Introduction
Weak and jointed rock formations present serious challenges in geotechnical engineering due to low strength, high permeability, and unstable block structures. Rock fissure grouting has been widely adopted in such conditions to improve rock mass integrity, reduce seepage, and enhance stability. This article discusses representative case studies highlighting the effectiveness of rock fissure grouting in weak and jointed rock formations across different infrastructure projects.
Case Study 1: Dam Foundation on Jointed Rock
Problem Description
A concrete gravity dam was founded on highly jointed and weathered rock with open fractures and high permeability. Excessive seepage and uplift pressure posed risks to dam stability.
Grouting Solution
- Curtain grouting using microfine cement
- Primary, secondary, and tertiary grouting stages
- Controlled injection pressure based on depth
Performance Results
- Lugeon values reduced by more than 70%
- Significant reduction in uplift pressure
- Improved shear strength of foundation rock
Outcome: Long-term seepage control and enhanced dam safety.
Case Study 2: Tunnel Excavation in Weak Fractured Rock
Problem Description
A transportation tunnel passed through weak, jointed rock with heavy groundwater inflow, causing face instability and overbreak during excavation.
Grouting Solution
- Pre-excavation fissure grouting around tunnel perimeter
- Use of low-viscosity cement and chemical grouts
- Stage-wise grouting with inflatable packers
Performance Results
- Groundwater inflow reduced significantly
- Improved tunnel face stability
- Reduced support pressure on shotcrete and rock bolts
Outcome: Safe and uninterrupted tunnel excavation.
Case Study 3: Rock Slope Stabilization in Jointed Formation
Problem Description
A rock slope consisting of jointed and weathered rock showed signs of block detachment and seepage-induced instability.
Grouting Solution
- Fissure grouting to fill joints and cracks
- Combined with rock bolts and wire mesh
- Low-pressure injection to avoid rock mass disturbance
Performance Results
- Improved cohesion and interlocking between blocks
- Reduced seepage through rock mass
- Enhanced slope stability during monsoon seasons
Outcome: Long-term slope stabilization with minimal maintenance.
Case Study 4: Foundation Improvement for Heavy Structures
Problem Description
An industrial structure was planned on weak, jointed rock with low bearing capacity and uneven settlement risk.
Grouting Solution
- Fissure grouting beneath foundation footprint
- Microfine cement grout for narrow joints
- Monitoring of grout take and pressure
Performance Results
- Increased bearing capacity
- Reduced settlement and differential movement
- Improved load distribution
Outcome: Successful foundation performance under operational loads.
Key Observations from Case Studies
- Rock fissure grouting significantly improves rock mass continuity
- Permeability reduction is more pronounced in interconnected joint systems
- Stage-wise and pressure-controlled grouting ensures effective treatment
- Integration with structural supports enhances overall stability
Challenges Observed
- Uneven grout distribution in highly irregular fractures
- Higher grout consumption in open joint zones
- Requirement of skilled execution and continuous monitoring
Lessons Learned and Best Practices
- Detailed geological mapping is essential
- Selection of grout material must match joint aperture
- Continuous monitoring ensures quality and safety
- Combination with other stabilization measures yields better results
Conclusion
Case studies from dams, tunnels, slopes, and foundations demonstrate that rock fissure grouting is a highly effective technique for stabilizing weak and jointed rock formations. When properly designed and executed, it enhances strength, reduces seepage, and ensures long-term performance of geotechnical structures in challenging rock conditions.
