Environmental Engineering Reference
In-Depth Information
TABLE 3.15
Seepage Tests in Soils
Test
Field Conditions
Method
Procedure
Constant head
Unsaturated
(a) Shallow-depth small pit, 12 in deep and square
1. Uncased holes, backfill with fine gravel or coarse
granular soils
(percolation test)
(b) Moderate depth, hand-auger hole
2. Saturate ground around hole
(c) Greater depth, install casing (open-end pipe test)
a
3. Add metered quantities of water to hole until
quantity decreases to constant value (saturation)
4. Continue adding water to maintain constant
level, recording quantity at 5 -min intervals
5. Compute
k
as for laboratory test
Falling or variable head
Below GWL, or in
Performed in cased hole
a
1. Fill casing with water and measure rate of fall
slow-draining soils
2. Computations
b
Rising-head test
Below GWL in soil
Performed In cased hole
a
1. Bail water from hole
of moderate
k
2. Record rate of rise in water level until rise
becomes negligible
3. After testing, sound hole bottom to check for
quick condition as evidenced by rise of soil in
casing computations
b
a
Tests performed in casing tan have a number of bottom-flow conditions. These are designed according to geologic conditions, to provide measurements of
k
mean
,
k
v
, or
k
h
.
●
k
mean
: determined with the casing flush with the end of the borehole in uniform material, or with casing flush on the interface between an impermeable layer over a per-
meable layer.
k
v
: determined with a soil column within the casing, similar to the laboratory test method, in thick, uniform material.
●
k
h
: determined by extending an uncased hole some distance below the casing and installing a well-point filter in the extension.
●
b
References for computations of
k
with various boundary conditions:
●
NAVFAC Desigh Manual DM-7.1 (1982).
Hoek and Bray (1977).
●
Lowe and Zaccheo (1975).
●
