Rib for supporting and strengthening sequential excavation section and method for installing rib within sequential excavation section

Abstract

To provide a rib for supporting and strengthening a sequential excavation section and a method for automatically installing a support rib in the sequential excavation section.SOLUTION: A rib for supporting and reinforcing an excavation section comprises a plurality of structural elements (15, 16, 17) movably connected to one another such that the rib can move from a pre-assembled, at least partially collapsed, configuration prior to installation, to a partially extended support configuration intermediate a top end of a sequential excavation at a top plane, to a final configuration for support on a base plane at an elevation lower than the top plane. The structural elements are secured in structural continuity with one another in mutual positions that define a generally arched rib.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to ribs for supporting and strengthening a sequential excavation section and a method for automatically installing support ribs in a sequential excavation section.

[0002] The term "sequential excavation" shall mean excavation carried out by the sequential excavation method (SEM) or NATM (New Austrian Tunnelling Method). [Background technology]

[0003] For example, it is known to use reinforcing arches known as ribs to support excavations, such as road and railway tunnels. Ribs, in particular, consist of multiple formed structural elements, typically made of steel, connected to one another in an arched fashion. These elements are constructed of open-ended profiles with H-, HEB, HEM, IPE, INP, C-, or double-T cross sections. In some cases, the elements may be tubular. In most cases, the structural elements of the ribs are formed in a formwork workshop and then connected to one another within the reinforced area of ​​the excavation. After assembly and installation, each rib is typically constructed via rigid elements, technically known as "chains," connected to adjacent ribs through connecting members, the ends of which are joined to support members welded along the body of the rib's profile. The space between two consecutive ribs and the excavation wall is typically reinforced with shotcrete, which forms a structural cover member that also surrounds the ribs.

[0004] An excavation can be constructed as a full-length excavation or, more generally, as a sequential excavation. Sequential excavation, the field to which this specification pertains, involves sequentially repeating different steps, regardless of the section. More specifically, starting from the top face, tunnel excavation begins from that excavation section. Then, tunnel excavation proceeds using conventional excavation methods, ribs, and shotcrete positioning methods. After a distance appropriate to the geological structure is excavated, excavation continues with the so-called bench excavation, i.e., excavation of the sub-top layer. This leads to the excavation of one of the two sections of the excavation's side wall, also known as a side excavation, bench widening excavation, or pier, which gradually progresses as the top excavation progresses. Next, the other section of the excavation's side wall, i.e., the other bench widening excavation or pier excavation, is carried out, which also gradually progresses as the top excavation and the first side excavation progress. The excavation of a central ramp for access to the excavation face also gradually progresses as the top excavation progresses. Finally, the formation of an inverted arch is carried out.

[0005] The structural elements forming conventional ribs are joined by flanged joints. A development and improvement of this system is described in WO2015 / 186029, which describes an articulated connection system for automatically fastening the structural elements forming the rib, which have an arched shape that generally resembles the shape of the excavation reinforced by the rib itself. The structural elements forming the rib are made of a metal material, such as construction steel, and are connected to each other by rotatable joints, such as hinges, which are housed within a structural joint and are movable from a first position in which the structural elements are substantially folded over each other to a second position in which they are arranged to form at least one substantially continuous rib portion.

[0006] Another system of this type is described in WO2022 / 254325.

[0007] Although the systems described in WO2015 / 186029 and WO2022 / 254325 have proven effective for use in full-section excavations, they have characteristics that limit their use in sequential excavations. The staged and sequential nature of the excavation means that the known systems cannot be used, in particular because the ribs cannot be fully opened to support the crown, which is not possible until the sidewall excavation, or bench widening or pier excavation, has been completed. This carries the risk of the crown wall collapsing, leaving it unsupported for a period of time, with obvious and significant risks to personnel and equipment near the front of the excavation.

[0008] Therefore, there is a recognized need for ribs with improved features that can be advantageously used in the construction of tunnels constructed by sequential excavation. Summary of the Invention

[0009] The object of the present invention is therefore to provide a rib for supporting and strengthening successive excavations, which allows a quick and safe connection between structural elements in a way that is particularly stable for supporting the crown wall, without even having to wait for the corresponding side wall excavations, or bench extension excavations or pier excavations, which will always be referred to in the remainder of this specification as right and left side excavations, respectively.

[0010] Another object of the present invention is to provide a rib for supporting and strengthening a sequential excavation that can be easily used to support the walls of the excavation without the need to discontinue support of the crown portion, even when the side excavation of the sequential excavation is completed.

[0011] Another object is to provide a rib that is relatively economical and easy to manufacture.

[0012] Another object is to provide a rib which can be installed quickly and automatically using solely or at least primarily automatic means and which is particularly safe for the operator and employees of the excavation.

[0013] These and other objects are achieved by a pre-assembled rib consisting of a plurality of structural elements movably connected to one another so that the rib can be moved successively from an initial compact configuration before installation, to a partially extended intermediate configuration for supporting the top of the excavation at a top plane, to a final configuration for supporting and strengthening the overall shape of the excavation, the rib being supported on a base plane having a lower elevation than the top plane. The structural elements are secured to one another in structural continuity at their relative locations to define a generally arcuate rib, initially supporting only the top and thereafter fully supporting the walls of the excavation.

[0014] One advantage of the present invention is that it allows for immediate and integral reinforcement of the excavated crown portion before the right and left lateral excavations are completed. Another advantage of the ribs of the present invention is that they can support the excavated wall independently of the progress of excavation during the crown excavation, as well as the progress of the right lateral excavation relative to the left lateral excavation.

[0015] In a first aspect, a rib for supporting and reinforcing an excavation is described. The rib may be comprised of a plurality of structural elements. The structural elements may be connected to one another. The structural elements may be movably connected to one another. The connections between the structural elements may be configured to allow the rib to move from a pre-assembled configuration before installation, to an intermediate, partially extended, supporting configuration, and to a final, fully extended, installed configuration. The pre-assembled configuration may be at least partially collapsed. In the intermediate configuration, some of the structural elements may be fixed relative to one another. In the final configuration, all of the structural elements of the rib may be fixed relative to one another. The structural elements may be fixed with structural continuity, i.e., capable of resisting forces exerted by the excavation wall as if they were a single element or as if they were fixed by fixed connecting members such as bolts. The structural elements may be fixed in mutual positions that, in the final configuration, define a rib having a generally arched shape.

[0016] In certain aspects, the structural elements can be articulated to hinge or swing relative to one another. The structural elements can be connected to one another by connecting members that include hinges.

[0017] In another aspect, a method for installing a rib in an excavation is described. The method can include providing structural elements to the rib. The method can include connecting the structural elements to one another to obtain a pre-assembled rib. The connection can be a flexible connection. The method can include preferably at least partially folding the rib before installing the rib. The method can include transporting the rib into the excavation, preferably in an at least partially folded state. The method can include installing the rib in an intermediate configuration, partially extended, to support the excavation at the top of the sequential excavation. The method can include the additional step of placing the rib in the intermediate configuration to support the top of the sequential excavation, with extension supporting a lateral excavation area to be excavated after the top excavation. The method can include installing the rib in a final configuration to support both the lateral excavation area to be excavated sequentially and after the top excavation. Preferably, in these steps, the structural elements can be gradually secured sequentially while having structural continuity with one another. In another aspect, the method can provide for the structural elements to be irreversibly secured to one another. [Brief explanation of the drawings]

[0018] Further features and advantages will be apparent from the following detailed description of preferred embodiments given purely by way of non-limiting example with reference to the accompanying drawings in which: FIG. 1 is a cross-sectional schematic view of an example of a sequential excavation section reinforced with ribs incorporating aspects of the present invention; FIG. 2 is a perspective view of a rib incorporating elements of the present invention in an intermediate, partially extended configuration; Figures 3-6 show some steps of the installation procedure of the rib of Figure 2 in the area where the sequential excavation of Figure 1 is gradually progressing; Figure 7 is a detailed enlarged view of the adjustment part of the support leg of the rib on the top excavation surface; Figures 8 and 9 show additional steps in the installation procedure of the ribs of Figure 2 in the area where the segmented excavation of Figure 1 is further progressively advanced; Figure 10 is a detailed view showing an enlarged view of the support legs of the ribs in the side excavation area. DETAILED DESCRIPTION OF THE INVENTION

[0019] In the following embodiments, features for implementing the present invention are described. The described features can be combined with each other in various ways and are not necessarily limited to the exact embodiments referred to in the drawings and related descriptions. In other words, a person skilled in the art reading the following description will know how to obtain information useful for knowing how to implement one or more of the described features by combining them with one or more of the other described features, without limiting the possibility that a description, paragraph, term, or specific configuration of the drawings may separate one or more of the described and illustrated features.

[0020] Referring to Figure 1, there is shown a schematic representation of the progression of a sequential excavation of a tunnel reinforced with ribs incorporating aspects of the present invention. For example, a road or rail tunnel wall excavation S has a top end C and a bottom end B, which in the illustrated example is flat, but which could also be configured with a concave central section to form a so-called "inverted arch."

[0021] Excavation section S proceeds in stages. First, excavation of the top T proceeds, followed by excavation of the underside of the top. In the example of Figure 1, the right-side lateral excavation DX (bench widening excavation or pier) proceeds first, followed by the left-side lateral excavation SX. The central ramp area R also proceeds in stages, and as excavation of the top T proceeds, access to the top surface P is gradually secured.

[0022] Figure 2 illustrates a rib 10 for supporting and reinforcing a sequential excavation S incorporating aspects of the present invention. Figure 2 illustrates the rib 10 in an intermediate configuration prior to final installation. The rib 10 includes an arcuate portion 15 terminating at each end in two intermediate legs 12. Two additional rib sections are attached near the intermediate legs 12 and terminate in two respective end legs 14.

[0023] 2 shows one of the lateral end legs 14, in particular the right end leg 14a, already in its final extended configuration so as to abut against the corresponding right side planar area of ​​the base B of the excavation S when the right side excavation DX is carried out along the axis of the tunnel in the region of the location of the rib 10. However, the other left end leg 14b of the rib is still shown in its folded position. In this position, the left middle leg 12b, which is intended to rest on the top surface P, is supported in an extended state and is intended to be supported on the top surface P when the left side excavation SX is not yet completed. When the left side excavation SX is completed, the left end leg 14a can be extended from the folded position shown in FIG. 2 so as to move against the left side planar area of ​​the bottom B of the excavation S until it reaches its final position symmetrical to the right end leg 14a. In this way, the rib 10 reaches its final fully extended configuration for supporting the entire section of the excavation S with both end legs 14 supported on the bottom B.

[0024] The rib 10 is formed by a number of structural elements, including, but not limited to, three structural elements 15, 16, and 17, in addition to the intermediate leg 12 and the end leg 14. The structural elements 15, 16, and 17 are preferably made of a metal material, such as, for example, construction steel (e.g., Fe430). According to a preferred embodiment, each structural element 15, 16, and 17 is formed by a member made of a profile having, for example, an H-shaped, C-shaped, or double T-shaped opening cross section, such as a standard European profile, e.g., HEA, HEB, HEM, or IPE. However, it is not excluded that one or more of the structural elements 15, 16, and 17 may be made of a different profile, e.g., a tubular profile having a cross section of a circle, oval, square, rectangular, etc.

[0025] Rib 10 has an arched shape that is substantially symmetrical about a vertical plane of symmetry defined by one or more structural elements, e.g., three structural elements 15, 16, 17 that form the sides and upper side of rib 10 in the region of crown T. The symmetrical arched shape of rib 10 generally replicates the cross-section of excavation S that is to be reinforced by the rib itself in an extended configuration with both end legs 14 extended, such as right end leg 14a in FIG. 2.

[0026] The rib 10 shown in the figures comprises a first lateral structural element 15, a central structural element 16 connected to the first lateral structural element 15, and a lateral structural element 17 connected to the central structural element 15. In an embodiment not shown, the rib 10 may comprise additional sub-structural elements that are, or preferably can be, connected to the second lateral structural element 17 to strengthen the inverted arch of the excavation S, if provided. As shown, the first lateral structural element 15 and the second lateral structural element 17 are positioned in substantially mirror-reflecting positions relative to the vertical plane of symmetry of the rib 10. In other words, in this exemplary configuration of the rib 10, the first lateral structural element 15 and the second lateral structural element 17 are lateral structural elements of the rib 10. The central structural element 16 preferably extends symmetrically between the first lateral structural element 15 and the second lateral structural element 17 relative to the same vertical plane of symmetry. In the example of the rib 10, the central structural element 16 is an upper structural element, also called a top structural element or superstructure element, intended to support the upper region of the crown T.

[0027] The ends of the individual structural elements 15, 16, 17 are operatively connected to one another, for example, via articulating members. The middle legs 12 are also operatively connected to the ends of the respective side structural elements 15, 17 in an articulated manner. The end legs 14 are in turn operatively connected to the middle legs 12. The connection of the end legs 14 to the middle legs can be selectively made after the ribs 10 have been positioned to support only the excavation portion of the top T.

[0028] The connecting members between the individual elements, including the legs, forming the rib are advantageously articulated, pivoting, and / or rotating, e.g., hinges. The structural elements and legs connected by these connecting members can thus be moved from a folded-over position to an at least partially extended intermediate position. In the intermediate support position at the top T of the excavation section S, the rib 10 does not need to have end legs 14, which are only connected and extended when the rib 10 needs to be supported laterally following the progression of lateral excavation. This makes it particularly easy and advantageous to transport the folded rib 10 into the excavation section S, with the structural elements 15, 16, 17, together with the intermediate legs 12, and in some embodiments, also the end legs 14 already attached to the rib 10, continuously connected to one another.

[0029] The legs 12, 14 are preferably extendable and are extendable an adjustable amount to rest on the top surface P and bottom surface B, respectively.

[0030] 7 shows an enlarged view of one embodiment of the intermediate leg 12, which includes a support element 20. The support element 20 includes a movable or telescopic portion that is extensibly attached to a fixed structure of the intermediate leg 12, which is fixed to the corresponding lateral structural element 15 or 17, preferably near its end. The fixed structure of the leg 12 can be fixed to the lateral structural element 15 or 17 by any known system, such as welding, bolts, rivets, or other such connecting members, but is preferably movably attached, for example, by a joint or hinge 22.

[0031] The mobile structure 20 can be preferably made of a tubular member, for example, with a square or rectangular cross section, and in either case, is configured and dimensioned to slide linearly, preferably telescopically, relative to the fixed members of the legs 12 without the possibility of rotation. The legs 12 are provided with a blocking and non-return mechanism, for example with a ratchet gear, which allows the mobile structure 20 to be fixed at a desired height relative to the top surface P. A support plate 24 is fixed to the lower end of the mobile structure 20, which is intended to be supported on the top surface P. The support plate 24 has dimensions larger than the cross section of the mobile structure 20 to form a support base that is sufficiently extended to distribute the weight over a relatively wide surface of the top surface P. Once the extension operation of the mobile structure 20 is complete, the telescopic tubular portion can be filled with concrete, thereby forming a one-piece leg 12 that does not move in any direction.

[0032] The fixed structure of the leg 12 is provided with a connecting element 26 to which a corresponding connecting element 27 of the end leg 14, shown enlarged in Figure 10, is connected when it is necessary to support the rib after the lateral excavation to remove the top surface. The end leg 14 also comprises a mobile structure 28 having similar functional characteristics to the mobile structure 20 of the intermediate leg 12, which terminates in a support plate 30, similar in function to the support plate 24, intended to form a support base sufficiently extended to distribute the weight over a relatively large surface of the bottom B of the excavation S. The end leg 14 is preferably articulated to the intermediate leg 12 in order to move from a raised position, partially shown hatched in Figure 10, in which it supports the rib 10 by being supported on the bottom B of the excavation S, to a final extended position. The connection formed by the connecting members 26, 27 of the intermediate leg 12 and the end leg 14, respectively, is preferably formed so that it can be irreversibly fixed when the end leg 14 is extended to reach the final support position shown in solid lines in FIG. 10.

[0033] The placement of the ribs 10 in the excavation S can be carried out automatically or semi-automatically using known machines equipped for this purpose to follow the sequential progress of the excavation S.

[0034] The above-mentioned rib 10 is transported to its location in the excavation S in a configuration in which the structural elements 15, 16, 17 and the intermediate legs 12 are folded in order to obtain a compact configuration, the extent of which in the plane including the structural elements and the intermediate legs is smaller than the extent of the excavation cross section at the top T. The support elements 20 of the intermediate legs 12 are preferably raised or retracted, as can be seen in Figure 3, so as to take up little space during storage of the rib 10 and during its initial positioning in the tunnel. Thus, transportation is easy and the elements that make up the rib are in any case already prepared for correct placement in their final configuration.

[0035] As shown in Figure 4, when the rib 10 is in its installed position in the excavation S, which advances as the excavation of the top T progresses, the central structural element 16 is raised so that the lateral structural elements 15, 17 rotate in the area of ​​the joints to which they are connected in order to gradually open up. As shown in Figure 5, the central structural element 16 is positioned in the area of ​​the upper wall of the excavation of the top T, while the adjacent lateral structural elements 15, 17 are positioned next to the arched ceiling of the excavation.

[0036] At the end of the relative rotation, the lateral structural elements 15, 17 are fixed in the installation position shown in Figure 5 as a result of the snap-fit ​​fixing of the connecting members between the structural elements. The design of the snap-fit ​​connecting members ensures that the structural elements are held firmly in the desired position to complete the installation without the risk of closing onto each other again.

[0037] As can be seen in Figure 6, in the intermediate position where the rib 10 is installed in the excavated portion of the top end T, the intermediate legs 12 are extended and positioned to be supported on the top end surface P. In this position, the movable portion of the support element 20 of the intermediate legs 12 can be lengthened to ensure stable support on the top end surface P. In this intermediate configuration, the first application of shotcrete can be performed on the portion of the rib that occupies the excavated portion of the top end T.

[0038] As the excavation S progresses, side excavations are initiated in the area where the ribs 10 are installed, first (as in the non-limiting example of the figure) the right side excavation DX, followed by the left side excavation SX. As can be seen in FIG. 8, provision is made to connect the end legs 14 to the middle legs 12 in consideration of the progression of these side excavations. As precisely shown in FIG. 8, the end legs 14 are initially in a folded position relative to the extent of the ribs of the top excavation so as to rest on the top surface P. As shown in FIG. 9, once the right side excavation DX is completed, the right leg 14 is extended and lengthened so as to rest on the bottom B of the excavation, as shown in FIG. 9. Similarly, once the left side excavation SX is completed, the left end leg 14 is extended and lengthened to reach a similar support position on the bottom B of the excavation. Thus, the support element of the end leg 13 is positioned laterally and downwardly relative to the side wall of the excavation and extends or rotates until it contacts the ground in the area of ​​the bottom B. In this state, the reinforcement of the ribs with shotcrete can be completed in the lateral areas of the excavation that are released by the lateral excavation.

[0039] Therefore, the installation of the ribs is carried out quickly and almost automatically.

[0040] Each rib is then connected to an adjacent rib by a connecting member called a "chain" or a known equivalent, which is preferably configured so that one rib automatically connects to another rib.

[0041] Ribs used to support and strengthen excavations can have elastic joints of known types that can be inserted between two sections of the rib's structural element, such that one or more elastic joints can be employed to absorb forces exerted on the rib by the walls of the excavation through an elastic reaction thereto.

[0042] The main inventive concept of the present invention does not depend on the type of rib profile used to construct the structural element and / or the intermediate and end legs. Although profiles with an open cross section have been described above as preferred, the use of the present invention with tubular profiles to completely or partially construct the overall profile of the rib and / or one or more of its structural elements is not excluded. Generally speaking, it is possible in any case to use different profiles for different parts of the rib, and the possibility of using different profiles for parts of the structural element with open and / or closed / tubular profiles separated from each other by the above-mentioned elastic joints is also not excluded.

[0043] Naturally, the principles of the invention will remain the same, and the details of the embodiments and construction may vary widely from those described and illustrated without departing from the scope of the invention.

Claims

1. A rib for supporting and strengthening the excavation, The present invention comprises a plurality of structural elements (15, 16, 17) movably connected to one another so that the ribs can move from a pre-assembled at least partially folded configuration before installation, to a partially extended support configuration intermediate the top end (C) of the successive excavation at the top surface (P), to a final configuration for support on a plane of the bottom (B) arranged at a lower height relative to the top surface (P), A rib, wherein said structural elements (15, 16, 17) are secured in structural continuity with one another at mutual locations defining a generally arcuate rib.

2. 2. A rib according to claim 1, wherein a pair of intermediate legs (12) are articulated to the ends of the group of structural elements.

3. 3. A rib according to claim 2, wherein said intermediate leg (12) is extensible.

4. A rib according to claim 2 or 3, comprising a pair of end legs (14) selectively connectable to the ends of the structural element or to the intermediate legs (12).

5. A rib according to claim 4, wherein said end legs (14) are extensible.

6. A rib according to any one of claims 1 to 5, comprising at least three structural elements (15, 16, 17) articulated to one another and fixable in an intermediate configuration, the intermediate leg (12) being capable of being supported on the top end surface (P).

7. A method for installing the rib according to any one of claims 1 to 6 into a trench, comprising: - providing a plurality of structural elements (15, 16, 17) on the rib (10); - movably connecting said structural elements (15, 16, 17) to one another to obtain a pre-assembled rib; - folding the rib at least partially before installing the rib; - transporting said rib in an at least partially folded state into said excavation (S); - placing the rib (10) in an intermediate configuration in a partially extended state, supporting the top end (C) of the sequential excavation at the top surface (P); - connecting the end legs (14) to the ribs; - constructing said rib in its final configuration for support on a plane of a base (B) constructed at a height lower than the top surface (P), said structural elements (15, 16, 17) being fixed in structural continuity with one another in their mutual positions defining a generally arched rib; A method comprising:

8. 8. The method of claim 7, wherein the rib comprises a pair of intermediate legs (12) articulated to the ends of a group of structural elements, and the step of installing the rib in the intermediate configuration includes extending and / or lengthening the intermediate legs (12) and positioning them so as to be supported on the top surface (P).

9. the rib comprises a pair of end legs (14) selectively connectable to the end or intermediate legs (12) of the structural elements (15, 16, 17), and the step of installing the rib in the final configuration comprises: - connecting the end legs (14) to the ends or intermediate legs (12) of the structural elements (15, 16, 17); - lengthening said end legs (14) and positioning said end legs (14) so ​​that they are supported on said bottom (B); 9. The method of claim 7 or 8, comprising:

10. 10. The method according to claim 9, wherein, upon connection of the end legs (14) to the end or intermediate legs (12) of the structural elements (15, 16, 17), the end legs (14) assume a folded configuration, after which the end legs (14) are extended in order to form with the structural elements (15, 16, 17) an arched shape supported on the bottom (B).

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