Services
UNDERPINNING
DFI/CSCE 13th Annual Geotechnical Seminar: Earth Slope Engineering
September 17th, 2010
Dam Safety 2010
September 19th, 2010
The 10th International Workshop on Micropiles
September 22nd, 2010
Ground Modification Underpinning Methods
Ground Freezing
The ground freezing process converts in situ pore water to ice through the circulation of a chilled liquid via a system of small-diameter pipes placed in drilled holes. The ice acts to fuse the soil or rock particles together, creating a frozen mass of significantly improved compressive strength and impermeability.
For temporary structural underpinning, the minimally intrusive pipe installation technique means that foundation soils, and thus the foundations themselves, remain largely undisturbed, a significant advantage for sensitive structures. As well as imparting increased compressive strength, the ground freezing operation can also provide the added benefit of groundwater cut-off where required.
Grouting Systems
In congested urban environments, restricted access and/or low headroom situations, permeation grouting and jet grouting offer viable alternatives to conventional structural underpinning. Additionally, grouting methods of underpinning do not require dewatering of the area as would conventional underpinning pits.
Permeation Grouting is the flow of chemical or particulate grout into the pores of the soil without displacing or changing the soil structure. The characteristics of the ground are modified with the hardening or gelling of the grout. Depending on the requirements of the application, grout materials can be temporary or permanent.
Jet Grouting uses high-pressure, high-velocity jets to hydraulically erode, mix and partially replace the in situ soil or weak rock with cementitious grout slurry to create an engineered soil-cement product of high strength and low permeability. Jet grouting can be performed above or below the water table and in most subsurface stratigraphies, from cohesionless soils to highly plastic clays.