Grout injection of masonry, scientific approach and modeling

Abstract

The results of the experiments programme provided an enhanced physical understanding of the injection process. Most important achievements are the findings with regard to the injectability of the masonry and the rheological properties of the grouts: stability, viscosity and shear strength. New tests have been developed or existing tests have been adapted to the peculiarities of grounting. The originality and the main point of this work lie in the finite element model that simulates the flow of the grout through the masonry. The masonry is simulated by a pattern of nodes. A network of discrete flow channels connects these nodes representing the big channels through which starting from the injection hole, the grout penetrates the masonry. The penetration of the grout into the areas with finer voids is built in by means of capacitive elements that are connected to the nodes. The water absorption is incorporated in the model, not by altering the rheological properties of the grout, but by narrowing the flow channelgradually. The model enables to study the penetration of the grout in function of the time. Examples demonstrate how the model can be used for analyzing the effect of the viscosity or the other rheological properties of the grout on the progress of the grout in the masonry. Similarly, the influence of process parameters, i.e. the injection pressure, is analyzed. Even the effect of the sealing of a leakage is demonstrated by using the model. It is shown that the model is a useful design tool to determine the injection parameters: grout composition; viscosity, shear stress and hardening evolution injection holes pattern and the injection pressure.