ABSTRACT
The Spanish Administration has carried out the construction of the Road Variant of Alcalá del Rio, which includes a bridge over the Guadalquivir River with nine isostatic spans, whose geometric definition is described later.
The mentioned structure consists of nine spans equal of 30.00 m. each one, which sums up a total length of 270.00 m. The deck comprises 10.00 m. of pavement plus two sidewalks of 1.00 m., totaling a width of 12.00 m.
The bridge was designed with deep foundation in all its supports, due to the existing soft ground in the zone.
The foundation of the bridge is made by two circular pier-piles of 1.50 m. of diameter for any support of the bridge and 25 m. of length in the case of piers. In the piers, the piles has 2 m. were embedded in gravels and 12 m. (8 diameters) in blue marls; the remaining 11 m. corresponds to the exempt part of the pier, with the lowest 2 m. corresponding to the average water depth of the Guadalquivir River in the above mentioned zone.
In the first week of opening the bridge, it was observed a vertical angle in the metal vehicles barriers and in the handrails of the bridge that was indicating the possibility of a descent of the deck, at the level of the piers P-4 and P-5 in the center of the river. Bridge in phase of construction. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig352_1.jpg"/>
It was decided to verify the level of the mentioned piers by topography, observing average settlements in piers P-4 and P-5 of 13.9 and 5.4 cm. respectively. Due to this it was decided to carry out a following-up of the settlements by means of topography fixed bases of leveling on both sides of the bridge.
The following topographic observation showed vertical settlements of 13.9 cm and 5.4 cm in each pier. After a revision of the project, it was concluded that according with the existing geotechnical investigations, the safety coefficient could be enough, but a new Geotechnical Campaign showed a dropping of the compaction of the soil, just in the area of piers P-4 and P-5. Using the new parameters of the soil it was concluded that the safety coefficient was not enough. After studying different solutions, it was concluded that the best technically and economically procedure, was Jet Grouting. With this technique, it was lifted 10.0 cm and 2.5 cm the pillars P-4 and P-5, increasing dramatically at the same time the safety coefficient. Finished bridge. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig352_2.jpg"/>
