Optimizing Foundations Based on CSM Panels Using Rapid Load Tests

This paper describes the foundation for apartment buildings at Cosun Park in Breda. This ambitious urban development project transforms a former office site (the former headquarters of the Suikerunie) into a residential area with six residential buildings and provides the possibility of underground parking. Since a Cutter Soil Mixing (CSM) rig would already be present for constructing the required retaining walls at the site, it was decided also to use CSM walls as the foundation for the buildings. However, the current codes limit the maximum loads on CSM panels, which would require many panels under each pile cap.  Moreover, the current calculation methods appear to overpredict settlements under working loads, thereby exceeding acceptable values. To address this, the load-bearing capacity of the CSM panels was tested in advance. Rapid Load Tests were conducted according to the Dutch code for pile testing, NPR 7201, to prove the capacity and stiffness of the CSM panels. The CSM panels showed minimal pile head displacement at a load of 9 MN. This demonstrated that the CSM barrettes could be assigned a higher load-bearing capacity than initially determined by the standards. Consequently, this led to a significant optimisation, reducing the number and size of CSM panels. These findings raise the question of whether the current method of calculating the pile resistance for these CSM panels is appropriate and whether the assigned pile design factors from the codes are correct for design for this type of foundation element. Further research is needed to obtain more economical foundation designs using CSM panels.