Preventing groundwater intrusion into sheet-piled excavations using jet grouting - A literature review and a case study comparing semi-theoretical prediction models for column diameters

Abstract

When carrying out deep excavation projects, a common concern is inflow of groundwater. One possible solution to seal excavations is to use jet grouting technology. The practice entails an initial drilling to a pre-determined depth, followed by an injection of a cementing agent by a high-velocity jet. This stream erodes and remolds the immediate soil matrix, creating a column with improved characteristics. By merging columns into one another, a water barrier can be formed. The overall purpose of this master’s thesis was to gain an in-depth knowledge about jet grouting. This by writing a comprehensive guide about the technology, focusing on the application of sealing the toe of a sheet pile wall driven to sloping bedrock. To achieve this, a literature review was conducted followed by an analysis of three semi-theoretical prediction models and one commercial prototype model to estimate jet grouted column diameters. These models were thereafter verified through a case study of a current Swedish infrastructure project. The main finding from this thesis was that the models generally overestimate the columns’ diameter, which indicates a risk of groundwater inflows if used when determining the operational parameters. Two of the models can however be considered as adequate since they predicted the diameter mainly within the suggested error margin. This thesis also found that excavation of test columns and the so-called “painted bars” test are two suitable verification methods of column diameters. Furthermore, observations made during the trial have been described of which may be of assistance when planning future test programs.