Influence of Limited Soil Improvement on Lateral Pile Stiffness

A series of p-y and elastic 3-D finite element analyses have been performed to investigate the influence of limited soil improvement on lateral pile stiffness at soft soil sites. The purpose of the analyses is to provide guidance on the depth and lateral extent of soil improvement and improved soil properties required to significantly increase lateral pile stiffness. Modeled soil improvement methods consisted of treating the soft clay with cement and removal and replacement with dense cohesionless fill. Analyses with cement treated clay show lateral pile stiffness increased 2 times with a treated soil modulus 5 times greater than the soft soil and a depth and lateral extent of improvement of 2 and 5 pile diameters, respectively. Analyses with the dense cohesionless fill indicate an increase of lateral pile stiffness of at least 2 times requires a depth and lateral extent of soil improvement of 5 and 10 pile diameters, respectively. Limited soil improvement appears to be an economically viable option for improving foundation performance.