Introduction
Consolidation grouting, also known as compaction grouting, is a widely used ground improvement technique in geotechnical engineering. It involves the injection of stiff, low-mobility grout into soils or fractured rock to densify, strengthen, and stabilize the ground. This method is particularly effective in addressing problems such as settlement, voids, seepage, and inadequate bearing capacity in urban and infrastructure projects. The following case studies illustrate practical applications of consolidation grouting and highlight its performance in different scenarios.
Case Study 1: Metro Tunnel Settlement Control
During the construction of a metro tunnel beneath a congested urban street, consolidation grouting was carried out to protect nearby masonry buildings from excessive settlement. Grout bulbs were created beneath foundations to densify loose sands and fill small voids. Monitoring confirmed that settlement remained within safe limits, ensuring the safety of overlying structures.
Case Study 2: Underpinning of a Historic Building
A century-old masonry structure exhibited progressive settlement due to loose fill beneath its shallow foundations. Consolidation grouting was applied in small, carefully controlled stages beneath the footings. This stabilized the ground without disturbing the building, successfully halting differential movement while preserving the historic structure.
Case Study 3: Bridge Abutment Strengthening
A highway bridge abutment founded on collapsible fills suffered settlement and loss of bearing capacity after flooding. Consolidation grouting beneath and around the abutment densified the fill, restored capacity, and improved stability against future flooding. Post-treatment load tests confirmed significant improvement in performance.
Case Study 4: Roadway Sinkhole Remediation
A sudden sinkhole formed beneath a busy urban roadway due to underlying karst cavities. Emergency consolidation grouting was used to fill voids and stabilize overburden soils. The rapid intervention restored traffic safety and prevented further subsidence, although grout consumption was high due to unpredictable cavity geometry.
Case Study 5: Dam Foundation Seepage Reduction
Excessive seepage through fractured rock at the base of an earthfill dam raised concerns about long-term stability. Consolidation grouting was applied to seal large fractures, combined with localized permeation grouting for finer fissures. This dual approach reduced seepage and improved foundation integrity, as confirmed by post-grout permeability testing.
Case Study 6: Airport Runway Stabilization
Localized settlement occurred on an airport runway constructed over old utility trenches. Consolidation grouting was executed through small-diameter holes to densify the subgrade. Non-destructive testing after treatment confirmed restored stiffness, and the runway was reopened with minimal disruption to operations.
Conclusion
These case studies demonstrate the versatility and effectiveness of consolidation grouting in addressing ground-related challenges in urban and infrastructure projects. Whether used for settlement control, underpinning, seepage reduction, or void stabilization, consolidation grouting provides a reliable solution when applied with careful design, pressure control, and monitoring. Its integration into complex projects continues to play a vital role in ensuring safety, durability, and performance of critical structures.
