The Groutability of Sands—Results from One-Dimensional and Spherical Tests

In addition to the application of empirical injection criteria also one-dimensional injection tests have become a suitable technique for the evaluation of the groutability of sands. Both procedures have been applied to the injection of microfine cement suspensions for the sealing of construction pits in Berlin, Germany. The mostly unsatisfying results clearly indicate the limitations of the above mentioned evaluation practice. Starting from this background an extensive investigation program has been carried out at the Geotechical Institute at the Technical University of Berlin, Germany. Different combinations of sand and microfine cement grout have been used in one-dimensional and spherical injections, accompanied by rheological and grain-size analyses. This paper focuses on the filtration effects which represent the main difference between the penetration of chemical grouts and that of suspensions of microfine cements. The deposition of particles within the soil skeleton leads to a dynamic reduction of the hydraulically effective pore-space and to a change in the rheological properties. Although basically known, these effects are not considered in the formulation of injection criteria.