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E-M:/ Water volume in soil pore space


Here is a correction to my calculation on how much water could be in the pore space between soil particles.  A careful reading of  "Groundwater" by Cherry would give you a better set of calculations that I posted earlier.  My apologies for the error.  See below the correct information provided by my good friend and geotechnical engineer, Tim Carpenter.  As always, Tim, I am in your debt.  Thanks.

Regards, Chuck


There are occasions where you can find soils with 50% pore space – but it is rare (you can approach that condition with well-rounded sand particles, all the same size, and gently rain them under water – but don't sneeze). Normal in-place soils would be in a rough range from 29 to 33 percent voids. {Geotechnical engineers, like me, use a measure, called the Void Ratio, e, to characterize the void space. I'm using a range from e = 0.4 to e = 0.5). The densest natural condition might get down to about 12% void space – that would be a well graded mix of silty sand and gravel that had been subjected to some form of external compaction.

I bet that 25-years ago you asked me what the average void ratio of Michigan soils would be – and I said something like "O, about .4 to .5". And you translated that into 50 Percent then figured that 50% of the soil volume is voids. It ain't. Void ratio, e, is the Volume of Voids divided by the Volume of Solids.


Timothy Carpenter, P.E., Pres.,
GeoDynamics Consultants, Inc.
geodynamics@comcast.net (primary)