Microtunnelling and Pipe Jacking

Microtunnelling is a remotely operated guided excavation process that controls the face and line and grade, often using slurry to transport spoil. Pipe jacking is the structural process of pushing the pipeline from a launch shaft. Most microtunnel drives use pipe jacking, but other pipe-jack methods can use different excavation systems.

Machine and cutterhead selection can address soft clay, sand, gravel, cobbles, mixed face, and rock within defined ranges. Groundwater pressure, boulder frequency, abrasivity, strength, contamination, and obstruction risk matter as much as soil name. A targeted geotechnical program and drive-specific equipment selection are required before launch.

A surveyed launch network feeds a laser, target, gyroscopic, or combined guidance system that reports machine position and attitude. Operators make small steering corrections while independent survey checks verify control. Harrowgate monitors launch-frame stability, joint deflection, and trend by chainage so error is corrected early rather than near reception.

Drive length depends on pipe jacking capacity, ground friction, alignment, lubrication, shaft space, machine and slurry performance, joint deflection, and available intermediate jacking stations. Harrowgate models expected and maximum forces, tracks actual load per metre, and activates lubrication or intermediate stations within the engineered operating plan.

Settlement control combines stable face pressure, excavation-volume balance, suitable steering, prompt pipe advance, lubrication, annular control, shaft support, and groundwater management. Surface and structure points are monitored at defined frequency. Harrowgate links movement readings to face pressure, slurry data, advance, and chainage so trends trigger immediate operational response.

Return slurry passes through separation equipment that removes excavated solids and conditions fluid for reuse. Solids, spent slurry, and additives are characterized and managed under project and Ontario requirements. O. Reg. 406/19 includes current provisions for soil excavated by slurry or micro-tunnel boring machines where polymers or foaming agents are added.

Harrowgate recovers the machine, surveys the installed drive, completes specified annulus treatment, inspects or tests pipe and joints, constructs chambers and carrier connections, manages shaft conversion or backfill, and restores roads and landscapes. Closeout includes alignment, jacking force, lubrication, slurry, settlement, pipe, and material records.