CMC Columns

Description

Specially designed displacement auger, powered by equipment with large torque capacity and high static down thrust displaces the soil laterally. After displacing the soil beyond the extent of the column, cement mixture is injected under pressure. The amount of the grout is selected so that to achieve the design stiffness ratio of the column with relation to the surrounding soil. The result is a composite of soil-CMC acting as a homogeneous structure with enhanced bearing capacity. The column construction process does not cause any damage to the surface and any unsafe vibration impacting the surrounding environment. Efficiency of the work reaches up to several hundred meters of columns per shift. During the drilling process the column construction parameters are monitored and recorded providing continuous soil condition control at a certain spot. Under uniformly loaded structures such as road embankments or foundation slabs, a load transfer platform is designed which evenly transfers stresses from the structure to the column heads at the same time minimizing the forces causing the cut-through. This load transfer platform is made of well compacted granular material depending on the type of the structure and the soil conditions.

Application

CMC technology can be applied in almost any types of soil. The technology works well in loose sands, soft loams, organic soils (peat, muds, gyttjas) with a moisture content above 100% and anthropogenic soils (uncompacted fills, heaps).
The length of the CMCs depends on the planned load values and maximum allowable subsidence values, which translate into the length of the anchoring depth in load bearing soils. All types of enclosed buildings, infrastructure and special structures are well suited for the CMC technology, which is an alternative to deep foundation, shallow foundation on the subsoil improved with the CMCs. Depending on the load per column, the following parameters are chosen:

  • the diameter, ranging from 0.25 to 0.60 m;
  • spacing, usually ranging from 1.2 to 2.5 m, using rectangular or triangular columns grid.

 

Advantages

  • High bearing capacity – bearing capacities (up to 40%) higher than in case of piles of the same diameter.
  • High performance – the CMC technology is a highly effective method reaching even several hundred of linear meters of the installed column per day (with the use of a single drilling machine unit).
  • No spoil – in the course of the column formation the surface soil structure is undamaged and there is no excavated material. As a result there is no need for removal and utilization of large mass of excavated material.
  • Versatile application – can be applied to almost any soil type including compressible, organic and anthropogenic soils.