Critical Hydraulic Gradient

Critical hydraulic gradient, abbreviated as \(i_c\), is the change in height (pressure) to length between any two points.

 

Critical hydraulic gradient formulas

\(\large{ i_c =  \frac{ \gamma_{sub} }{ \gamma_w }  }\)
\(\large{ i_c = \frac{ SG_s \;-\; 1 }{ 1 \;-\; e }   }\)

Where:

Units	English	Metric
\(\large{ i_c }\) = critical hydraulic gradient	\(\large{ dimensionless }\)
\(\large{ \gamma_{sub} } \)  (Greek symbol gamma) = submerged unit weight	\(\large{ lbm }\)	\(\large{ N }\)
\(\large{  \gamma_w } \)  (Greek symbol gamma) = unit weight of water	\(\large{ \frac{lbm}{ft^3} }\)	\(\large{ \frac{N}{m^3} }\)
\(\large{ SG_s }\) = specific gravity of soil	\(\large{ dimensionless }\)
\(\large{ e }\) = void ratio	\(\large{ dimensionless }\)