Environmental Engineering Reference
In-Depth Information
Soil Penetration Tests (CPTU, DMT)
The piezocone CPT (Sections 2.3.4 and 3.4.5) and the flat dilatometer test ( Section 3.4.5)
provide estimates of the horizontal coefficient of permeability, k h .
Pumping Tests
Tests are made from gravity wells or artesian wells in soils or rock masses as described in
Table 3.16. See Section 8.3.3 for additional discussion.
Pressure Testing in Rock Masses
General Procedures
The general arrangement of equipment is illustrated in Figure 3.17, which shows two
packers in a hole. One of the two general procedures is used, depending on rock quality.
The common procedure , used in poor to moderately poor rock with hole collapse prob-
lems, involves drilling the hole to some depth and performing the test with a single
packer. Casing is installed if necessary, and the hole is advanced to the next test depth.
The alternate procedure , used in good-quality rock where the hole remains open, involves
drilling the hole to the final depth, filling it with water, surging it to clean the walls of fines,
and then bailing it. Testing proceeds in sections from the bottom-up with two packers.
Packer spacing depends on rock conditions and is normally 1, 2, or 3 m, or at times 5 m.
The wider spacings are used in good-quality rock and the closer spacings in poor-quality
rock.
Testing Procedures
1.
Expand the packers with air pressure.
2.
Introduce water under pressure into the hole, first between the packers and then
below the lower packer.
3.
Record elapsed time and volume of water pumped.
4.
Test at several pressures, usually 15, 30, and 45 psi (1, 2, and 3 tsf) above the nat-
ural piezoelectric level (Wu, 1966). To avoid rock-mass deformation, the excess
TABLE 3.16
Pumping Tests a
Test
Field Conditions
Method
Procedure
Disadvantages
Gravity well
Saturated, uniform
Pump installed in
Well is pumped at
Provides values for
(Figure 8.31)
soil (unconfined
screened and filtered
constant rate until
k mean
aquifer)
well and surrounded
cone of drawdown
by a pattern of
measured in observation
observation wells
wells has stabilized
(recharge equals
pumping rate)
Gravity well
Rock masses
Similar to above
Similar to above
Flow from entire hole
measured. Provides
an average value
Artesian well
Confined aquifer
Similar to above
Similar to above
Provides values for
(Figure 8.32)
(pervious under
k mean k mean in aquifer
thick impervious
layer)
a
For field arrangement and evaluation of data see Section 8.3.3.
 
 
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