Abstract:
Grouting is a technique used to improve the engineering properties of soils and rocks. Grouting techniques
are classified under different criteria: injection method used, type of grout material injected, typical
application, and the sequence of construction. The best-known criterion is the mode of entrance or admission
of grout into the soil or rock. It is possible to identify therefore several grouting techniques: compaction,
fracture, jet/mixing and permeation. The function of penetration grouting is to reduce the permeability of
the soil or rock and/or increase the strength and density. In order to avoid displacement, permeation grouting
shall be carried out at carefully controlled pressures and flow rates, using appropriate grouts. Colloidal silica
is an innovative binder which has low viscosity (about 5 m·Pas), it is not toxic (~pH=9) and it is workable
between +5°C and +45°C. This paper presents several case histories: a consolidation job related to the
installation of a new sewer in North Italy in cohesionless soils, water stopping injection in a weathered
granitic bedrock in California, permeation works in the US in sandy soils to improve excavation and the
installation of sheet piles in the UAE. Results show that the colloidal silica an innovative and robust
technology to perform grouting in very fine soils where conventional binders or micro-fine cements cannot
penetrate.