Prediction of jet grouting efficiency and columns average diameter

Even though jet grouting technology has noticeably progressed since the first applications, and treatment efficiency has accordingly improved, there is still a great level of uncertainty on the results of treatment, in terms of both column diameter and mechanical properties of cemented material. This paper focuses on the estimate of the average diameter, which is by far the most important geometrical parameter of jet grouted columns at the design stage: it is fundamental for overlapping of adjacent columns in linear barriers and massive treatments, but plays a still important role in reinforcements made with isolated columns. In principle, the diameter of a column is strongly dependent on the characteristics of the injected fluids and on the physical and mechanical properties of soils, being the result of a very complex interaction between these two elements. Comprehensive analyses of these mechanisms have been rarely attempted, but several studies can be found in the literature trying to establish relations, on empirical or sound theoretical basis, between diameters and injection parameters or soil properties. In the attempt to establish more rational and complete design correlations, in the paper the evidence gained from a large number of experimental data collected in time by the authors have been compared with the simulations provided by a theoretical model of the formation of jet grouting column, for the case of single fluid jet grouting. The analyses and observations reported in the paper represent a preliminary step towards the production of reliable charts for the design of jet grouting treatments.