The boundary between deep foundations and ground improvement

Deep foundations by implementation of piles have been the historical and conventional solution for supporting heavy loads in low-strength or highly compressible soils. During recent decades, however, ground improvement has successfully been able to provide competitive and economical technical foundation solutions by increasing the ground's mechanical properties, thereby increasing bearing capacity and reducing total, differential and creep settlements. Controlled modulus columns are formed by installing cementitious columnar rigid inclusions into soft ground, and can be considered as the boundary between the classical deep foundations and ground improvement technologies. These elements have a pile-like appearance, but are designed as ground improvement inclusions. This paper discusses the concept of the controlled modulus column, its design philosophy and the way it behaves; a case study of the world record for depth of a controlled modulus column installation is also presented to demonstrate its application.