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Question 5.8: Compute the critical hydraulic gradients for the following m...

Compute the critical hydraulic gradients for the following materials: (a) Coarse gravel, k=10 cm / sec , G_{s}=2.67, e=0.65 \text { (b) sandy silt, } k=10^{-6} cm / sec , G_{s}=2.67, e=0.80

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As per Eq. (5.20), the critical gradient i_{c} may be expressed as

 

i_{c}=\frac{G_{s}-1}{1+e} (5.20)

 

i_{c}=\frac{G_{s}-1}{1+e}

 

(a) Coarse gravel

 

i_{c}=\frac{2.67-1}{1+0.65}=1.01

 

(b) Sandy silt

 

i_{e}=\frac{2.67-1}{1+0.80}=0.93

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