Statistical Interpretation of Jet Grouting Field Data Regarding Its Strength and Stiffness

Jet-grouting technique is one of the most widespread methods for soil reinforcement, used to make soil suitable to withstand forces transmitted by structures or the redistribution of stresses following excavations. The result of the treatment however is influenced by several factors, including type of treatment, type of soil, original stress state of the soil, machine operating parameters, and water-to-cement ratio. In particular, the strength of the treated material and its stiffness are very useful for designing the intervention for a specific case. Due to the uncertainty of the final strength and stiffness values, a test field is almost always required. But the design of the test field itself and the subsequent design of the intervention require some preliminary information on the expected values of the strength and the elastic modulus. An in-depth analysis of the scientific and technical literature was conducted, allowing for the selection of a significant number of cases. For each case, the type of treatment, the type of soil, uniaxial compressive strength (UCS), and elastic modulus (E) values were recorded. It was possible to determine the trend of the average UCS values and the E/UCS ratio for each type of analyzed soil and for the two studied jet-grouting techniques. In addition to the average values, the variability intervals, centered on the mean, capable of enclosing 90% of the data in the sample were identified. The obtained graphs represent a useful tool for obtaining a preliminary estimate of the strength and stiffness of the treated soil using the jet-grouting technique.