Cut & Cover – Lane Cover structures are considered the optimum restoration solution, particularly where road alignments pass through areas of deep excavations.
These structures are constructed by excavating the relative area, implementing additional temporary support measures where required, constructing the permanent structure, and subsequently backfilling above and alongside the completed structure in accordance with the design.
The following aspects should be considered during the design and dimensioning of these restoration structures:

1. Compliance with the Required Environmental Conditions

Compliance with the environmental requirements is a determining factor during the design stage, as it significantly affects the geometry of the structure, its structural thicknesses, and the height of the backfill above the structure (e.g., free excavation height above the final backfill level less than 25m).

2. Maintenance of Traffic on the Existing Roadway During Construction

Maintaining traffic on the existing roadway is an important design consideration. The construction sequence should therefore be incorporated into the detailed design drawings, including the location of concrete construction joints, provisions for reinforcement continuity with adequate lap lengths, the available working space due to traffic management arrangements, and the successive traffic diversion stages during construction.

3. Type of Foundation (Shallow or Deep Foundation – Piles)

The foundation system is selected based on the evaluation of the geotechnical conditions of the area. Where one side of the structure is adjacent to the excavation slope and the opposite side borders steep downhill terrain, a deep foundation system (pile foundation) should be investigated.
Special attention is also required in critical local areas not fully covered by the model analysis during the preparation of the relative design drawings. These areas may require additional reinforcements due to the bursting forces.

When a concentrated load from a column or pile enters a wider concrete element (the wall), it creates transverse tensile stresses (bursting). The total bursting force Fbst is calculated using the Strut-and-Tie Method.

More details and indicative illustrated pictures are presented in the following file.

Cut & Cover – Lane Cover structures