The first stage of the project took place on November 2017 and included the thorough visual inspection of the culverts and the assessment of the damages and of the structural integrity of the structures from ENKA engineers. The structural condition of the culverts was characterized by the engineers of DENCO P.C. as “Very Poor (#2): Deteriorated with severe damages. Culvert integrity in risk”. The existing culverts could not safely bear the loads of the earth pressure and of the traffic of the highway. Moreover, due to the small embankment height up to the pavement (<1.0m), a potential failure of the culvert would jeopardize the highway operation. Olympia Odos asked for an immediate retrofit design and execution of the strengthening measures of the structure.
The required design and construction drawings were completed in 30 days. The design resulted in the construction of a new box-shaped culvert in contact with the existing one and with small thickness so that the hydraulic section in still sufficient. The existing structure was completely ignored as for its load bearing capacity.
The construction of the project took place on February-April 2018 and included:
- Removal of the loose concrete and shoring of the existing culvert.
- Cleaning of the corroded reinforcement with sandblasting and application of corrosion inhibitor.
- Shaping of the upstream and downstream river bed.
- Installation of Φ250 pipes on metal racks for retaining the culvert fully operational regarding floodwater flow rate during the works.
- For the new box-shaped culvert, expansion joints were constructed every maximum 7.0m and at all positions of the existing expansions joints, so that the latter are not affected.
- Construction of the floor slab of the new box-shaped culvert with cast-in-situ reinforced concrete.
- Construction of the side walls up to 25cm beneath their top side with cast-in-situ reinforced concrete.
- Construction of the upper 25cm of the walls and of the roof slab with reinforced shotcrete.
- The joints were sealed with PVC waterstop tape and with hand applied polymer modified bitumen sealant at the full perimeter of each segment of the new culvert.
- Addition of XYPEX Admix C-1000NF in all cast-in-situ concrete and shotcrete for permanent waterproofing and protection against future corrosion of the structure.
- Repair and strengthening of the wingwalls with cast-in-situ concrete or shotcrete.