The project involved the construction of two twin-tunnels, Har Nof and Yefe Nof, and, also underground, an entrance ramp and an exit ramp of the Yefe Nof tunnel.
The Har Nof tunnel has a length of about 1400 m and has maximum overburdens in the order of 140 m. The characteristic section can accommodate two traffic lanes and has a roadbed width of 10 m. Near the Revida (Southeast) side entrance, the platform of both tubes widens, up to 14.7 m in the North tube and 19 m in the South tube, to contain the deceleration and acceleration lanes planned at the tunnel exit itself.
The Yefe Nof tunnel has a development of about 1250 m and has maximum covers in the order of 80 m. The tunnel accommodates three traffic lanes and has a roadbed width of 13.6 m. Near the Revida (Northwest) side entrance, the design includes two ramps, one inbound and one outbound, that connect to the main axes within two chambers that have a maximum road platform width of 22.5 m. The same section, with a 22.5 m platform to contain a deceleration lane, is also provided at the Bayth (Southeast) side entrance in the South tube, while in the opposite tube the platform widens to 14.7 m to contain an acceleration lane.
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At this inlet, the excavation of an already challenging section by virtue of its considerable size is aggravated by the reduced distance between the tunnels and the presence of low overburdens, on the order of 10 m, only part of which consists of rock material. In addition, at this adit, both tunnels underpass in low cover and for an extension of more than 100 m, an area in which there are three soccer fields to be kept constantly usable. It should also be noted that the Yefe Nof tunnel route, shortly after the area of the soccer fields, runs parallel to Shaarei Zedek Hospital with overburdens on the order of 30-40 m and underpasses its underground multi-story parking lot.
Along the route there are lay-bys at a maximum distance of 500 m and pedestrian and driveway cross-passages every 250 m (10 cross-passages connecting main tubes, 5 for each tunnel, 8 of which are pedestrian and 2 are driveways). At pedestrian cross-passages, 32 m long lay-bys are provided, while at vehicular cross-passages, the lay-bys are 44 m long.
The main issues that were addressed in the excavation of the two tunnels can be traced to:
✓ Crossing of the formation presenting an alternation of limestone and marly strata. The latter, of metric order, presented geomechanical characteristics significantly inferior to limestones and were potentially subject to swelling phenomena. Moreover, being characterized by low permeability, they represented the substrate of the water table present in the overlying limestone-dolomitic formation;
✓ Excavation in piles subject to large karst phenomena;
✓ Strong variability in the width of the roadbed, from a minimum of 10 m at the 2-lane section to a maximum of 22.5 m at the chambered sections;
✓ Low overburdens with the presence of buildings on the surface;
✓ Excavation of extremely large sections.
Geologically, the subsoil crossed was generally composed of rather competent dolomite and limestone with sub-horizontal stratification, except for a predominantly marly formation.
