ABSTRACT
Underexcavation was executed with the aid of a complex preventive bracing system for the purpose of controlling any unexpected deformations and to prevent any structural damages. This system operated during the full process to adjust it to the gradual changes induced. The technique involves lowering of the high parts with respect to the low points through the slow and controlled extraction of the soil that underlies the foundation. Soil extraction was carried out from the bottom of the shafts, in the soft clay at the contact with the upper clay formation. In the first target the basic idea was to close the cracks and gaps that affected the Cathedral and the Sagrario Church. The second proposal postulated that the Cathedral should undergo a rigid body rotation towards the north-east as well as the western portion of the Sagrario Church, whereas its east side would rotate towards the north. Pumping was maintained throughout the soil extraction process.
