Introduction
Tube-à-Manchette (TAM) grouting, also known as tube-with-sleeve grouting, is a specialized pressure grouting technique widely used for ground improvement, seepage control, and structural strengthening in geotechnical engineering. By injecting grout under controlled pressure through perforated pipes fitted with rubber sleeves (manchettes), TAM grouting allows targeted soil treatment with precision and repeatability.
This article outlines the design principles of TAM grouting, focusing on geotechnical applications, grout selection, pressure control, and quality assurance.
1. Objectives of TAM Grouting in Ground Improvement
- Soil Strengthening: Enhancing bearing capacity of weak soils.
- Permeability Reduction: Creating cut-off barriers against groundwater flow.
- Void Filling: Stabilizing loose soils, fractured rocks, or karstic voids.
- Structural Support: Improving soil-structure interaction for foundations and tunnels.
2. Components of a TAM Grouting System
2.1 TAM Pipes
- Steel or PVC pipes with manchette valves at regular intervals (0.3–0.5 m spacing).
- Installed in boreholes with a primary grout sheath (sleeve grout) to seal around the pipe.
2.2 Grout Types
- Suspension Grouts: Cement-based, used for coarse soils and rocks.
- Solution Grouts: Chemical grouts (sodium silicate, polyurethane) for fine soils.
- Microfine Cements: High penetration for sands and silts.
2.3 Injection Equipment
- Double-packer systems to isolate a single manchette.
- High-pressure pumps with flow and pressure monitoring devices.
3. Design Considerations for TAM Grouting
3.1 Geotechnical Characterization
- Soil type and gradation: Determines groutability (e.g., fine sands vs. silts).
- Permeability: Guides grout viscosity and injection pressure.
- Groundwater conditions: Influences grout setting time and spread.
3.2 Grout Selection
- Low-viscosity chemical grouts for fine soils (D10 < 0.1 mm).
- Microfine cement grouts for sands and silty sands.
- Standard cement grouts for gravels and coarse sands.
3.3 Injection Pressure and Control
- Pressure must be sufficient to displace soil void water without causing hydrofracture.
- Typical design: 0.5–2.0 MPa above in-situ pore pressure.
- Step-wise or stage grouting is used for better control.
3.4 Grouting Sequence
- Carried out in multiple passes (primary, secondary, tertiary) for uniform improvement.
- Re-injection through previously grouted manchettes ensures full coverage.
3.5 Grouting Geometry
- Grout bulbs should overlap to form a continuous treated zone.
- Spacing between TAM pipes depends on soil type and treatment objectives (generally 1.5–2.0 m).
4. Quality Control and Monitoring
4.1 Grouting Parameters
- Continuous recording of injection pressure, flow rate, and volume.
- Comparison with design values to detect anomalies.
4.2 Verification Testing
- Permeability tests (Lugeon, packer) before and after grouting.
- Core sampling to confirm grout penetration.
- Geophysical surveys (e.g., GPR, seismic) for non-invasive verification.
5. Applications of TAM Grouting
- Tunnels and Shafts: Pre-excavation grouting to minimize inflow and stabilize ground.
- Dam Foundations: Cut-off barriers against seepage.
- Building Foundations: Underpinning and ground stabilization in urban projects.
- Karst and Mining Areas: Void filling to prevent collapse.
6. Advantages of TAM Grouting
- Precise control of injection location and volume.
- Ability to re-inject multiple times at the same point.
- Suitable for complex ground conditions and sensitive environments.
- Less disruptive compared to other ground improvement techniques.
Conclusion
The design of TAM grouting systems hinges on soil characterization, grout selection, injection pressure, and execution control. By adopting proper monitoring and verification strategies, engineers can achieve reliable improvements in soil strength and permeability reduction. TAM grouting remains a versatile and highly controllable technique, making it a preferred solution for ground improvement, seepage control, and structural stability in challenging geotechnical projects.
