The Agua Negra tunnel is the main component of the "Bioceanic Corridor", an international project aimed to set an efficient roadway crossing through the Andes Cordillera, connecting Porto Coquimbo (Chile) to Porto Alegre (Brazil). The project includes the construction of a 13.9 km long twin tunnel, linking the two portals at 4'080 m a.s.l. (Argentina) and 3'605 m a.s.l. (Chile). The tunnel is provided with cross passages every 250 m, two ventilation caverns (one provided with a vertical ventilation shaft of 500 m, the other with a 4.5 km long ventilation tunnel). The project includes also the ramps and the control building. The cross section is horse-shoe shaped and the carriage way is two lane wide, with a free section 7.50 m wide and 4.80 m high. There are walk ways on both sides. According to the concept for a longitudinal ventilation, the tunnel is not provided with an intermediate slab. The construction concept is to excavate the tunnel from both portals, with two contemporary and independent excavation faces each. The excavation will be drill & blast in order to assure the maximum adaptability to the geological conditions. Particular aspects of the project are the high elevation of the portals, the distance to the nearest urban center (>200 km), the extreme meteorological conditions in terms of wind and thermal excursion and the high seismic risk. Lombardi is responsible of the new conceptual study, the preliminary project and the technical tender documentations for the underground and external civil works as well as for the electromechanical equipment.

The new Garibaldi Bridge connects the island of La Maddalena to the island of Caprera and was built as part of the extraordinary works planned for the G8 meeting in July 2009, which was later moved to the city of L'Aquila. The project involves the removal of the temporary Bailey-type bridge and the construction of a new road and pedestrian bridge. The longitudinal profile of the new deck is circular curved, the cross-section and overhangs of the pavement are of constant size while the core has a variable width and thickness. The bridge extends above the sea along a straight axis for about 52 m, with a maximum height of about 5.6 m above the water level. The cross section of the bridge is 10 m wide, the space dedicated to vehicular traffic is 6 m. On the sides there are two tapered corbels which constitute a protected pedestrian and bicycle space of 1.8 each. The deck structure is composed of 2 inverted symmetrical arches with an upper slab-chain. In the intermediate section, the connection between the arch and the slab is a system of metal props inclined in a fan shape in longitudinal and transverse direction to form a regular mesh of supports for the slab. The slab is pre-compressed in the longitudinal direction by means of a diffused system of post-tensioning cables composed of compact, non-adherent 0.6" section single-stranded viplate and protected by HDPE sheathing. Due to the extraordinary requirements imposed by the client, the construction was completed in just 4 months.

The selection of the excavation method is a key aspect for the design of tunnels. The mechanized excavation by means of Tunnel Boring Machines (TBM) is possible and convenient only in specific geomechanical conditions. The preliminary TBM design becomes therefore relevant in order to define the main features of the TBM, determining the feasibility of this methodology, and considering schedules and costs. The main characteristics of the TBM, i.e. advancement thrust, cutter head torque, shield geometry, cutter head properties and power of the hydraulic equipment, can be established by studying the geological framework and carrying out a proper geomechanical analysis. Other relevant aspects as the drilling machinery for the grouting works and geological investigations as well as the equipment required for the backfilling of the annular void can also be defined at this stage. In specific geomechanical conditions, advanced calculations (typically 3D) could be required. The performance of such models must take into account the interaction between mechanized excavation and the geological setting. Lombardi Ltd. has been actively involved in this engineering framework, carrying out successfully the preliminary TBM design regarding multiple underground works: highway, railway and hydraulic tunnels, rocky and soil ground, with high overburden or in urban areas.

Los Cóndores is a 150 MW HPP, including a 12 km long headrace tunnel (4.6m diam, excavated by D&B and a DS hard rock TBM), a 120 m high surge shaft (6m diam), a 480 m high pressure shaft (2.6m diam), both being excavated using a raise borer machine RBM, and a 1.6 km long subhorizontal pressure tunnel leading to an underground powerhouse accommodating 2 Pelton units. The region is volcanic, with several active volcanoes in the recent geological eras. Maule Laguna volcanic complex is one of the major and the geological formation are essentially dacitic and rhyolitic lava field with rich tuff and volcanic breccia presence in subhorizonal sedimentation and several lava and basalt domes and dikes crossing these formations. Excavation of the upper waterway (HRT) is foreseen in two phases through a central adit by TBM, in order to shorten the time for accessing and execute the vertical works. During the excavation of the HRT lower reach, the TBM got stuck in a cohesionless material, likely the seat of a paleo-basin (syncline) or a paleo-canal within the lava and breccia banks. The services targeted the understanding of the situation, definition of the operations required for the TBM to be safely unlocked from the jammed conditions and option for realizing a bypass around the TBM in case no success was provided by other means. Because of the significant modification of the working program, the evaluation was required of the options for realizing the upper reach of the HRT by other mechanized means (second TBM) or other excavation method, given the logistic conditions at site. Possible optimization of vertical works, in terms of efficiency and realization concept was also part of the required services; in particular, a preliminary study considering 5 alternatives of the scheme combined with different excavation methods options (D&B and/or RBM) were carried out, in order to analyze the possibility to disassociate the construction of the vertical works from the TBM advance and to better manage the geological and construction risks associated with vertical works construction.