Madrid's Prado Museum is the largest art gallery in the World, but only a tenth of its immense collection of works are normally on show at any one time in the museum's two buildings: the Villanueva and the Casón del Buen Retiro.
But that will soon change. Celebrated architect Rafael Moneo's plan to extend the museum is nearing completion. Most of the work is below ground, it involves joining the existing neo-classical building with two nearby historical buildings, the cloister of the San Jerónimo church and a 17th-century palace, by buried passageways, and construction of a 400-seat underground auditorium.
The most geotechnically demanding component of the project has been how to create a 20m deep, 46m by 20m hole right beside these historic buildings and adjacent roads.
Main contractor ACS controlled the ground movements by the novel use of 34 integrated hydraulic jacks that in effect reacted and pushed back the retained walls as they started to move.
Dutch hydraulics lifting expert Enerpac Hydraulic Technology developed and supplied the 700 bar hydraulic system, which is believed to be the largest active propping system ever devised.