DESCRIPTION

The present invention relates to a submerged tunnel with buoyant suspension for a road and/or rail connection between two shores which are separated by an expanse of water and in the region of which the tunnel has respective ends, of the type comprising a plurality of tubular modules of predetermined axis which are connected rigidly to one another head to tail and which are anchored to a bed of the expanse of water between the shores in order to resist buoyancy. As is known, road and/or rail connections between opposite shores separated by an expanse of water, such as, for example, a stretch of sea, are nowadays obtained by the construction of bridges or subterranean tunnels. In particular, the building of bridges is the preferred solution, both from the technical point of view and from the economic point of view, for the connection of tracts less than 1 km in length or for shallow tracts for which it is possible to construct bridges having several bays. It will be appreciated that the construction of a bridge having a single bay longer than 1 km involves the solving of problems connected with the design and, above all, construction of the bridge which, in addition to being difficult to solve, entail a substantial increase in the cost of the work. It is also considered that the solution of using bridges having a long bay is not suitable for earthquake zones.

With subterranean runnels, however, it is possible to produce the above- mentioned connections even for stretches of sea a few kilometres long. However, the excavation carried out to produce such tunnels involves very high costs, especially where the bed of the expanse of water is of the rocky type,

which does not encourage the production of such tunnels, except in cases where it is not possible to use other solutions. Furthermore, in cases where the bed of the expanse of water is at a great depth, the production of the subterranean tunnel presents additional difficulties associated with the need to ensure that the structure is impermeable to the ingress of water in view of the high hydrostatic pressures reached on the bed of the expanse of water.

One way of avoiding the above-mentioned disadvantages is to produce a submerged tunnel with buoyant suspension anchored to the bed of the expanse of water, the practicability of which, however, requires the surmounting of numerous difficulties, such as, for example:

- the construction and laying of the tunnel between the ends,

- the production of a runnel having a structure of a rigidity such that it is not subject to axial deformation,

- the production of a tunnel having a structure capable of absorbing the dimensional variations caused by thermal expansion,

- the production of a tunnel having a structure capable of absorbing conjoined and disjoined telluric motions between the shores,

- the production of a tunnel having a structure capable of absorbing at least small internal explosions, - permitting navigability above the tunnel.

The problem underlying the present invention is that of providing a submerged tunnel with buoyant suspension for a road and/or rail connection between two shores separated by an expanse of water, which tunnel exhibits structural and functional characteristics enabling the above-mentioned

difficulties to be overcome and which is at the same time simple and economical to produce.

This problem is solved by a submerged tunnel with buoyant suspension of the type specified, which tunnel is characterised in that each module comprises a buoyancy chamber defined between an external casing and at least one internal duct.

Other characteristics and the advantages of the tunnel with buoyant suspension according to the present invention will become clear from the following description of a preferred embodiment given by way of non-limiting example with reference to the appended drawings in which:

- Figure 1 is a diagrammatic side view of a tunnel according to the invention connecting two opposing shores,

- Figure 2 is a diagrammatic plan view of the tunnel of Figure 1 , - Figure 3 is a perspective partially sectional view of a portion of the tunnel of Figure 1 , - Figure 4 is a perspective partially sectional view of one end of the tunnel of Figure 1 ,

- Figure 5 is a cross-sectional diagrammatic view of the tunnel of Figure 1 ,

- Figure 6 is a detail of Figure 5,

- Figure 7 is a diagrammatic partially sectional plan view of the intermediate portion of the tunnel of Figure 1,

- Figures 8, 9 and 10 are respective views in perspective and in partial section of some details of the tunnel of Figure 1 ,

- Figure 11 is a cross-sectional diagrammatic view of a detail of the runnel of Figure 1 ,

- Figures 12 and 13 are views of a detail of the tunnel of Figure 1 in two different functional configurations, and

- Figure 14 is a diagrammatic side view of the tunnel of Figure 1 in a different configuration. Referring to the appended drawings, a tunnel with buoyant suspension for a road and rail connection between two shores 2 which are separated by an expanse of water 3 and in the region of which the tunnel has respective ends 4 is generally indicated 1.

The tunnel 1 is formed by a plurality of identical tubular modules 5 connected rigidly to one another head to tail and is supported at its ends 4 by respective connecting structures 6 (Figure 4) which are fixedly joined to the shores 2 of the expanse of water 3.

Each module 5 comprises an external casing 7 having a substantially circular cross-section and extending along an axis X-X over a predetermined straight stretch. Purely by way of example, the diameter of the modules is 15 m while the length of each module is 50 m. The modules 5 are joined rigidly to one another end to end by means of a connection having bolted end flanges 8 between which are interposed annular packing elements, known per se and not shown in the drawings, which seal the connections against water ingress. Alternatively, the cross-section of the external casing 7 may be substantially elliptical, polygonal or in similar forms.

The external casing 7 of the modules 5 is formed by a plurality of stringers of predetermined thickness S of which there are 24 in the example and which are indicated 9 and which extend parallel to the axis X-X between the flanges 8 and are joined to one another side by side along axial joint lines by

means of continuous welds 10 in such a manner as to form the external casing

7 having a circular cross-section. It will be appreciated that each stringer 9 may be composed of several parts welded to one another until the required length is obtained. The stringers 9 have a curved cross-section and are arranged side by side in the region of the joints in such a manner as to form apices and to ensure that the concavity faces the outside of the module 5. Tubular joint covers 11 having a substantially circular open cross-section extend axially astraddle the axial joint lines of the stringers 9 at the outside of the module 5, in order to enclose the apices inside them. The joint covers 11 are secured to the stringers 9 by means of continuous welds 12 (Figure 11).

Each module 5 comprises two tubular ducts 13 and 14, of the road and rail type, respectively, which extend axially inside it one above the other and which are maintained radially separate from one another and from the external casing 7 by a plurality of radial centring diaphragms 15 spaced along the axis X-X of the module 5. In the example provided, each module comprises eleven diaphragms 15, of which two are arranged in the region of the flanges 8 of the modules 5 and the remainder are arranged at an equal distance from one another along the axis X-X. The diaphragms 15 have an external profile corresponding to the internal cross-section of the external casing 7 so that they mate with the latter, and they are welded continuously to the external casing 7 along their entire external periphery in order to form therewith a continuous sealed connection. The diaphragms 15 have openings in which the tubular road and rail ducts 13 and 14 are inserted. These openings have a profile corresponding to the profile of

the respective tubular duct inserted inside so that they mate therewith Along the entire profile of the openings, the diaphragms 15 are welded continuously to the tubular ducts 13 and 14, producing a continuous sealed connection therewith As an alternative to what has been described, in order to connect the external casing 7 to the tubular ducts 13 and 14, it is possible to employ longitudinal diaphragms arranged radially relative to the axis X-X of the tubular module, for use optionally in combination with the transverse diaphragms 15

Defined between the external casing 7 and the tubular ducts 13 and 14 is a module buoyancy chamber which is subdivided by the diaphragms 15 into a plurality of buoyancy chambers, which, in the example given, are ten in number for each module 5, are indicated 16 and are advantageously independent of one another Each buoyancy chamber 16 is associated with first and second valve means, of a type known per se and not shown in the Figures, which bring the buoyancy chambers 16 into fluid communication with the outside of the tunnel 1 and with a compressed air circuit associated with the tunnel 1 , respectively

The road 13 and rail 14 tubular ducts are provided with water tight security doors 55 through which it is possible to gam access to stairs 52 inside the buoyancy chambers 16, which stairs connect the two tubular ducts (Figure 9)

By means of a flanged connection, the modules 5 at the opposite end ot the tunnel 1 are respectively connected rigidly end to end with end sleeves 18 which have a tubular cross-section of a diameter substantially equal to that of the modules 5 and inside which the road and rail tubular ducts 13 and 14 extend The sleeves 18 have a smooth cylindrical outer surface and are engaged

with the above-mentioned connecting structures 6 by articulated connection means 19 which enable the sleeves 18 to slide axially and, to a limited extent, to move angularly relative to the connecting structures 6, especially in a plane which is vertical relative to the surface of the expanse of water 3. Each connecting structure 6 comprises a parallelepipedal reinforced concrete base 20 having a through hole which is aligned with the axis X-X of the tunnel 1 and into which the sleeve 18 is slidably inserted with radial play from a front side of the base 20 (Figure 4). A flexible annular membrane 17 acting as a packing joins the sleeve 18 to the front side of the base 20 in order to prevent the ingress of water into the connecting structure 6. At a predetermined distance A from the front side of the base, the base opens out to form a hollow seat 21 which is substantially spherical and coaxial with the axis of the hole. In the example provided, the articulated connection means 19 are formed by a plurality of segments 22 inteφosed between the sleeve 18 and the seat 21 and disposed circumferentially in a pitched manner about the sleeve

18. The segments 22 have a cylindrical surface which is complementary to the outer surface of the sleeve with which it is in contact and an opposite spherical cover which is in contact with the seat 21 and which has the same radius of curvature. The segments 22 form, with the seat 21 , a ball joint which permits limited angular articulation of the sleeve 18 relative to the base 20, especially in the above-mentioned vertical plane. The segments 22 also enable the sleeve 18 to slide axially in the hole in the base 20.

In order to reduce wear, the segments 22 are produced from high- resistance plastics material, for example of the type known commercially as

RILSEN, while the seat 21 is covered with steel plates. Alternatively, the seat 21 may be covered with plates of anti-friction material.

At the middle, the tunnel 1 comprises a first and a second module, 23 and 24, having first ends 25 connected by means of a hinged joint 26 which permits limited variations in the angle of inclination a of one module relative to the other. Consequently, the tunnel 1 is subdivided into a first and a second portion which are rigid and are articulated to a limited extent to one another about the joint 26.

The joint 26 comprises means 27 for the end to end hinged connection of the above-mentioned first and second modules 23 and 24 so that they can rotate relative to one another about a horizontal hinge axis Y-Y which is parallel to the surface of the expanse of water 3 and which passes through the modules 23 and 24. In the example under consideration, the hinge axis Y-Y coincides with the horizontal diameter of the cross-section of the modules 23 and 24 and passes between the road tubular duct 13 and the rail tubular duct 14

(Figure 10). These means 27 are preferably in the form of arms 28 which project, respectively, from the first end 25 of the first module 23 and of the second module 24 in the horizontal plane containing the hinge axis Y-Y. The arms 28 projecting from the first module 23 are staggered and partially overlap the arms 28 projecting from the second module 24, the above-mentioned arms being connected to one another by means of a hinge pin 29 extending along the hinge axis Y-Y.

The first ends 25 of the above-mentioned first and second modules 23 and 24 comprise respective flanges 30 which face one another and are spaced axially from one another by a predetermined distance in such a manner as to

permit limited rotation of one portion of the tunnel 1 relative to the other about the hinge axis Y-Y, without the flanges 30 of the first and second modules 23 and 24 interfering with one another. A resiliently deformable annular element 31 is inserted in a partially compressed state between the flanges 30 in order to follow the movements thereof during the rotation of the modules 23 and 24 about the hinge axis Y-Y and to act therebetween as a packing.

In the region of the first ends 25 of the first and second modules 23 and 24, two opposing wings 32 extend perpendicularly in the horizontal plane extending through the hinge axis Y-Y over a predetermined distance, for example 45 metres. Advantageously, the wings 32 of the first module 23 are connected to the wings 32 of the second module 24 by hinged connection means 33 similar to the means 27 described above and having the same hinge axis Y- Y. This increases the resistance of the hinged connection between the two portions of the tunnel 1 to stresses caused, for example, by the sea currents acting in the horizontal plane.

In the region of the second ends, the above-mentioned first and second modules 23 and 24 comprise flanges which are inclined at a predetermined limited angle, for example, one degree, relative to the perpendicular to the axis X-X so that they are respectively inclined towards the ends 4 of the tunnel 1. This enables the angle of inclination formed between the two portions of the tunnel 1 in the region of the joint 26 to be distributed over a larger portion of the tunnel 1.

The tunnel 1 comprises two opposing pluralities of side lattices 34 which are spaced axially from one another and which extend perpendicularly from the modules 5, in the above-mentioned horizontal plane parallel to the surface of

the expanse of water 3, from a base 35 to an apex 36 over a distance L, for example 40 m. The side lattices 34 are arranged in the region of the ends of the modules 5 so that the side lattices 34 of one plurality are positioned axially in the region of the side lattices 34 of the other plurality. The side lattices 34 of each plurality are connected to one another by tie-rods 37 extending along the axis X-X of the tunnel 1. Preferably, the tie-rods 37 comprise a first type of tie-rod extending from the apex 36 of a side lattice 34 to the base of the adjacent side lattices 34, and vice versa, and a second type of tie-rod extending from the apex 36 of a side lattice 34 to the base of the side lattices 34 which are not immediately adjacent, and vice versa, so as to form an interlaced network which holds all the modules 5 of the tunnel 1 laterally, increasing the rigidity of the tunnel 1 towards deformation in the above-mentioned horizontal plane (Figure 7).

A plurality of lower lattices 38, positioned axially in the region of the side lattices 34, extend vertically from the tunnel 1 towards a bed 39 of the expanse of water 3 from a base to an apex 40 (Figure 5). The apices 40 of the lower lattices 38 and the apices 36 of the side lattices 34 are connected by means of tie-rods 41 , for example sheared link chains, to anchoring plinths 42 associated with the bed 39 of the expanse of water 3 in order to resist the buoyancy acting on the tunnel, as will be seen more clearly hereinafter. Uncouplable coupling means 43 are inserted along the tie-rods 41 to permit the operation of coupling/uncoupling the modules 5 of the tunnel 1 from the anchoring plinths 42.

The coupling means 43 are preferably formed by a slip hook, of a type known per se, comprising a body 44 of which one end is fixedly joined to a tie-

rod 41 connected to the tunnel 1. Hinged to the opposite end of the body 44 is a movable arm 45 held in the closed position by a locking lever 46. The locking lever 46 is caused to move out of and into an operative position in which it locks the movable arm 45 in the closed position. When the movable arm 45 is held in the closed position (Figure 12) it forms with the body 44 of the slip hook an eyelet which permits the engagement of the end of a tie-rod 41 , which end is connected to an anchoring plinth 42. When the locking lever 46 frees the movable arm 45, the end of the tie-rod 41 fixedly joined to the anchoring plinth 42 is released (Figure 14). The tunnel 1 comprises a plurality of upper lattices 47, which are positioned axially in the region of the side lattices 34 and which extend vertically from the tunnel 1 towards the surface of the expanse of water 3 from a base to an apex 48. The apices 36, 40 and 48 of side lattices 34, lower lattices 38 and upper lattices 47 positioned axially in the region of the same cross-section of the tunnel 1 are connected by peripheral tie-rods 49. The peripheral tie-rods 49 limit the deflection of the side lattices 34 towards the bed 39 of the expanse of water 3 resulting from the action exerted thereon by the tie-rods 41 (Figure 5).

Deflector elements 50, otherwise known as spoilers, are associated laterally with the tunnel 1 on both sides in order to reduce the hydrodynamic resistance thereof in the horizontal plane. In the example, the deflector elements 50 are in the form of opposing upper and lower plates 51 having a first side fixedly joined to the upper and lower portion, respectively, of the modules 5, relative to the surface of the expanse of water 3, and extending along the axis X-X thereof between the bases 35 of the side lattices 34. An opposite side of

the plates 51 extends parallel to the axis X-X in alignment with the apices 36 of the side lattices 34, the ends of this opposite side being fixedly joined to the apices 36 of the side lattices 34. The plates 51 have a curved cross-section and are positioned in such a manner that the concavities of opposing upper and lower plates 51 face one another (Figure 3). Support struts known per se and not shown in the drawing are inserted between opposing upper and lower plates 51 and prevent the plates 51 from pressing against one another owing to the effect of the sea currents acting on them. The deflector elements 50 cooperate with the lattices and tie-rods to stiffen the structure of the tunnel 1 transversely. Side anchoring plinths 53 fixedly joined to the shores 2 are arranged on both sides of the tunnel 1 at a predetermined distance, for example 500 m in the example under consideration, from the axis X-X of the tunnel 1 in the region of the shores 2. A plurality of side tie-rods 54 connect the tunnel 1 to the above-mentioned side plinths 53, thus helping to keep it aligned and in position between the opposing connecting structures 6 (Figure 2). T h e side tie-rods 54 are preferably formed by several tubular elements which are rigidly connected to one another head to tail and which have, by way of example, a thickness of 4 cm and a diameter of 90 cm. The opposite ends of the side tie-rods 54 are connected, respectively, to the modules 5 of the tunnel 1 and to the side plinths 53 by means of hinges which enable the side tie-rods

54 to rotate in the plane vertical to the surface of the expanse of water 3. This enables the side tie-rods 54 to move in the vertical plane in order to follow the tunnel 1 from the top to the bottom and vice versa in the immersion/- surfacing movements thereof, as will be seen more clearly hereinafter.

Owing to the fact that the side tie-rods 54 are hollow inside, the buoyancy acting thereon is sufficient to oppose their weight, thus preventing the side tie-rods 54 from assuming a catenary profile.

Advantageously, the above-mentioned tubular elements which form the side tie-rods 54 are closed at the ends in order to prevent any water which has entered one of them from being transmitted to the others.

Alternatively, the side tie-rods 54 may be formed by chains, cables and the like.

Alloy steel containing copper, for example of the type known commercially as ITACOR, is preferably used to produce the modules, the lattices, the tie-rods, the deflector elements and the other parts of the tunnel which are to come into contact with the water.

The tunnel 1 comprises lighting means, air-conditioning means, anti-fire devices, electrical equipment, road and rail infrastructures and the like which are of known type and are not described hereinafter.

With reference to the above-mentioned drawings, a description will now be given of the assembly of the tunnel 1 referring to a distance, given purely by way of example, of 4 km between the opposite connecting structures 6 fixedly joined to the shores 2 of the expanse of water 3. The connecting structures 6 described above are manufactured in such a manner that the front side of the base 20 is in contact with the water and the above-mentioned hole is below the surface of the expanse of water 3 by a predetermined amount. Each connecting structure 6 is already prearranged with a sleeve 18 inserted inside and connected thereto by the articulated connection means 19.

The tubular modules 5 are constructed in a plant adjacent to the expanse of water 3 and are completed with all the infrastructures which are not damaged by coming into contact with water. It should be emphasised that the plant for the construction of the tubular modules 5 does not have to be in the vicinity of the site where the tunnel 1 is installed because the tubular modules 5 can be towed on the water even over a great distance from the place of manufacture. When construction is complete, each module 5 is lowered into the water where it floats, the volume of the buoyancy chambers 16 being sufficient to permit flotation thereof. Optionally, the road 13 and rail 14 tubular ducts of the modules 5 can be closed in the region of the opposing flanged ends of the modules in order to prevent them from being filled with water.

Each module 5 is then completed with the side lattices 34, the lower lattices 38 and the upper lattices 47 and with the peripheral tie-rods 49. The modules 5 are then joined rigidly to one another head to tail by means of the above-mentioned connection with bolted flanges 8 in order to obtain a tunnel

1 floating on the expanse of water 3. In the example given, it is necessary to use eighty modules to cover the distance of 4 km between the connecting structures 6.

During the connection of the modules 5, the hinged joint 26 is inserted between the two adjacent modules positioned in the region of the middle of the tunnel, in such a manner as to subdivide the tunnel into two rigid portions which are articulated to one another to a limited extent about the joint.

There are then added to the modules 5 thus connected the tie-rods 37 between the side lattices 34, the deflector elements 50 and the tie-rods 41 which are used for connection to the anchoring plinths 42.

The tunnel 1 , which is still floating on the surface of the expanse of water 3, is then pulled along and positioned with its ends 4 in the region of the opposing shores 2 in such a manner that the axis X-X of the tunnel 1 is aligned with the connecting structures 6. After the positioning operation, the floating tunnel 1 is connected by the side tie-rods 54 (Figure 2) to the side anchoring plinths 53.

By flooding the buoyancy chambers 16 of the modules 5 nearest to the ends 4 of the tunnel 1 , the tunnel 1 assumes a configuration (Figure 14) in which the part in the region of the joint 26 is raised relative to the surface of the expanse of water 3, while the ends 4 are below the surface. By regulating the amount of water introduced into the buoyancy chambers 16 by means of the above-mentioned first valve means, it is possible to vary the sinking of the ends 4 of the tunnel 1 relative to the surface of the expanse of water 3. The ends 4 of the tunnel 1 are sunk until the end modules 5 of the tunnel 1 are aligned with the sleeves 18 inserted in the connecting structures 6, so that it is possible to effect flanging therebetween.

It should be emphasised that the tunnel 1 can assume this configuration owing to the existence of the hinged joint 26 which enables one portion of the tunnel to be articulated relative to the other. Once the ends 4 of the tunnel 1 have been connected to the sleeves 18, the buoyancy chambers 16 of all the modules 5 are flooded to different extent depending on their position relative to the ends 4 of the tunnel, in such a manner as to cause each part of the tunnel 1 to sink to the depth provided for. In particular, the tunnel is caused to sink to such an extent as to bring the central portion in the region of the joint 26 to a predetermined depth P, for

example 40 metres, from the surface of the expanse of water 3, in order to render the expanse of water 3 navigable above the tunnel over a wide central tract II, for example from 700 to 800 m, between the two shores 2 (Figure 1). The inclination at which the two portions of the tunnel descend from the ends 4 towards the central joint 26 is approximately 2 % , which value is lower than the maximum value which can be overcome by a train. In addition, the hydrostatic pressure acting on the tunnel 1 is maintained at values which do not give rise to problems of water entering from the joints.

It should be emphasised that the above-mentioned immersion movement towards the bed 39 effected by the tunnel 1 is rendered possible both by the existence of the hinged joint 26 and by the existence of the articulated connection means 19, which enable the sleeves 18 to slide axially and to rotate in the vertical plane relative to the connecting structures 6.

Once the tunnel 1 has been positioned at the depth provided for, the tie- rods 41 are connected to the anchoring plinths 42 by the coupling means 43, in order to anchor the modules 5 securely to the bed 39 (Figure 5). The water previously introduced is then evacuated from the buoyancy chambers 16 by the introduction of pressurised air into the buoyancy chambers 16 by the above- mentioned second valve means. This confers sufficient buoyancy on the tunnel 1 to tension the tie-rods 41 for anchoring to the bed 39. After this last operation, the tunnel 1 is under forced immersion owing to the tie-rods 41 , while it is maintained in position laterally by the side tie-rods 54 which, as described above, are capable of following the vertical movements of the tunnel 1. Furthermore, the network formed by the tie-rods 37 contributes to increasing the rigidity of the tunnel 1 towards deformation in the horizontal plane.

Once the positioning operation has been completed, the tunnel 1 is supplemented with lighting means, air-conditioning means, anti-fire devices, electrical equipment, and road, rail and similar infrastructures necessary for its use. The axial sliding of the sleeves 18 and the articulation thereof permitted by the articulated means 19 enable the structure of the tunnel 1 to tolerate conjoined and disjoined sussultatory and undulatory telluric motions between the shores 2, and also any severe sea storms, without its integrity being compromised. If an explosion were to occur inside one of the road 13 or rail 14 tubular ducts, the pressure of the explosion gases would rupture the walls of the ducts, but there would be a useful volume in the buoyancy chambers 16 in which the gases could expand so that the energy of the explosion was reduced. In addition, the special structure of the external casing 7 of the tubular modules 5 as described above is expressly designed to deform in the case of explosion in such a manner as to turn the concavity of the stringers towards the outside. This requires the absorption on the part of the external casing 7 of a large deformation work at the expense of the pressure of the explosion gases before it tears. Then, if necessary, it is possible to uncouple the coupling means 43 in order to unfasten the tunnel 1 from the anchoring plinths 42. This entails the surfacing of the tunnel 1 owing to the effect of the hydrostatic buoyancy and the possibility of exchanging damaged tubular modules.

Analogously to what was stated in connection with the immersion movement, the above-mentioned surfacing movement is rendered possible owing to the existence of the hinged joint 26 which enables the two portions of

the tunnel to be articulated to one another, the existence of the articulated connection means 19 which enable the sleeves 18 to slide axially and to rotate in the vertical plane relative to the connecting structures 6, and the existence of the side tie-rods 54 which are capable of following the vertical movements of the tunnel 1.

The ability to maintain air inside the buoyancy chambers at a greater pressure than that of the water acting on the tubular modules prevents any ingress of water. Furthermore, by the continuous monitoring of the pressure inside the buoyancy chambers, it is possible rapidly to locate any leakage. As will be appreciated from the above, the submerged tunnel with buoyant suspension for a road and/or rail connection between two shores separated by an expanse of water has structural and functional characteristics such as to enable the above-mentioned problem underlying the present invention to be solved. One of the advantages of the submerged tunnel with buoyant suspension according to the invention resides in the modularity of its structure, which enables the length of the tunnel to be adapted to the distance between the two shores to be connected simply by varying the number of modules used. Furthermore, the modular structure provides important advantages in the construction, transport and assembly of the components of the tunnel.

A further advantage of the submerged tunnel with buoyant suspension according to the invention resides in the lower overall cost of the work compared with different solutions, because the production of the tunnel does not require large-scale intervention on the land, such as the excavation of

subterranean tunnels or the construction of large towers for supporting bridges having a long bay.

Another advantage of the submerged tunnel with buoyant suspension according to the invention resides in the safety it offers in the case of seismic phenomena, sea storms and internal explosions.

Another advantage of the submerged tunnel with buoyant suspension according to the invention resides in the fact that it does not impede navigability.

A further advantage of the submerged tunnel with buoyant suspension according to the invention resides in the ability to exchange any damaged parts thereof.

It will be appreciated that, in order to satisfy specific and contingent requirements, a person skilled in the art could introduce numerous modifications and variations to the submerged tunnel with buoyant suspension described above, but all contained within the scope of the invention as defined by the following claims.

Thus, for example, instead of connecting two shores which are separated by an expanse of water, the tunnel according to the invention can be used for connecting two different points of the same shore, in order to realize a submerged by-pass. In this case the tunnel is substantially "U" shaped and the hinged joint is not necessary.