Tunneling and deep excavation projects often encounter unpredictable ground conditions—ranging from loose soils and fractured rock to pressurized groundwater. In such environments, precise control over grouting is critical to ensure safety, control inflows, and stabilize ground ahead of excavation. TAM grouting—short for Tube-à-Manchette grouting—has emerged as one of the most refined and effective techniques for targeted ground treatment in these high-risk settings. This article explores the methodology, applications, advantages, and limitations of TAM grouting in tunneling and excavation works.
1.What is TAM Grouting?
TAM grouting involves injecting grout through a sleeve pipe system (Tube-à-Manchette), which consists of:
- A steel or PVC pipe perforated at regular intervals (the “manchettes”),
- Rubber sleeves that act as one-way valves over the perforations,
- A double-packer system that isolates each manchette during injection.
This setup allows engineers to inject grout in multiple stages, at specific depths, under controlled pressure—enabling selective soil or rock treatment with minimal disturbance to the surrounding ground.
2.Key Features and Mechanism
- Selective Injection: Grout is delivered only to pre-planned zones, avoiding waste and overpressure.
- Stage-Wise Control: Injection is done sleeve-by-sleeve, allowing precise treatment.
- Repeatability: Multiple grouting cycles can be applied at the same sleeve if needed.
- Low Mobility Grout: Typically uses microfine cement or chemical grout for better penetration into fine soils or microcracks.
3.Applications in Tunneling and Excavation Projects
TAM grouting plays a critical role in a range of underground works, particularly where ground stabilization and seepage control are required ahead of or during excavation:
a) Pre-Excavation Grouting (Pre-Grouting)
Used to strengthen and seal ground before tunnel boring or NATM excavation, especially in:
- Fractured rock zones,
- Loose or mixed-face soils,
- Fault zones with high groundwater inflow.
b) Contact Grouting
Fills voids between the tunnel lining and excavated ground in segmentally lined tunnels.
c) Curtain Grouting
Creates impervious barriers around shafts, station boxes, or deep excavations to block water migration.
d) Underpinning and Retrofitting
Stabilizes existing foundations or adjacent structures during cut-and-cover tunnel or deep excavation work.
4.Advantages of TAM Grouting in Underground Works
| Advantage | Description |
| Precision | Grout is injected at controlled locations and pressures, reducing risk of overbreak or heaving. |
| Efficiency | Reduces grout consumption by targeting only necessary zones. |
| Ground Improvement Without Excavation | Strengthens ground without major surface disruption. |
| Effective Seepage Control | Seals microfractures and pores, creating water-tight barriers. |
| Versatility | Can be used with cementitious or chemical grouts in various soil types. |
5.Typical Grouting Materials
- Microfine cement: For permeation into fine-grained soils and fissured rock.
- Silicate-based chemical grout: For quick-setting, waterproof sealing.
- Acrylate/Acrylamide grouts: Low-viscosity solutions for ultrafine fractures and water cutoff.
Grout mix selection depends on:
- Permeability and void size,
- Strength requirements,
- Set time constraints,
- Environmental safety.
6.Case Example: TAM Grouting in Metro Tunnel Construction
Location: Urban metro station shaft in soft clay with sandy lenses and groundwater at 4 m depth.
Challenge: Prevent water ingress and soil inflow during diaphragm wall construction and shaft excavation.
Solution:
- Installed TAM tubes around the shaft perimeter at 1.5 m spacing.
- Used double-packer system for targeted injection of microfine cement grout.
- Achieved permeability reduction by over 90%, with no measurable water ingress during excavation.
Outcome: Project completed on schedule with no surface settlement or impact to adjacent buildings.
Limitations and Considerations
| Limitation | Mitigation |
| Requires Skilled Operation | Careful control of pressure, volume, and sleeve identification is essential. |
| Limited Reach from Single Borehole | Multiple grout holes may be needed to cover large areas. |
| Monitoring and Verification | Must use piezometers or permeability testing to confirm effectiveness. |
| Higher Initial Setup Time | Pre-installation of sleeve pipes takes more time than traditional grouting. |
Despite these limitations, the benefits in control and performance far outweigh the challenges in complex ground conditions.
Conclusion
In the high-stakes environment of tunneling and deep excavation, TAM grouting offers unmatched precision and adaptability. Its ability to deliver grout exactly where needed—at controlled pressures and volumes—makes it an indispensable technique for pre-excavation ground treatment, water control, and stabilization. Whether in fractured rock or saturated granular soils, TAM grouting ensures that underground construction progresses safely, efficiently, and with minimal risk to adjacent structures or utilities.
As underground infrastructure continues to expand beneath crowded cities, TAM grouting will remain a vital tool in the geotechnical engineer’s arsenal—bringing precision under pressure to the most demanding projects.
