Compensation grouting, also know as fracture grouting, is the injection of a cement slurry grout, hydrofracturing soil, creating lenses. The lenses compact surrounding soil and then lift the overlying soil and structures.

Compensation fracture grouting technique illustration

Common uses

Relevel structures
Stabilize and mitigate settlement of overlying structures during tunneling

Process

Fracture grouting, also known as compensation grouting, hydrofractures in situ soil using cement slurry grout. A sleeve port pipe is grouted into a pre-drilled hole beneath a structure. The grout is injected under pressure at strategic locations through the ports in the pipe. 

Once the hydrofracture pressure of the soil is exceeded, fractures open in the soil and are immediately expanded by the influx of grout. This process results in controlled heave of the overlying soils and structures.

Advantages

Unobtrusive, as it can be done from shafts or tunnels without access to affected buildings
Precise control and reporting when linked to an effective monitoring system

Quality assurance

Keller can provide complete solutions which combine fracture grouting with real-time monitoring of affected structures.

Extensive experience has allowed us to develop advanced drilling and computerized grouting systems that integrate the grouting injection process and real time monitoring. Grout injection data is plotted against time and summarized in three dimensional plots and reports.