What diameter (DN) and maximum length ranges are common in remote-controlled microtunnelling depending on the geology?

Q: What diameter (DN) and maximum length ranges are common in remote-controlled microtunnelling depending on the geology?

In remote microtunneling (MTBM), the diameter ranges (DN) and maximum length per drive (between boreholes) depend on geology and hydrogeology (permeability, water pressure and face stability), as well as available thrust and friction. As a guideline, the usual DN are approximately between DN 150 and DN 3,000 mm, and the drives are usually designed in the order of 200-500 m. In cohesive soils it is common to use EPB closed shields; in saturated granular soils, hydroshields (slurry). For longer lengths, intermediate thrust stations and a specific lubrication and pressure control design, validated on a case-by-case basis, are used.

At microtunneling remote sensing (MTBM) -also known as pipe ramming- the ranges of diameter (DN) and the maximum length per advance (between wells) depend mainly on the geology and hydrogeology (front stability, permeability and water pressure), in addition to the thrust available, the friction and the use or not of intermediate push stations. For context of the method, see Pipe jacking y Choice of tunnel boring machine.

Usual“ ranges (indicative)

Diameters (DN): in microtunneling usually works in a wide range (approx. DN 150-3,000 mm, according to project, equipment and piping).
Length per advance (between wells): most often drives are designed in the order of 200-500 m by driving, adjusting according to DN, friction and ground.
Longer lengths: can be feasible by incorporating intermediate thrusts and a specific lubrication/friction and pressure control design (case by case).

How geology influences (practical guide)

Clay/silt and cohesive soils (with or without water): usually fits with EPB closed shield, with good control of the front if the terrain conditioning and pressure balance are well adjusted.
Permeable sands/gravels and saturated soils (high water pressure): priority is usually given to Closed shield Hydroshield (slurry) for its ability to pressure control and stability of the front.
Mixed or highly variable terrain: a conservative approach in length per drive and equipment selection within the range of Closed shield tunnel boring machines, to maintain stability and operational control.
Competent rock or abrasive sections: may be suitable for a Open shield, where the practical length may be conditioned by abrasiveness/wear, tool changes and logistics.

If the main constraint is “more length” or different layouts

If you are looking to maximize length or solve specific geometries, it is worth comparing with other trenchless technologies such as Horizontal directional drilling (HDD) o Direct Pipe, in addition to supporting you in Technical assistance and engineering to define the realistic range with your terrain data.