Page 374 - Trenchless Technology Piping Installation and Inspection

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Inspection Guide for Microtunneling (MT)

Preinspection Plan Review

Review geotechnical and soil reports.
Ensure DOT/agency facilities and nearby utility information are shown on the
plans and profiles and that the proposed alignment does not interfere with them.
Note the minimum cover above the top of the pipe and below the pavement surface,
or ground elevation (for longitudinal installations outside the influence of the
roadway) is _____ ft.
Note proposed pipe characteristics:
Pipe material class ________________.
Pipe material yield strength ______ ksi.
Allowable pipe-jacking force _____ ton.
Pipe diameter _______________ in.
Pipe wall thickness __________ in.
Overcut diameter ___________ in.
Review contingency plan.
Review job-site layout including: distance from access pits to roadbed, proposed
sheeting and bracing, materials storage and fabrication area, safety devices (barrels,
guardrail, etc.), and dewatering pit locations.

Note unique or special items /circumstances: ___________________
Construction Inspection
Verify traffic control is consistent with the permit requirements, one call service
has been contacted, and the DOT/agency permit is on-site.

Verify job-site layout is consistent with the approved plans, especially the alignment
of the pipe and machine.
Verify continuous monitoring records indicate bearing and grade of the leading edge
of the pipe is consistent with the approved plans, dewatering effort is satisfactory, soil
volume removed is consistent with projection, and that workers understand the
contingency plan.
Verify pipe characteristics are consistent with permit requirements.
Verify jacking pipe is certified for microtunneling, the pipe has a smooth interior and
exterior surfaces, is used within the entire influence area of the roadbed, has clean and
square ends, joints are watertight, defective pipe is not used, and damaged pipe is
jacked through to the receiving access pit and removed.
Verify the MTBM has the capability to steer, align the face, simultaneously remove
spoil and install pipe, and remotely control the line and grade.

FIGURE 8.12 Sample checklist for inspection of microtunneling operations.