# Hydraulic Conductivity Question

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### #1 jaa046

jaa046

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Posted 10 April 2012 - 12:10 PM

Can someone help me solve this:

Bore-hole logs show interbedded soil layers with the following characteristics. What is the overall hydraulic conductivity through the soil layers?

Layer Thickness (cm) Soil Class
1 70 SP
2 109 GC
3 88 SM
4 46 SC

(a) 5.0 x 10-8 cm/s
( 1.3 x 10-7 cm/s
(d) 5.0 x 10-4 cm/s

Thank you

### #2 terzaghi83

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Posted 10 April 2012 - 03:43 PM

I think this problem is too open ended for the PE.

There are two formulas to use to get the equivalent overall permeability of a layered system depending on which way your layers are oriented with respect to your flow direciton. However, the permeability of the material types you have listed have a wide range, and many references will not report the exam same range of permeability for the material type.

### #3 terzaghi83

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Posted 10 April 2012 - 03:44 PM

exam=*exact

### #4 envirotex

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Posted 10 April 2012 - 05:57 PM

Seems like a question where they would give you the expected permeability for the soil class...anything you would get from a reference for those classes would have a range of at least a few orders of magnitude.

### #5 jaa046

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Posted 11 April 2012 - 08:07 PM

Thank guys!

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