ABSTRACT
In 1962, the Italian engineer Fernando Terracina proposed a technique called underexcavation to straighten the leaning Tower of Pisa. His objective could not be fulfilled, but some years later his proposal was applied to several buildings in Mexico City. Other deep underpinning techniques were analyzed, such as the “pali radice”, constituted by inclined small-diameter micro-piles that, when intertwined, create stiff blocks to transmit the loads to the deeper strata. This solution also required reinforcement of the existing foundation to enable it to support the micro-piles. All remedial works for deep underpinning projects based on piles, drilled shaft foundations or “pali radice” have as an added shortcoming that their complex construction procedure would imply closing of the Cathedral during many months, an unwanted situation for the religious authorities. The piers would be capable of supporting all the weight of the Cathedral and the negative skin friction generated when the soil settles due to the regional subsidence.
