ENFORCE26805

• Permit No: C1981013
• IBM Index Class Name: Enforcement
• Doc Date: 2/1/2001
• Doc Name: REPORT CONCERNING AN INVESTIGATION INTO CONTINUED DAMAGE TO THE HOUSE & WATER SUPPLY PIPELINE AT THE
• Violation No.: CV2000009
• Media Type: D
• Archive: No

SOILS
into a 1/8" thread. The sample will crumble when it is Table 9.9
at the plastic limit when rolled to that diameter. Typical Permeabilities
typical coefficient
Ezample 9.5 of permeability
A clay has the following Atterberg limits: liquid limit group symbol (cm/sec)
= GO o; plastic limit = 40 0:. shrinkage limit = 25%. GW 2.5 EE-2
The clay shrinks from 15 cubic centimeters to 9.5i cu- GP 5 EE-2
bic centimeters when the moisture content is decreased GM > 5 EE-i
from the liquid limit to the shrinkage limit in the At- GC > 5 EE-6
terberg tests. What is the clay's specific gravity (dry )? SW > 5 EE-4
The water reduction is 15 - 9.57 = 5.93 cubic centime- SP
SM > 5 EE-9
> 2.5 EE-S
ters. Since 1 cubic centimeter of water weighs 1 gram. SM-SC > EEC
the weight loss is 5.93 grams. The percentage weight.
SC
> 2.5 EE-i
loss (drr' basis) is 60°io - 25% = 35t7. Therefore, from ML > 5 EEC
equation 9.6, the solid weight is ML-CL > 2.5 EE-7
~N'w
5.93 CL > 5 EE-8
_
_ 15.5 g
~I' -
~w 0.35 MH > 2.5 EE-7
The water volume at the shrinkage )imit is CH > 5 EE-8
OH -
Lw _(0.25)(15.5) = 3.875
Since at and above the shrinkage limit there are no air
voids, the volume of solid at the shrinkage limit is
_ VL
~ hAt
For loose filter sands, k is given approximately by equa-
tion 9.25.
k x 100(1710) 9.25
9.57 - 3.875 = 5.G95
The density of the solid is
15.5
p - 5.695 - •, r 2 glom"
Actual numerical values can be calculated from con-
trolled permeabilit}• tests using constant- or falling-head
permeators (figure 9.7). For constant-head tests, k can
be found from equation 9.26. (1% is the water volume.)
SG = 2.72
H. PERME.ABILITI' TESTS
Petvneabilih• o{ a soil is a measure o{ continuous voids.
A permeable material permits a significant. flow of wa-
ter. The flow of water through a permeable acquifer or
soil is given by equation 9.23. known as Darcy's taw.
v=kGx/n 9.23
Q = nAv 9.24
The area A in equation 9.29 is the cross sectional area
of the aquifer, not the actual area in flow. Water can
only flow through the area between the solids. This
open area is nA.
Typical values of the coefficient of permeability, k, are
given in table 9.9. Soils with permeabilities of less than
EE-G are essentially impervious. The soil is considered
pervious if k is greater than EE-4.
9-13
9.26
For Jailing-hend tests, k can be found from equation
9.27.
k = .A9i tn(h,/h!) 9.27
A ~`
I
lei constant head
Figure 9.7
Permeators
PROFESSIONAL PUBLICATIONS INC. • P.O. Box 799, San Carlos, CA 94070
Ib) falling head