Introduction
Excessive and differential settlement is a common problem in foundations constructed over loose or granular soils, especially in urban and groundwater-rich environments. Permeation grouting has been successfully used in many projects to control settlement by injecting low-viscosity grout into soil pores without disturbing the existing soil structure. This article presents representative case-study-based insights demonstrating the effectiveness of permeation grouting for settlement control.
Case Study 1: Settlement Control beneath an Existing Building
Project Background
A multi-storey residential building constructed on sandy soil experienced differential settlement due to groundwater level fluctuations and loose subsoil conditions.
Problem Identified
- Uneven settlement cracks in walls
- Reduction in bearing capacity
- Constraints on excavation due to existing structure
Grouting Solution
- Permeation grouting using microfine cement
- Grout injected through closely spaced boreholes
- Injection pressure maintained below fracture pressure
Performance Outcome
- Significant reduction in further settlement
- Improved soil stiffness and load distribution
- No damage to the existing structure during grouting
Case Study 2: Foundation Stabilization for Historical Structure
Project Background
A heritage building founded on loose sand deposits showed progressive settlement over time.
Challenges
- Strict limitation on vibration and disturbance
- Need for reversible and non-invasive solution
Grouting Solution
- Chemical permeation grout with very low viscosity
- Stage-wise injection and continuous monitoring
- Settlement markers installed for real-time assessment
Performance Outcome
- Arrested settlement immediately after grouting
- Improved foundation performance without alteration of soil fabric
- Preservation of historical integrity
Case Study 3: Settlement Control in Metro Tunnel Construction
Project Background
During metro tunnel excavation in alluvial soils, nearby buildings exhibited early signs of settlement.
Ground Conditions
- Loose to medium dense sands
- High groundwater table
Grouting Solution
- Pre-excavation permeation grouting around tunnel alignment
- Creation of treated soil zone to increase stiffness
- Grouting performed in multiple stages
Performance Outcome
- Settlement values reduced to within permissible limits
- Improved tunnel face stability
- Reduced groundwater inflow
Case Study 4: Industrial Facility Foundation Rehabilitation
Project Background
An industrial plant experienced settlement due to increased loading after expansion.
Constraints
- Continuous plant operation
- Limited access for heavy equipment
Grouting Solution
- Targeted permeation grouting beneath loaded foundations
- Optimized grout mix for deep penetration
- Real-time pressure and volume monitoring
Performance Outcome
- Enhanced bearing capacity
- Stabilized foundation performance
- Avoided costly shutdown and reconstruction
Monitoring and Verification Methods Used
Across all cases, performance was verified using:
- Settlement markers and precise levelling
- Pre- and post-grouting SPT/CPT tests
- Injection pressure–volume records
- Long-term settlement trend analysis
Key Lessons Learned from Case Studies
| Aspect | Observation |
| Soil suitability | Best performance in granular soils |
| Grout selection | Microfine and chemical grouts most effective |
| Pressure control | Essential to avoid soil disturbance |
| Staged grouting | Improves uniformity and effectiveness |
| Monitoring | Critical for safe execution |
Advantages Demonstrated by Case Studies
- Non-invasive settlement control
- Immediate improvement in soil stiffness
- Minimal disturbance to existing structures
- Long-term stability and durability
Limitations Observed
- Reduced effectiveness in clayey soils
- Higher cost for chemical grouts
- Need for strict quality control
Conclusion
Case studies clearly demonstrate that permeation grouting is a reliable and effective solution for settlement control in foundations founded on granular soils. When properly designed, executed, and monitored, permeation grouting successfully arrests settlement, improves soil stiffness, and extends the service life of existing structures. Its non-disruptive nature makes it especially suitable for urban and rehabilitation projects.
