Road tunnel

ROAD TUNNEL (EN: road tunnel, traffic tunnel; DE: Autobahntunnel; FR: tunnel autoroute; ES: tunel en carretera; RU: автодорожный тоннель) is used for the traffic of the automobile transport in the mountains (mountain road tunnel), under water (underwater road tunnel), for the regulation of the traffic of the ground transport on the city streets and roads (urban road tunnel).

The construction of the road tunnel (Figure 1) started in the 20th century with the development of the automobile transport and of the road network.The construction of the road tunnel

They construct the road tunnels for the 2-, 3-, 4-, 6- and 8- lanes traffic of the automobile transport in one level, and sometimes in two levels. Depending on the laying depth of the tunnel structure from the surface of the ground or water, they distinguish the deep (more than 10-12 metres) and shallow (less than 10-12 metres) laying road tunnels.

In the horizontal (plan) projection, the road tunnels may be placed on the straight and curved sections; in the last case the least acceptable radius of the curvature is 400-250 metres; the longitudinal profile of the road tunnel has the one-slope and the two-slope convex (mountain road tunnels) or concave (underwater and urban road tunnels) shape. The largest longitudinal inclination of the roadway in the road tunnels is 40 ‰ (in the special cases, 60 ‰), the least inclination is 3 ‰. According to the geotechnical conditions and the method of the works performance, the road tunnels have the arched, circular, or rectangular transverse profiles.

They choose the cross-sectional dimensions of the road tunnels taking into account the clearances to the nearest built structures and equipment (GOST 24451-80) and the placement of the operating devices. The most widely used methods for the construction of the road tunnels; in the mountains, the mining with the usage of the drilling and blasting, or with the tunnel boring machines and shielded; under water, the shielded or using the sunk sections; in the cities, mostly the open method of the works. Under the certain conditions, they use the heading method by the punching, chemical fixation, artificial freezing of the soils, decreasing of the level of the ground water, etc.

They make the lining of the road tunnels using the concrete, reinforced concrete, pig iron or steel; the linings of the arched profile mostly using the cast or (shotcrete) sprayed concrete in the form of the gently or sharply sloping arch, which is based on the rock, and using the closed profile with the inverted arch (Figure 2a). They construct the circular linings (Figure 2b) using the individual elements, which are made from the reinforced concrete or metal, with solid or ribbed cross section, namely the blocks or tubings, which are connected by the bolts, clamps, welding of the rebar, etc.The construction of the road tunnel

They construct the linings of the rectangular profile in the form of the frame structures, which are made from the reinforced or the precast concrete (Figure 2c). In the places of the entries and exits of the mountain road tunnels, they construct the load bearing and the retaining wall structures, making the portal, which ensures the stability of the slopes of the approach excavation, and forms the tunnel in the architectural sense. In most cases, they construct the access parts of the urban and underwater road tunnels in the form of the ramps with the variable height along the road.

They equip all road tunnels with the systems and devices, which ensure the normal operating conditions, of drainage, lighting, ventilation, etc. The supply of the air into the road tunnels reaches up to several thousand cubic metres per second (for example, the air flow rate in the St. Gotthard road tunnels is 2152 cubic metres per second, which corresponds to the passage of the 1850 automobiles per hour). In order to create the safe conditions, they equip the road tunnels with the modern means of communication, signaling, and fire protection. See the (Table) for the main parameters of the large road tunnels.

The main parameters of the tunnels Length, kilometres The quantity of the traffic lanes The intersected rocks The year of construction
Susamyrskiy, on the Frunze-Osh highway, USSR 2 2 Crystalline schists 1964
Sevanskiy, under the Semenov pass, on the Erevan-Dilizhan highway, USSR - 2 Sandstones, tuff breccias, tuffs, porphyries Is constructed
Under the Sea channel, in Leningrad, USSR - 2 Sand, clay Is constructed
Rockskiy, on the Dzhama-Zaramag highway, USSR - 2 Granite -
Mont Blanc, in the Alps, Italy-France 11.6 2 Granite 1965
Fréjus, in the Alps, Italy-France 12.8 2 Limestones, schists 1980
Enasan, on the "Kinki" highway (now Chūō Expressway), Japan 8.48. 2 Granites, rhyolites 1975
Lincoln, under the Hudson river, USA 2.5 4 Silt, hard rocks 1945
Under the Elbe river, in Hamburg, Germany 3.2 6 Sand, gravel, marl 1974
St. Gotthard, in the Alps, Switzerland 16.9 4 Granites, gneisses 1980
Arlberg, Austria 14 2×2 Gneisses, schists 1978
Gran Sasso, Italy 10.1 2 Limestone, dolomite, marl 1978