ABSTRACT
In looking at the Cathedral’s long-term behaviour within the context of its continued exposure to regional subsidence, it was convenient to analyze other solutions to eliminate or at least mitigate its consequences. Differential settlements appeared early on and were first noticed in 1906, when its foundation slab was being constructed. Theoretical and experimental research began in 1997 to study the effect of mortar grouts injected into soft clays in order to selectively reduce their compressibility. Introducing grouts into the subsoil was questioned because many engineers doubted its efficacy. Experience gained from mortar injections at the Palace of Fine Arts was considered, and an investigation was made into the expected volume and characteristics of the grout. Field tests were made sequentially to profit from the knowledge that was progressively acquired; at the beginning, the test results were poor, but they improved with time until they became reliable.
