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Tolerances in pipe jacking (microtunneling) are expressed as shaft deflection (mm) y slope (mm/m or ‰). A larger L and smaller DN, The more difficult it is to maintain strict values, the more difficult it is to maintain strict values. geotechnics and the water table condition the design and control.
Useful thumb rulers
DN 400-800 - L 50-150 m: axis ±30-50 mm - pending ±1.5-2.5 mm/m.
DN 800-1600 - L 80-250 m: axis ±20-40 mm - pending ±1.0-2.0 mm/m.
DN 1600-3000+ - L 100-300 m: axis ±15-30 mm - pending ±0.5-1.5 mm/m.
Adjust according to Rmin, The following information is available: soil type, soil type, NF, pipe material, guidance system and sheeting.
What moves the needle the most
Control and guidance: laser/gyroscope with landmark recalibrations and stable topographic network.
Front pressure and rheology: maintaining the soil-water balance; lubrication/injection uniform.
Correction capacity: joint/ring and pause protocols for corrections.
Real-time QA/QC: records of thrust, torque, pressure, and injection volume, with as-built per tranche.
Three typical scenarios (realistic goals)
Gravity sewer (DN 1200, L 180 m, saturated sands): axis ±25-35 mm - pending ±1.0-1.5 mm/m.
Crossing under infrastructure (DN 600, L 90 m, silt with gravel): axis ±35-50 mm - pending ±1.5-2.0 mm/m.
Large DN in competent clays (DN 2200, L 240 m): axis ±15-25 mm - pending ±0.5-1.0 mm/m.
What to ask the contractor (to validate tolerances)
Plan of topographical control y guided (equipment, verification frequencies).
Parameters of chamber pressure, rheology and plan for lubrication/injection.
Registrations per ring/span and as-built; acceptance criteria (watertightness/validation).
Contingency plan (loss of ground, backflow) and alarm thresholds.
Independent reference: standard ASCE CI/36-15 - Standard Construction Guidelines for Microtunneling (design and control criteria).
Next step: Request a quotation
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