Introduction
Jet grouting has become a widely adopted ground improvement technique for foundation strengthening and excavation support, especially in urban and geologically complex environments. By forming soil–cement columns or panels, jet grouting enhances soil strength, reduces permeability, and controls deformation. This article presents representative case studies highlighting the effectiveness of jet grouting in real-world foundation and excavation projects.
Case Study 1: Foundation Strengthening beneath an Existing Building
Project Background
A multi-storey heritage building constructed on weak silty soil experienced excessive settlement. Conventional underpinning was not feasible due to restricted access and the need to avoid vibration.
Jet Grouting Solution
- Jet-grouted columns installed beneath existing footings
- Triple-fluid jet grouting system adopted
- Columns overlapped to form a continuous reinforced block
Performance Outcome
- Bearing capacity increased by nearly 3 times
- Post-construction settlement reduced significantly
- No damage observed to the existing structure
Case Study 2: Deep Excavation Support in Urban Area
Project Background
A deep basement excavation (15–18 m depth) was planned in a congested city area with high groundwater levels and nearby buildings.
Jet Grouting Application
- Jet-grouted panels formed a cut-off wall
- Combined excavation support and groundwater control
- Continuous monitoring of ground movement implemented
Performance Outcome
- Groundwater inflow effectively controlled
- Lateral ground movements within allowable limits
- Adjacent structures remained unaffected
Case Study 3: Tunnel Shaft Excavation in Mixed Ground Conditions
Project Background
A vertical access shaft for a metro tunnel had to be constructed through mixed soil layers including sand, clay, and fill.
Jet Grouting Method
- Jet-grouted ring formed around the shaft perimeter
- Double-fluid system used to improve cutting efficiency
- Columns overlapped to ensure continuity
Performance Outcome
- Stable excavation achieved without collapse
- Reduction in water ingress
- Improved safety and construction speed
Case Study 4: Bridge Foundation Improvement in Loose Sandy Soil
Project Background
A bridge foundation located in loose sandy soil with high permeability required ground improvement to prevent excessive settlement and seepage.
Jet Grouting Technique
- Jet-grouted columns installed beneath pile caps
- Single-fluid system adopted
- Strength and permeability targets specified
Performance Outcome
- Significant increase in shear strength
- Hydraulic conductivity reduced to 10⁻⁷ m/s
- Long-term foundation stability ensured
Case Study 5: Excavation Support for Underground Utility Corridor
Project Background
An underground utility corridor excavation passed beneath existing roads and buildings in a dense urban environment.
Jet Grouting Implementation
- Jet-grouted blocks formed as temporary excavation support
- Low-vibration execution minimized disturbance
- Real-time settlement monitoring conducted
Performance Outcome
- Excavation completed safely
- Minimal surface settlement recorded
- No service disruptions reported
Key Observations from Case Studies
- Jet grouting is highly effective in restricted-access urban sites
- Provides simultaneous strength improvement and seepage control
- Performance depends strongly on execution control and monitoring
- Well-suited for complex and heterogeneous ground conditions
Advantages Demonstrated by Case Studies
- Adaptability to varying soil types
- Minimal vibration and noise
- Flexible geometry for foundations and excavations
- Reliable performance when combined with monitoring
Conclusion
Case studies on jet grouting for foundation and excavation support clearly demonstrate its versatility, reliability, and effectiveness in challenging geotechnical environments. When properly designed and executed, jet grouting provides robust ground improvement, ensuring safety, durability, and performance in both temporary and permanent works.
