Methods for predicting unknown phase relationships

ERDC TN-DOER-D1

August 2004

approximately 60-deg angle) into the surface of the material and observe if the pencil remains in

a vertical position. The maximum water content at which the pencil freely stands without top-

pling over is the approximate liquid limit.

Methods for predicting unknown phase relationships. Phase relationships include void

ratio, percent solids, bulk density, porosity, and dry density, among others. They are calculated

from parameters such as water content, percent saturation, and specific gravity, which generally

require laboratory testing to determine.

To predict the saturated wet bulk density (or the bulk unit weight) of a dredged material when

only the water content is known, the following equation may be used:

γ = 233.21W 0.2051

(6)

where

γ = bulk unit weight (commonly called the bulk density), lb/cu ft

W = water content percent

Equation 6 is based on 146 data points with R2 = 0.96.

To predict the void ratio (volume of voids / volume of dry solids) when the water content is

known, but specific gravity is not, conduct a single slump test and use:

e = 0.028W 0.055N 0.065

(7)

where

e = void ratio

W = water content percent

N = normalized slump = slump / cylinder height

Equation 7 is based on 185 data points with R2 = 0.99, which is an excellent correlation.

If water content and specific gravity are both known, and the material is fully saturated, use the

textbook equation:

e = WGs/100

(8)

where

W = water content percent

Gs = specific gravity of solids

Combining Equations 7 and 8 allows estimation of the specific gravity, Gs:

Gs = 2.8 5.5N/W 6.5/W

(9)