Preparation of trenches
Page 106 OmniTrax Product Guide
1. For each trench, make two parallel cuts through the hard surface, 15 cm (6 in.) away from the
cable path (i.e., two cuts 30 cm (12 in.) apart, centered on the sensor cable route).
OR if micro-trenching equipment is being used:
1. Dig two parallel 2.5 to 7.5 cm (1 to 3 in.) wide trenches to a depth of 30 cm beneath the top of
the paved surface at the specified separation (micro-trenching cannot be used for narrow
cable spacing installation).
2. Remove the cut sections of asphalt and dig two 30 cm (12 in.) wide trenches to a depth of
30 cm beneath the top of the paved surface.
3. Pour a 7.5 cm stone dust layer on the bottom of the trench.
4. Lay the cable in the trench.
5. 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.
6. Compact the stone dust in the trench.
7. Place cable marker tape on the stone dust above the sensor cable (optional).
8. Backfill the trench with native soil and compact the soil.
9. Restore the cut section of asphalt.
Figure 70: Trench dimensions under a large asphalt surface (narrow spacing/micro-trench)
Note For dual trench installation keep the cable spacing to ±5 cm (2 in.).
For single trench installation with narrow cable spacing, keep the cable
spacing to +2.5 cm (1 in.) (no minus tolerance).
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).
soil from micro-trench
asphalt removal
trench depth
30 cm (1 ft.)
stone dust
30 cm
(12 in.)
asphalt
cable depth
23 cm (9 in.)
2.5 to 7.5 cm
sensor cable
(micro-trench example - dual trench installation)
(narrow cable spacing example - single or dual trench installation)
soil from trench
micro-trench
stone dust
asphalt
(1 to 3 in.)
sensor cables
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