Introduction
Settlement of foundations and ground surfaces is a major concern in urban construction, especially where soils are loose, compressible, or groundwater conditions are unfavorable. Tube-à-Manchette (TAM) grouting is a controlled ground improvement technique that can effectively reduce settlement and improve soil stiffness. This article presents selected case studies from real urban projects where TAM grouting was used to mitigate settlement issues.
Case Study 1 — High-Rise Foundation Under Vertical Expansion
Project Summary
- Location: Metropolitan city center
- Structure: Existing commercial building undergoing vertical expansion
- Soil Conditions: Loose to medium dense sand with high groundwater
- Problem: Differential settlement risk under increased loading
TAM Grouting Solution
- Target: Increase stiffness and reduce compressibility beneath foundation footprint
- Grout Type: Microfine cement
- Injection Pattern: Close spacing grid beneath footings
- Pressure Control: Low pressure to prevent heave
Results
- Surface settlement reduced by ~60% compared to untreated prediction
- Differential settlement controlled within allowable limits
- No adverse heave or lateral movement observed
Lessons Learned
✔ Pre-grouting soil investigation enhanced design reliability
✔ Close monitoring allowed optimization of grout volumes
Case Study 2 — Metro Station Excavation in Loose Silts
Project Summary
- Location: Urban transit corridor
- Scope: Deep excavation for underground station
- Soil Conditions: Loose silt and fine sand with perched water table
- Problem: Predicted settlement threatening adjacent utilities
TAM Grouting Strategy
- Grouting performed ahead of excavation in treatment curtain
- Multi-stage grouting to ensure permeability reduction
- Grout pressures controlled to avoid ground heave
Outcome
- Measured settlement behind support reduced by ~75%
- Groundwater inflow also controlled
- Adjacent utility lines remained undisturbed
Key Notes
✔ Staged grouting synchronized with excavation reduced risk
✔ Post-grouting field tests confirmed improvement
Case Study 3 — Underpinning of a Heritage Structure
Project Summary
- Location: Historic city square
- Situation: Nearby deep basement construction caused concern
- Soils: Soft clays with interbedded silts
- Problem: Predicted settlement and cracking in heritage structure
TAM Grouting Application
- Grout injected beneath heritage structure foundation
- Advanced monitoring installed (inclinometers, settlement points)
- Grout type: Low-viscosity blend for permeation and compaction
Results
- Settlement reduced to imperceptible levels
- Monitoring confirmed absence of new cracks
- Works proceeded without structural damage
Lessons Learned
✔ TAM grouting can be a non-intrusive settlement control measure
✔ Combining grouting with instrumentation enhances safety
Case Study 4 — Industrial Facility Floor Improvement
Project Summary
- Location: Urban warehouse and logistics hub
- Issue: Excessive floorslab settlement under heavy loads
- Soils: Loose granular fill and soft alluvial soils
Approach
- Grid pattern TAM grouting beneath slabs
- Grout mixture designed for both permeation and compaction
- Refusal and grout take used as quality control
Outcome
- Post-grouting load tests showed stiffness improvement
- Long-term monitoring showed negligible settlement
- Floor performance improved for heavy equipment loads
Key Insight
✔ TAM grouting can retrofit problematic soils beneath existing slabs
Common Implementation and Monitoring Strategies
| Aspect | Best Practice |
| Grout Selection | Microfine cement or tailored mixes for granular soils |
| Pressure Control | Start low and increase gradually; avoid hydraulic fracturing |
| Pattern Design | Close spacing and overlapping bulbs in compressible soils |
| Instrumentation | Settlement markers, piezometers, strain gauges |
| Adaptive Grouting | Adjust based on grout take and soil response |
Observed Benefits Across Case Studies
- Substantial reduction in total and differential settlement
- Enhanced soil stiffness and bearing capacity
- Controlled groundwater inflow
- Minimal disruption to surrounding structures
- Smooth construction sequencing in urban settings
Challenges and Mitigation
| Challenge | Mitigation |
| Grout loss in high permeability zones | Use low-viscosity grouts; pre-grouting |
| Surface heave risk | Careful pressure control and staging |
| Soil variability | Detailed investigation and adaptive strategy |
| Access constraints | Compact drilling and modular rigs |
Conclusion
TAM grouting has proven to be an effective settlement control technique in urban construction when carefully designed and executed. By improving soil stiffness and reducing compressibility, TAM grouting enabled safer foundation performance, minimized settlement risks, and protected adjacent structures. Real-world applications have shown that pressure control, grout selection, monitoring, and adaptive sequencing are key to successful implementation.
