Drilling & Grouting

Grouting, as applied to civil and geotechnical construction, involves the injection under pressure of a liquid or suspension into the voids of a soil or rock mass or into voids between the soil or rock mass and an existing structure. The injected grout must eventually form either a solid or gel within the injected voids. The purpose of pressure grouting a soil or rock mass is to improve the strength and durability of the grouted mass and/or to reduce its permeability.

Grouting applications relating to permeability reduction include: Reduction of hydrostatic forces acting on the base of water retention structures or tunnel linings Reduction of reservoir water loss, Reduction of erosion of foundations and embankments, Excavation shoring by stabilization, consolidation, and water control Improvement of Mechanical Properties Grouting applications relating to mechanical property improvement include: Enhancement of bearing capacity Consolidation of an overburden of either soil or fractured rocks to facilitate an underground excavation. Void filling either at the surface or subsurface Stabilization and lifting (jacking).

Types Of Grouting

Pressure / Consolidation

Pressure grouting in a soil or rock mass is used to improve the strength and durability of the grouted mass. In cases where rock strata have developed fractures, voids, holes or even caves, grouting can be used to fill in the void spaces and increase the strength of the foundation or rock while also decreasing groundwater flow. This process is used in mine subsidence, sinkholes, diaphram walls, grout curtains, dam seepage remediation and many other applications.

Curtain & Permeation

This technique consists of direct pressue injection of a fluid of liquefied materials into a problem area. This is accomplished by drilling a hole in the soil, inserting an injection pipe into the ground, and then pumping fluid grout to fill the spaces between the soil particles. Injection methods are tailored specifically to a project – how the hole is drilled, what type of injection pipe is used, and what material is used are all determined by the specifics of the repair being performed.

Compaction

Low mobility grouting is a displacement method of improving the bearing capacity of soil. where low strength, low capacity or unstable soil does not have the required bearing capacity for a specified load, a high density, very low slump grout is injected into the soil. The grout is injected at designed depths and locations in a grid pattern at high pressure. As a result, the viscous grout forms into a bulb or column at the desired depth, displacing the soil, densifying or “compacting” it, resulting in improved bearing capacity. Compaction grouting is a proven method of foundation grouting with a long history of successfully completed projects. With the correct soil conditions, it is an advantageous technique for new construction and as a means of correcting soil failure under an existing structure where unacceptable settlement is occurring or has occurred.

Chemical

Chemical Grouting – What is it and how is it used? Chemicals are mixed with water and reagents, such as sodium silicates, or various urethanes for permeation into dense granular soils for excavation shoring or to increase bearing capacity and strength. Sodium Silicate is most commonly used for strength. In essence, the material is a soluble glass that begins to harden as the pH of surrounding material decreases below about 10.5. As an alternative, another additive can be included to drop the pH. Although, care must be given to site-specific conditions, a typical mix design for chemical grouting would look like the following: Chemical grouting is also used for water control. In this case, a polymer or polyurethane may be used.