JPS6217299A - Timbering for tunnel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is based on the N ATM (New Au5trian
Regarding tunnel shoring applied to mountain construction methods such as tunneling method, it is particularly lightweight and inexpensive, has good assembly processability and workability, and is excellent because it fits reliably on the excavated surface of the ground. This article relates to tunnel shoring that exhibits a reinforcing effect.

・[Conventional technology 1 NATM construction method is a type of tunnel construction method that prevents the collapse of earth and sand by reinforcing the strength of the ground in the excavated tunnel with sprayed concrete, rock bolts, and steel shoring. It is widely adopted as a rational reinforcement method because it allows construction while actually measuring the deformation state of the excavated surface.

By the way, the steel shoring used in the NATMT method is H-shaped steel (for example, 125X125X6X9I, or 150
X150X7XIO■■, etc.) is the most common, and it is said that about 90% of iron shoring is made of H-shaped steel (hereinafter referred to as H-shaped steel shoring). In use, the H-shaped steel shoring is pre-curved into an arc shape or an arch shape according to the shape of the inner wall of the tunnel to form flanges at both ends, and these are assembled together along the inner wall of the tunnel. They are installed at intervals of 0.8 to 1.5 m in the length direction, and the adjacent supports in the longitudinal direction are connected by connecting members, and lock bolts are installed at the intermediate position of each adjacent support or at the attachment point of each support. Rock bolts are sometimes driven before shoring is installed), and then concrete mixed with a quick-setting agent is sprayed to form an internal reinforced wall.

However, conventional H-shaped steel shoring has many drawbacks as shown below, and there is a need for improvement in terms of overall performance, including transportability and workability.

(1) The diameter of the tunnel excavation hole was excavated considerably larger than the designed value, but under these circumstances it was difficult to install highly rigid H-shaped steel supports that were in close contact with the ground. It is easy for voids to form between the ground and the shoring. If such a void forms, stress will be concentrated on the shoring, reducing its load-bearing capacity, and the excavated surface of the ground will gradually loosen, causing unloading. Shoring and spraying may cause the load on the concrete to exceed the design value.

(2) The final strength of the tunnel is mainly provided by rock bolts and shotcrete concrete, and shoring is mainly used to prevent the ground from collapsing during tunnel construction. The cross-over ratio on the subsequent shoring is not so large, so high strength H'! i! Using steel is
Rather, it becomes over-designed, uneconomical and wasteful.
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(3) As will be explained in detail later, it is known that the locations where particularly large stresses occur in shoring are generally the top and legs of tunnels, so these areas should be strengthened with particular emphasis. By doing so, the performance of the shoring as a whole can be sufficiently improved, but with H-shaped steel shoring, it is difficult to partially change the cross-sectional dimensions in the circumferential direction, so it is determined based on the maximum stress. Therefore, as mentioned above, this leads to over-design and promotes waste.

(4) The flanges and webs of H-type steel shoring are formed of surface elements, and when spraying concrete with a spraying machine, a part of the concrete tends to bounce off the flat plate If & (flange part and web part). , Spraying involves a lot of material loss.

(5) In addition, the flange surface of H-shaped steel becomes a steric obstacle,
When spraying onto the back surface, it is necessary to spray with the sprayer oriented diagonally in order to prevent concrete filling failure, and in this case, there is a particularly large amount of material rebound loss during spraying.

(8) The sprayed concrete used in the NATM construction method is a cylindrical reinforced structure that is integrated with the ground and H-shaped steel shoring to resist the load of the ground, but the H-shaped steel shoring is When used, as shown in Fig. 22 (partial sectional view), when spraying the back side of the H-type steel shoring 1 or the part sandwiched between the flange and the web, the concrete 2 cannot be sufficiently filled and remains as a void N. The continuity in the axial direction is lost, resulting in a structural defect (3 in the figure indicates the ground).

(7) When constructing a tunnel using the NATMT method, the rock bolts 4 are not only driven perpendicularly to the ground 3, but also toward the front of the excavated hole, as shown in Figure 23 (partial cross-sectional view). In some cases, the ground in the area to be excavated after driving the rock bolt 4 is preliminarily reinforced (generally, the first hit is called a rock bolt).In this case, the first hit that is driven forward is the first place where the rock bolt 4 is driven. It is said that it is more effective to keep the direction as close to horizontal as possible along the longitudinal direction of the excavated hole (second
However, when H-shaped steel shoring is used, the web surface of the shoring l becomes an obstacle and the driving direction cannot be brought close to horizontal, making it difficult to achieve the purpose of strengthening the ground. cannot be carried out effectively.

(8) H-type steel shoring is extremely heavy; for example, one for a two-lane expressway tunnel weighs 500 to 700 kg.
It is not easy to handle in narrow tunnels as it reaches
In addition, the human burden increases, and at the same time, mechanical equipment for assembly is required.

[Problem to be solved by the invention 1 The present inventors have focused on these circumstances, and have developed a structure that is lightweight, has good workability and transportability, and in which the ground, rock bolts, and spraying are integrated with concrete, etc. Various studies have been conducted in an attempt to provide support that can form a strong, defect-free tunnel inner wall. As a result, for example, as shown in Fig. 20 (partial sketch) and Fig. 21 (partial sketch showing the assembled condition), two or more (four in the figure) bars (mainly steel bars), Other metal rods, hard synthetic resin rods, FRP rods,
We have developed a shoring structure (hereinafter referred to as "bar shoring material") in which F (which may be reinforced carbon rods, etc.) are joined and integrated with connecting members S arranged at a pitch of 1, a, and have separately applied for a patent. I did this. This bar support A is lightweight and has good workability, and has a certain degree of flexibility, so it can easily follow the excavated surface of the ground.

Furthermore, since it is essentially composed of linear elements, concrete spraying has good workability. It has the following characteristics and can be said to be extremely superior to conventional H-shaped steel shoring. However, as the present inventors proceeded with their research, the following problem became apparent. In other words, tunnel construction using the NATM construction method.

(a) An excavation hole slightly larger than the design dimensions is formed in the ground, and concrete is sprayed onto the inner surface of the hole for the primary spraying (this spraying may be omitted depending on the case).

(b) Erect shoring along the inner surface of the excavated hole.

(c) Install reinforcing wire mesh. (d) For secondary spraying, spray concrete. (e) Drive rock bolts and fix them together. However, when excavating the ground in (a) above, the excavation is often much larger than the design dimensions in consideration of the workability of installing the shoring. It has been confirmed that a considerable gap remains between the excavated hole and the shoring, causing structural defects (increase in local load due to the collapse of excavated sand into the gap). Such defects cannot be avoided not only in the conventional H-shaped steel shoring but also in the case of using the above-mentioned bar shoring.

Under these circumstances, the present invention aims to provide a shoring structure that can minimize the gap between the shoring material and the excavated hole, thereby increasing the integrity of the two and forming a strong reinforced wall. It is.

[Means for solving the problems] The structure of the shoring of the present invention that achieves the above objectives is as follows:
Two or more rods are arranged approximately in parallel, and at least one
Connecting length if! to one end or both ends of the shoring, which is assembled into one piece with two connecting members! The main point is that one flexible connection part is provided.

[Function] The shoring of the present invention has a basic structure in which two wood fiber rods are arranged approximately parallel to each other as described above, and these are assembled together with at least one connecting member, Since there are no 7-rungs or webs as seen in conventional H-type shoring, and most of the structure is made up of linear elements, it is prone to overstrength and spraying as pointed out in (1) to (8) above. It does not cause problems such as poor filling of concrete, is lightweight, has good transportability and workability, and has the additional features that the strength can be adjusted freely by increasing or decreasing the number of bars and the diameter of the bars as necessary. have. Moreover, this shoring is provided with a connecting length adjustable joint at either end or both ends, and as will be described in detail later, the combination can be adjusted by changing the tightening position of the connecting rod with a nut or the like at the connecting part. The length of the connecting part between the supporting supports can be adjusted arbitrarily, and the diameter of the ring or the size of the arch or dome made up of a group of supporting supports can be finely adjusted according to the size of the excavated hole. Can be done. As a result, the shoring can be reliably aligned with the inner circumferential surface of the excavated hole, and its integrity with the excavated hole can be improved, thereby increasing pressure resistance.

[Embodiment] Fig. 1 is a partial sketch showing an embodiment of the present invention, and the shoring A is constructed of 4 parts as shown in Fig. 20.21 above.
The rods F are arranged parallel to each other, and each rod F is welded and fixed near the four vertices of an H-shaped cross-section connecting member S arranged at an arbitrary pitch. , and plate-shaped connecting members P are integrally fixed to both ends in the longitudinal direction, respectively.

By connecting a plurality of such supports A in the longitudinal direction, one can be assembled into a shape that matches the tunnel shape, for example, as shown in Fig. The number and assembly structure of the rods F constituting each shoring A can be changed in various ways. In addition to the example shown in Fig. 1, for example,
Alternatively, as shown in FIGS. 4 to 15 (partial sketch), the strength can be increased by using two to eight bars F. In addition to the structure in which the bar F and the connecting member S are fixed by welding, for example, as shown in Figs. 15 to 17, a pair of strip-shaped iron plate S1 provided with a bar gripping part H and a rod S2 are assembled together. The shoring A can also be constructed by configuring the connecting member S and gripping and integrating each bar F with four gripping portions H.

The present invention has the greatest feature in that a connection part such as a connection length adjustment part is provided at one end or both ends of the shoring A constructed in this way, and specifically, for example, the first
As shown in the figure, connection plates P are fixed to both ends of shoring A.
Bolt holes (four in the figure; not shown in the figure) are formed in P, and threaded connecting rods M are inserted into these holes and fastened and fixed with bolts (N) to connect shoring A in the longitudinal direction. go.

In the case of an arch-shaped tunnel, it is best to use a combination of two supports that stand along the vertical walls on both sides and two supports that form a semicircle at the ceiling (one set of four in total). Although this is common, it is of course not limited to this, and depending on the size of the tunnel, three or five or more can be assembled to form one arch or ring. In this case, by shifting the fastening position of the anchors 7 in the -hF direction in FIG. 1, the connection spacing between the supporting structures A adjacent in the circumferential direction can be freely changed. It is possible to fine-tune the overall size and circumferential length of the arch-shaped shoring as shown in Figure 1. Therefore, even if there is a gap between the support and the inner wall of the excavated hole, by setting the length L of the connection part to 31q as described above, the overall size of the support (
By increasing the outer diameter (outer diameter), the outer surface of the shoring can be aligned with the inner circumferential wall of the excavated hole. As a result, the collapse of earth and sand that tends to occur in the gap is reliably prevented, and a fully reinforced wall can be formed. In addition, although Fig. 1 shows an example in which connection length can be adjusted using four-wood threaded connecting rods M, the number of connecting rods M is not limited to this, and five or more or three connecting rods M are used. Of course, it is also possible to connect using a connecting rod M smaller than this one. In addition, such connection parts with adjustable connection lengths can be provided at both end connections of each shoring A, but if all the connection parts are made adjustable in connection length, the work for assembling the shoring would be complicated. Therefore, at least one location, usually two to three locations in consideration of the ground excavation process, etc.
The length of the connecting part is adjustable as shown in the figure, and the other connecting parts are simply fixed with bolts, nuts, etc. By the way, in Figure 2 (A), the supports A+, A2, A3
, As, A2 and A3 are provided with connection parts at both ends that can freely adjust the connection length.

A1 and A4 are provided with a connecting portion whose length can be freely adjusted at one end only. Also, in Figure 2 (B), shoring A1 + A2
+ Both A3 and A4 are provided with a connection part that can freely adjust the connection length at one end only, and the top of the arch is a simple bolt fastening type. In the top view, the connection length is mI by the threaded connecting rod M and nut N! 1, but it is of course possible to employ other means that allow length adjustment.

FIG. 18 is a partial sketch showing another embodiment of the present invention, in which a connecting plate Q is welded and fixed to one end of a threaded connecting rod M, and the connecting plate Q is connected to the connecting plate of the lower support A1. Connect the other end of the connecting rod M to the upper support A2.
It is configured so that it can be inserted into a bolt hole drilled in the connecting plate P at the tip and fastened and fixed at an arbitrary interval using a set of two nuts N. In this case, the connecting rod M may be directly welded and fixed to the connecting plate P of the lower support A1. U shown in Figure 0 indicates a bolt hole. For example, if a connection part with adjustable connection length is provided at the so-called spring line position, which is the curvature change part of an arch-shaped support as shown in Figure 19 (A), the height of the excavated hole will change slightly. Even in such a case, it is preferable to adjust the spacing between the connecting rods M so that the shoring can be reliably aligned with the ceiling surface. A connecting plate Q made of connecting rod material whose connecting length can be adjusted is also attached to the lower end of the shoring A1 placed in the area, so that the height of the arch can be adjusted by adjusting the length of the downward protrusion. You can also do that. Furthermore, Fig. 19 (A), (B)
In this example, the shoring A2 is not provided with a connection part whose connection length can be adjusted freely, but it is also possible to provide a similar connection part whose connection length can be adjusted at the top end of the support A2.

The present invention is generally constructed as described above, but the key point is that at least one end of the shoring constructed by combining a bar, a joining member, and a connecting member is provided with a connecting portion that can be adjusted to a connecting length tJR, and the spacing is The greatest feature of the present invention is that the structure is adjustable, and within the scope of this configuration, the shape and dimensions of the shoring can be changed as necessary; It is within the technical scope of the present invention. Also, what are the typical examples of tunnel construction using this type of shoring?

(a) Forming an excavation hole in the ground and driving rock bolts, (b
) The primary spraying on the inner circumferential wall of the excavation hole is concrete spraying (this step may be omitted), (c) Erection of reinforcing steel support (at this time, using the ladder of the connection part with adjustable connection length) (adjusting the circumferential length of the entire shoring and bringing the shoring into close contact with the inner peripheral wall of the earth), (d) laying reinforcing wire mesh, (
e) Secondary spraying is a method of sequentially carrying out concrete spraying, which allows for efficient construction of tunnels with excellent pressure resistance, but the construction method itself is of course not limited to the above method. do not have.

[Effects of the Invention] The present invention has been achieved as described in 1 below, and its effects can be summarized as follows.

(a) Most of the shorings of the present invention are made of bar elements with 4R construction, so they are light compared to their strength and have good workability.Moreover, unlike the H-shaped steel shoring, spraying of concrete does not result in loss. There is no possibility of filling defects, etc., and rock bolts can be driven between the bar elements in the shoring.
Shoring, rock bolts, reinforcing wire mesh, and concrete all work together to create a strong tunnel.

(b) By adjusting the spacing between the shoring elements using connecting rods, the shoring can be reliably aligned with the inner circumferential wall of the excavated hole, and a reinforced wall without gap defects can be formed.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention, and Fig. 2 is a schematic front view showing an example of how to assemble the shoring. is a sketch showing other examples of shoring, Figures 4 to 13 are partial sketches showing examples of the assembly of bars and joint members, Figures 14 and 15 are cross-sectional views showing examples of the same assembly, Figures 16 and 17 are sketch diagrams showing other examples of joining members, Figure 18 is a partial diagram showing other examples of connection length-adjustable joints, and Figure 19 is a diagram showing the left half of the shoring assembly as an example. Figures 20 and 21 are partial sketches illustrating the bar shoring that is the basis of the present invention, and Figures 22 and 23 are cross-sectional views showing an example of tunnel construction using conventional H-shaped steel shoring. It is an explanatory diagram.

Claims (1)

[Claims] A shoring structure is formed by arranging two or more rods substantially parallel to each other and assembling them into one piece with at least one connecting member, and having a connecting portion that allows the connection length to be adjusted at one end or both ends of the shoring structure. Shoring for tunnels.