Preparation of trenches
Page 108 OmniTrax Product Guide
• reduced burial depth of 15 cm (6 in.)
• soil replacement is required
• expanded stone dust or sand buffer and geotextile fabric required
• gravel bed strongly recommended for drainage
• the surface above the trench must be graded to allow runoff
• a dual cable system must be used (OC2, SC2)
• maximum cable spacing is 1 m (3.3 ft.)
• narrow cable spacing (10 cm) may be used
1. Dig one trench 1.1 m to 2 m wide (depending on cable spacing) and 30 cm to 1 m deep
(depending on the size of the crushed stone bed that is required for adequate drainage.
2. Fill the bottom of the trench with clear crushed stone to a depth of 30 cm from ground level.
3. Lay the geotextile fabric in the trench above the crushed stone layer to the width of the trench.
4. Pour a 15 cm layer of stone dust or sand on the geotextile fabric in the trench.
5. Lay the sensor cables in the trench at the specified cable spacing (10 cm to 1 m).
6. Pull the cable taut and partially backfill the trench with 7.5 cm (3 in.) of stone dust, or sand, as
you go to hold the sensor cable in place.
7. Place cable marker tape on the stone dust or sand above the sensor cables (optional).
8. Complete the backfilling of the trench with 7.5 cm (3 in.) of the heavy clay soil. Ensure that the
native soil layer is graded to allow rainfall to run off the cable path.
Figure 73: Installation in heavy clay soil
Note Do not cover the ends of the sensor cables as ferrite beads,
connectors, and decouplers must be installed first.
Note Before backfilling the trench to ground level, install the ferrite beads and
connectors, but do not seal the heatshrink at this time (see Installing
cable fittings on page 121). Next, do the cable tests (see Cable tests on
page 146) and then do a sensitivity profile to verify the installation (see
OmniTrax calibration - Sensitivity Profile and Transmitter Power
on
page 197).
marker tape
sensor cables
heavy
clay soil
geotextile fabric
stone dust or sand
10 cm to 1 m
15 cm
crushed stone bed for drainage
7.5 cm
30 cm
0.5 m 0.5 m
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