Tunnel construction method and machine

Abstract

A method for building a natural tunnel comprises the steps of: a) advancing an excavation front (EF) of a tunnel (1) by point excavation by a predetermined advance length using one or more self-propelled excavation machines (100); b) removing excavated material from a working area by means of one or more automatic dump trucks (500), said working area being located between an excavation front (EF) and a final lining front (FLF) of said tunnel (1); c) applying a primary lining (2) to the wall exposed by excavation at the advance length of the excavation front (EF); d) advancing said final lining leading edge (FLF) by a predetermined advance length by forming a final lining (4) on the primary lining (2) applied with the same advance length in a previous advance cycle; and e) repeating the steps a) to d) until the tunnel (1) is completed. The step d) of advancing said final lining front (FLF) comprises assembling at least one complete loop (42 ') of prefabricated segments (41) and proceeding simultaneously with the step a) of advancing said excavation front (EF). Furthermore, the step d) of advancing the final lining front (FLF) is carried out by a segment placement machine (200) having a tubular frame (201), and during the steps b) and c), the passage or displacement of the operating machine (100), vehicle or equipment out of / to the work area takes place by the tubular frame (201) of the segment placement machine (200). A segment placement machine (200) for use in the method is also described.

Description

Technical Field

[0001] The present invention generally belongs to the technical field of the construction of natural tunnels. In particular, the present invention relates to a method and a machine for constructing a natural tunnel by excavation using "traditional" techniques. Background Art

[0002] Generally speaking, the construction of natural tunnels by excavation consists of three main operations: digging underground, removing the excavated material, and applying one or more lining layers to stabilize and reinforce the excavation walls. These operations form the basis of the most widely used techniques for the construction of natural tunnels by excavation today, namely the "conventional" technique and the "mechanized" technique.

[0003] According to the "traditional" technology, the above basic operations are performed discontinuously, mostly successively, and are repeated cyclically until the tunnel is completed. Each of the above basic operations requires direct and extensive labor intervention and requires the use of multiple operating machines, vehicles and equipment, which must repeatedly pass or move along the tunnel during the construction of the tunnel to reach the corresponding working front or area. In more detail, in a typical embodiment of a known method for building a natural tunnel by excavation using "traditional" technology, each forward cycle includes first advancing the excavation front of the tunnel by a predetermined advance length. The excavation front is excavated by a conventional excavation machine by point excavation. While and / or after excavation, the excavated material is removed by a dump truck, which transports the excavated material to the outside of the tunnel being constructed and repeatedly passes through the tunnel.

[0004] Once the tunnel length just excavated has been cleared of the excavated material, a primary lining (also called first stage lining or temporary lining) is applied to the walls exposed by the excavation, especially the radial walls, the purpose of which is to stabilize the cavity in the short term so as to allow workers to operate safely therein. The initial lining is usually made of shotcrete. Usually, before the application of the shotcrete, large metal reinforcement profiles, which are called ribs, are laid. Such reinforcement profiles are shaped according to the excavation cross-sectional profile and are arranged longitudinally at regular intervals along the excavation. In this case, the shotcrete is then applied to the inner arc of the ribs and between the ribs themselves, so as to combine them into a single structure. For these operations, suitable operating machines are used, such as pumping machines for applying the shotcrete and machines for lifting and laying the ribs, as well as related service vehicles, such as concrete mixers and load trucks for transporting the ribs and other materials, which should be able to pass through the tunnel being constructed up to the newly excavated tunnel length.

[0005] Subsequently, further working fronts are advanced upstream of the excavation front (with reference to the direction of advance of excavation), at which work is carried out aimed at forming the final lining of the tunnel (also called second stage lining), which is required to ensure the long-term stability of the tunnel.

[0006] In particular, at a first working front upstream of the excavation front, two lateral shoulders (also referred to in the art as curbstones) made of reinforced concrete and parallel to each other are further constructed on opposite sides of the tunnel base. At a second working front upstream of the advancing front of the curbstones, an invert, also made of reinforced concrete, is constructed at the bottom of the tunnel between the two previously constructed curbstones. Finally, at a third working front upstream of the advancing front of the invertstones, the final lining of the tunnel is constructed at the vault and the sidewalls. Typically, this operation includes laying waterproof sheets on the corresponding surfaces, constructing steel reinforcement frames and casting concrete with a radial thickness of 30 cm to 120 cm by means of large monolithic formworks, which are transversely shaped according to the final tunnel cross-sectional profile and have a length of, for example, 10 m, which can be moved along the tunnel on tracks temporarily laid on the previously constructed curbstones.

[0007] The operations associated with the casting of the final lining at the vault and side walls and the invert at the bottom significantly hinder or completely block the passage of operating machines, vehicles or equipment through the tunnel section involved and therefore the passage of operating machines, vehicles or equipment away from / to the excavation front. During these operations, which may take 10-12 hours in the case of the final lining, it is not possible to advance the excavation. The excavation is resumed in the subsequent advance cycle, when the tunnel section involved in the advancement of the final lining or invert is again free.

[0008] It will be evident from the foregoing that the rate of excavation progress achieved using "conventional" techniques (which is the factor that has the greatest impact on tunnel construction time and therefore cost) is inherently limited by the nature and sequence of operations being performed. Furthermore, it is often found in practice that the rate of excavation progress achieved using "conventional" techniques is greatly affected by the experience and skills of the workforce involved and by site management.

[0009] Under the same external conditions, higher excavation advance rates can be achieved by "mechanized" technology. In this case, the basic operations mentioned at the beginning are carried out continuously and simultaneously by large, specially designed automated machines called TBMs (Tunnel Boring Machines). These machines perform excavation in an integral and continuous manner, while removing the excavated material from the excavation front and laying the tunnel lining upstream of the excavation front. In this case, there is no need to form a primary lining, and the final lining is immediately built by sequentially placing lining rings on the entire perimeter of the excavation section, each of which is formed by a plurality of appropriately shaped precast concrete elements, which are called segments. All these operations are carried out in a completely mechanized manner and require a minimum of labor; in this case, the work of the workers is essentially limited to monitoring the progress of the excavation and operation of the TBM. Although "mechanized" technology generally allows higher excavation advance rates, the extremely high cost of TBMs makes it economically feasible only when building sufficiently long tunnels, especially tunnels of at least 2 km in length, and in land with a sufficiently uniform composition, so as to avoid as much as possible expensive machine downtime due to unforeseen events during excavation.

[0010] For the construction of shorter tunnels, in particular tunnels shorter than 2 km, and / or in land with a very heterogeneous composition, the "traditional" techniques, even if not the most suitable for technical reasons, are still the most favourable solution in terms of cost-benefit ratio. Therefore, the "traditional" techniques for digging natural tunnels are still very common today and need to be developed and improved. Summary of the invention

[0011] In view of the above, the main object of the present invention is to reduce the construction time of natural tunnels by excavation using "traditional" techniques.

[0012] Another object of the present invention is to reduce the impact of the experience or skills of the on-site workforce on the time it takes to build a natural tunnel by excavation using "traditional" techniques.

[0013] As mentioned above, the Applicant has realised that the objects can be achieved in a particularly effective manner by using a different way of constructing the final lining of the tunnel than by constructing natural tunnels by excavation using "traditional" techniques according to the prior art.

[0014] In particular, in a first aspect of the invention, the invention relates to a method for constructing a natural tunnel, wherein the tunnel being constructed comprises an excavation front, a final lining front upstream of the excavation front in the direction of advance of excavation, and a working area between the excavation front and the final lining front, the method comprising the following steps:

[0015] a) advancing the excavation front by a predetermined advancement length by point excavation using one or more self-propelled excavation machines;

[0016] b) removing excavated material from said work area by one or more dump trucks;

[0017] c) applying a primary lining to the wall exposed by the excavation at the advanced length of the excavation front;

[0018] d) advancing the final lining front by a predetermined advancement length by forming the final lining on the primary lining applied in a previous advancement cycle by the same advancement length;

[0019] e) repeating steps a) to d) until the tunnel is completed,

[0020] wherein step d) of advancing the final lining front comprises assembling at least one complete ring of prefabricated segments and is performed simultaneously with step a) of advancing the excavation front,

[0021] wherein step d) of advancing the final lining front is performed by a segment placing machine having a tubular frame, and

[0022] Therein, during step b) of removing excavated material and step c) of applying the primary lining, the passage or displacement of operating machines, vehicles or equipment to / from the working area occurs through the tubular frame of the segment placing machine.

[0023] Within the framework of a method of building a natural tunnel by excavation using "traditional" techniques, the present invention proposes to form the final lining of the tunnel by placing prefabricated segments assembled to form a ring extending along the entire perimeter of the excavated section, instead of building the lining entirely on site, as in the prior art, by building a steel reinforcement framework and subsequently casting concrete with the aid of appropriate formwork. The segments are placed in a mechanized manner while the excavation front is advanced, by means of specially designed segment placement machines.

[0024] These measures significantly speed up each forward cycle of the method according to the invention for building a natural tunnel and have an advantageous effect on the overall time and costs for building the tunnel.

[0025] Firstly, the fact that the choice of a final lining made of segments advantageously allows to omit the steps of building the curbstones and inverts at the bottom of the tunnel, which steps are essential in the prior art methods of building tunnels by excavation using "traditional" techniques in order to subsequently form the final lining at the crown and the side walls.

[0026] Secondly, while keeping the lining length constant, the speed of constructing the final lining by placing segments is inherently significantly faster than constructing a final lining with the same characteristics by casting in situ. For example, for a tunnel length of 1m, the final lining by placing segments may typically take about 1 hour or even less, while casting in situ may take several hours.

[0027] In the method of the invention, the shorter duration of the final lining front advancement step allows it to be completely overlapped in time with the excavation front advancement step, which (again with reference to the 1 m front advancement) typically requires 3 to 12 hours depending on the rock conditions. This temporal overlap brings two advantageous effects. On the one hand, the final lining front advancement step is masked by the excavation front advancement step in terms of time and therefore no longer affects the overall tunnel construction time. On the other hand, the step no longer causes downtime for the execution of the other steps of the method, since the temporary blocking of the tunnel section affected by the operation of advancing the final lining front now occurs during the excavation step, which can usually be carried out and completed autonomously, without the need for simultaneous and repeated passages of operating machines, vehicles or equipment out of / to the working area of ​​the tunnel, which is required for the removal step of the excavated material and the primary lining application step.

[0028] In addition to the above, the prefabricated segments are placed by a self-propelled segment placement machine specially designed for the above method, having a tubular frame through which the operating machines, vehicles or equipment required for performing the other steps of the method (in particular the removal step of the excavated material and the primary lining application step) can freely pass or be displaced away from / to the working area at the excavation front, at least when the machine is not working, i.e. it is not placing segments. Thus, downtimes caused by the segment placement machine being repeatedly displaced away from its working position in order to free up access away from / to the working area and repositioning the machine to resume the placement of segments in a new final lining front advancement step can be avoided. This aspect also helps to speed up each advancement cycle of the method for building a natural tunnel according to the invention.

[0029] Furthermore, since the final lining front advancement step is now performed in a mechanized manner, its execution time and quality are only slightly affected by the experience and skills of the on-site workforce. Thus, the step can be standardized in terms of duration and quality and, if desired, also fully or partially automated.

[0030] Another advantage associated with the method for building a natural tunnel according to the invention is that the distance between the excavation front and the final lining front is reduced due to the elimination of the advancing fronts of the kerb and invert and the possibility of rapidly advancing the final lining front. The short tunnel length between the two fronts, where only the primary lining is present, improves the safety conditions on site, especially in difficult geological conditions, reducing the probability of the primary lining sinking without the need for additional reinforcement works, which would have a negative impact on the construction time and costs of the tunnel.

[0031] Preferred embodiments of the above-described method for constructing a natural tunnel are subject matter of the respective dependent claims, the content of which is fully incorporated herein by reference.

[0032] In a second aspect of the invention, the invention relates to a self-propelled segment placement machine for placing prefabricated segments for the final lining of a natural tunnel, comprising:

[0033] - a longitudinally extending tubular frame, the transverse dimensions of which allow the passage or displacement through said tubular frame of operating machines, vehicles or equipment used during the construction of said tunnel, and

[0034] - segment handling means associated with the tubular frame and displaceable relative to the tubular frame between a segment retrieval position and a plurality of segment placement positions for assembling a complete ring of segments at the wall of the tunnel,

[0035] wherein, in the rest configuration of the segment placement machine, the tubular frame is freely implementable by the operating machine, vehicle or equipment, and

[0036] Therein, the tubular frame comprises a plurality of anchoring devices which may extend radially from the tubular frame for temporarily anchoring the segment placement machine to the wall of the tunnel.

[0037] Within the framework of a method of constructing a tunnel by excavation using "conventional" techniques, the segment placement machine of the present invention allows the final lining of the tunnel being constructed to be constructed in a completely mechanized manner, thereby significantly limiting the labor required. Moreover, at least in its rest configuration, i.e. when it is not placing segments, the segment placement machine of the present invention does not hinder the passage or movement of operating machines, vehicles or equipment away from / to the working area at the excavation front of the tunnel being constructed, since in this case the passage or movement can take place by the segment placement machine itself. Therefore, there is no need to repeatedly move the machine away from and back to the respective working fronts in order to allow the other steps of the construction of the tunnel to be carried out. The segment placement machine of the present invention therefore contributes to achieving all the advantages described above with reference to the method of the present invention, in particular with regard to the reduction of construction time and the impact of the on-site labor in this regard.

[0038] Preferred aspects of the above-described segment placement machine are subject matter of the respective dependent claims, the content of which is fully incorporated herein by reference. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Additional features and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention, which is for illustrative and non-limiting purposes, with reference to the accompanying drawings, in which:

[0040] Figure 1 A schematic perspective longitudinal cross-sectional view showing the steps of constructing a tunnel according to the method of the present invention;

[0041] Figure 1a For the corresponding Figure 1 A schematic longitudinal cross-sectional view of

[0042] Figure 1b For Figure 1a A schematic cross-sectional view at plane BB of ;

[0043] Figure 2 A schematic perspective longitudinal sectional view showing another tunnel construction step of the method according to the invention;

[0044] Figure 2a For the corresponding Figure 2 A schematic longitudinal cross-sectional view of

[0045] Figure 3 and 4 A schematic perspective longitudinal sectional view showing another tunnel construction step of the method according to the invention;

[0046] Figure 3a and 4a Corresponding to Figure 3 and 4 A schematic longitudinal cross-sectional view of

[0047] Figure 5 A schematic perspective longitudinal sectional view showing another tunnel construction step of the method according to the invention;

[0048] Figure 6 A schematic perspective longitudinal sectional view showing another tunnel construction step of the method according to the invention;

[0049] Figure 7 A schematic perspective view of a segment placement machine according to the present invention in a rest configuration;

[0050] Figure 7a for Figure 7 A schematic front view of a segment placement machine;

[0051] Figure 8 for Figure 7 A schematic perspective view of a segment placement machine in a working configuration, and

[0052] Figure 8a for Figure 8 Schematic front view of a segment placement machine. DETAILED DESCRIPTION

[0053] Figure 1-6 The method according to the invention is shown in the steps of constructing by excavation a natural tunnel, generally indicated by the reference numeral 1 .

[0054] As in Figure 1a As can be better seen in FIG. 1 , in the tunnel 1 under construction, it is possible to identify the excavation front EF, the primary lining front PLF upstream of the excavation front EF, and the final lining front FLF upstream of the primary lining front PLF. Upstream of the final lining front FLF there is also the lane surface front CF, upstream of which the lane surface 5 has already been constructed in the tunnel 1 (see FIG. 1 ). Figure 2 , 3 , 4, 5 and 7).

[0055] Unless otherwise indicated, in the context of this specification and the following claims, the terms "upstream" and "downstream" should be referred to as if Figure 1a The excavation forward direction shown by the arrow A is understood.

[0056] Furthermore, in the context of the present description and the subsequent claims, the area of ​​the tunnel 1 between the excavation front EF and the final lining front FLF is also denoted as "working area".

[0057] During the construction of the tunnel 1, each of the fronts mentioned above gradually advances until the tunnel 1 is completed. If the excavation conditions permit, during the construction of the tunnel 1, the mutual distances between the fronts may be kept substantially constant.

[0058] In the region between the excavation front EF and the primary lining front PLF, the radial walls of the tunnel 1 can be free of any lining, ie bare, during the excavation step and the removal step of the excavated material (see Figure 1a-3a ), or may be provided with a primary lining 2 being constructed (see Figure 4a , Figure 5 ).

[0059] In the area between the primary lining front PLF and the final lining front FLF, the radial walls of the tunnel 1 are provided with a finished primary lining 2 intended to achieve short-term stability conditions for the excavated cavity and to allow the workforce to operate safely.

[0060] Preferably, the primary lining 2 comprises in a known manner metal reinforcing ribs 21 arranged longitudinally along the tunnel 1 at regular intervals, for example at a mutual distance of about 1 m, and a layer of sprayed concrete 22, possibly reinforced with wire mesh or metal fibers, applied on the inner curvature of the ribs 21 and between the ribs.

[0061] The rib 21 can be made of, for example, structural steel and have an open cross-sectional shape, such as an H-shaped shape (HEA-HEB beam) or a double T-shaped shape (IPE beam), or a closed cross-sectional shape. In the latter case, the internal volume of the rib 21 can be conveniently filled with concrete by pumping after the rib 21 is installed.

[0062] In any case, the ribs 21 preferably have a circumferentially closed shape, for example substantially circular, and extend continuously along the entire periphery of the cross section of the tunnel 1. For the sake of clarity, in the longitudinal cross-sectional views, the ribs 21 are clearly shown only at the working area, however it should be understood that they are present in the same way in any part of the tunnel 1 upstream of the primary lining front PLF.

[0063] In the working area, in particular in the area between the primary lining front PLF and the final lining front FLF, there is a temporarily compacted earth working floor 3 at the bottom of the tunnel 1, which is made of a part of the excavated material resulting from the advancement of the excavation front EF.

[0064] Upstream of the final lining front FLF, the radial wall of the tunnel 1 also has a final lining 4 applied to the primary lining 2 .

[0065] Here, the final lining 4 is made of prefabricated segments 41 which are assembled to one another to form a plurality of circular closed rings 42 adjacent to one another in the longitudinal development direction of the tunnel 1 .

[0066] The segments 41 are prefabricated elements made of reinforced concrete, possibly reinforced with metal fibers. Preferably, when installed, each segment 41 is mechanically interconnected with adjacent segments 41 in the circumferential direction (i.e. within the same ring 42 of segments 41) and in the longitudinal direction (i.e. for the ring 42 of segments 41 immediately adjacent to the ring 42 comprising the segment 41 at hand). The segments 41 of each ring 42 can conveniently be arranged circumferentially offset relative to the segments 41 of the adjacent ring 42 (not shown in the figures).

[0067] Preferably, the segments 41 of the final lining 4 are not placed in direct contact with the underlying primary lining 2 , but an annular gap is left which is subsequently pressure filled with hydraulic mortar 43 .

[0068] refer to Figure 1-6 With the tunnel 1 described above, a preferred embodiment of the method for building a natural tunnel by excavation according to the present invention will now be explained in detail. In particular, the steps of a general forward cycle that forms the core of the method and is repeated until the tunnel 1 is completed will be explained.

[0069] In particular, as from Figure 1 , 1a As can be clearly seen from Figure 1b, each advancement cycle includes the step of advancing the excavation front EF by a predetermined advancement length by point excavation using one or more excavation machines. The excavation machines operate in the working area between the excavation front EF and the final lining front FLF. For example, Figure 1 , 1a 1b shows an excavation machine 100 provided with a crusher; alternatively or additionally, depending on the type of rock or land found, an excavation machine provided with, for example, a backhoe bucket, a ripper or a roadheader may be used for point excavation at the excavation front EF.

[0070] Preferably, the advancement of the excavation front EF is carried out by full-face excavation. Figure 1b It can be clearly seen that by using the point excavation technique, the excavated cross section is not limited to a circular shape as in the case of excavation using "mechanized" technology by TBM.

[0071] As from Figure 1 , 1a1b It can also be clearly seen that while excavation is being carried out to advance the excavation front EF, the final lining front FLF is also advanced by a predetermined advancement length by assembling at least one further complete ring 42' of segments 41 onto the previously applied primary lining 2. Figure 1 and 1a , the further ring 42' is shown still in the construction phase. Preferably, the advancement length of the excavation front EF and the advancement length of the final lining front FLF are substantially equal and preferably correspond substantially to the width of the ring 42 of the segment 41. Thus, the longitudinal extension of the working area between the excavation front EF and the final lining advancement front remains substantially constant in subsequent advancement cycles for the construction of the tunnel 1. However, the possibility of advancing the excavation front EF and the final lining advancement front FLF by respective different advancement lengths is not excluded. For example, if during the construction of the tunnel 1 an area with less viscous ground is encountered, it may be advantageous to advance the final lining front FLF by a longer length than the corresponding advancement length of the excavation front EF, at least in one advancement cycle, in order to reduce the longitudinal extension of the working area in which the wall of the tunnel 1 is provided with only the primary lining 2. In this case, for example, the advancement length of the excavation front EF can be kept constant and the advancement length of the final lining front FLF can be doubled by placing two complete rings 42 of the segment 41.

[0072] The segments 41 are placed in a robotic manner by a self-propelled segment placement machine 200 which is specially designed for the method of the present invention and is used in Figure 7 , 7a , 8 and 8a are shown in more detail.

[0073] As especially from Figure 7 and 8 As can be clearly seen, the segment placement machine has a longitudinally extending tubular frame 201. The tubular shape of the frame 201 is adapted to the shape of the inner section of the tunnel 1 resulting from the placement of the final lining 4. In particular, in the case shown here, the frame 201 has a substantially circular cross section.

[0074] The frame 201 preferably has a reticular structure formed by a plurality of circumferential ribs and a plurality of longitudinal cross members. A first longitudinal end of the frame 201 (hereinafter also referred to as the "front end") preferably extends in a plane substantially perpendicular to the longitudinal development direction of the frame 201, while a second longitudinal end (hereinafter also referred to as the "rear end") preferably extends in a plane inclined towards the first longitudinal end relative to the longitudinal development direction. These features generally produce a "rib cage"-like shape of the frame 201, which is particularly advantageous for providing stability and structural resistance of the segment placement machine 200 under static and dynamic conditions, and at the same time, for reducing its weight and limiting the amount of material required to construct the frame 201.

[0075] In any case, regardless of the specific shape and configuration, the internal transverse dimensions of the tubular frame 201 allow an operating machine, vehicle or equipment used to construct the tunnel 1 to pass or shift therethrough, and in the rest configuration of the segment placement machine 200, the tubular frame 201 can be freely implemented by the operating machine, vehicle or equipment, as further described in detail below with reference to the method of the present invention.

[0076] In order to allow the above-mentioned passage or movement to occur easily, the segment placement machine 200 preferably includes a drivable motor vehicle plane 202 extending longitudinally inside the tubular frame at the base of the tubular frame 201, preferably throughout the length of the tubular frame. As an alternative to the drivable motor vehicle plane 202, for example, a pair of parallel tracks can be provided.

[0077] The segment placement machine 200 comprises segment handling means associated with a tubular frame 201 and displaceable relative to the tubular frame 201 between a segment acquisition position and a plurality of segment placement positions to form a ring 42 of segments 41 of the above-mentioned final lining 4 of the tunnel 1, such as Figure 1 , 1a , as shown in 1b and described in further detail below.

[0078] In a preferred embodiment of the segment placement machine 200, the segment movement means comprise a robot arm 203 displaceable along a circular guide track 205 which is integral with the tubular frame 201 and arranged perpendicularly to the longitudinal extension of the tubular frame 201. This design has proven to be particularly effective in combining a simple construction and operational flexibility with the need to avoid, at least in the rest configuration of the segment placement machine 200, the presence of fixed obstacles which prevent the passage of operating machines, vehicles or equipment through the tubular frame 201.

[0079] The circular guide rail 205 has a closed shape and is preferably arranged at the front end of the tubular frame 201 , preferably inside the tubular frame.

[0080] The robot arm 203 is configured and dimensioned for handling segments 41 in order to place the segments to form the final lining 4 of the tunnel 1. In particular, the robot arm 203 can be conveniently configured as a robot arm with three articulation axes, preferably parallel to each other, and comprising four sections articulated to each other at said articulation axes, wherein the two end sections respectively comprise or consist of a segment acquisition head and a base for coupling to the guide rail 205.

[0081] Preferably, the segment placement machine 200 further comprises at least one movable bridge 204 for temporary vehicular connection between the segment placement machine 200 and the working area of ​​the tunnel 1. The bridge 204 may comprise a plane for a single vehicular movement, or, as in the embodiment shown in the figure, a pair of parallel tracks. Preferably, the bridge 204 is mounted to the same circular guide track 205 as the robot arm 203 and may be displaced along the guide track in a coordinated manner with the robot arm 203.

[0082] Taking into account the high loads that the segment placement machine 200 has to withstand when placing the segments 41 due to the weight of the robot arm 203 (e.g., 1.8-2 t) and the weight of the segments additionally supported and carried by it (typically, 2-2.5 t), the tubular frame 201 includes a plurality of anchoring devices 206 for temporarily anchoring the segment placement machine 200 to the wall of the tunnel 1, in particular the final lining 4. In this way, the stability of the segment placement machine 200 during the placement operation can be effectively ensured, which is a basic requirement for performing the placement operation accurately and without problems.

[0083] The anchoring means 206 are configured as anchoring means which can extend radially towards the outside of the tubular frame 201 and can consist, for example, of hydraulically thrust jacks. Preferably, the anchoring means are distributed on the tubular frame 201 so as to preferably form at least one loop at least at the guide rail 205.

[0084] The segment placement machine 200 preferably comprises a plurality of motorized wheels 207 associated with the tubular frame 201, by means of which the segment placement machine can be displaced inside the tunnel 1 on the previously laid final lining 4. The motorized wheels 207 preferably have independent and rotating axes of rotation. The motorized wheels 207 are arranged at least at the base of the segment placement machine 200, in particular according to at least two rows extending longitudinally along the tubular frame 201. Further motorized wheels 207 may also be located individually or in rows in other locations of the tubular frame 201, for example in the vault region thereof.

[0085] Figure 7 and 7a The segment placement machine 200 is particularly shown in a rest configuration, in which no segments 41 are placed by the segment placement machine. In this configuration, the robot arm 203 is preferably arranged to extend substantially parallel to the tubular frame 201 along the inside, preferably in the region of its vault, so that it does not constitute an obstacle to the passage of operating machines, vehicles or equipment through the tubular frame 201. On the other hand, the bridge 204 is in a use position at the base of the tubular frame 201 to form a drivable motor vehicle connection between the drivable motor vehicle plane 202 of the tubular frame 201 and the drivable motor vehicle surface of the tunnel 1, in particular a temporary working surface 3 (not shown here), which is located downstream of the segment placement machine 200.

[0086] on the other hand, Figure 8 and 8a The segment placement machine 200 is shown in a general working configuration for placing segments 41. In this configuration, the robot arm 203 at least partially protrudes longitudinally and / or laterally from the tubular frame 201 in a position along a circular guide rail 205, which varies depending on the placement position of the segment 41. In contrast, the bridge 204 is located in a non-use position along the circular guide rail 205, which can vary depending on the position of the robot arm 203.

[0087] Reference again Figure 1 , 1a , 1b, the assembly of at least one additional complete ring 42' of segments 41 for advancing the final lining front FLF performed with the aid of the above-mentioned segment placement machine 200 preferably includes repeatedly moving the robot arm 203 along a circular path defined by a guide rail 205 between a segment retrieval position and a plurality of segment placement positions distributed along the circular path.

[0088] The segments 41 required for building another complete ring 42 ′ of segments 41 may conveniently be provided in batches to the segment placement machine 200 , for example on a suitable self-propelled segment carrier 300 , which is preferably equipped to carry all the segments 41 required to form a complete ring 42 simultaneously.

[0089] In order to move the segment carrier 300 from the area of ​​the tunnel 1 upstream of the segment placing machine 200 where the lane plane 5 has been provided to the segment placing machine 200, preferably a self-propelled service platform 400 is used, which can be moved back and forth between the lane plane front CF and the rear end of the segment placing machine 200. The self-propelled service platform 400 moves on the final lining 4 of the tunnel 1 similarly to the segment placing machine 200 and, for said purpose, is preferably provided with a plurality of motorized wheels with rotating and independent axes of rotation. In general, the self-propelled service platform 400 can advantageously be used to transfer all operating machines, vehicles or equipment used for the construction of the tunnel 1 according to the method of the invention within the section of the tunnel 1 between the rear end of the segment placing machine 200 and the lane plane front CF, although this will not be explicitly mentioned below.

[0090] While the segment placing machine 200 is placing the segments 41, other operating machines, vehicles or equipment cannot pass through the segment placing machine and therefore cannot reach the working area and the excavation front EF or move away therefrom. However, in the method according to the invention, during the step of advancing the final lining front FLF, a temporary blockage of the section of the tunnel 1 in which the segments 41 are being placed no longer constitutes an obstacle to the execution of the other steps of the method, because the blockage occurs during the excavation step for advancing the excavation front EF, which, on the one hand, can be carried out and completed without the need for operating machines, vehicles or equipment to leave / go to the working area and the excavation front EF simultaneously and repeatedly, and, on the other hand, assuming the same advancement length, has a longer duration, typically 1 to 10 times longer than the duration of the step of advancing the final lining front FLF by placing the segments 41, so that it completely masks the latter in terms of time.

[0091] Once the step of advancing the final lining front FLF has been completed, the segment placement machine 200 may remain in the same position in the tunnel 1 but be set to its rest configuration, as has been described above with reference to Figure 8 and 8a In this way, the operating machine, vehicle or equipment can leave / go to the working area of ​​the tunnel 1 again.

[0092] Once the step of advancing the excavation front EF has also been completed, the resulting excavated material is removed, if necessary, after the operating machine used for excavation (such as excavation machine 100) moves away from the work area, such as Figure 2 and 2aFor the described operation, one or more dump trucks 500 are used, which can be loaded by one or more loading shovels 600. The dump trucks 500 and the loading shovels 600 are moved away from / towards the working area of ​​the tunnel 1 by the segment placement machine 200, which remains in its position in the tunnel 1.

[0093] After the working area of ​​the tunnel 1 has been cleared of excavated material, the primary lining front PLF is advanced by applying the primary lining 2 to the walls, in particular radial walls, exposed by the excavation carried out in the previous step of advancing the excavation front EF.

[0094] like Figure 3 , 3a As shown in , 4, 4a, the application of the primary lining 2 comprises laying at least one further rib 21'. The rib 21 used in the method according to the invention can conveniently be of the type comprising hinged sections, as described, for example, in patent application WO2015 / 186029 A2, the content of which is incorporated herein by reference in its entirety. In this case, the rib 21 is preassembled outside the tunnel 1 and inside the tunnel 1 in a folded configuration ( Figure 3 and 3a ) are transported to the corresponding laying point, in particular the previously excavated advance length of the excavation front EF, and finally unfolded for laying at the laying point. In this case, the transportation and / or placement of the ribs 21 can be carried out with the help of a universal excavation machine 700, or also with the help of a special machine, which is particularly provided with two or more movable arms (not shown). However, it is not excluded to use traditional ribs 21 formed by individual sections, which are transported inside the tunnel 1 in a disassembled state and then assembled on site during installation.

[0095] The formation of the primary lining 2 preferably also comprises applying a layer of shotcrete on the walls exposed by the excavation, in particular the radial walls, and on the inner curvature of at least one further rib 21' previously laid (see Figure 5 ). The operation is carried out in a known manner with the help of at least one pumping machine 800 for applying shotcrete, which is supplied by a concrete mixer 900. In this case too, the pumping machine 800 and the concrete mixer 900 are moved away from / towards the working area of ​​the tunnel 1 by the segment placing machine 200, which remains in its position in the tunnel 1.

[0096] Once the formation of the new length of primary lining 2 has been completed, the final lining 4 can be completed at the advanced length of the final lining front FLF. In particular, the hydraulic mortar can be pumped into the gap between the further ring 42' of the placed segments 41 and the underlying primary lining 2 by a suitable pumping machine (not shown) of known type.

[0097] Once the formation of the new portion of the final lining 4 has been completed, the segment placement machine 200 can be moved forward on the previously applied final lining 4 by a length substantially equal to the advanced length of the final lining front FLF so that its front end is again at the (new) final lining front FLF.

[0098] At this point, a new forward cycle including the steps previously described may begin.

[0099] In addition to the above steps, the method for building a natural tunnel of the invention may optionally include further steps assisting the implementation of the above steps in a manner known to a person skilled in the art, in all or only some of the forward cycles required to build the tunnel 1 .

[0100] For example, Figure 6 An optional step of consolidating the excavation front EF is shown, which step may be required before advancing the excavation front EF in ground with no or low cohesion. In particular, again by way of example, Figure 6 Concerning the case of reinforcing the excavation front EF by glass fiber reinforcement, the glass fiber reinforcement is formed by making a series of perforations in the excavation front EF using a drilling machine 1000, inserting glass fiber ties into the perforations, and then pressure-injecting concrete.

[0101] from Figure 6 It can also be clearly seen that once the operating machine has reached the working area via the segment placing machine 200, the latter can be temporarily moved away from the final lining front FLF, i.e. in a direction opposite to the forward direction A of excavation, to ensure further operating space for the operating machine in the working area if necessary.

[0102] Besides the "industrialization" of the step of building the final lining, i.e. the corresponding step of advancing the front, the invention thus speeds up the time for building a natural tunnel by excavation using "traditional" techniques and reduces the influence of the experience and skills of the on-site workforce on the construction time of the structure and its final quality.

Claims

1. A method for constructing a natural tunnel, wherein: A tunnel (1) under construction comprises an excavation front (EF), a final lining front (FLF) upstream of the excavation front (EF) in an advancing direction (A) of excavation, and a working area between the excavation front (EF) and the final lining front (FLF), the method comprising the following steps: a) advancing the excavation front (EF) by a predetermined advancement length by point excavation using one or more self-propelled excavation machines (100); b) removing excavated material from the work area by one or more dump trucks (500); c) applying a primary lining (2) to the wall exposed by the excavation at the advanced length of the excavation front (EF); d) advancing the final lining front (FLF) by a predetermined advancement length by forming a final lining (4) on the primary lining (2) applied at the advancement length in a previous advancement cycle; e) repeating steps a) to d) until the tunnel (1) is completed, wherein step d) of advancing the final lining front (FLF) comprises assembling at least one complete ring (42') of prefabricated segments (41) and is performed simultaneously with step a) of advancing the excavation front (EF), wherein step d) of advancing the final lining front (FLF) is performed by a segment placement machine (200) having a tubular frame (201), and Wherein, during step b) of removing excavated material and step c) of applying the primary lining (2), passage or displacement of operating machines (100, 600, 700, 800), vehicles (500, 900) or equipment to / from the working area occurs through the tubular frame (201) of the segment placing machine (200).

2. The method according to claim 1, wherein: Assembling at least one complete ring (42') of the segments (41) by the segment placement machine (200) comprises repeatedly moving a robot arm (203) along a circular path between a segment acquisition position and a plurality of segment placement positions distributed along the circular path.

3. A method according to any one of the preceding claims, wherein: The excavation front (EF) and the final lining front (FLF) advance substantially the same advancement length respectively.

4. The method according to any of the preceding claims, further comprising, after step d) of advancing the final lining front (FLF), advancing the segment placement machine (200) on the previously formed final lining (4) by a length preferably equal to the advanced length of the final lining front (FLF).

5. The method according to any of the preceding claims further comprises moving a self-propelled service platform (400) for transferring an operating machine (100, 600, 700, 800, 1000), a vehicle (300, 500, 900) or equipment in a tunnel section between a rear end of the segment placement machine (200) and a lane plane front (CF) of the tunnel (1), wherein the lane plane front is located upstream of the segment placement machine (200).

6. A self-propelled segment placement machine (200) for placing prefabricated segments (41) for a final lining (4) of a natural tunnel (1), comprising: - a longitudinally extending tubular frame (201) having transverse dimensions allowing the passage or displacement through said tubular frame (201) of operating machines (100, 600, 700, 800, 1000), vehicles (500, 900) or equipment used during the construction of said tunnel (1), and - a segment handling device (203) associated with the tubular frame (201) and displaceable relative to the tubular frame (201) between a segment acquisition position and a plurality of segment placement positions for assembling a complete ring (42, 42') of segments (41) at the wall of the tunnel (1), wherein, in the rest configuration of the segment placement machine (200), the tubular frame (201) can be freely implemented by the operating machine (100, 600, 700, 800, 1000), vehicle (500, 500) or equipment, and The tubular frame (201) comprises a plurality of anchoring devices (206) which can be radially extended from the tubular frame for temporarily anchoring the segment placement machine (200) to the wall of the tunnel (1).

7. The segment placement machine (200) according to claim 6, wherein: The pipe segment handling device (203) comprises a robot arm (203) which can be displaced along a circular guide track (205) which is integral with the tubular frame (201) and is arranged perpendicular to the longitudinal extension direction of the tubular frame (201).

8. The segment placement machine (200) according to claim 7, wherein: In the rest configuration of the segment placement machine (200), the robot arm (203) extends along the inner side of the tubular frame (201), preferably substantially parallel to the tubular frame in the region of its vaults.

9. The segment placement machine (200) according to claim 7 or 8, wherein: In the working configuration of the segment placement machine (200), the robot arm (203) at least partially protrudes longitudinally and / or transversely from the tubular frame (201).

10. The segment placement machine (200) according to any one of claims 6 to 9, further comprising at least one movable bridge (204) for establishing a connection between the segment placement machine (200) and the working area of ​​the tunnel (1) for drivable motor vehicles.

11. The segment placement machine (200) according to claim 10 as appended to claim 7, wherein: The movable bridge (204) can be displaced along the circular guide track (205) of the robotic arm (203) in coordination with the robotic arm (203).

12. The segment placement machine (200) according to any one of claims 6 to 11, wherein: The anchoring means (206) are positioned to form at least one loop around the tubular frame (201).

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