Page 66

2017WinterShotcreteEMag

2016 Honorable Mention Mexico City Deep Sewer Rehabilitation with Shotcrete By Raúl Armando Bracamontes Jiménez Mexico City’s deep drainage system is a complex underground network composed of a series of tunnels designed to convey sewage and storm water to discharge and treatment facilities. The system covers almost 125 miles (200 km) of tunnels. Construction on this deep drainage system began in 1967, with its first phase concluding in 1975. Evaluation of two of the interceptor lines found significant damage to this concrete tunnel primarily in the top quadrant of the tunnels. Exposure to corrosive gases from the sewage and storm water contributed to this damage. The two interceptor lines were 16 ft (5 m) in diameter and had 11 access “ports,” which totaled 11 miles (18 km) in length. Additional problems included thinning of the walls of the channel from chemical attack and corrosion from the reinforcing steel. The repair process started with hydrodemolition to remove the damaged concrete, then preparing the remaining concrete surface, placement of a corrosion inhibitor on the existing reinforcing steel, placing a new layer of supplemental steel reinforcement, and applying a 6 in. (150 mm) thick shotcrete layer to reinforce the existing drainage sections in the upper middle of the tunnel. For the placement of the shotcrete, we had a concrete pump at the ground surface to pump concrete from the surface up to 4900 ft (1500 m) below ground to a second pump that discharged to the final shotcrete delivery hose and nozzle. We opted for a robotic application to increase Fig. 1: Initial conditions—note deterioration at the top of the drainage tunnel Fig. 3: Shotcrete equipment in position within the tunnel Fig. 2: Surface prepared and supplemental reinforcement in place ready to cover with shotcrete 64 Shotcrete | Winter 2017 www.shotcrete.org


2017WinterShotcreteEMag
To see the actual publication please follow the link above