Input
last drop near exit
Results
q per unit length—
Avg head loss per drop Δh—
Exit gradient i_e—
Critical i_c = (Gs−1)/(1+e)—
FS = i_c / i_e—
Method
Casagrande: q = k·H·(Nf/Nd) per unit length. Δh = H/Nd. i_e ≈ Δh / Lexit. Critical gradient i_c = (Gs − 1)/(1 + e). Recommended FS against piping ≥ 3.0 for cohesionless soil.