Per ASCE 36, the North American design and construction standard, a method qualifies as microtunneling if it's remote-controlled from the surface, uses a guidance system (typically laser-guided) to hold line and grade within tight tolerances, and provides continuous support to the excavation face as it advances — a combination that distinguishes it from simpler pipe-jacking or auger-boring methods, and doesn't actually depend on tunnel diameter despite the name. The two main variants are slurry microtunneling, which uses a closed-loop slurry system to remove excavated spoil, and auger (pilot-tube) microtunneling, which manages the excavation face through auger rotation and soil conditioning instead. Because it holds precise line and grade without surface disruption, microtunneling is typically reserved for larger-diameter gravity sewers, deep installations, or crossings where settlement tolerance is tight — highways, rail lines, and sensitive utilities above the alignment — and it's meaningfully more expensive per foot than open-cut installation, which usually only pencils out where full excavation isn't realistic. Microtunneling projects carry some of the highest per-foot costs and the tightest technical requirements in the trenchless toolkit, which makes early, accurate scope extraction — depth, diameter, soil conditions, crossing length — especially valuable before committing significant estimating time. That's the kind of document-level detail Nonlinear pulls out of drawings and geotechnical reports automatically.
Knowledge Base
What is microtunneling?
Microtunneling is a remote-controlled, guided trenchless method for installing new pipe by simultaneously excavating a tunnel and jacking pipe sections through the ground behind a specialized boring machine, without anyone entering the tunnel itself.
