A slurry separation plant sets the maximum sustainable advance rate of a microtunneling drive: the machine can only advance as fast as the plant removes solids. It removes excavated solids in stages defined by particle size, conditions the slurry back to its working density and viscosity, and returns it to the face. If it cannot
Slurry Separation Plants for Microtunneling: Sizing, Stages and Cost Drivers Lire plus »
Curved microtunneling – steering a remotely controlled, non man-entry jacked pipeline along a horizontal or vertical curve between shafts so the line can follow a road, a river, a rail corridor or an existing utility instead of running straight between two fixed points – has a minimum radius (the tightest curve the pipe string and
Curved Microtunneling: Minimum Radii, Pipe Stress and What Is Achievable Lire plus »
Microtunneling tolerances – the permitted departure of a remotely controlled, non man-entry jacked pipe from its design alignment – define how far the installed pipe may sit from its design line (horizontal position in plan) and its design grade (the designed fall, expressed as a percentage or an elevation), and they are the first thing
Microtunneling Design: Line, Grade and Tolerance Requirements Explained Lire plus »
A microtunneling geotechnical investigation is the desk study and ground investigation package that decides whether a drive is feasible and what machine, face support and jacking force it needs. Its three outputs are a borehole layout, a parameter list and a baseline deliverable set, and its placement rule is fixed: boreholes are sunk beside the
Geotechnical Investigation for Microtunneling: What to Bore, Test and Baseline Lire plus »
Microtunneling grade control is the closed loop of measurement, reporting and steering that keeps the machine on its design line (horizontal position in plan) and its design grade (the designed fall, expressed as a percentage or an elevation) as it advances. Accuracy as good as ±10 mm has been reported for microtunneling in one published
Grade Control and Steering Accuracy in Microtunneling: How ±10 mm Is Achieved Lire plus »
Microtunneling groundwater control is the package of measures that keeps water out of launch and receiving shafts and holds the face and annulus stable while a remotely controlled machine advances below the water table. It combines shaft dewatering or cut-off, entry and exit seals, a balanced support medium at the face, and a discharge route
Groundwater Control for Microtunneling Shafts and Drives Lire plus »
Microtunneling jacking force is the total thrust the jacking frame must deliver to advance the machine and push the pipe string from the launch shaft, and it is the sum of face resistance at the machine, friction along the pipe string, and any force added by curvature. Published friction values fall between 0.5 and 2.5
Jacking Forces in Microtunneling: Face Resistance, Friction and Lubrication Lire plus »
Overcut in microtunneling is the annular clearance the machine cuts beyond the outside diameter of the pipe, and it is the single dimension that ties steering, lubrication and settlement together. Its normal size is about 12 to 19 mm on the radius in soil and more than 25 mm in rock. That annulus makes steering
Overcut, Lubrication and Settlement: The Three Variables That Decide a Microtunnel Lire plus »
Microtunneling pipe materials are selected on one governing criterion: whether the pipe and its joint can carry the jacking load at the governing point of the drive while staying watertight and on line. Direct jacking is dominated by reinforced concrete pipe (RCP), vitrified clay pipe (VCP), polymer concrete and glass-reinforced plastic (GRP); steel is usually
Microtunneling Pipe Materials: RCP, Steel, FRP, GRP and Ductile Iron Compared Lire plus »
Microtunneling settlement is ground movement caused by the drive, and it is controlled by limiting volume loss: face loss and over-excavation, the overcut annulus, slurry or lubricant loss into the ground, joint drag, shaft-related loss, and groundwater drawdown with consolidation all contribute, and they are managed with face pressure control, excavated volume accounting, lubrication quality
Ground Settlement Control in Microtunneling: Monitoring, Limits and Mitigation Lire plus »
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