JPS5858398A - Crack prevention of tunnel coating concrete - 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 The present invention relates to the creation of a method for preventing cracks in tunnel lining concrete 1. It is an object of the present invention to prevent the occurrence of cracks in the lining of various tunnels, and to form stable and strong linings. The aim is to provide a construction method that allows for

In tunnel construction these days, instead of supporting the ground using shoring and sheet piles inside the excavated tunnel, as was the case in the past, concrete is immediately poured onto the excavated ground. The unevenness of the rock caused by the excavation is smoothed with a layer of shotcrete, and the rock is blocked from the air as quickly as possible to suppress the expansion of the exposed rock surface.In this state, rock bolts are installed radially to the tunnel cross section. Alternatively, anchor bolts are driven and anchored to the bedrock, and the expansion of the rock at the excavated surface layer is supported by connecting and integrating with the rock at a certain depth. In other words, in recent L-channel construction, after excavation, the ground is stabilized by primary lining with shotcrete using rock bolts or anchor bolts, and then the thickness is generally 20 to 35 mm.
A secondary lining is formed with a concrete layer of about ttn to further strengthen the tunnel wall surface, provide a finishing touch, improve waterproofing and aesthetics, and reduce water flow resistance when used as a waterway tunnel. There is. However, in recent years, attention has been drawn to the fact that cracks often occur on the surface of the sprayed construction, which causes spring water to flow into the tunnel. Therefore, various studies have been made to prevent the occurrence of racks, and the preferred method is to attach wood thin plates or sheets to the primary lining as described above, and then apply the secondary lining. By doing so, it is possible to effectively prevent the occurrence of cracks on the secondary lining. However, according to the results of practical studies using such thin plates or sheets, there is a primary lining that is integrated with rock bolts or anchor bolts against the bedrock, and a primary lining that is integrated with rock bolts or anchor bolts.
The structure is stratified by thin plates or sheets, which greatly impairs the integration characteristics with the bedrock, resulting in vibration pressure and pressure fluctuations in the headrace.
It has the disadvantage that it is difficult to obtain sufficient strength against repeated pressurization and depressurization.

The present invention has been devised after repeated studies in view of the above-mentioned circumstances, and has been developed so that the expansion and contraction action between the primary lining and the secondary lining is greater than that of each of the above-mentioned linings. Moreover, it is proposed to form an intervening layer using a cement mixture that can obtain approximately the same adhesive strength with the concrete lining, and specifically, the intervening layer is
It has a compressive strength of about 1001cs'/J, and has a resistance strength of around IKr/crA or more than 2, and is made of aerated mortar concrete, lightweight mortar, pearlite mortar, foamed resin-containing concrete, etc. . Such an intervening layer can be easily formed by simply changing the material using the spraying equipment used to form the primary lining or secondary lining as described above, but a particularly preferred method is to increase the water-cement ratio ( A wet fluid mortar or foam mortar is pumped through a single line, and sand and lightweight aggregates (including perlite) are added to this via a separate system. Alternatively, both materials may be air-fed under dry conditions and then combined and added near a spray nozzle and then sprayed. Alternatively, as described above, both materials may be supplied onto a rotating disk and sprayed by projection using the rotational force. Also, a quick setting agent may be mixed into these aggregates.
Furthermore, depending on the case, the mortar or foam mortar may be sprayed by combining only compressed air. The state of the tunnel lining to be formed is as shown in Fig. 1. Rock bolts 3 are driven into the excavated rock 1 from inside the tunnel 2 in a radial direction, and the rock bolts 3 are After forming the lining 4, the intervening layer 5 is formed, and the secondary lining 6 is formed on the intervening layer 5. For the primary lining 4, steel shoring, wire mesh, etc. can be used as appropriate, and its thickness is about 10 to 15 m, and the rock bolt 3 has a thickness of about 20 to 30 wn and a length of about 20 to 30 m. A thickness of approximately 1.5 to 3 m is appropriately selected in consideration of the composition of the rock mass 1.

The thickness of the intervening layer 5 is generally 0.5 to 5 crn, and the secondary lining 6 provided on the intervening layer 5 has a thickness of 20 to 3 crn.
As mentioned above, there are about 5 servings.

The specific equipment is as shown in Figure 2.
6 is connected to material supply mechanisms 41, 43 and 42 and to a mortar pump 44, which conveys the mortar by means of a hose 12 to the spray nozzle 13, i.e. from a separate trolley at a position directly in front of the spray nozzle 13 as shown. The high-pressure air pipes 11 are mixed together in a mixing pipe 53, and the mixture is ejected from a nozzle 13 to be sprayed.

The operation panel 45 is provided on the trolley 40 as shown in FIG. 2 when the trolley 40 approaches the nozzle 13, but under conditions where the trolley 40 is located at a remote location, it is installed at a location close to the nozzle 13. An operation panel 45 is provided at the top of the sprayer so that the pressure conditions, amount, etc. can be adjusted appropriately while checking the spraying situation.

The invention can be sprayed not only by a nozzle but also by a rotary projection mechanism. That is, the central tube 23 connected to the conduit 11 from the pressure pump 44 as shown in FIG. The rotary plate 18 has an opening facing the center of the rotary plate 18 having the rotary blades 16 and an appropriate distance between the rotary plate 18 and the rotary plate 18 . A stirring mechanism section 35 is provided. A dry material supply cylinder 22 is provided concentrically with the central pipe 23, and between the supply cylinder 22 and the central pipe 23, a transfer screw 19 is inserted from the hopper 11 toward the rotary plate 18. As shown in FIG. 5, the stirring mechanism section 35 is provided protruding from a base plate 36 attached to the center of the rotary plate 18, and the stirring mechanism section 35 is provided with stirring blades 37 and 38 arranged in multiple stages. Member 39 and pressing member 3
The fixing member 39a is fixed to the rotary plate 18 by the fixing member 39a, and is arranged so that it can be removed for cleaning or adjustment as appropriate by gripping the handle portion 36a and under the condition that the fixing member 39a is relaxed. The supply tube 22
A drive wheel 22a is attached to the supply tube 22 so that it can be rotated as appropriate, but the supply tube 22 may be a fixed one. By rotating the left end side in the figure from the joint 23b, the material stored in the hopper 21 can be appropriately transferred and supplied to the rotary plate 18, and the amount supplied is approximately proportional to the rotational speed of the screw 19. The rotary plate 18 is attached to the tip of the rotary tube 14 provided outside the supply tube 22, and the rotary plate 18 is attached to the tip of the rotary tube 14 provided outside the supply tube 22.
) The material is supplied onto the rotary plate 18 at a speed proportional to the driving speed by 14a, stirred by the stirring mechanism 35, and then supplied and dispersed onto the rotary plate 18. The above-mentioned supply cylinder 220
The tip of the rotating plate 18 side covers the stirring blades 37 and 38 and is close to the surface of the rotating plate 18.
FIG. 4 shows that the spraying direction is appropriately restricted by forming a groove b, discharging from the notch 22b onto the rotary plate 18, and rotating and adjusting the supply tube 12 by the drive wheel 22a. As a result of such a limit adjustment operation, [7] If we add a limit adjustment effect regarding the blowing direction of the rotary blowing mechanism according to the shape of the arched blowing surface and other shapes in the excavated tunnel 2 having vertical walls on both sides. It is clear that a suitable spray application can be obtained.

Specific examples according to the present invention will be described below.

Example 1 Normal Portland cement 272 Kg/u/, Oi fine sand 712 Kg/lt? , Fuji Tsukisan River Gravel 11
55Kf/J, water 15aKy/m, water reducing agent 0.68 to 9
As shown in Figure 1 above, 100 rock bolts with a diameter of 25wn and a length of 2m were installed into a tunnel excavated in crystalline rhyolitic bedrock using ready-mixed concrete mixed at a ratio of /-.
According to the conventional general method, 1.0 cm thick on average is used for lining under the condition that the lining is placed at crn intervals.
After the next lining, the secondary lining was sprayed to an average thickness of 30 ctn, with a thickness of 0.5 van between the first symmetrical area and the primary lining and secondary lining as described above. In addition to the above composition, 150 Ky of expanded pearlite (specific gravity: 0.2) with a diameter of 1 to 2 is added between the second symmetrical section using a vinyl sheet and the above primary lining and secondary lining according to the present invention. /rr? Blended pearlite mortar (specific gravity 0.81 strength 45Ky)
/cra) was sprayed to a thickness of 2 m to form an intervening layer.

That is, the crack occurrence status after construction in these symmetric areas and invention areas was measured as crack area (crack length layer x crack width rMl/resistance), and the results are shown in Table 1 below.

Table 1 (ia/W?) After 91 days, ultrasonic pulses transmitted sound waves of 9,000 psi between the secondary eco-concretion 1 and the bedrock for each of the above-mentioned areas, and the primary lining and secondary lining were constructed. As a result of examining the state of separation between the two symmetrical areas, the one in the second symmetrical area was almost completely separated and the ultrasonic waves did not propagate, whereas the first symmetrical area and the invention area were both stable7. A state of adhesion was observed, and the propagation of ultrasonic waves was confirmed.

Example 26 Primary lining and secondary lining were performed in the same manner as in Example 1,
In spraying the intervening layer between the primary lining and the secondary lining in the present invention, the nozzle 13 is used as shown in FIG.
The first pipe line 11 and the second pipe line 12 are connected at a position 3 m in front of the pipe, and the foam paste with a specific gravity of 08 is pumped from the first pipe line 11, and the sand and quick-setting agent are pumped from the second pipe line. The first and second pipes are conveyed by air pressure, and the first pipe line and the second pipe line meet at the confluence point, that is, the mixing pipe 53, and then bubble mortar and soot with a specific gravity of 1.2 are sprayed from the nozzle 13. That is, in this case (1
1) The crack occurrence status after construction was measured in the same manner as in Example 1, and the results are shown in Table 2 below.

Table 2 also shows that the state of layer adhesion between the primary lining and secondary lining 91 days after construction was examined laterally using ultrasonic pulses, while the layer in the second symmetrical area had peeled off. It was confirmed that there was no peeling at all in the first symmetric area and the invention area.

Example 3 In carrying out the same procedure as in Example 2, glass fiber foam mortar (specific gravity 1.0) was used from the first pipe (12).
1 strength of 35 Kf/crI), and only high-pressure air is sent under pressure from the second pipe line, which is merged into the first pipe line and sprayed. That is, even in the case where Example 17 was carried out in this manner, substantially the same results as in Example 2 described above could be obtained.

Example 4 In constructing the same composition as in Example 2, the slurry mortar in Example 2 was pumped using a central pipe directed toward the center of the rotary plate, and sand and quick setting agent were mixed. The material was similarly supplied onto a rotary disk using a screw conveyor in a supply pipe provided concentrically with the central tube, and the material was projected onto the inner wall of the tunnel by the high speed rotation of the rotary disk.

That is, in this case, the occurrence of cracks in the lining after construction was measured in the same manner as in each of the examples described above, and the results are shown in Table 3 below.

Table 3 (Crack length x Crack width un /'m') Also, the layer adhesion between the primary lining and the secondary lining 91 days after construction was examined. It was confirmed that the samples in the first symmetrical area and the invention area were not peeled off at all, whereas the samples in the second symmetrical area were found to be completely peeled off.

According to the present invention as described above, it is possible to effectively prevent the occurrence of cracks in this type of tunnel lining, and also to construct a stable, strong, and integral tunnel lining, and it is possible to achieve this from an industrial perspective. This is a highly effective invention.

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[Brief explanation of the drawing]

The drawings show embodiments of the present invention, and FIG. 1 is a cross-sectional view showing the state of formation of the lining according to the present invention, and FIG. 2 shows the form of a nozzle as an example of spraying. 3 is a partially cutaway side view of the spraying mechanism using rotational projection force, FIG. 4 is a vertical sectional side view of the rotary plate portion thereof, and FIG. 5 is a slope view of the stirring mechanism portion thereof. In these drawings, 1 is the rock mass, 2 is the tunnel, 3 is the rock bolt, 4 is the primary lining, 5 is the intervening layer, and 6 is the secondary lining. Patent Applicant Hajime Ito Inventor Habe Ito Tokuji Horinouchi Yasuhiro Yamamoto 1) Hide Naka Rema
Similar appearance 2 Fumiya F, 1 Den agent patent attorney Shirakawa -- 1P・j・t・'yūjō・ (16)

Claims (1)

[Claims] 1. Rock bolts are installed in the bedrock of the excavated tunnel. After that, a primary lining is applied, and when forming a secondary lining on the primary lining, spraying is characterized in that an intervening layer of a cement mixed material, which has a larger expansion and contraction effect than each of the linings, is applied. A method to prevent cracks in tunnel lining concrete. 2. The foamed mortar flowing in the form of a slurry is pumped in the first pipe line, the high-pressure air is sent in the second pipe line, and the air is merged in front of the nozzle to form the intervening layer, as described in claim 1. A method to prevent cracks in tunnel lining concrete. 3 In the first pipe, to the slurry cement paste or mortar which has been pumped 17, one of sand, gravel or lightweight aggregate or 2'N4 or more is added by pneumatically pumping 7 and sprayed to form an intervening layer. 4. A method for preventing cracks in tunnel lining concrete according to claim 1, which comprises: 4. A rotating disk containing slurry cement paste or mortar and any one of sand, gravel, or lightweight aggregate in a dry state. 1
A method for preventing cracks in tunnel lining concrete according to claim 1, in which seeds or two or more seeds are supplied separately, and are projected and blown by centrifugal force caused by high-speed rotation of the rotating disk.