Whether we are densifying granular soils to mitigate liquefaction around a bridge abutment or installing drilled displacement columns to provide bearing capacity for a new distribution center, Condon-Johnson has the engineers, experience and equipment to provide the most cost effective ground improvement solution for your challenging project.
Deep soil mixing (DSM) is the mechanical process of breaking apart the in-situ soils while injecting and mixing a cement grout to create in-situ soil-cement. Deep soil mixing methods are flexible; it can be used to increase strength, control deformation, create low permeability discrete elements, massive blocks, continuous deep cutoffs to supporting embankments, tanks and footings on compressible soils. Moreover, interlocking grids of DSM will mitigate liquefaction and lateral spread while overlapping discrete elements provide excavation bottom seals that can be combined with watertight DSM shoring systems.
Single Axis DSM
Single auger mixing tools construct discrete columns of uniform diameter soil-cement. Column diameters typically range from 3 feet to 6 feet but can be installed from 1 foot to 10 foot in diameter depending on soil conditions or specific project requirements. Fluid grout is injected into the soils at the tip of the mixing auger as it is rotated and advanced/retracted through the vertical soil profile. A paddle type mixing tool shears the in-situ soils to enable mixing and blending with fluid cement grout.
Multiple axis mixing tools utilize two to six overlapping mixing augers to effectively create a DSM panel with each stroke of the mixing head through the soil. The multiple axis method has the advantages of counter-rotating mixing paddles to better shear and mix the soils in-situ as compared to single axis tooling, and increased production when constructing grid patterns or linear work such as cutoff or shoring walls.
Cutter soil mixing (CSM) equipment utilizes two horizontally rotating drums to turn a set of four mixing wheels that are attached to the bottom of a rigid, non-rotating Kelly bar. While injecting grout through the base of the tool, the mill-like action of the CSM wheels thoroughly cut and mix the soil to create a high quality rectangular panel with each application. Condon-Johnson has single axis, multiple axis and CSM soil mixing capabilities, all with the latest in real-time computerized data monitoring and collection, to provide the right application for any given project.
Stone columns are a proven ground improvement technique that utilizes continuous vertical columns of dense interlocking aggregate to yield densification and replacement. Stone columns densify granular soils, reinforce all soils, increase bearing capacity, mitigate liquefaction and reduces both static and seismic settlements.
Aggregate piers are vertical load-bearing elements constructed by tamping/vibrating or otherwise compacting crushed gravel into a preformed vertical hole to create a vertical displacement element of densified gravel. Aggregate piers are a very cost-effective way to deal with shallow, undocumented fills or soft soils below your proposed building footprint.
Drilled displacement columns (DDC) are grouted displacement elements installed to reinforce soft or compressible soils, to densify granular soils, and/or to increase bearing capacity and/or reduce settlement. DDCs produce essentially no drill spoils during installation which can be an advantage in brownfield sites. DDC’s are typically 12 inches to 24 inches in diameter depending on the soil types and loading conditions.
When confronted with soils susceptible to long term consolidation, Rigid Inclusions can collect and transfer applied loads to deeper more competent soil layers and keep loading influences away from adjacent utilities or any other underground structures. As the loads are redirected or removed from the soft ground, limited consolidation, if any, will occur. This can substantially improve the construction schedule, as soft soils often require weeks or months for consolidation settlements to be complete.
Rigid inclusions are frequently used for support of mat foundations, storage tanks, embankments and spread footings. In order to transfer the uniform bearing pressures into the rigid inclusions, a Load Transfer Platform (LTP) is typically designed to bridge between the rigid inclusions. The LTP generally consists of well-compacted 1 to 5 feet granular soil layer and may include 1 to 3 layers of embedded geo-grids.