Faculty of Applied Engineering and Urban Planning Civil Engineering Department Soil Mechanics ECGD3303 2D Seepage (Cont.) Lecture 13 Week 8 1 st Quadester 2007/2008 UP Copyrights 2007

Flow Nets Number of flow Channels N f Number of potential drops N d

Seepage Calculation from a Flow Net

Example

Mathematical Solutions S/T΄ q/kH Previous Example Flow Net Method q = 3×2.45×10 -5 m 3 /s/m Mathematical Method q = 0.5×4.2×10 -5 ×3.5 m 3 /s/m NfNf ΔqΔq q = 7.35×10 -5 m 3 /s/m From FigurekH

Uplift Pressure

Example – Flow Calculation N f = 3 N d = 10 q = kH N f /N d = ×8.5 × 3/10 = 2.55 × m 3 /s/m

Example - Uplift Pressure Point 1: P 1 = [(10 + 3) – 0.85]γ w = γ w kN/m 2 Potential Drop = H/N d = (10 – 1.5)/10 = 0.85 m Point 2: P 2 = [(10 + 3) – 2×0.85]γ w = 11.3 γ w kN/m 2