Axial loading of jet grouting columns

Jet grouting provides convenient solutions for improving the bearing capacity and reducing settlements of new or pre-existing foundations. Among all the different possible layouts, regularly spaced arrays of isolated columns are often adopted to create reinforcement systems similar in principle to piled foundations. While for these latter a significant knowledge has been cumulated on the effects of the installation procedures and a variety of empirical and theoretical methods has been proposed to formulate load settlement analyses, solutions for jet grouting columns are still limited basically due to the lack of direct experimental investigations. The objective of the present paper is to analyse by means of combined experimental investigations and numerical simulations the load settlement response of axially loaded jet grouting columns with the aim of defining a theoretical methodology for the design of jet grouting reinforced foundations. The results of a well documented experimental campaign including full scale axial loading and pull-out tests on different jet grouting columns are first presented together with preliminary investigations. Interpretation of the load settlement response is then performed by a back analysis with a finite element code. The adopted model allows interpretation of the interaction between columns and surrounding soil and a back analysis of the load transfer mechanisms taking place along the shaft and the base of columns. This analysis has been conducted by focusing on the role of the characteristics of jet grouting columns.