Grant: Frozen-Ground Waste Containment

3

Table 2. Total lengths of pipe and the lengths in unsaturated and saturated soil under the revised design

for three thicknesses of the perched water table

Perched

water table

Total pipe length (m)

thickness (m)

Unsaturated soil Saturated soil

2

580.20

99.52

4

493.40

186.32

6

405.64

274.08

Table 3. Calculated thermal properties of the saturated and unsaturated soils and the attendant times to

freeze and total energy demand.

Soil

cvu

cvf

ku

kf

t

Q

MJ C m-3

◦ -1

◦ -1

-1

MJm-1

W C m

days

Unsat.

2.4813

1.8610

0.9233

1.7361

17.519

202.58

Sat.

3.8225

2.5316

1.7361

1.7361

17.121

252.70

Calculation of time and energy

other factors, inefficiencies in the refrigeration and

brine-distribution systems and pumps needed to cir-

requirements

culate the brine.

The time required to form a frozen ground wall was

calculated via:

Revised design

a2-1

R2L + ( 2 lrn ar )cuf νs

t

=

(8)

By a similar calculation, the revised design with a

4kf νs

2-m-thick perched aquifer would require 32,501 kilo-

c

.

2

R

vf νs

watt hours of energy. The 4-m-thick and 6-m-thick

)-

ln(

2-1

a

r0

perched aquifers would require 33,491 and 34,493

L + ( 2 lrn ar )cuf νs

kilowatt hours of energy. These are more than six

The energy required to form a frozen ground wall

times the energy requirement of the original design.

was calculated via:

L

(

2

a -1

cvf νs

+( r

Q = πR2

)cuf νs +

9)

R

2 ln ar

2 log( r )

Concluding remarks

0

[Sanger and Sayles, 1979]. The calculated times and

energy requirements are presented in Table 3.

The estimated capital and operating costs of the re-

vised design were roughly 6.4 times the original de-

sign. This dramatic increase in costs suggested that

Original design

the expected benefits of the revised plan should be

evaluated to determine if they were commensurate.

The original design had a total of 107.87 m of pipe

installed in unsaturated soil. Each meter of pipe

would withdraw 202.58 MJ for a total of energy re-

quirement of 4,977.5 kilowatt hours. The actual en-

ergy consumption would be higher due to, among