WO2012114249A2

WO2012114249A2 - A method and equipment for tunnelling

Info

Publication number: WO2012114249A2
Application number: PCT/IB2012/050753
Authority: WO
Inventors: Cristiano Bonomi
Original assignee: ELAS GEOTECNICA Srl
Current assignee: ELAS GEOTECNICA Srl
Priority date: 2011-02-21
Filing date: 2012-02-20
Publication date: 2012-08-30
Anticipated expiration: 2013-08-21
Also published as: ITBO20110072A1; AR085269A1; WO2012114249A3; TW201239188A; IT1404615B1

Abstract

A method for tunnelling uses equipment comprising a tubular structure (10) with a substantially empty tubular cavity corresponding to the cross section of the tunnel to be constructed. The front portion (13) of the tubular structure is placed close to the excavation face (F), which is made to advance over a predetermined distance by means of excavation with one or more excavators moved into the tubular cavity to a point close to the excavation face (F). In a rear area of the tubular structure, at least one course of segments is laid, and pushing members (22) then bear on these segments, causing the tubular structure (10) to advance over the predetermined distance until the front portion (13) is brought to a point close to the excavation face (F). The steps are then repeated until the tunnel is complete.

Description

A METHOD AND EQUIPMENT FOR TUNNELLING

TECHNICAL BACKGROUND

The present invention relates to a method and equipment for tunnelling.

The invention has been developed with particular regard to tunnelling in soft ground and/or ground with low cohesion, but is not limited to this use.

PRIOR ART

A tunnel is constructed by the operations of advancing the excavation face by breaking up rock or soil, clearing away the debris from the excavation face for a further advance, carrying the debris to the outside, and temporarily lining the excavation while awaiting the preparation of the final concrete lining for the work.

Two main methods are currently used for the excavation of tunnels. In the more conventional method, an excavation face worked by excavating machines is progressively advanced. The newly completed excavation is then reinforced with large shaped metal sections, known as ribs, shaped to match the profile of the excavation cross section, which support the tunnel arch. The ribs are spaced apart from each other and are connected by what are known as "braces", which are sets of stays which stabilize the rib assembly. A layer of sprayed concrete is then applied to the ribs and to the walls and roof of the tunnel, in order to create a first radial

protective structure which enables the personnel to carry out all the other procedures required for the construction of the work .

However, this method of excavating tunnels is slow and requires a certain amount of specialized manual labour; it is therefore costly and is limited to the excavation of short tunnels .

For constructing tunnels of considerable length, such as underground railway tunnels, a different

excavation method is generally used, in which large machines called TBMs (Tunnel Boring Machines) excavate the ground in a continuous and integrated way. There are known TBMs which are essentially composed of large steel cylinders carrying large cutters on their front ends,

substantially preventing access to the excavation face, while the central and rear parts of such a machine are provided with a long train of cars which supply the head end with all the machinery and equipment required for the operation of the machine and for the automatic removal of debris. The steel cylinder supports the tunnel arch while the excavation proceeds. Behind the steel cylinder, courses of concrete segments are progressively laid to line the tunnel arch. In its rear part, the steel cylinder is provided with a set of jacks which bear on the newly laid segments and are then operated to advance the TBM in the excavation. The jacks are then retracted to allow another course of segments to be laid and to allow the advance of the front end into the excavation and the automatic removal of the debris.

The cost of these automatic TBMs is very considerable, and is normally only recovered if the tunnel is long and the excavation takes place without difficulties. If an unforeseen obstacle is encountered, such as an unpredictable area of soft ground, the advance of the TBM has to be stopped

immediately to avoid a risk of collapse.

In such cases, in other words if the excavation face encounters problems caused by soft ground, the conventional excavation method described above, using ribs, would allow the excavation face to be consolidated and/or reinforced, by boring long holes in the ground, for example, and then injecting pressurized concrete into them to incorporate long fibreglass stays inserted previously into the holes in the ground. This effective method also enables the ground to be drained if necessary.

However, this consolidation method either cannot be used, or proves much more expensive, if the excavation is carried out by automatic TBMs. This is because the tion of the ground is made extremely difficult by the fact that access to the excavation face is seriously impeded by the front cutter and all the internal equipment of the TBM. In such cases, the TBM may remain idle for a

considerable time, while the problem of the softness of the ground is being resolved by highly expensive and complicated operations such as boring auxiliary tunnels to reach the excavation face, resulting in very serious financial losses and delays in the construction of the tunnel.

There are also known TBMs which are described as "open", in which the excavation is carried out by means of various types of equipment, depending on the ground, such as a backhoe loader, a cutting element, a pneumatic pick, or the like, mounted in the front part of the steel cylinder. This front part of the cylinder can then be partially closed by movable steel plates, in a petal configuration for example, which serve to support, at least partially, the excavation face. All the equipment for automatic debris removal, such as a line of service cars, is located inside the cylinder, as in enclosed TBMs. These open TBMs also advance by making the jacks located in their rear parts bear on segments laid to support and line the walls and arch of the tunnel. This method of excavation using open TBMs again suffers from the drawback that the problem of a possible collapse of the excavation face cannot be effectively resolved, owing to the bulk and complexity of the equipment located inside the steel cylinder and in its front part, which prevent easy access to the excavation face. Such access is impeded even further by the presence of service cars in the rear of the TBM which serve all the equipment mounted in the steel cylinder of the TBM.

Another disadvantage of TBMs is their vulnerability in the event of a collapse of the ground surrounding the steel cylinder, which could be subjected to pressure on the outer shell and remain trapped in the tunnel until the pressures on the ground are released in some way. A further drawback of TBMs is that the excavation cross section is practically always circular, and in any case is determined by the characteristics of the automatic machine, so that designers are unable to choose a tunnel cross section which is different from a circle or an arc of the circle, even if it might be advisable or preferable, because of the morphology of the ground, to use different tunnel cross sections, such as a flat arch, a horseshoe, or other cross section .

BRIEF DESCRIPTION OF THE INVENTION

The objects of the present invention are to overcome the aforementioned drawbacks by providing an excavation method and equipment enabling tunnels to be constructed rapidly, simply, economically and safely, using procedures such that even very soft ground can be excavated rapidly and

successfully .

Using the proposed method and equipment, when any necessary consolidation and reinforcement of the body of ground before the front part of the face has been completed, the excavation is carried out inside a tubular protective structure which is substantially empty and practically entirely open both in the front part facing the excavation face and in the rear part after the laying of the lining segments. In the rear part of the tubular protective

structure, the segments for supporting the walls and arch of the tunnel are positioned, for example by means of suitably designed self-powered machinery which is preferably

operational only during the laying of the segments; the segments are assembled substantially in a ring formation (with a shape corresponding to the cross section of the tubular structure) inside the terminal, that is to say the rear, part of the tubular structure, which in this step operates as a template for the assembly of the whole ring structure. A set of jacks or other pushing members connected to the tubular structure bears on the segments, in order to push the structure progressively into the previously excavated area of the excavation face while simultaneously allowing the last assembled ring of segments to move out of the rear part of the tubular structure. The actual excavation can therefore be carried out by means of conventional self- powered machines, and the debris can be removed simply by motor vehicles such as civil engineering vehicles (dumper trucks) or lorries and the like. The segments can also be laid by suitably equipped self-powered vehicles which can be driven to the rear part of the tubular structure which they can access freely.

In its front part, the tubular structure is entirely open and has substantially the same outside radius as the ring of concrete segments to be assembled in the rear part, so that the excavation face can be consolidated easily, for example by the method of drilling the face and injecting pressurized concrete to incorporate long stays made of fibreglass, for example.

The tubular structure proposed herein does not include any excavating members or any members for cutting or drilling the ground. This is because, in the tunnelling method

proposed herein, the breaking of the material and the advance of the excavation take place in a way which is substantially similar to conventional procedures, using independent

vehicles which can enter the tubular structure to reach the excavation face. Unlike the conventional excavation methods, however, the tubular structure proposed herein eliminates the need to provide reinforcing ribs to support the area in the vicinity of the excavation face, since this function is provided by the tubular structure itself, and subsequently by the segments which are progressively laid in the rear part of the tubular structure. In other words, the tubular structure proposed herein essentially has no cutting or excavating function, nor any function of forced penetration into the ground or rock, and is therefore considerably simpler and more economical to manufacture than known TBMs of both the enclosed and open types. The tubular structure proposed herein can advantageously be provided with one or more covering and protective elements which can project selectively forwards from the front part of the tubular structure in the axial direction, to cover the arch area of the tunnel excavation that has just been

completed, in other words the area closest to the excavation face, before the advance of the tubular structure by

thrusting against the rear segments causes the structure itself to cover the newly excavated area. The provision of the aforesaid covering elements provides shelter from any falls of material, soil or rock for the excavating personnel working at the face to remove the material as required for the advance of the tunnel.

According to another advantageous characteristic, the tubular structure proposed herein can be provided with adapter means for reducing or increasing the outer tubular diameter. In this way the tubular structure can, for example, be expanded to oppose any strong radial pressures imparted by the ground, or contracted to slide more easily inside the preliminary bore, thus allowing it to advance without

stoppages or additional costly work. In particular, the radial dimensions of the tubular structure can be varied within specified limits, to adapt to ground conditions which may vary along the tunnel excavation path. To achieve this, the shell of the tubular structure is cut longitudinally in at least one direction, and one or more pressure elements, such as a hydraulic system preferably composed of one or more hydraulic jacks in an array, fixed to the two flaps of the shell on both sides of the longitudinal cut, enable the radial dimensions of the tubular structure to be increased or decreased .

The invention has considerable advantages by comparison with the known methods, and enables tunnels of various sizes and lengths to be constructed with great economy and

efficiency. By comparison with the conventional methods of manual excavation, it clearly saves the costs incurred by forming the tunnel reinforcement from ribs and sprayed concrete, and by comparison with the TBM excavation methods it has the considerable advantage of a very low investment in equipment. Furthermore, the procedure proposed herein enables highly flexible operation to be maintained, allowing

adaptation if any difficulties and unforeseen circumstances are encountered in the construction of the tunnel.

For example, the tubular structure proposed herein can have its radial dimensions altered so that it avoids being trapped in a tunnel following an unexpectedly high

compression of the surrounding ground. Furthermore, the entirely open excavation face makes it possible to use efficient methods of ground consolidation and drainage, allowing the proposed procedure and equipment to be used in the presence of ground with highly variable properties, regardless of whether the ground is compact and cohesive or has poor cohesion, or in the presence of groundwater, for example .

The flexibility of the procedure and equipment proposed herein is evident even in the case of an unexpected collapse of the ground which cannot be resolved immediately by varying the radial dimensions of the tubular structure, which would therefore remain trapped in the tunnel under construction. In this case, where very considerable problems would arise and high costs would be incurred if a known type of TBM were used, the procedure proposed herein makes it possible to use the simple solution of continuing to advance the excavation by a conventional method, while consolidating the ground and excavating and reinforcing the tunnel by means of

conventional ribs, until the collapse is rectified and the tubular structure can be released so as to advance to the excavation face once more to resume its original operation. BRIEF DESCRIPTION OF THE DRAWINGS

A preferred but non-limiting embodiment of the invention will be described with reference to the appended drawings, provided by way of non-limiting example, in which - Figure 1 is a schematic perspective view of a tubular structure according to the present invention,

- Figure 2 is a perspective view similar to that of Figure 1, wherein the tubular structure is partially bearing on segments and has been represented as transparent to aid the understanding of its internal features,

- Figures 3 to 6 are sectional views of the tubular structure of Figure 1 in various operating steps in the construction of a tunnel according to the method of the present invention, and

- Figure 7 is a perspective view of a preferred

embodiment of a segment laying machine.

DETAILED DESCRIPTION

With reference to Figures 1 and 2, a tunnel is

constructed according to the present invention by means of equipment which comprises a tubular structure 10 having a shell 12 made preferably from sheet metal shaped in the form of a tunnel, which in most cases comprises a large crown 14 connected to a moderately curved base 16. Clearly, the configuration of the shell 12 can be different from that which is illustrated by way of example, and could have different shapes according to the cross section of the tunnel to be constructed, such as a circular cross section or a cross section with vertical sides. Thus the designer of the tunnel to be excavated has considerable freedom when choosing a tunnel cross section, for example a cross section which is most suitable for the geomorphological characteristics of the ground. Because of transport requirements, the tubular structure 10 is preferably made up of sectors which are assembled at the tunnel construction site in order to form the desired profile.

The shell 12 preferably comprises at least one

longitudinal joint, in other words a joint running

substantially along a generatrix of the tubular structure, forming two flaps 18, 19 which can be moved away from or towards each other in order to expand or contract the shell in the radial direction. The flaps 18, 19 are held together by size changing elements (not shown) , preferably comprising hydraulic cylinders for moving the flaps 18, 19 selectively away from or towards each other. The joint enables the tubular structure 10 to be contracted radially in an

emergency, in order to avoid trapping due to abrupt curves or local constrictions.

Inside the shell 12, the tubular structure 10 has an array of stiffening beams, ribs or frames 20 which act as a reinforcing and stiffening skeleton for the shell 12, and which support a plurality of pushing members 22, preferably hydraulic cylinders, which are spaced apart from each other and are preferably positioned around the whole inner

perimeter of the shell 12. The pushing members 22 are movable selectively from a retracted position, shown in Figure 2, to an extended position, shown in Figure 1. In the retracted position, the pushing members 22 leave a rear portion 24 of the shell 12 free for the laying of at least one course of segments 26, preferably made of concrete, as explained more fully below. The pushing members 22 are preferably operable independently of each other, and can be extended singly, in groups, or simultaneously. In simultaneous operation, the pushing members are coordinated by a computerized control system to advance the tubular structure 10 in a straight or slightly curved direction as necessary, the direction being determined by the degree of extension of the each pushing member 22 with respect to the others. On the other hand, the selective extension of individual cylinders or groups of cylinders is helpful for retaining each individual segment in the correct and desired position while it is being laid, until the complete course of segments has been completed.

Preferably, in the base area 16, the beams 20 and the corresponding pushing members are at least partially covered to allow the passage of vehicles and equipment for

consolidating and excavating the tunnel, as described more fully below. In a variant, the whole interior of the tubular structure 10 is covered by a covering wall spaced apart from the outer shell 12 by the beams 20, to which it is fixed, by electric welding for example.

In the front area 28 of the tubular structure 10, that is to say in the area which is closest to the excavation face during tunnelling, one or more movable plates 30 are placed on top of the crown 14, and can project forward from the shell 12 to cover and shelter the excavation area while the face advances, before the tubular structure 10 is also advanced to provide protection. In particular, the plates 30 are connected, as shown in Figure 2, to hydraulic cylinders 32 which can push the plates 30 forward selectively, in an axial direction parallel to the axis of the tubular structure 10 and of the tunnel, or can retract them so that they do not project beyond the front edge 13 of the shell 12.

The use of the equipment described above for tunnelling according to the procedure proposed by the present invention is both simple and efficient. As shown in Figure 3, in one step of the construction of the tunnel the tubular structure 10 is positioned so as to protect and support the section of tunnel close to the excavation face F. In the condition shown in Figure 3, the front edge 13 of the shell 12 is

substantially in contact with the excavation face F, which remains entirely free and accessible because there are no obstructions of any kind inside the tubular structure 10 which might impede access to the face.

In this condition, it is particularly convenient to work at the excavation face F, for example in the case of soft ground and/or ground with low cohesion. This is because the excavation face F is entirely free and can therefore be consolidated using methods generally known in the art, for example by making long axial bores P into which stays, made of fibreglass for example, with lengths of up to 20 metres, can be inserted, after which the bores are filled with pressurized concrete or slurry which consolidates the ground and allows the excavation face F to be advanced thereafter. The bores can be made and the stays can be installed easily by means of a well-known machine known as a "positioner", or alternatively a "Jumbo" or "Boomer" machine, which is a special vehicle used for tunnelling by the conventional method. In the case of the present invention, the positioner, or alternatively the Jumbo or Boomer machine, can reach the excavation face F without any obstruction because the tubular structure 10 is entirely open from the front to the rear area .

Figure 3 also shows how a course of concrete segments 26 has already been laid in the rear portion 24 of the shell 12. The segments 26 are preferably laid in a step preceding the step of consolidating the excavation face F, by procedures described more fully below with reference to Figure 6. In this step, the pushing members 22 are in their retracted positions, with the pushing ends 22a close to the segments 26.

On completion of the consolidation step, if required, and of any other necessary or useful operations on the excavation face F, such as drainage, the actual excavation can be commenced, as shown by way of example in Figure 4, by advancing the excavation face F with the use of conventional machines and vehicles 38 such as bucket diggers, excavators, self-loading sectional cut heading machines, and the like, which can easily reach the excavation face F, while the removed material is loaded on to lorries and transported out of the tunnel. In this step also, the operations and the entry and exit of vehicles can take place easily because the tubular structure 10 is not obstructed in any way from the front area to the rear area.

During the excavation step, the tubular structure 10 remains stationary, while the excavation face F advances with removal of material, while the plates 30 are progressively extend, if necessary, to cover the top of the excavation arch. These plates 30 have the important function of

protecting the machines and personnel located in the proximity of the excavation face F from possible local collapses, in other words from possible falls of rock, debris and the like from the arch of the excavation. This system also offers the possibility of avoiding the presence of personnel in the area purely concerned with advancing the face, where personnel remain present in the convention excavation method during the laying of the segments, this area being considered a lethal hazard zone even at the present day.

After the excavation face F has been advanced for a predetermined distance, preferably approximately equal to the size of a new course of segments, the tubular structure 10 is advanced. In this step, shown in Figure 5, the pushing members 22 are operated in such a way as to extend them.

Their ends 22a bear against the segments 26 positioned in the rear area 24 of the shell 12, which in turn bear against the course of segments behind them, laid previously to line the tunnel. The action of the pushing members 22 on the segments 26 causes the tubular structure 10 to advance towards the excavation face F, until the front edge 13 of the shell 12 substantially bears on the excavation face F, so as to cover the newly excavated ground. During this operation of

advancing the tubular structure 10, the plates 30 which previously protected the area in front of the front edge 13 of the shell 12 are correspondingly withdrawn. Also during the advance of the tubular structure 10, materials for filling any voids left between the radial excavation cross section and the shell 12 are pumped, if necessary, from the inside to the outside of the tubular structure through a number of passages, preferably of small size, formed in the shell 12, in order to avoid leaving any empty spaces which might cause collapses and concentrations of pressure of the ground on the machine and on the segments of the lining.

Subsequently, as shown in Figure 6, the pushing members 22 are retracted, leaving the rear portion 24 of the shell 12 free for a new course of concrete segments 26 to be laid therein, the segments being on the course of segments 26 located behind them, on which the pushing members 22 bore in the preceding step. The segments 26 can advantageously be laid by means of a special vehicle or machine 40, suitably designed for this purpose, making it unnecessary to provide the tubular structure with incorporated systems for moving and laying the segments.

Figure 7 shows a preferred embodiment of a self-powered segment laying machine 50, for the fast automatic laying of the segments between the advances of the tubular structure 10. The self-powered machine 50 comprises a platform 51 for carrying the segments, mounted on wheels 52, preferably with tracks 53. A sliding member 54 for feeding the segments to a segment laying head 55 is mounted on the side of the platform 51. The sliding member 54 slides on guides 56, preferably hinged to the side of the platform 51 in such a way that they can be raised and occupy less space at the side when the self-powered machine 50 moves towards or away from the tubular structure 10, at the start and end of the segment laying step respectively.

The segment laying head 55 is mounted rotatably on two columns, namely a rear column 57 and a front column 58, which support a shaft 59 fixed to a hub body 60 of the segment laying head 55. The front column 58, preferably supported by wheels, is provided with means (not shown in the drawing) for its electronic and mechanical connection to the tubular structure 10. The mechanical connection is preferably made by a system of hydraulic cylinders, which lock the self-powered vehicle 50 so as to fix its position in a unique way with respect to the tubular structure 10 and therefore with respect to the portion of tunnel to be lined with the

segments .

Two parallel beams 61 joined at one end by a

counterweight 62 are fixed to the hub body 60 of the segment laying head 55. On the two beams 61 there are mounted, by a telescopic mounting for example, two corresponding extendable arms 63 joined by a block 64 to which is pivotably connected a gripper 65 having pick-up means 66, such as suction cups, for selectively taking hold of a concrete segment 26 which is fed, to the same position in all cases, by the sliding member 54. The gripper 65 can preferably move in various directions, while making small movements for adjustment to allow each individual segment 26 to be laid correctly in the desired position .

The electronic connection between the self-powered segment laying machine 50 and the tubular structure 10 permits a dialogue between the two pieces of equipment for the correct automatic positioning of the segments in the desired position, and also enables commands to be given. In particular, the electronic connection enables the self- powered machine 50 to know the positions of the pushing members 22 of the tubular structure 12, in such a way that the segments can be placed in the best position for their retention in position by the pushing members 22 which are selectively operated. When the individual segment 26 has been placed in position against the tunnel wall, the self-powered machine 50 sends a command for the operation of the pushing members 22 located next to the newly laid segment, which is thus retained in position. The gripper 65 can therefore release the newly laid segment 26, and can return to the position shown in Figure 7, in order to take hold of the next segment to be laid.

At the end of this segment laying operation, the self- powered machine 50 can be withdrawn and leave the access to the tubular structure 10 free once more for the resumption of the excavation by the procedures described above.

As is clear from the above description of a preferred embodiment of the invention, the method and equipment which have been described make the construction of tunnels

particularly simple, economical and flexible, especially, but not exclusively, if it is carried out in soft ground and/or ground with low cohesion. The tubular structure 10 is substantially open in its front and rear parts and along its whole length, thus allowing convenient passage for the working machines and vehicles and for personnel, and enabling efficient operations to be performed in a simple way for consolidating the excavation face. The equipment according to the present invention is particularly economical by

comparison with known TBMs, and provides considerable

flexibility in tunnelling, by allowing changes to be made in the procedures for excavation, consolidation, advancing, and lining the tunnel under construction, in response to changes, which may or may not be foreseen, in the characteristics of the ground and rock. Compared with the conventional methods, the procedure and equipment proposed herein offer a high level of safety and a faster working rate for tunnelling, especially in soft ground and/or ground with low cohesion.

In a variant of the present invention, the plates 30 are not only axially movable as described above, but can also be bent or orientated, partially or completely, in a radial direction, for the partial support and covering of the excavation face F where necessary. However, this possibility of covering does not impede substantially free access to the excavation face F, for any necessary consolidation and/or reinforcement by the procedures described above.

Clearly, provided that the principle of the invention is retained, the detailed features and embodiments of the invention can be varied widely without departure from the scope of the invention.

Claims

1. A method for tunnelling, comprising the following steps :

a) providing equipment comprising a tubular structure (10) with a substantially empty tubular cavity, corresponding to the cross section of the tunnel to be constructed, in such a way that a front portion (13) of the tubular structure (10) is located close to the excavation face (F) ;

b) working on the excavation face (F) and advancing it for a predetermined distance by excavation with one or more self-powered excavating machines which are moved into the tubular cavity of the tubular structure (10) up to a point close to the excavation face (F) ;

c) laying at least one course of segments in a rear area of the tubular structure (10);

d) making the tubular structure (10) advance over the predetermined distance, by pushing on the at least one course of segments until the front portion (13) is brought to a point close to the excavation face (F) ; and

e) repeating steps (b) to (d) until the tunnel is complete .

2. A method for tunnelling according to Claim 1, comprising the step of consolidating the excavation face (F) where necessary because the softness and/or low cohesion of the ground, before the excavation face (F) is worked on and advanced .

3. A method for tunnelling according to Claim 2, wherein the consolidation of the excavation face (F) is carried out by making axial bores (P) which have elongate reinforcing members inserted into them and which are subsequently filled with pressurized concrete or slurry.

. A method according to Claim 3, wherein the bores are made and the stays are installed by means of a self-powered machine moved into the tubular structure (10) up to a point close to the excavation face (F) .

5. A method according to any one of the preceding claims, wherein the at least one course of segments is laid by means of at least one self-powered machine.

6. A method according to any one of the preceding claims, wherein the material excavated by the one or more excavating machines is removed by means of one or more automatic goods vehicles .

7. A method according to any one of the preceding claims, wherein the tubular structure (10) is provided with

selectively extendable protective members (30) positioned in at least one upper area of the front portion (13), which are extended during the advance of the excavation face (F) with removal of material, while the tubular structure (10)

remaining stationary during the advance of the excavation face (F) with removal of material, thereby covering the top of the arch of the excavation.

8. Equipment for tunnelling, comprising a tubular structure (10) having a substantially empty tubular cavity

corresponding to the cross section of the tunnel to be constructed, an outer shell of the tubular structure (10) being capable of protecting self-powered machines which are moved, during use, into the tubular cavity for carrying out tunnelling work in the proximity of a front portion (13) of the tubular structure (10).

9. Equipment according to Claim 8, comprising a plurality of pushing members (22) fixed to the tubular structure (10) and capable of causing the structure to advance, in use, by bearing against at least one course of segments which can be positioned in a rear area of the tubular structure (10) .

10. Equipment according to Claim 8 or 9, wherein the tubular structure (10) is provided with selectively extendable protective members (30), positioned in at least an upper region of the front portion (13) to cover the top of the arch of the excavation.