Mathematical Model for Bore-Injected Cement Grout Installations

Abstract

There are many geotechnical engineering support systems (for example, bore-injected minipiles, grouted anchors, grout in the void around a tunnel liner) where it is advantageous to inject a cement grout under pressure. A mathematical model is developed in this paper for the physical process that occurs as the grout consolidates (similar to a clay soil) under the applied pressure and expels its excess water into the surrounding soil under conditions of impeded drainage. The model is then used to calculate such parameters as the average degree of consolidation of the grout as a function of time prior to set and the change in the borehole radius. A series of specially designed experiments for a variety of conditions provide data that compare favorably with the theoretical predictions and thus lend credibility to the usefulness of the mathematical model for characterizing the physical situation that occurs during such operations in the field.