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CLSM part of the National Geotechnical Experimentation Site, the
types of soils and clays at the sites have been well documented.
For this project, test pits on both sites were excavated using a
backhoe-mounted auger to collect and analyze the soil and
clay. The clay site is underlain by four distinct layers. The sur-
face layer is mottled red and gray clay. This clay layer is very
(a) uniform in thickness down to about 1.83 m below the surface.
The plastic and liquid limits of the clay were 20.9 and 53.7 per-
SOIL
cent, respectively. The hydraulic conductivity coefficient was
4.99 × 10-3 m/year. The surface layer at the sand site is mot-
tled red and tan silty sand. The percentage of fine particles
was 17.4 percent, and the hydraulic conductivity coefficient
was 5 × 10-2 m/year.
Metal pipes were placed in six trenches on each site using
CLSM
three different trench conditions. The trenches were 12.19 m
(b)
long, 0.76 m deep, and 0.46 m wide. Figure 4.22 shows the
three trench conditions used in the test:
· Condition I: Metallic pipes are completely embedded in
CLSM (Figure 4.22(a)).
· Condition II: Metallic pipes are placed on a CLSM bedding
SOIL and backfilled with soil from the site (Figure 4.22(b)).
(c) · Condition III: Metallic pipes are completely embedded in
soil (Figure 4.22(c)).
Figure 4.22. Three trench conditions used for
the field test.
Commercially available ductile iron pipes and corrugated
steel culverts were delivered to the site. Both types of pipe were
the site, which aims to replicate field conditions that lead to cut into 0.76 m long pieces. The ductile iron pipes had an
corrosion and to accelerate the rate of deterioration. asphalt coating that was removed by sandblasting after soaking
in lacquer thinner. Copper wires (2.32 mm diameter) were
attached to each ductile iron and culvert sample to be used for
Site Layout and Construction
corrosion observations later. After drilling and tapping the
Two sites, a clay site and a sand site, were selected to observe ductile iron pipe pieces, screws and washers were used to attach
the corrosion performance of embedded ductile iron pipes the wires as shown in Figure 4.23(a). Exposed wires and screws
and galvanized corrugated steel culverts. Because the sites are were coated with epoxy to prevent corrosion. Grounding clips
(a) (b)
Figure 4.23. Wiring of ductile iron pipes and corrugated steel culverts.
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were used to attach wires to corrugated steel culvert pieces.
After the wires were connected, the exposed sections of the
wires and clips were coated with enamel. Epoxy was applied
after the enamel was cured as shown in Figure 4.23(b).
Twelve of the cut ductile iron pipe samples and twelve of the
cut corrugated culvert samples were painted with epoxy inside
and outside leaving only a 0.15 m diameter circular area ex-
posed. Counter electrodes for polarization studies were 0.15 ×
0.15 m nickel-chromium wire mesh. Copper wires (2.32 mm
diameter) with alligator clips were attached and soldered to the
meshes. The alligator clips, the solder area, and exposed wires
were coated with epoxy. These 24 pieces of pipes with limited
exposure areas together with the counter electrodes can be used
later for long-term corrosion rate measurements. Figure 4.24
shows three of the samples prepared for polarization testing.
The six trenches were excavated on each site in a 6 × 30.5 m
rectangular area using a backhoe with a 0.46 m wide bucket.
After the bottoms of the trenches were cleared, pipes were
placed with 0.6 m space between them. Four ductile iron pipe
samples and four corrugated steel culvert samples, including
one of each with limited exposure areas, were placed in each
trench. The pipe pieces were placed on steel chairs to allow free
flow of CLSM mixture underneath the pipes. Each piece of
pipe was also secured using four stakes, driven 1 foot into the
ground to prevent lateral and vertical movement. Figure 4.25
Figure 4.25. Clay site trench with pipes.
shows a trench in the clay site with pipes.
The pipes prepared for polarization testing were placed at
the two ends of the trenches. These pipes were placed with the cement, and 135 kg/m3 fly ash. The watercementitious ma-
exposed areas facing sideways so that when the trenches were terial ratio was 0.8. The CLSM was delivered in ready-mixed
backfilled they would be exposed to a CLSM and soil environ- concrete trucks and was placed into the trenches using a chute
ment. Counter electrodes were placed adjacent to the exposed as shown in Figure 4.26.
areas. The average time to fill the condition I (completely filled
After the placement of the pipes, trenches were backfilled with CLSM) trenches was 8 minutes. The truck was placed at
with a CLSM mixture provided by a local concrete supplier. one end at the trench and the trench was completely filled from
The CLSM mixture contained 1483 kg/m3 sand, 34 kg/m3 this point (Figure 4.26(a)). The average time to fill the condi-
tion II (CLSM bedding and soil backfill) trenches was 11 min-
utes, and the truck had to be moved three times to ensure
uniform thickness of bedding layer. Condition II and III
trenches were filled with native soil after the setting of the
CLSM backfill. The soil was placed into the trenches in layers
with a backhoe and compacted with an average of three passes
of a jumping jack compactor. The average time to compact an
approximately 0.25 m thick by 12 m long layer of soil was
approximately 5 minutes. This speed equals approximately
30 minutes for sample sized trenches filled with CLSM (3 to
4 times longer).
The wires connected to the pipe pieces in each trench ran
along the bottom of the trenches and were collected in PVC
boxes at the surface of each trench. The wires entered into the
boxes through an inverted U-shaped conduit to prevent rain-
Figure 4.24. Metal pipes with 0.15 m diameter water from entering into the boxes. A smaller box was placed
exposed surface and a counter electrode. inside each PVC box and wires were soldered to female con-
