(B-9)

if the equilibrium moisture profiles of figure 5-1 (para

5-4b) are used.

(5-3), (5-4), or (5-5).

surcharge pressure may be evaluated using

the soil suction test procedure on undisturbed speci-

tor a is the ratio of the change in volume for a corre-

mens or may be calculated from equation (B-7) and

sponding change in water content, i.e., the slope of the

the natural (initial) water content.

without surcharge pressure may be calculated from

density. The value of a for highly plastic soils is close

the assumption

to 1, and much less than 1 for sandy and low plasticity

soils. High compressibility y factors can indicate highly

(B-8)

swelling soils; however, soils with all voids filled with

water also have a equal to 1.

coefficient of effective lateral earth pres-

(1) Figure B-5 illustrates the compressibility fac-

sure

tor calculated from laboratory data for a silty clay

final vertical effective pressure, tons per

taken from a field test section near Clinton, Missis-

square foot or from equation (B-1) setting

sippi. Extrapolating the line to zero water content, as

a

shown in the figure, provides an estimate of l/R with

The final vertical effective pressure may be found

from