Abstract:
The paper will describe the function of jet grout bodies in terms of both groundwater and movement control. It will show that the inter-relation of jet grout diameter, diameter variability, spacing and drill hole deviation is critical to ensure a successful solution. The paper will introduce statistical methods of analysis to determine the risk of gaps between columns and retaining structures are minimised or avoided. The paper will show a method of analysis that examines a jet grout plug and cut-off for gaps and determines how many gaps exist and of what size. In addition to theoretical column layouts, the paper will introduce practical examples of how the jet grout plug and cut-off can be constructed to minimise gaps. These practical methods include changing jetting energies, the level of jet grouting to enhance overlaps and examination of spoil densities to determine the degree of closure. Finally the paper will discuss the relationship between the design or characteristic jet grout strength and the required achieved field strength which is often not specified correctly. Keywords: Jet Grouting, Cut-Off Design, generic design guidelines, probability analysis