JP2828589B2 - Rock bolt method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a rock bolt method for tunnel construction.

[0002]

2. Description of the Related Art In tunnel construction, rock bolts are installed at predetermined intervals in a peripheral wall of an excavated tunnel in order to effectively utilize the strength of the ground itself for supporting the ground.

In the rock bolt method, a rock drill is used to drill holes in the ceiling and side walls of the cross section of the tunnel and, in some cases, the floor, and insert a bolt into the hole, and then insert the bolt into a free end (hole). This is a method in which a bearing plate or washer is applied to the end that protrudes forward, and the nut is tightened. At this time, an adhesive lock bolt is used to inject a fixing material into the hole and the gap between the bolt and fix the bolt in the hole. The construction method is generally adopted.

As a fixing material, a synthetic resin such as polyester or epoxy may be used, but a cement-type fixing material using cement as a binder, that is, a cement paste or cement mortar is usually used. . The fixing material may be injected before the bolt is inserted or after the bolt is inserted.

In this case, the fixing material injected into the holes may drop. This problem occurs especially in the case of a perforation near the top because the direction of the hole is close to the vertical direction. Regardless of the method of inserting the fixing material into the perforation and then inserting the bolt, or the method of inserting the fixing material after inserting the bolt, the same problem occurs until the bolt tightening operation is completed.

[0006] For this purpose, it has been proposed to reduce the dripping by giving the fixing material itself a certain degree of viscosity. Known thickeners for this purpose include cellulose-based thickeners and acrylic acid polymer-based thickeners.

[0007]

However, if a conventional thickener is provided with a viscosity that can prevent dripping of the cement-based fixing material, the fluidity is extremely reduced. For this reason, the filling property is deteriorated, and the fixing failure of the bolt is caused, which causes not only the strength to be insufficient and the rust of the bolt, but also the injection pump and the injection pipe may be blocked.

In addition, it is not particularly necessary to inject a fixing material containing a thickener into a portion where drooling is not a problem (a hole having a gentle slope or a reverse slope). However, there is a problem that it is practically impossible to use the same injection equipment for the injection of the compound with the thickener and the compound not mixed with the thickener. This is because conventional thickeners have a strong tendency to stick to mixers, pumps, and piping systems, which makes it difficult to knead and feed them alternately with ordinary fixing materials. is there.

An object of the present invention is to solve the conventional problems in such a lock bolt method.

[0010]

Means for Solving the Problems The present invention provides a lock bolt in which a fixing material is injected into a hole drilled in a ceiling or a side wall of a tunnel and then a bolt is inserted, or a fixing material is injected after the bolt is inserted. Cement paste not containing welan gum as the fixing material in the method of construction
Or using a cement mortar, the cement paste or cement mortar formulated with welan gum, the former
A rock bolt construction method characterized by injecting the fixing material into the deep part of the hole and the latter fixing material near the hole .

[0011]

[0012]

When a proper amount of welan gum is mixed with cement paste or cement mortar as a fixing material, it is possible to prevent dripping from the pores without significantly reducing fluidity. The appropriate amount of welan gum to achieve this effect is 0.50 per unit water in cement paste or cement mortar with a water-cement ratio of 25-50%.
It is about 01 to 2.0% by weight.

[0013] In particular, according to the method of injecting a welan gum-free fixing material into a deep portion of a perforated hole whose hole is downward, and injecting a welan gum-added fixing material only near the perforated hole of the perforated hole, the method of adding welan gum is described. Of the fixing material without welan gum acts as a stopper for preventing dripping of the fixing material. In this case, most of the deep part and the body part can be filled with a cement paste or mortar having good fluidity and filling properties.

[0014]

EXAMPLES Welan gum used in the present invention is, for example, K.K. Clare in CHEMSSPEC USA '88
APPLICATION submitted to SYMPOSIUM
As described in the article entitled OF NOVEL BIOGAMS, the ATCC of Alcaligenes strain
Microbial polysaccharide (BIO) produced by subjecting 31555 cells to aerobic fermentation under carefully controlled conditions
GAM), the general structure of which is disclosed, for example, in Japanese Patent Laid-Open No. 5-139806 filed by the same applicant as the present application.

[0015]

That is, the backbone of this BIOGAM has two D
-Glucose, one D-glucuronic acid and one L
-Consisting of rhamnose, the side chains being composed of one rhamnose or one mannose.

Such welan gum is available as a dry powder product. However, when a very small amount of this welan gum powder is added to a cement-based fixing material, it exhibits remarkable pseudoplastic properties, exhibits a suspension effect of fine particles, and exhibits fluidity. Without sacrificing so much, it is possible to impart sufficient viscosity to prevent drooling.

When welan gum is added to the fixing material, the content is preferably in the range of 0.01 to 2.0% by weight based on the amount of water. If the amount is less than 0.01% by weight, a sufficient dripping prevention effect cannot be obtained. On the other hand, if it is added in excess of 2.0% by weight, the viscosity rises sharply and the fluidity decreases, and good workability cannot be obtained. A preferable addition range of welan gum is 0.02 to 0.1% by weight with respect to a unit water amount.

In practicing the present invention, it is preferable to inject a welan gum-free fixing material into the deep portion of the perforation and to inject the welan gum-containing fixing material only near the hole of the perforation. In this case, the fixing material added with welan gum acts as a stopper for preventing the fixing material from dripping. According to this method, the deep part and most part of the body can be filled with ordinary cement paste or mortar with good fluidity and filling properties, and only for inclined perforations where there is a risk of drooling. It suffices to inject a small amount of welan gum-added fixing material near the hole.

FIG. 1 schematically shows the state of implementation of this method. As shown in the lower part of Fig. 1, in the rock bolt method, the strength of the ground is used by inserting and tightening the lock bolt 2 from the inside of the tunnel to the ground at necessary intervals to the peripheral wall of the tunnel 1 that has been cut and cut To prevent the collapse of loose ground.

In the present invention, as shown in the upper part of FIG. 1, of the perforations 3 drilled to the required depth by a rock drill, the entire length of the perforated hole 3 is downward. A longer bolt 4 is inserted (step at the left end), and a fixing material 5 without welan gum is first injected into a gap between the hole 3 and the bolt 4, and then a fixing material 6 with welan gum added is injected (middle step). Then, a bearing plate or a washer 7 is applied to a protruding end of the bolt 4 on the tunnel side, and tightened with a nut 8 (the process at the right end).

The operation of injecting the fixing material is performed from a pump wheel 9 through a pressure feed pipe 10. In this case, the fixing materials 5 and 6 with and without welan gum can be injected in a continuous operation. That is, when a predetermined amount of the welan gum-free fixing material 5 is injected, it is possible to add a predetermined amount of welan gum into the pump 11 or the pressure feed pipe 10 and then continuously inject the welan gum-added fixing material 6. it can. This can be achieved due to the thickening effect peculiar to welan gum. When cellulose ether-based thickeners are used, they tend to mix with each other, which hinders such a continuous switching type injection operation. Sometimes.

Alternatively, the welan gum-added fixing material 6 may be prepared in another pumping pump, and the operation may be switched to the operation of injecting the fixing material 6 after the completion of the injection of the non-added fixing material 5. In this case, the fixing materials 5 and 6 are operated by operating a switching valve near the injection nozzle using a double-wire type pressure feed pipe.
Is convenient.

FIG. 2 shows the same lock bolt construction as in FIG. 1 except that the fixing materials 5 and 6 are injected into the perforations 3 and then the bolts 3 are inserted. The operation of injecting the fixing materials 5 and 6 in this case can be performed in the same manner as in the case of FIG.

[0025]OhElan gum-added fixing materialTo 6
Is usually added to the concrete in addition to welan gum.
Dispersants used to impart fluidity to compounds
If high performance water reducing agent or high performance AE water reducing agent is blended,
The fluidity and filling property of the fixing material can be improved. Like
New agents include naphthalene sulfonate and melamines
Sulfonate, polycarboxylate, aminosulfonic acid
Some are salt-based.

The amount of such a high-performance water reducing agent or high-performance AE water reducing agent to be added to the fixing material has an appropriate range depending on the kind of the water-reducing agent or the high-performance AE water reducing agent.
(If a fine powder is also present in addition to cement, the total unit powder amount thereof) may be in the range of 0.1 to 4.0% by weight. If it is less than 0.1% by weight, the effect of imparting fluidity is small, and the fluidity intended in the present invention cannot be secured. On the other hand, if the content exceeds 4.0% by weight, the effect is saturated and uneconomical.

Pressure is applied when the fixing material is injected. Therefore, even if no breathing occurs under non-pressure, a phenomenon of forcible dehydration occurs at the time of injection, so that breathing may occur. However, the fixing agent to which welan gum is added according to the present invention can eliminate bleeding under the action of pressure even when the water cement ratio is 30% or more. For this reason, the adhesive strength of the fixing agent is improved.

Hereinafter, properties of the fixing material used in the present invention will be described with reference to test examples.

Test materials: The following two types of fixing materials were prepared. "Sample 1" Water / premix cement ratio: 25% Premix cement: 20 kg (portland cement and sand mixed in a ratio of 1: 1 in advance) Water: 5 kg "Sample 2""Premix cement 20 in sample 1"
2.5 kg of welan gum with respect to “kg + 5 kg of water” (the proportion of welan gum per unit water is 0.05%
Is).

[Test 1] The fluidity of each sample was evaluated by a mortar flow test. As a result, the flow value of sample 1 was 244 mm, and the flow value of sample 2 was 216 mm. When the viscosity of each sample was measured using a B-type viscometer, the viscosity of sample 1 was a maximum of 54000 Cp (centipoise) and a stable value of 46000 Cp, and the viscosity of sample 2 was a maximum of 100000 Cp or more and a stable value of 75000 Cp. .

[Test 2] After loading the material of sample 1 to a depth of 250 cm from the open end of a steel pipe having a diameter of 5 cm and a length of 300 cm and closed at one end, the material of sample 2 was loaded and the inside of the pipe was filled. Completely filled. Immediately after this filling, dripping from the opening was observed with the pipe vertical with the closed end up. As a result, no dripping of the filler from inside the pipe was observed at all until hardening.

Comparative Example Sample 3: The same material as in Sample 2 was prepared except that welan gum was replaced with 2.5 g of carboxymethylcellulose powder. In test 1, the flow value of sample 3 was 235 mm, the viscosity was 45,000 Cp at the maximum, and the stable value was 54000 Cp. In Test 2, dripping was observed, and after 20 minutes, all the samples fell from the pipe.

[0033]

As described above, in the lock bolt method according to the present invention, the fixing material can be loaded into a drilled hole having a downward opening without fear of dropping.
The fixing strength of the lock bolt is sufficiently achieved even with a perforated hole having a downward opening. As a result, it became possible to complete the adhesive rock bolt construction on the tunnel ceiling, where there is the greatest danger of collapse, and the original purpose of the support work using rock bolts utilizing the strength of the ground has been completed.

Moreover, the lock bolt method according to the present invention can be carried out with almost the same equipment and work procedure as the conventional one, so that the economic burden is small.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a tunnel cross section and a rock bolt construction portion showing an example of a lock bolt construction method of the present invention.

FIG. 2 is a schematic cross-sectional view of a tunnel cross section and a lock bolt construction portion showing another example of the lock bolt construction method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Excavated tunnel 2 Rock bolt construction part 3 Drilling hole 4 Lock bolt 5 Fixing material without welan gum 6 Fixing material with welan gum 7 Base 8 Nut 9 Pump car

──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuo Shigematsu Inventor Kashima Construction Co., Ltd. 2-9-1-1 Tobita-Shi, Kabuto, Tokyo (72) Inventor Masayoshi Minami 1st Kitahama Higashi, Chuo-ku, Osaka-shi, Osaka No. 29 Inside Mitsui Co., Ltd. (72) Inventor Masato Yoshizaki 1-29 Kitahama Higashi, Chuo-ku, Osaka City, Osaka Prefecture Inside Mitsui Co., Ltd. (56) References JP-A-63-315547 (JP, A) (58 ) Surveyed field (Int.Cl. ⁶ , DB name) E21D 20/00

Claims (1)

(57) [Claims] In a rock bolt method in which a fixing material is injected into a hole drilled in a ceiling or a side wall portion of a tunnel and then a bolt is inserted, or a fixing material is injected after inserting a bolt, the fixing material is used as the fixing material. Cement paste or cement mortar without welan gum,
A rock bolt method using a cement paste or cement mortar containing welan gum and injecting the former fixing material into the deep part of the hole and the latter fixing material near the hole.