 mm nominal width transverse crack was cut into the embankment, and a reservoir maintained constant head on the upstream side of the crack. Flow through the cracks was measured using a flow metre and by monitoring reservoir levels. The scaling relationships for fluid velocity through the cracks with respect to g-level and fluid viscosity are discussed.