Permeation grouting of granular soils by innovative materials

The injection technique based on cement mixtures had a constant evolution since its first application in 1802 by Bérigny for the rehabilitation of masonry diving. Later it was implemented in France and England in the mid-1800s, but by the twentieth century it has started to spread and to globalize the method for applications related to the ground treatment. Initially it was used for the construction of hydraulic works mainly by injecting unstable cement suspensions, with which they could only deal fissured rocks and were therefore excluded granular soils. Then techniques moved to stable cement mixtures and finally to chemical solutions. These technologies have been widely used in the construction of underground structures for roads, subways, as well as for the construction of underground structures in the proximity of existing buildings, where it is necessary the treatment of the soil in order to obtain an improvement of the mechanical and hydraulic characteristics of themselves. Nowadays, the research and experimentation are oriented towards innovative materials so as to broaden the application fields, in order to increase the penetration, and the achievement of high mechanical strength. This thesis has focused on performing injection tests on various soils with different characteristics. In the tests was set as a target, the study of two new materials such as colloidal nanosilica and microcements, through their characterization, their behavior during permeation in granular soils and consolidation that these materials can get. The application of these mixtures depends on several external parameters which vary from the characteristics of the soil, up to the used techniques of injection; for this reason, even today the fields of application are not well defined. The tests carried out in the laboratory of Tunnel and Underground Space Center of the Politecnico di Torino, since there is no normative references, was based on procedures designed ex novo, or in some cases, on standards for geotechnical methods and to the concretes, depending of appropriate theoretical and practical considerations.