Displacement piles are installed without excavation or removal of material from the ground. They are driven into the ground using impact, vibration, pressing, screwing or a combination of these methods.
CMM® Hybrid Columns (Colonnes à Module Mixte) is a soil reinforcement technique that combines a rigid inclusion at the bottom and a vibro replacement column at the top last meter(s). This method, developed by Keller, is the successful development of several years of research and tests.
Benefits of the technique
CMM® Hybrid Columns combine the benefits of each method and avoid their disadvantages. For instance, in the case of soil improvement by rigid inclusions we often have to adapt the shear strength of the upper part due to horizontal stresses linked to wind or sometimes to seismic loads. The footing resting on several rigid inclusions have to be adapted as well. For foundation slabs on soils improved by rigid inclusions, obtaining compatible bending moments often implies either the use of a very thick granular distribution layer, or the implementation of two steel reinforcement layers in the slab.
CSC® Rigid Inclusions – Controlled stiffness column or rigid inclusion is the name for a soil improvement method offered by Keller. The procedure is described in the European standard EN 12699.
Rigid inclusions increase the bearing capacity of the soil and reduce its compressibility. With rigid inclusions the advantages of piles and shallow foundations are economically combined.
This soil improvement method can be applied in all construction sectors (houses, industrial and commercial buildings, embankments for highways and rail, harbour structures). This method is most suitable for compressible soils. Based on the initial compressibility of the soil the distance between the rigid inclusion reinforcement elements is adapted depending on the allowable settlement of the structure.