Introduction
Loose and granular soils such as sands and gravels often exhibit low bearing capacity, high permeability, and susceptibility to settlement. Tube-à-Manchette (TAM) grouting is an effective ground improvement technique used to enhance the mechanical and hydraulic properties of such soils. This article discusses the effectiveness of TAM grouting in improving loose and granular soils, focusing on its mechanisms, benefits, and performance outcomes.
Characteristics of Loose and Granular Soils
Loose granular soils typically show:
- High permeability and rapid groundwater flow
- Low cohesion and limited self-supporting capacity
- Susceptibility to settlement and liquefaction
- Difficulty in uniform improvement using conventional methods
These characteristics make controlled grouting techniques like TAM particularly suitable.
Mechanisms of TAM Grouting in Granular Soils
Permeation Grouting
- Low-viscosity grout penetrates soil pores
- Soil structure remains largely undisturbed
- Cementation increases interparticle bonding
Compaction Effect
- Controlled grout injection densifies loose particles
- Reduces void ratio and compressibility
- Improves stiffness and load-carrying capacity
Void Filling and Cementation
- Grout fills interconnected voids
- Reduces permeability significantly
- Enhances resistance to erosion and piping
Design Considerations for Granular Soils
Grout Selection
- Microfine cement or chemical grouts preferred
- Low viscosity essential for effective permeation
- Controlled setting time to ensure penetration
Injection Parameters
- Low to moderate injection pressures
- Gradual pressure increase to avoid soil disturbance
- Strict pressure limits to prevent hydro-fracturing
Grouting Pattern
- Close spacing to ensure overlapping grout bulbs
- Multiple stages for uniform treatment
- Adjusted based on grout take and soil response
Performance Improvements Observed
| Property | Improvement After TAM Grouting |
| Bearing capacity | Significantly increased |
| Settlement | Substantially reduced |
| Shear strength | Improved due to cementation |
| Permeability | Reduced by several orders |
| Liquefaction resistance | Enhanced |
Monitoring and Quality Control
- Pressure–volume recording during grouting
- Observation of surface heave or settlement
- Post-grouting tests (SPT, CPT, permeability tests)
- Validation of improvement through instrumentation
Advantages of TAM Grouting in Granular Soils
- Precise control of grout placement
- Minimal disturbance to surrounding structures
- Suitable for heterogeneous soil layers
- Effective under existing foundations
Limitations and Challenges
- Ineffective in very fine sands without microfine grout
- Requires experienced operators and monitoring
- Cost may be higher than conventional densification methods
Applications
- Foundation improvement beneath existing structures
- Seepage control for excavations and tunnels
- Liquefaction mitigation in loose sandy soils
- Ground treatment for underground constructions
Conclusion
TAM grouting is highly effective in improving loose and granular soils when properly designed and executed. Through controlled permeation and compaction mechanisms, it significantly enhances soil strength, stiffness, and permeability characteristics. With appropriate grout selection, pressure control, and monitoring, TAM grouting provides a reliable solution for ground improvement in challenging granular soil conditions.
