A remote-controlled microtunneling machine It can achieve high precision in plan, elevation, and grade, but the final tolerance should not be defined in general terms: it depends on the diameter, section length, depth, radius of curvature, geology, water table, guidance system, type of tunnel boring machine, and the hydraulic or functional requirements of the pipeline.
In projects of pipe ramming y microtunneling in terrestrial and subway applications, accuracy is controlled through guidance systems, topographic tracking, advance control, and continuous corrections from the command post. Laser systems can be used on straight sections; on curved alignments or complex sections, gyroscopic systems, supplementary topographic measurements, and specific elevation and orientation control can be incorporated.
Factors Affecting Accuracy
Geometry of the layout: total length, depth, slope, diameter, radii of curvature, and permissible tolerances for axis and dimensions. The more demanding the layout, the more important it is to define the guidance and control system from the design phase.
Geotechnical conditions: Variable terrain, mixed soils, the presence of boulders, rock, abrasiveness, cavities, or sudden changes in material can affect the cutterhead’s performance, thrust, and ability to correct course during advancement.
Presence of water and head pressure: The water table, permeability, and water pressure determine the stability of the face and can influence the selection of a EPB tunnel boring machine or a hydro-shield for water-logged terrain.
Guidance system used: Laser systems are commonly used for straight alignments, while curved or longer alignments may require more advanced navigation solutions and additional topographic checks.
Operational oversight during excavation: Accuracy also depends on monitoring parameters such as thrust, torque, chamber pressure, excavated volume, lubrication, deviations from the axis, and ground response.
How Accuracy Is Monitored on Site
During operation, the technical team continuously compares the microtunneling machine’s actual position with the projected axis. If deviations are detected, gradual corrections are made using the cutting head’s articulation and guidance systems, avoiding sudden maneuvers that could affect the pipe, the ground, or the final tolerances.
In sensitive projects, such as infrastructure crossings, at underpasses beneath roads, railways, waterways, or urban areas, precision control is supplemented by monitoring, settlement tracking, and topographic verification of the surrounding area.
In practical terms, the achievable accuracy must be determined on a project-by-project basis. To ensure a reliable assessment, Eurohinca analyzes the alignment, geotechnical conditions, diameter, length, gradient, required tolerances, and the most appropriate guidance system.
Minimum checklist for assessing expected accuracy: plan view, longitudinal profile, length, diameter, slope, depth, radius of curvature, axis and dimension tolerances, geotechnical engineering, water table, affected utilities, and type of pipeline.
Request a technical review of the microtunnel's alignment and tolerances to assess the achievable accuracy based on the actual conditions of the project.
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