Tunnel lining structure and process

Abstract

A lining structure (1) for an arched tunnel is described. The structure comprises a plurality of arched sections (10) arranged adjacent and consecutively along an axis of extension (X) of the said structure. Each section comprises a pair of sidewalls (20), each comprising a respective prefabricated lattice slab (21), and a pair of prefabricated cap segments (30, 40). Each cap segment is arc-shaped and is laid with the respective bottom end (31, 41) placed above the top end (23) of a respective sidewall, at a distance (H) therefrom. The cap segments also have their respective distal ends (32, 42) arranged facing and opposite each other. Each section of the lining structure also comprises base connection means (50) for connecting the bottom end of each cap segment to the respective sidewall, and capstone connection means for connecting together the distal ends of the two cap segments arranged facing and opposite each other.

Description

[0001] TUNNEL LINING STRUCTURE AND PROCESS

[0002] Technical field

[0003] The present invention relates to the civil engineering field, in particular the infrastructures field. The present invention relates more particularly to a lining structure for a tunnel, such as a road tunnel, railway tunnel or the like, and to a lining process which uses such a structure.

[0004] Prior art

[0005] As is known, a tunnel is a perforation in the subsoil which allows the transit of pedestrians or vehicles. A tunnel generally has a shell with a lining, typically consisting of concrete.

[0006] The lining of a tunnel over time could be subject to deterioration or degradation both owing to ageing of the construction materials used for the lining and as a result of continuous interaction with aggressive atmospheric agents (infiltration of water, exhaust gases, etc.).

[0007] The degradation of the lining may be of a superficial nature, namely may be due to carbonation, the presence of relatively small cracks, fissures, splitting or so-called “gravel nests”.

[0008] In other cases, owing to the infiltration of water through the fractured rock mass, or geological stresses (fractures, active landslides, etc.) or owing to prolonged absence of maintenance, said lining may become seriously damaged, negatively affecting in some cases also the stability of the structure.

[0009] In the first case, in order to repair the lining, it is usually sufficient to remove the outermost layer of the lining (about 3-5 cm thick) and then line the surface using special mortars, for example fiber- reinforced mortars, using the known so-called “spritzbeton” or “shotcrete” method.

[0010] In the case where the damage is more extensive and involves for example also the reinforcing bars, it is instead necessary to replace completely the concrete lining.

[0011] A known process used for this purpose involves the removal of a layer of the lining of considerable thickness (generally at least about 25-30 cm), by means of milling or hydrodemolition; then the lining is reconstructed using prefabricated lattice slabs (so-called “predalles slabs”) which act as a structural formwork. The predalles slabs are arranged against the walls of the tunnel and then a concrete casting is performed in the cavity between the tunnel walls and the rear surface of the predalles slabs.

[0012] Summary of the invention

[0013] The object of the present invention is therefore to provide a lining structure for a tunnel (in particular, but not exclusively, for repairing the lining of an already existing tunnel) and the associated process.

[0014] In particular, an object of the present invention is to provide a lining structure for a tunnel which has a good performance in terms of both resistance and duration which are substantially uniform along the entire section undergoing the lining work.

[0015] Another object of the present invention is to provide a lining structure for a tunnel, which allows a reduction in the time needed for the work, in particular which does not require the provision of shoring, thereby reducing also the risks associated with this activity.

[0016] An object of the present invention is also to provide a lining structure for a tunnel and a lining process which, when used to repair the lining of an already existing tunnel, are able to reduce significantly the traffic closure time along the tunnel section undergoing the work.

[0017] A further object of the invention is to provide a lining structure for a tunnel which is able to reduce to a minimum the assembly tolerances and, in the case of repair of the lining of an already existing tunnel, is able to optimize therefore the milling depth required for the existing lining.

[0018] These and other objects are all achieved, according to a first aspect of the invention, by a lining structure comprising a plurality of arched sections arranged adjacent and consecutively along an axis of extension of the said structure, wherein each section comprises a pair of sidewalls, each comprising a respective prefabricated lattice slab (referred to below also as “predalles slab”), and two prefabricated cap segments being arc-shaped; each of the cap segments is laid with its bottom end above the top end of a respective sidewall, at a distance H from its upper surface; the two cap segments are also laid with the respective distal ends arranged facing and opposite each other; the lining structure also comprises base connection means which, when laid, connect the bottom end of each cap segment to the respective sidewall; and capstone connection means which, when laid, connect together the distal ends of the two cap segments arranged facing and opposite each other.

[0019] Advantageously, the prefabricated cap segments are monolithic elements with features (material and thickness) which are determined and optimized during the course of their factory production process. Therefore, they are able to ensure a lining structure which has a good performance in terms of both resistance and duration. Owing to the repeatability of the manufacturing process it is also possible to obtain cap segments which have repeatable features, such as to ensure a substantially uniform performance of the lining structure along the entire tunnel section undergoing the lining work.

[0020] The lining structure according to the present invention also advantageously requires a limited amount of shoring, thereby reducing the time needed for the work and also the risks which are associated with shoring operations. In order to construct the sidewalls, in fact, a casting which requires temporary shoring of only the predalles slabs is carried out; however, considering the height of the sidewalls (about 3 to 3.5 m) the shoring has dimensions such as to allow in any case the transit of vehicles in the tunnel, possibly only a restricted carriageway. Once the two cap segments have been laid and connected together, the section of the resultant lining structure is in fact self-supporting and does not require either further shoring or casting work. With this configuration of the lining structure the laying work may be carried out in a significantly faster and safer manner compared to conventional methods. In the case where the lining structure is used for the repair of the lining of an already existing tunnel, the road section closure times are thus advantageously reduced to a minimum.

[0021] Moreover, the prefabricated cap segments may have very precisely defined dimensions and, during the installation work, may be handled by gripping them from below. Both these factors, together with the distance H between the bottom end of each segment and the top end of the respective sidewall, advantageously help reduce to a minimum the required tolerance when laying the segments. Said tolerance, namely the radial distance between the extrados of the said segments and tunnel wall, may be less than 10 cm. In this way, if the lining structure is used to repair the lining of an already existing tunnel, it is possible to reduce to a minimum the milling depth.

[0022] According to a first aspect of the present invention, a lining structure comprising a plurality of arched sections suitable for being arranged adjacent and consecutively along an axis of extension of the lining structure is provided, wherein each section comprises a pair of sidewalls, each comprising a respective prefabricated lattice slab, a first prefabricated cap segment and a second prefabricated cap segment (below also referred to only as “cap segments”), each of which is arc-shaped, the first cap segment and the second cap segment being configured to be laid with the respective bottom end placed above the top end of a respective sidewall, at a distance H from its upper surface, and with the respective distal ends arranged facing and opposite each other; each section of the lining structure also comprises base connection means for connecting the bottom ends of the first cap segment and the second cap segment to the respective sidewalls; and capstone connection means for connecting together the distal ends of the first cap segment and second cap segment arranged facing and opposite each other.

[0023] According to an embodiment of the invention, the prefabricated lattice slab in each of the sidewalls has a rebar. When the prefabricated lattice slab is laid in order to construct the sidewall, it is preferably positioned with the rebar projecting on the extrados side. Each sidewall is configured to be completed with a casting on the extrados of the respective prefabricated lattice slab.

[0024] Preferably, the prefabricated lattice slab in each of the sidewalls is curved and has a variable thickness. In particular, the thickness of each prefabricated lattice slab preferably is not constant between the base and the top end (the latter preferably has a greater thickness). Preferably, the thickness of each prefabricated lattice slab is between 10 cm and 30 cm. The overall thickness of each sidewall, once the casting has been performed, is preferably between 30 cm and 45 cm.

[0025] The prefabricated first and second cap segments are instead solid. They also preferably have a smooth surface both on the extrados and on the intrados.

[0026] The cap segments are preferably made of reinforced concrete. Preferably, the cap segments are made by means of a controlled and certified process, in order to ensure both the quality of the materials and the dimensional precision.

[0027] The size of the cap segments, in particular the angular extension and the radius of the intrados and extrados surfaces, depends on the dimensions of the tunnel to be lined. The depth of each of the cap segments, namely the extension in the direction along the axis of extension of the lining structure, is preferably between 0.6 m and 1.25 m.

[0028] According to a preferred variant, the base connection means comprise, for each cap segment / sidewall pair, at least one connection bar which can be housed in respective seats provided in the bottom end of the cap segment and in the top end of the sidewall.

[0029] Said connection bar is preferably fixed together with the respective cap segment and the respective sidewall by means of a chemical anchoring operation. More preferably, the chemical anchoring is performed by means of injection of grouting material, which is capable of flowing into the cap segment and sidewall seats and, once hardened, fixes the connection bar in place.

[0030] The seats for the connection bar are preferably arranged in a plane orthogonal to the axis of extension of the lining structure. Moreover, preferably, the seats for the connection bar are preferably inclined, in the aforementioned plane, at an angle of between 10° e 35° with respect to a vertical plane parallel to the axis of extension of the lining structure. In this way, when the connection bar is housed in the respective seats, it is also inclined at the same angle with respect to the vertical plane parallel to the axis of extension of the lining structure. The connection bar is thus capable of withstanding mainly shearing loads, namely stresses acting in a substantially horizontal plane.

[0031] According to an embodiment of the invention, the distance H between the bottom end of each of the cap segments and the upper surface on the top end of the respective sidewall is adjustable. In this way advantageously, a space is created between the bottom end of each of the cap segments and the upper surface on the top end of the respective sidewall, said space being able to compensate for any errors in laying of the cap segment on the respective sidewall (errors normally of not more than 5 cm).

[0032] For this purpose, according to an embodiment, the bottom end of each of the cap segments is provided with at least one support foot configured to rest on an upper surface of the top end of the respective sidewall. The at least one support foot is preferably adjustable heightwise, so as to allow adjustment of the distance H. The at least one support foot is configured to keep the bottom end of the cap segment at a distance H from the top end of the respective sidewall. The distance H preferably has a maximum value of 5 cm. As will be explained more clearly below, said space between the bottom end of the cap segment and the upper surface of the top end of the sidewall is filled by the aforementioned grouting material during execution of the work.

[0033] Preferably, the at least one support foot is configured to be completely retracted inside the bottom end of the cap segment. This allows the foot to be kept in a completely retracted position inside the bottom end of the cap segment during the installation of the said cap segment, so as to improve handling of the cap segment when it is moved and arranged close to the top end of the respective sidewall. According to one embodiment of the invention, each section of the lining structure preferably also comprises, for each cap segment / sidewall pair, temporary connection means for connecting the bottom end of the cap segment to the top end of the sidewall. According to a preferred variant, said temporary connection means include a plate fixable (for example by means of threaded members such as bolts or screws) to the bottom end of the cap segment and to the top end of the sidewall. These temporary connection means are capable of supporting mainly vertical loads transferred from the bottom end of the cap segment to the sidewall, before execution of the grouting operation. These temporary connection means are preferably suitable for being removed once grouting has been completed or, as required, also at a later stage, before completion of the work.

[0034] The temporary connection means are preferably configured to connect the bottom end of the cap segment to the top end of the respective sidewall along the intrados of the cap segment and the respective sidewall. As a result, advantageously, the temporary connection means are accessible from the inside of the tunnel and may thus be easily removed (in particular, the plate which connects together the bottom end of the cap segment and the top end of the respective sidewall may be easily removed) once grouting has been completed or, as required, also at a later stage, before completion of the work.

[0035] According to one embodiment of the invention, each section of the lining structure also comprises means for coupling together the distal ends of the cap segments. These coupling means preferably comprise respective complementary profiles, for example a male profile and a female profile (i.e. projecting profile and inset profile, respectively) formed on the faces of the distal ends of the cap segments, extending along the axis of extension of the lining structure and configured to engage with each other. Below, the cap segment provided with female profile will also be called “female cap segment”, while the cap segment provided with male profile will also be called “male cap segment”.

[0036] According to an advantageous embodiment, the female profile has a semi-circular cross-section inset within the face of the distal end of the female cap segment, and the male profile has a semi-circular cross-section projecting from the face of the distal end of the male cap segment. According to an advantageous variant, the female profile has a radius greater than the radius of the male profile.

[0037] According to a preferred embodiment, the capstone connection means comprise at least one threaded rod (or screw) suitable for being housed in respective seats provided in the distal ends of the first and second cap segments. Preferably, the threaded rod can be inserted in a through-hole provided in the distal end of one of the two cap segments (for example, male cap segment) and is screwed into a blind threaded seat provided in the distal end of the other oppositely arranged cap segment (for example, female cap segment).

[0038] According to one embodiment of the invention, the lining structure comprises centering means configured to center relative to each other the cap segments of sections arranged consecutively with respect to each other in a plane perpendicular to the axis of extension of the lining structure.

[0039] According to a preferred variant, the centering means comprise at least one pin configured to be inserted in two seats formed respectively on the front face of one of the cap segments of the section and on the rear face of a cap segment included in a further adjacent section. The at least one pin preferably has a double twincone shape and the seats configured to house them have corresponding conical shapes.

[0040] The at least one pin and the respective seats are configured and have dimensions such as to ensure an adequate shear strength and so as to be able to withstand any relative movements of adjacent cap segments in the plane perpendicular to the axis of extension of the lining structure.

[0041] According to an embodiment of the invention, the cap segment and sidewall front and rear surfaces are provided with seats for housing a sealing gasket configured to contain the casting and / or the grouting material.

[0042] According to an embodiment of the invention, the covering layer of the cap segments is provided with one or more through-holes between intrados and extrados, through which the grouting material in liquid form can be injected. Preferably, non-return valves are installed in the region of said holes.

[0043] According to an embodiment of the invention, the covering layer of the cap segments, in particular along the intrados, may have formed in it engaging seats which may pass through the thickness of the latter. Said engaging seats act as a housing for receiving pins or other connection means forming part of the equipment for moving and laying the cap segments.

[0044] According to an embodiment, the cap segments of a same section are arranged staggered along the axis of extension of the lining structure. The distal end of each cap segment is thus arranged facing and opposite two cap segments adjacent to each other along the axis of extension of the lining structure. This allows the cap segments to settle into position in a natural manner.

[0045] According to a second aspect of the invention, a process for lining a tunnel is provided, said process comprising at least the following steps: a) forming a pair of sidewalls on the sides of the tunnel by laying prefabricated lattice slabs with rebars facing the wall of the tunnel and carrying out a concrete casting on the extrados of said prefabricated lattice slabs which incorporates the rebars; b) laying at least a first prefabricated cap segment and a second prefabricated cap segment, each being arc-shaped, the laying comprising: placing each of the cap segments with the respective bottom end above the top end of a respective sidewall and spaced from its upper surface by a distance H; and placing the distal ends of the first cap segment and the second cap segment so that they are arranged facing and opposite each other; c) connecting the bottom end of each of the first cap segment and the second cap segment to a respective sidewall; and d) keying together the distal ends of the first cap segment and the second cap segment arranged facing and opposite each other.

[0046] Prior to casting, preferably shoring of the prefabricated lattice slabs is performed.

[0047] Preferably, the sidewalls placed on the respective sides of the tunnel are formed along a tunnel section, preferably having a length of at least 5 meters. The maximum length of the section depends instead on the features of the work site.

[0048] In the case where the process is used to repair the lining of an already existing tunnel, step a) is preceded by total or partial demolition of a pre-existing lining layer of the tunnel and / or by one of the following steps: demolition of at least one foundation curb and / or of at least one existing sidewalk and construction on-site of at least one new foundation curb; spray application of a lining material on the wall of the tunnel; and application of waterproofing sheet on the wall of the tunnel and / or preparation of at least one drainage channel along the at least one foundation curb.

[0049] The total or partial demolition of a pre-existing lining layer is preferably performed by means of milling, using methods and machinery known per se. The thickness of the pre-existing lining layer removed varies depending on the thickness of the lining itself and is preferably between 25 cm and 40 cm.

[0050] If necessary, before demolition, it is possible to carry out improvement and safety work, such as the arrangement of radial tierods and / or the injection of material in order to fill any empty zones behind the lining.

[0051] As regards the spray application of a lining material on the wall of the tunnel, it preferably allows a lining layer of a few centimeters thickness (preferably 2-3 cm) to be obtained on the milled wall, so as to render the surface thereof uniform and provide protection.

[0052] Preferably, step b) is performed after maturing of the concrete casting, preferably for at least eight hours. Preferably, it is in any case checked that an adequate degree of resistance has been achieved. Step b) is also preferably performed once the shoring of the predalles slabs has been removed.

[0053] Step b) preferably comprises the following substeps: b1 ) lifting and rotating the first cap segment in a plane substantially orthogonal to the axis of extension of the lining structure; b2) displacing the first cap segment along the axis of extension of the lining structure until it reaches an axial position next to another cap segment already installed or (in the case of laying of the first section of the lining structure) next to an abutment arch which has been previously constructed on-site or prefabricated; b3) lifting and rotating the second cap segment in a plane substantially orthogonal to the axis of extension of the lining structure; and b4) displacing the second cap segment along the axis of extension until it reaches an axial position next to another cap segment already installed or (in the case of laying of the first section of the lining structure) next to an abutment arch which has been previously constructed on-site or prefabricated; so that the distal ends of the first and second cap segments are arranged facing and opposite each other and at least partially in contact with each other.

[0054] Preferably, during the substeps b2) and b-4), centering means (preferably comprising at least one pin) are applied in the seats provided on the rear face of the first cap segment and the second cap segment, said centering means engaging with the seats provided on the front face of the cap segments of the already laid adjacent section (or abutment arch), as the first and second cap segments are moved towards an already laid adjacent section (or abutment arch).

[0055] Once coupling together of the centering means has been completed, the first cap segment and the second cap segment remain resting on the top surface of the respective sidewall by means of the respective support feet.

[0056] In steps b2) and b-4), during the axial sliding of the first cap segment and the second cap segment, in the case where the first and second (male and female) cap segments are placed staggered along the axis of extension of the lining structure, preferably the coupling means (namely the complementary male and female profiles) provided on the face of the distal end of each cap segment engage with those provided on the face of the distal end of an already laid opposite cap segment.

[0057] Preferably, in the first laid section, the first laid cap segment has a depth which is halved in relation to the other cap segments so as to create a staggered arrangement for the laying of the following cap segments. Once the first cap segment has been positioned (steps b1 ) and b2)) temporary supports are preferably applied pending the positioning of the second opposite cap segment.

[0058] As regards step c) (connection of the bottom end of each cap segment to the top end of the respective sidewall), this step preferably comprises the application of the base connection means, namely the insertion of the connection bar into the seats provided in the bottom end of each cap segment and in the top end of each sidewall. Step c) may also comprise the application, if necessary, of the temporary connection means. For each cap segment / sidewall pair, this step preferably involves fixing the plate included in the temporary connection means to the bottom end of the cap segment and to the top end of the sidewall, for example by means of threaded members such as screws or bolts.

[0059] The order of laying of the cap segments of each section is not binding for the stability of the lining structure, namely a male cap segment may be laid first, followed by a female cap segment, or vice versa.

[0060] As regards step d) (keying together of the distal ends of the cap segments arranged facing and opposite each other), it preferably involves applying the capstone connection means in order to fix together the distal ends of the two cap segments.

[0061] Steps a), b), c) and d) are repeated until several consecutive sections are arranged over a distance of several meters, for example 10 to 20 meters.

[0062] Advantageously, after the completion of the section, or where applicable after laying of only the first cap segment of the section, it is possible to remove the temporary supports placed under the first cap segment which has been laid. For the following sections, said temporary supports are not necessary, since the lining structure is stable and safely secured.

[0063] Preferably, after step d), a step involving grouting of the cavity between the extrados of the cap segments of the laid cap segment and tunnel wall is performed by means of injection of a grouting material in liquid form. The grouting material may be for example a liquid mortar.

[0064] The injection of the grouting material is preferably performed at several points, where a plurality of injection holes are provided on the covering layer of the cap segments, so as to ensure correct and complete filling of the cavity.

[0065] All the steps described above (formation of the sidewalls, laying of the cap segments, application of the base connection, temporary connection - if provided - and capstone connection means, and grouting) are repeated until the tunnel section undergoing the lining work has been completed.

[0066] Brief description of the drawings

[0067] The present invention will become clearer from the following detailed description, provided by way of a non-limiting example, to be read with reference to the attached drawings in which:

[0068] - Figure 1 is a perspective view of a lining structure according to embodiments of the present invention;

[0069] - Figure 2 is a front view of the two cap segments of the section of the lining structure according to Figure 1 ;

[0070] - Figures 3a and 3b are, respectively, a side view and a front view of a detail of the base connection zone between the cap segments and the sidewalls;

[0071] - Figure 4 is a side view of a detail of the capstone connection zone of the two cap segments;

[0072] - Figure 5 is a top plan view of a plurality of adjacent sections of the lining structure according to the present invention; - Figure 6 is a cross-sectional view of a tunnel in which a lining structure according to embodiments of the present invention has been installed;

[0073] - Figures 7 to 10 are respective cross-sectional views of a tunnel which show the steps of preparation of the tunnel for installation of the lining structure according to the present invention;

[0074] - Figures 11a and 11 b are respective cross-sectional views of a tunnel which show the steps for formation of the sidewalls;

[0075] - Figures 12a and 12b are cross-sectional views of a tunnel which show laying of the cap segments;

[0076] - Figure 13 is a top plan view of a tunnel section showing the step of laying of the cap segments;

[0077] - Figures 14a to 14c are cross-sectional views of a tunnel which show respective steps of the operation for grouting the cavity between the cap segments and the tunnel; and

[0078] - Figures 15 and 16 are cross-sectional views of a tunnel showing respective further steps for completing the lining of the tunnel.

[0079] Detailed description of preferred embodiments

[0080] With reference to the attached Figures 1-5, a lining structure 1 according to embodiments of the present invention is shown. The lining structure 1 comprises a plurality of arched sections 10 arranged adjacent to each other along an axis X. Said axis X will also be referred to below as “axis of extension of the lining structure” or also only “axis of extension”.

[0081] Figure 1 shows a plurality of sections 10 of the lining structure 1 .

[0082] Each section 10 of the lining structure 1 comprises two sidewalls 20. Each sidewall 20 comprises a respective prefabricated lattice slab 21 , also referred to below as “predalles slab”. The predalles slab 21 is preferably curved and has a variable thickness. Each predalles slab 21 preferably also comprises rebars 24. Each sidewall 20 preferably has a heightwise extension of about 3-4 meters, depending on the dimensions of the tunnel to be lined.

[0083] The section 10 also comprises a first cap segment 30 and a second cap segment 40.

[0084] Each of the cap segments 30, 40 is arranged with the respective bottom end 31 , 41 above the top end 23 of a respective sidewall 20. The cap segments 30, 40 also have respective distal ends 32, 42. The faces 32a, 42a of the distal ends 32, 42 preferably are arranged facing and opposite each other and partially in contact with each other.

[0085] Each of the cap segments 30, 40 is arc-shaped. The cap segments 30, 40 also preferably have a radial extension which is substantially identical to each other. In the example shown in the drawings, in which the section 10 comprises only two cap segments 30, 40, they preferably have the shape of a semi arc, namely the point of contact of their distal ends 32, 42 is substantially aligned with the center line of the lining structure 1 .

[0086] The thickness of each cap segment 30, 40 between the bottom end 31 , 41 and the distal end 32, 42 is preferably substantially uniform. Preferably, the thickness is between 20 cm and 35 cm.

[0087] The bottom ends 31 , 41 and the distal ends 32, 42 of each cap segment 40 have preferably a greater thickness, so as to allow the provision and housing of connection means.

[0088] In particular, the section 10 preferably comprises base connection means 50 which are configured to connect the bottom end 31 , 41 of each cap segment 30, 40 to the respective sidewall 20.

[0089] As shown in Figures 3a and 3b, the base connection means 50 preferably comprise, for each cap segment / sidewall pair, at least one connection bar 51 suitable for being housed partly in a blind seat 52 formed in the top end 23 of the predalles slab 21 of the sidewall 20 and partly in a through-hole 53 formed in the bottom end 31 , 41 of the cap segment 30, 40.

[0090] The blind seat 52 and the through-hole 53 preferably are arranged in a plane substantially orthogonal to the axis of extension X. Preferably, the blind seat 52 and the through-hole 53 are aligned along a direction which, in the aforementioned plane, is inclined with respect to a vertical plane parallel to the axis of extension X of the lining structure 1 .

[0091] According to a preferred embodiment, not shown in the drawings, each cap segment 30, 40 is connected to the predalles slab 21 of the respective sidewall 20 with at least two connection bars 51.

[0092] Each cap segment 30, 40 is configured to be positioned with the respective bottom end 31 , 41 at a distance H from the top end 23 of the respective sidewall 20. The distance H in general has a different value for each cap segment 30, 40. The distance H is preferably adjustable. The distance H has a maximum value preferably of 5 cm.

[0093] In order to keep the bottom end 31 , 41 of each cap segment 30, 40 at the distance H from the top end 23 of the respective sidewall 20, each cap segment 30, 40 preferably comprises at least one support foot. The at least one support foot is configured to project from the bottom end 31 , 41 towards the top end 23 of the respective sidewall 20 and to rest on the upper surface 22 of the top end 23 of the sidewall 20. The support feet are preferably adjustable heightwise, so as to allow the adjustment of the distance H. The at least one support foot is preferably configured so that it can be retracted completely inside the bottom end 31 , 41 of the respective cap segment 30, 40.

[0094] According to a variant, the bottom ends 31 , 41 of the cap segments 30, 40 may be connected to the predalles slabs 21 of the respective sidewalls 20 also using temporary connection means 55. For each cap segment / sidewall pair, the temporary connection means 55 preferably comprise a plate 56 fixed by means of threaded members (such as screws or bolts) onto the bottom end 31 , 41 of the cap segments 30, 40 and onto the predalles slab 21 of the sidewall 20 respectively.

[0095] The temporary connection means 55 preferably connect the bottom end of the cap segment 30, 40 to the top end of the respective sidewall 20 along the intrados of the cap segment 30, 40 and the respective sidewall 20. In particular, the plate 56 is fixed along the intrados of the cap segment 30, 40 and the sidewall 20, so that it may be easily removed at a later stage.

[0096] Preferably, the bottom end 31 , 41 of each cap segment 30, 40 also has a vent hole (not shown in the drawings). The vent hole allows the ventilation of the grouting material which is injected into the space between the bottom end 31 , 41 of the cap segment 30, 40 and the top end 23 of the sidewall 20, as will be described in greater detail hereinbelow.

[0097] The section 10 of the structure 1 also comprises capstone connection means 60 for connecting together the distal ends 32, 42 of the cap segments 30, 40 which, as mentioned above, are arranged facing and opposite each other.

[0098] Figure 4 shows in detail the contact zone between the distal ends 32, 42 of the cap segments 30, 40, where the capstone connection means 60 are provided. Said means comprise a threaded rod 61 suitable for being housed partly in a through-hole 62 formed in the distal end of one of the two cap segments (for example, the distal end 42 of the second cap segment 40) and partly in a blind seat 63 formed in the distal end of the other cap segment (for example in the distal end 32 of the first cap segment 30). The blind seat 63 preferably is also threaded. For example, the blind seat 63 may comprise a threaded bush or a plug.

[0099] The blind seat 63 and the through-hole 62 preferably are arranged in a plane orthogonal to the axis of extension X. Preferably, the blind seat 63 and the through-hole 62 are aligned along a direction which, in the aforementioned plane, is inclined with respect to a vertical plane parallel to the axis of extension X.

[0100] The faces 32a, 42a of the distal ends 32, 42 of the cap segments 30, 40 preferably have mutual coupling means. These mutual coupling means preferably comprise, on the faces 32a, 42a, respective complementary profiles configured to engage with each other. In detail, the first cap segment 30 has a female profile 34 preferably with a semi-circular cross-section, which is inset within the face 32a, while the second cap segment 40 has a male profile preferably with a semi-circular cross-section, projecting from the face 42a. The first cap segment 30 will therefore also be referred to below as “female cap segment”, while the second cap segment 40 will also be referred to below as “male cap segment”.

[0101] The female profile 34 and the male profile 44 preferably extend along the axis of extension X of the lining structure 1 . In this way, they substantially act as guides which allow the mutual alignment of the distal ends 32, 42 of the cap segments 30, 40 when they are laid. The female profile 34 preferably has a radius greater than the male profile 44 so that, when the two profiles 34, 44 are brought into contact with each other, the straight portions of the faces 32a, 42a do not make contact with each other, but play is present between them. This play allows both adjustment of the position of the cap segments 30, 40 in the plane orthogonal to the axis of extension X and a reduction of the friction between the two cap segments 30, 40 when one of them is moved with respect to the other one along the axis of extension X during the laying operations. As can be seen in Figure 5, the cap segments 30, 40 are preferably arranged staggered with respect to each other in the direction of the axis of extension X of the lining structure 1 . The distal end 32 of each cap segment 30 is therefore in contact with two distal end portions 42 of two cap segments 40 adjacent to each other along the axis of extension X and opposite thereto; similarly, the distal end of each cap segment 40 is in contact with two distal end portions 22 of two cap segments 30 adjacent to each other along the axis of extension X and opposite thereto.

[0102] In order to allow the connection of each cap segment 30, 40 to two cap segments 40, 30 adjacent to each other along the axis of extension X and opposite thereto, the distal end 32, 42 of each cap segment 30, 40 is preferably provided with double capstone connection means 60 in different positions along the axis of extension X of the structure 1 , each of which is configured to connect the cap segment 30, 40 to one of the two cap segments 40, 30 opposite thereto.

[0103] The front faces 33a, 34a and the rear faces 33b, 43b of the cap segments 30, 40 (namely the faces of the cap segments 30, 40 opposite to each other and perpendicular to the axis of extension X) have preferably formed therein a plurality of seats 74 suitable for housing the pins 72 (visible in Figure 5) which act as centering means 70 for centering cap segments 30, 40 which are arranged adjacent and consecutively along the axis of extension X, in the plane orthogonal to the axis of extension X. The seats 74 preferably have a substantially conical shape and, correspondingly, the pins 72 preferably have a biconical shape.

[0104] Said front and rear faces 33a, 43a, 33b, 43b also have preferably formed therein a seat 35, 45 comprising a substantially arc-shaped groove. As will be described below, the seats 35, 45 are preferably configured to house a sealing gasket.

[0105] Injection through-holes 37, 47 are also preferably formed in the covering layer of each of the cap segments 30, 40. As will be described in greater detail hereinbelow, the injection holes 37, 47 are configured to allow the flow of grouting material. Preferably nonreturn valves 37a, 47a are provided in the region of said holes.

[0106] The covering layer of the cap segments 30, 40 also preferably has, formed therein, engaging seats 38,.48 (such as holes, recesses, etc.) suitable for housing gripping means which allow the gripping, movement and laying of the cap segments.

[0107] Figures 7 to 16 show the steps of a process for lining a tunnel according to embodiments of the present invention. Below, reference will be made to the particular case where the work involves repair of the lining of an already existing tunnel G. As shown in Figure 7, the tunnel G is defined by a vault wall P and by a roadway surface S.

[0108] After carrying out any preparation work, such as the provision of fiberglass radial tie-rods and the filling of empty zones behind the lining to be repaired, the process may involve the demolition of the sidewalks M (Figure 7) and, thereafter, the complete removal of the lining R already present in the tunnel G by means of milling (Figure 8). The thickness of the removed lining varies depending on the shape of the lining itself and is preferably between 25 cm and 40 cm.

[0109] Foundation curbs CF are then preferably formed. The foundation curbs CF are preferably made of reinforced concrete and are provided with fixing irons for the subsequent casting of the sidewalls (Figure 9).

[0110] Where necessary, a lining material, which forms a smoothing and protective layer SH, may also be applied onto the intrados of the milled wall. The layer SH may for example be obtained by means of spray application of cement mortar (for example using the “shotcrete” method).

[0111] Then, preferably the work is continued with the laying of a drainage and waterproofing system along the tunnel G. This step may for example involve the application of a sheet T of non-woven fabric with polyolefin membrane on the intrados of the wall P and the provision of drainage pipes D along the respective end edges of the sheet (Figure 10).

[0112] Starting from this condition the steps for installation of the lining structure 1 are performed according to the process of the present invention

[0113] A first step involves the formation of a pair of sidewalls 20 along the sides of the tunnel G. This step preferably involves the laying of the predalles slabs 21 on the foundation curb CF (Figure 11a) and the provision of shoring (the latter is not shown in the figure). The predalles slabs 21 are preferably laid with their rebars 24 directed towards the intrados of the wall P of the tunnel G.

[0114] Then a concrete casting is performed between the intrados of the wall P of the tunnel G and the extrados of the predalles slabs 21 (Figure 11b) so as to surround the rebars 24.

[0115] Once the casting has set, usually after at least eight hours, the shoring is removed.

[0116] Then the cap segments 30, 40 are laid in place.

[0117] According to the example shown in the Figures, the laying of the cap segments 30, 40 involves firstly laying of the female cap segment 30 and then laying of the male cap segment 40. However, the laying may also start with laying of the male cap segment 40.

[0118] If the process involves the laying of cap segments 30, 40 staggered along the axis of extension X as shown in Figure 5, the first cap segment laid (whether it be a female cap segment or a male cap segment) has preferably a depth halved in relation to the other cap segments, so as to create the staggered arrangement for laying of the following cap segments.

[0119] Returning to the process, the female cap segment 30 is preferably gripped using special equipment, also by means of the engaging seats 38, and is moved to a height and a transverse position such that its bottom end 31 is situated above the top end 23 of one of the two sidewalls 20 formed. The final laying position is reached by means of displacement of the cap segment 30 along the axis of extension X. During the movement of the female cap segment 30, its support feet 31 b are retracted completely inside the bottom end 31 .

[0120] If the female cap segment 30 is not the first female cap segment to be laid, it is preferably displaced along the axis of extension X until its rear face 33b is in contact with the front face 33a of the last female cap segment laid, as shown in Figure 13. During the movement of the female cap segment 30 towards the last female cap segment laid, the relative centering of the cap segments in the plane orthogonal to the axis of extension X is preferably ensured by the pins 72 which engage inside the seats 74 provided on the rear face of the female cap segment 30 and on the front face of the last female cap segment laid.

[0121] Furthermore, if at least one section 10 of the lining structure 1 has already been laid, during the displacement of the female cap segment 30 along the axis of extension X, the latter is preferably arranged so that its female profile 34 engages with the male profile 44 of the male cap segment 40 of the section 10 which has already been laid, such that the two profiles guide the displacement of the female cap segment 30 and ensure the alignment of its distal end 32 with the distal end 42 of the male cap segment 40 of the already laid section 10.

[0122] If, instead, the female cap segment 30 is the first one to be laid, it may be laid up against an abutment arch which covers an initial section of the tunnel G, previously constructed on-site or prefabricated.

[0123] Once the final position has been reached, the support feet 31b are extracted from the bottom surface 31a of the bottom end 31 of the female cap segment 30 so that they rest against the upper surface 22 on the top end 23 of the sidewall 20. They are then adjusted heightwise so that the female cap segment 30 is positioned at a distance H (which, as mentioned above, may be up to 5 cm) from said upper surface 22.

[0124] During this step, temporary shoring I is also preferably provided in order to support the female cap segment 30 at the distal end 32, as shown in Figure 12a. Said shoring is generally provided only for the first cap segment which is laid in the tunnel G.

[0125] The process then involves the step of laying the male cap segment 40. The laying steps are substantially identical to those described above for the female cap segment 30. During the displacement of the male cap segment 40 along the axis of extension X, the latter is preferably arranged so that its male profile 44 engages with the female profile 34 of the female cap segment 30, such that the two profiles guide the displacement of the male cap segment 40 and ensure the alignment of its distal end 42 with the distal end 32 of the female cap segment 30 which has already been laid (Figure 12b).

[0126] The movement of the cap segments 30, 40 for laying thereof is also made possible by the play between the intrados of the wall P of the tunnel G and the said cap segments. Between the extrados of the cap segments 30, 40 and the intrados of the wall P there is in fact present a cavity with a thickness of about 5-10 cm, which allows the movement of the cap segments 30, 40 and adjustment of their relative position and their position with respect to the sidewalls 20. The process then involves the application of the capstone connection means 60, so as to rigidly fix together the distal ends 32, 42 of the cap segments 30, 40, and the base connection means 50 (and, if present, the temporary connection means 55), in order to connect the cap segments 30, 40 to the sidewalls 20.

[0127] In particular, in order to connect the bottom end 31 , 41 of each cap segment 30, 40 to the respective sidewall 20, the connection bar 51 of the base connection means 50 provided for each cap segment / sidewall pair is inserted in the through-hole 53 provided in the bottom end of the cap segment and slid through it until it engages with the blind seat 52 provided in the top end of the sidewall 20, in particular in the predalles slab 21 .

[0128] In order to connect together, instead, the distal ends 32, 42 of the cap segments 30, 40, the threaded rod 61 of the capstone connection means 60 is inserted in the through-hole 62 provided in the distal end 42 of the male cap segment 40 and slid until its end reaches the blind seat 63 provided in the distal end 32 of the female cap segment 30. The threaded rod 61 is then screwed into the blind seat 63.

[0129] At this point, the temporary shoring I may be removed and preferably the laying of a new section 10 of the lining structure 1 is performed, starting with the formation of a new pair of sidewalls 20 adjacent to those already made along the axis of extension X, and repeating all the steps described above.

[0130] In this situation, the stretch of the lining structure 1 made is already stable and it is therefore possible to open again the road section concerned, if need be.

[0131] Preferably, after constructing a stretch of the lining structure 1 along a length of about 10-15 m, the process involves the execution of the grouting of the cavity between the cap segments 30, 40 and the wall P of the tunnel G.

[0132] Figures 14a-14c show the grouting steps where a grouting material 80, for example a cement mortar, is injected through the injection holes 37, 47 of the cap segments 30, 40. As shown, the injection is performed first into the injection holes 37, 47 situated at a lower height and gradually in those which are higher The grouting is preferably performed so as to complete the grouting of an entire section 10 and then proceeding with the following sections along the axis of extension X, until completion of the stretch of the lining structure 1 .

[0133] As described above, the bottom end 31 , 41 of each of the cap segments 30, 40 is placed at an adjustable distance H from the top end 23 of the respective sidewall 20. Said space, which is sealed beforehand, is then preferably also filled with the grouting material 80. It should be noted that the grouting material 80, flowing into the various seats between the bottom end 31 , 41 of the cap segment 30, 40 and the top end 23 of the sidewall 20, once it has hardened, locks the connection bar 51 in place, thus performing chemical anchoring of the bar 51 to the cap segment 30, 40 and to the sidewall 20.

[0134] Before the grouting step, any other passages such as the engaging seats 38, 48, if they pass through the thickness of the covering layer of the cap segments 30, 40, are also preferably sealed. Moreover, preferably the seats 35, 45 provided on the front and rear faces 33a, 43a, 33b, 43b of the cap segments 30, 40 have, housed inside them, gaskets 36, 46 which act as seals for the grouting material 80 in liquid form before hardening.

[0135] Following the grouting step, the temporary connection means 55 of all the sections 10 which undergo grouting are preferably removed. This operation is advantageously made possible by their positioning along the intrados of the cap segments 30, 40 and the sidewalls 20. Figures 15 and 16 show further steps for completing the repair of the lining. These steps may comprise, by way of example, the formation of new sidewalks M and / or the application of a layer of paint V on the intrados of the predalles slabs 21 and possibly also on part of the cap segments 30, 40.

[0136] Obviously, the invention may be subject to various modifications and alternative constructional forms, and some preferred embodiments have been shown in the drawings and described in detail. It is to be understood, however, that there is no intention to limit the invention to the specific embodiment shown, but, on the contrary, it is intended to cover all the modifications, alternative constructional forms and equivalents which fall within the scope of the invention as defined in the claims.

Claims

CLAIMS1. A lining structure (1 ) for an arched tunnel (1 ), the lining structure (1 ) comprising a plurality of arched sections (10) suitable for being arranged adjacent and consecutively along an axis of extension (X) of the lining structure (1 ), wherein each section (10) comprises: a pair of sidewalls (20), each of said sidewalls (10) comprising a respective prefabricated lattice slab (21 ); a first prefabricated cap segment (30) and a second prefabricated cap segment (40), each one of said first cap segment (30) and said second cap segment (40) being arcshaped, said first cap segment (30) and said second cap segment (40) being configured to be laid with: the respective bottom end (31 , 41 ) placed above the top end (23) of a respective sidewall (20) and spaced from its upper surface (22) by a distance (H); and the respective distal ends (32, 42) arranged facing and opposite each other; wherein each section (10) further comprises: base connection means (50) for connecting the bottom ends (31 , 41 ) of the first cap segment (30) and the second cap segment (40) to the respective sidewalls (20); and capstone connection means (60) for connecting together said respective distal ends (32, 42) of the first cap segment (30) and the second cap segment (40) arranged facing and opposite each other.

2. The lining structure (1 ) according to claim 1 , wherein said base connection means (50) comprise at least one connection bar (51 ) suitable for being housed in respective seats (52, 53) provided in the top end (23) of each of the sidewalls (20) and in the bottomend (31 , 41 ) of each one of said first cap segment (30) and said second cap segment (40).

3. The lining structure (1 ) according to claim 1 or 2, wherein said capstone connection means (60) comprise at least one threaded rod (61 ) suitable for being housed in respective seats (62, 63) provided in the distal ends (32, 42) of each one of said first cap segment (30) and said second cap segment (40).

4. The lining structure (1 ) according to any one of the preceding claims, wherein the distance H between the bottom end (31 , 41 ) of each one of the first cap segment (30) and the second cap segment and the upper surface (22) on the top end (23) of the respective sidewall (20) is adjustable.

5. The lining structure (1 ) according to any one of the preceding claims, wherein the bottom end (31 , 41 ) of each one of said first cap segment (30) and said second cap segment (40) is provided with at least one support foot configured to rest on an upper surface (22) of the top end (23) of the respective sidewall (20).

6. The lining structure (1 ) according to claims 4 and 5, wherein the support foot is adjustable heightwise.

7. The lining structure (1 ) according to any one of the preceding claims, wherein each section (10) also comprises means for coupling together the distal ends (32, 42) of said first cap segment (30) and said second cap segment (40), said means comprising respective complementary profiles (34, 44) formed on the faces (32a, 42a) of the distal ends (32, 42), said respective complementary profiles (34, 44) extending along said axis of extension (X) and being configured to engage with each other.

8. The lining structure (1 ) according to claim 7, wherein said complementary profiles (34, 44) comprise a female profile (34) with a semi-circular cross-section provided on the face of thedistal end (32) of said first cap segment (30) and inset within the face of the distal end (32) of said first cap segment (30), and a male profile (44) with a semi-circular cross-section provided on the face of the distal end (42) of said second cap segment (40) and projecting from the face of the distal end (42) of said second cap segment (40).

9. The lining structure (1) according to claim 8, wherein said female profile (34) has a radius greater than the radius of said male profile (44).

10. The lining structure (1 ) according to any one of the preceding claims, wherein each section also comprises temporary connection means (55) suitable for connecting the bottom end (31 , 41 ) of each one of said first cap segment (30) and said second cap segment (40) to the top end (23) of the respective sidewall (20), said temporary connection means (55) comprising at least one plate fixable to the bottom end (31 , 41 ) of each one of said first cap segment (30) and said second cap segment (40) and to the top end (23) of the respective sidewall (20).

11. The lining structure (1 ) according to claim 10, wherein said temporary connection means (55) are configured to connect the bottom end of said first cap segment (30) or said second cap segment (40) to the top end (23) of the respective sidewall (20) along the intrados of said first cap segment (30) or said second cap segment (40) and said respective sidewall (20).

12. A process for lining a tunnel (G) comprising the following steps: a) forming a pair of sidewalls (20) on the sides of the tunnel (G) by laying prefabricated lattice slabs (21 ) with rebars (24) facing the wall (P) of the tunnel (G) and carrying out a concrete casting (25) on the extrados of said prefabricated lattice slabs (21 ) which incorporates said rebars (24);b) laying at least a first prefabricated cap segment (30) and a second prefabricated cap segment (40), each one of said first cap segment (30) and said second cap segment (40) being arc-shaped, said laying comprising: placing the first cap segment (30) and the second cap segment (40) with the respective bottom end (31 , 41 ) placed above the top end (23) of a respective sidewall (20) and spaced from its upper surface (22) by a distance (H); placing respective distal ends (32, 42) of the first cap segment (30) and the second cap segment (40) facing and opposite each other; c) connecting the bottom end (31 , 41 ) of each one of the first cap segment (30) and the second cap segment (40) to a respective sidewall (20); and d) keying together the distal ends (32, 42) of the first cap segment (30) and the second cap segment (40) arranged facing and opposite each other.

13. The process according to claim 12, also comprising, before step a), a total or partial demolition of a pre-existing lining layer of the tunnel (G) and / or at least one of the following steps: demolition of at least one foundation curb and / or at least one existing sidewalk, and construction on-site of at least one new foundation curb; spray application of a lining material on the wall (P) of the tunnel (G); application of a waterproofing sheet on the wall (P) of the tunnel (G) and / or preparation of at least one drainage channel along the at least one foundation curb.

14. The process according to claim 12 or 13, wherein before step c)temporary connection means (55) are provided for connecting the bottom end (31 , 41 ) of each one of said first cap segment (30) and said second cap segment (40) to the respective sidewall (20), and wherein said temporary connection means (55) are removed after the grouting step.

15. The process according to any one of claims 12 to 14, wherein step b) of laying said first cap segment (30) and said second cap segment (40) comprises the following sub-steps: b1 ) lifting and rotating the first cap segment (30) in a plane substantially orthogonal to the axis of extension (X); b2) displacing the first cap segment (30) along the axis of extension (X) until it reaches an axial position, next to another cap segment already installed or next to an abutment arch which has been previously constructed on-site or prefabricated; b3) lifting and rotating the second cap segment (40) in a plane substantially orthogonal to the axis of extension (X); and b4) displacing the second cap segment (40) along the axis of extension (X) until it reaches an axial position, next to another cap segment already installed or next to an abutment arch which has been previously constructed on-site or prefabricated, so that the distal ends (32, 42) of the first cap segment (30) and the second cap segment (40) are arranged facing and opposite each other and at least partially in contact with each other.

16. The process according to claim 15, wherein step b4) comprises guiding the displacement of the second cap segment (40) along said axis of extension (X) by means of coupling means comprising complementary male and female profiles (34, 44) respectively provided on the faces (32a, 42a) of the distal ends(32, 42) of the first cap segment (30) and the second cap segment (40).

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