Infiltration effects on sediment mobility under waves

Sediment mobility measurements with a horizontal sand bed under non-breakin g waves are reported. Conditions include no seepage and steady downward see page corresponding to head gradients up to 2.5. The results indicate that i nfiltration tends to inhibit sediment mobility for a horizontal bcd of 0.2 mm quartz sand exposed to moderated wave induced bed shear stresses. The ef fect is weak for the parameter range of the present study. The two opposing effects of shear stress increase due to boundary layer thinning and the st abilizing downward drag are successfully accounted for through the modified Shields parameter of Nielsen [Nielsen, P., 1997. Coastal groundwater dynam ics. Proc. Coastal Dynamics '97, Plymouth, ASCE, Dp, 546-555] using coeffic ients derived from independent studies. That is, from the shear stress expe riments of Conley [Conley, D.C., 1993. Ventilated oscillatory boundary laye rs. PhD Thesis, University of California, San Diego, 74 pp.] and the slope stability experiments of Martin and Aral [Martin, C.S. and M.M. Aral, 1971. Seepage force on interfacial bed particles. J. Hydraulics Div., proc. ASCE , Vol. 97, No. Hy7, pp. 1081-1100]. (C) 2001 Elsevier Science B.V. All righ ts reserved.