The wear on discs, picks, scrapers, and cutting tools During excavation, performance is monitored by combining a thorough preliminary geotechnical assessment, proper cutterhead selection, planning for spare parts, monitoring of excavation parameters, scheduled inspections, and recording of consumption and incidents. The goal is to maintain advance rate, prevent damage to the cutting head, reduce unplanned downtime, and anticipate when tools need to be replaced.
In projects of pipe ramming, microtunneling, infrastructure crossings or excavation with EPB tunnel boring machine e hydro shield, wear must be analyzed from the perspective of the material being processed, especially in rock, gravel, siliceous sand, mixed soils, soils containing boulders, or abrasive materials.
What factors contribute to wear and tear?
| Factor | How It Affects Tools |
|---|---|
| Abrasiveness of the terrain | Sales of discs, picks, scrapers, and protective gear are on the rise |
| Quartz content | Increases mineral abrasion wear |
| Rock Strength | It requires more cutting effort and can lead to breakage |
| Skittles or blocks | They cause impacts, uneven wear, and potential localized damage |
| Mixed Fronts | They produce uneven results between soft and hard areas |
| Coarse grain size | Increases abrasion and the risk of blockage |
| Water table | It can affect the cleaning of the front and the transport of the material |
| High-torque pair | Indicates higher mechanical demands on tools |
| Inadequate progress | It can cause overload, vibrations, or premature wear |
| Poor material removal | It causes recirculation of solids and secondary abrasion |
The wear assessment should be coordinated with the ground abrasiveness and with the Selecting the cutting head.
How to Prepare Before Construction Begins
Before excavating, the risk of wear is assessed by checking:
- Geology and Longitudinal Profile.
- Strength of rock or cemented materials.
- Abrasiveness.
- Quartz content.
- Particle size distribution.
- Presence of gravel, boulders, or blocks.
- Soil-rock transitions.
- Drive-in length.
- Excavation diameter.
- Type of tunnel boring machine.
- Accessibility to the cutting head.
- Possibility of intervention.
- Projected production.
- Experience in similar fields.
This information is used to define the configuration of discs, picks, scrapers, blades, abrasion-resistant guards, head openings, replacement parts, and the maintenance schedule.
In complex or highly abrasive terrain, wear forecasting should be part of the implementation strategy, not just the spare parts inventory.
Parameters Indicating Wear During Excavation
During the excavation, indirect signs that may indicate progressive wear or damage to tools are examined:
| Parameter | Possible interpretation |
|---|---|
| Increase in cutting torque | Greater resistance to cutting, worn tools, or harder material |
| Feed Rate Reduction | Lower excavation efficiency or less effective cutting head |
| Increase in thrust | Greater Efforts to Maintain Production |
| Vibrations or impacts | Pins, fractured rock, damaged tools, or uneven wear |
| High energy consumption | Loss of cutting efficiency |
| Change in excavated particle size distribution | Less effective tools or variations in the terrain |
| Unstable frontal pressure | Problems with excavation, flow, or drainage |
| Irregular flow of material | Blockages, buildup, or loss of cutting ability |
| Axis or dimensional deviations | Uneven excavation or heterogeneous face |
| Frequent stops | Sign of a blockage, wear, or insufficient maintenance |
No single parameter on its own confirms wear. The interpretation must be based on a combination of machine logs, geotechnical data, production data, and the behavior of the excavated material.
Tool Inspection and Replacement
The ability to inspect or replace tools depends on the type of tunnel boring machine, diameter, access, face pressure, water table, and ground conditions.
It can be done by:
- Scheduled inspections.
- Inspection from inside the machine, if the design allows it.
- Access under atmospheric conditions when the front is stable.
- Special measures are taken in cases of high water pressure or unstable ground.
- Preventive changes before critical sections.
- Tool inspection at the end of the section.
In closed-shield tunnel boring machines, if access at atmospheric pressure is not possible, it may be necessary to consider a hyperbaric treatment for inspection, cleaning, repair, or tool replacement.
Measures to Reduce Wear and Tear
To monitor and reduce wear, several measures can be taken:
- Select tools that are suitable for the terrain.
- Use discs, picks, or scrapers that are suitable for the predominant material.
- Incorporate abrasion-resistant protection into the head.
- Adjust the feed rate and rotational speed.
- Avoid torque and thrust overloads.
- Improve the removal of excavated material.
- Monitor the rheology of slurry in a hydroshield.
- Adjust conditioning in EPB.
- Plan for critical replacement parts.
- Schedule inspections.
- Record tool usage per excavated meter.
- Anticipate changes before intersections where traffic is heavy.
- Check the parameters when changes in terrain are detected.
At mixed soil-rock faces, the control must be more conservative because wear may be uneven and affect the direction of travel.
Traceability and Production Control
Wear and tear must be documented to compare projections with actual results. Typical records include:
- Type and number of tools installed.
- Position of each tool on the spindle.
- Meters excavated per tool.
- Rough terrain.
- Torque, thrust, and feed rate.
- Blockage or impact incidents.
- Spare Parts Usage.
- Tools replaced.
- Status of retired tools.
- Photographs or inspection reports.
- Relationship between wear and actual geology.
- Impact on deadlines and production.
This traceability helps justify maintenance decisions, adjust parameters, and improve forecasting for subsequent phases.
Risks of Not Monitoring Wear and Tear
Wear that is not detected in time can lead to:
- Loss of performance.
- Increased torque and thrust.
- Alignment deviations.
- Vibrations.
- Damage to the cutting head.
- Blockages.
- Over-excavation or irregular excavation.
- Higher energy consumption.
- Unplanned stops.
- Complex procedures.
- Cost overruns.
- Delays.
- Risks at intersections beneath sensitive infrastructure.
In construction projects beneath roads, railways, waterways, existing utilities, or in urban areas, settlement must be managed before it affects the control of the excavation face, the alignment, or the stability of the ground.
Information Needed to Review the Project
To evaluate the wear control of discs, picks, and tools, the following information should be provided: geotechnical profile, rock strength, abrasiveness, quartz content, particle size distribution, presence of boulders or blocks, mixed face, water table, excavation diameter, penetration length, depth, tunnel boring machine type, cutterhead type, planned cutting tools, anti-abrasion protection, available torque, expected thrust, estimated advance rate, extraction system, accessibility for inspection, possibility of intervention, anticipated spare parts, environmental sensitivity, and production requirements.
Request a Technical inspection of tool wear, cutting head, and tunnel boring machine maintenance Before finalizing the geotechnical report, cut configuration, or RFQ documentation.
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