JPH07208097A - Rock bolt method - Google Patents

Abstract

PURPOSE:To prevent the breakdown of a loose ground by inserting and clamping rock bolts from the inside of a tunnel into a bedrock against the circumferential wall of the excavated tunnel at necessary intervals. CONSTITUTION:A bolt 4 having the overall length longer than the depth of a hole is inserted into a bore with a downward opening among bores bored in the necessary depth with a drill, first of all, grout 5 without welan gum is injected into a gap between the bore 3 and bolt 4, and successively welan gum added grout 6 is injected. A bearing plate or a washer 7 is applied to the projecting end on a tunnel side of the bolt 4, and the bolt is clamped with a nut 8. After a certain amount of grout 5 without welan gum is injected, a certain amount of welan gum is added to the inside of a pump 11 or the inside of a conveying pipe 10, and successively welan gum additive grout 6 is injected, so that continuous switch system injection control is made.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In tunnel construction, rock bolts are installed at predetermined intervals in the 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 tunnel cross section, and in some cases, even on the floor, and the bolt is inserted into the hole and the free end (hole opening) of the bolt is inserted. It is a construction method in which a bearing plate or washer is applied to the end protruding further toward the front and tightened with a nut, but at that time, a fixing material is injected into the gap between the hole and the bolt to fix the bolt in the hole. The construction method is generally adopted.

Although a synthetic resin such as polyester or epoxy may be used as the fixing material, a cement-based fixing material using cement as a binder, that is, 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 hole near the top because the direction of the hole is close to the vertical direction. Whether the method of inserting the fixing material into the hole and then inserting the bolt or the method of inserting the bolt and then inserting the fixing material causes the same problem until the tightening work of the bolt is completed.

For this reason, it has also been proposed to impart a certain degree of viscosity to the fixing material itself to reduce drooling. Known thickeners for this purpose include cellulosic thickeners and acrylic acid polymer-based thickeners.

[0007]

However, when a conventional thickener is used to impart viscosity to the cement-based fixing material so as to prevent dripping, the fluidity is extremely reduced. For this reason, not only the filling property is deteriorated, but the fixing of the bolt is caused, which leads to insufficient strength and rusting of the bolt, and the injection pump and the injection pipe may be blocked.

Further, since it is not necessary to inject a fixing material containing a thickener into a portion (a hole having a gentle inclination or a reverse inclination) where drooling does not pose a problem, an ordinary fixing material is required. However, there is a problem in that it is practically impossible to carry out injection with the thickener and those without the thickener using the same injection equipment. This is because conventional blends with thickeners have a strong tendency to stick to mixers, pumps, and piping systems, making it difficult to knead and pump with regular fixing materials alternately. is there.

The present invention is intended to solve the conventional problems in such a rock bolt construction method.

[0010]

SUMMARY OF THE INVENTION According to the present invention, a lock bolt is used in which a fixing material is injected into a hole formed in a tunnel ceiling portion or a side wall portion and then a bolt is inserted, or a fixing material is injected after inserting the bolt. In the construction method, a cement paste or cement mortar containing welan gum is used as the fixing material.

In particular, the present invention relates to a rock bolt construction method in which a fixing material is injected into a hole formed in a tunnel ceiling portion or a side wall portion and then a bolt is inserted, or a fixing material is injected after inserting the bolt. Using cement paste or cement mortar containing no welan gum as the fixing material and cement paste or cement mortar containing welan gum, injecting the former fixing material into the deep part of the hole and the latter fixing material near the opening of the hole. A characteristic rock bolt construction method is provided.

[0012]

When a proper amount of welan gum is mixed with cement paste or cement mortar as a fixing material, drooling from pores can be prevented without significantly lowering fluidity. The appropriate amount of welan gum that fulfills this function is 0 per unit amount of water in cement paste or cement mortar with a water-cement ratio of 25 to 50%.
It is about 01 to 2.0% by weight.

In particular, according to a method of injecting a fixing material containing no welan gum into a deep portion of a hole having a downward opening, and injecting a fixing material containing welan gum only in the vicinity of the opening of the opening, welan gum is added. The fixing material serves as a stopper for preventing the fixing material containing no welan gum from dripping. In this case, almost all of the deep part and the body part can be filled with cement paste or mortar having good fluidity and filling property.

[0014]

EXAMPLES Welan gum used in the present invention is, for example,
AP submitted by CH Clare to 88 SYMPOSIUM
As described in a paper entitled PLICATION OF NOVEL BIOGAMS, it is a polysaccharide (BIOGAM) of microbial origin produced by subjecting ATTC 31555 of Alcaligenes strains to aerobic fermentation under carefully controlled conditions. , Its general structure is shown in Formula 1.

[0015]

[Chemical 1]

That is, the main chain of this BIOGAM has two D
-Glucose, 1 D-glucuronic acid and 1 L
-Rhamnose, the side chain is composed of one rhamnose or one mannose.

Such welan gum is available as a dry powder product, but when this welan gum powder is added to a cement-based fixing material in an extremely small amount, it exhibits remarkable pseudoplasticity, exhibits a suspension stabilizing effect of fine particles, and has a fluidity. It is possible to impart sufficient viscosity to prevent dripping without sacrificing so much.

When adding welan gum to the fixing material, it is preferable to add it in an amount of 0.01 to 2.0% by weight with respect to the unit amount of water. If it is less than 0.01% by weight, a sufficient effect of preventing drooling cannot be obtained. On the other hand, if it is added in excess of 2.0% by weight, the viscosity will rise sharply and the fluidity will decrease, resulting in poor workability. The preferred range of addition of welan gum is 0.02 to 0.1% by weight per unit amount of water.

In carrying out the present invention, it is preferable to inject a fixing material without addition of welan gum into the deep part of the perforation and to inject the fixing material with addition of welan gum only near the mouth of the perforation. In this case, the fixing material containing welan gum normally functions as a stopper to prevent the fixing material from dripping. According to this method, most of the deep part and the trunk part can be injected with ordinary cement paste or mortar with good fluidity and filling property, and only for the inclined holes where there is a risk of dripping. It is only necessary to inject a small amount of the welan gum-added fixing material near the mouth of the hole.

The state of implementation of this method is shown diagrammatically in FIG. As shown in the lower part of Fig. 1, in the rock bolt method, the strength of the rock is utilized by inserting and tightening the rock bolts 2 into the rock from the inside of the tunnel to the rock on the peripheral wall of the excavated tunnel 1 at required intervals. To prevent the loose ground from collapsing.

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

The fixing material is injected from the pump wheel 9 through the pressure feed pipe 10. In this case, the fixing materials 5 and 6 with or without welan gum can be injected by continuous operation. That is, when a predetermined amount of the fixing material 5 containing no welan gum is injected, a predetermined amount of welan gum may be added into the pump 11 or the pressure feed pipe 10 and then the fixing material 6 containing the welan gum may be injected. it can. This is possible due to the thickening effect peculiar to welan gum. When cellulose ether thickeners are used, they tend to mix with each other, which hinders such continuous switching type injection operation. There are things to do.

However, it is also possible to prepare the welan gum-added fixing material 6 in another pressure feed pump and switch to the injection operation of the fixing material 6 after the injection of the additive-free fixing material 5 is completed. In this case, a double-line pressure feed pipe is used, and the fixing valves 5 and 6 are operated by operating the switching valve near the injection nozzle.
It is convenient to switch between.

FIG. 2 shows the same lock bolt work 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 injection operation of the fixing materials 5 and 6 in this case can be performed in the same manner as in the case of FIG.

In addition to the examples shown in FIGS. 1 and 2, it is possible to inject only the fixing material 5 containing welan gum without using the fixing material 6 containing no welan gum in some cases. In this case, in addition to the addition of welan gum, the addition of a dispersant that is usually used to impart fluidity to concrete mixes, such as a high performance water reducer or a high performance AE water reducer, results in -Fillability can be improved. Preferred agents include naphthalene sulfonate, melamine sulfonate, polycarboxylate and amino sulfonate.

The amount of such a high-performance water-reducing agent or high-performance AE water-reducing agent added to the fixing material has a proper range depending on its type, but in general, it is a unit cement amount.
It may be in the range of 0.1 to 4.0% by weight relative to (the total amount of unit powder when fine powder is present in addition to cement). 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, the effect is saturated even if added in excess of 4.0% by weight, which is uneconomical.

Pressure acts upon injecting the fixing material. Therefore, even if breathing does not occur under non-pressure, breathing may occur because the phenomenon of forced dehydration occurs during injection. However, the fixing agent to which welan gum is added according to the present invention can reduce the breathing to zero under the action of pressure even if the water cement ratio is 30% or more. Therefore, the adhesive strength of the fixing agent becomes good.

The properties of the fixing material used in the present invention will be shown below with test examples.

Test materials: The following two types of fixing materials were prepared. "Sample 1" Water / premix cement ratio: 25% Premix cement: 20 kg (premixed Portland cement and sand in 1: 1) Water: 5 kg "Sample 2" Sample 1 "Premix cement 20
2.5g of welan gum in 5kg of water + 5kg of water (the proportion of welan gum per unit amount of 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. Moreover, when the viscosity of each sample was measured using a B-type viscometer, the viscosity of sample 1 was 54000 Cp (centipoise) at the maximum and the stable value was 46000 Cp, and the viscosity of sample 2 was at least 100000 Cp and the stable value was 75000 Cp. .

[Test 2] The material of Sample 1 was loaded 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 with one end closed, and then the material of Sample 2 was loaded to move the inside of the pipe. Fully filled. Immediately after this filling, the pipe was made vertical with the closed end facing upward, and the sagging from the opening was observed. As a result, no dripping of the filling material from the pipe was observed until hardening.

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

[0033]

As described above, in the rock bolt method according to the present invention, the fixing material can be loaded into a hole with a downward opening without fear of dropping.
The fixing strength of the lock bolt can be sufficiently achieved even in the case of a hole having a downward opening. As a result, it became possible to complete the adhesive rock bolt work on the tunnel ceiling, which is the most dangerous place to collapse, and the original purpose of the support work using the rock bolts, which utilizes the strength of the ground, was fully achieved.

Moreover, the lock bolt construction method of the present invention can be carried out with substantially the same equipment and work procedure as the conventional one, so that the economical burden is small.

[Brief description of drawings]

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

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

[Explanation of symbols]

 1 Excavated tunnel 2 Rock bolt construction part 3 Drilling hole 4 Rock bolt 5 Fixing material without addition of welan gum 6 Fixing material with addition of welan gum 7 Pedestal 8 Nut 9 Pump car

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Shigematsu 2-1-1, Tobita-yari, Chofu-shi, Tokyo Kashima Construction Co., Ltd. Technical Research Institute (72) Inventor Masayoshi Minami 1-29 Kitahamahigashi, Chuo-ku, Osaka-shi, Osaka Sansan Co., Ltd. (72) Inventor Masato Yoshizaki 1-29 Kitahamahigashi, Chuo-ku, Osaka-shi, Osaka Sanaki Co., Ltd.

Claims (4)

[Claims] 1. A lock bolt construction method in which a fixing material is injected into a hole formed in a tunnel ceiling portion or a side wall portion and then a bolt is inserted, or a fixing material is injected after the bolt is inserted. A rock bolt method characterized by using cement paste or cement mortar mixed with welan gum. 2. A lock bolt construction method in which a fixing material is injected into a hole formed in a tunnel ceiling portion or a side wall portion and then a bolt is inserted, or a fixing material is injected after the bolt is inserted. Cement paste or cement mortar containing no welan gum,
A rock bolt method characterized by using cement paste or cement mortar mixed with welan gum and injecting the former fixing material into the deep part of the hole and the latter fixing material near the mouth of the hole. 3. The rock bolt method according to claim 1, wherein the welan gum is blended in the range of 0.01 to 2.0% by weight with respect to the unit amount of water in the fixing material. 4. Welan gum is a strain of Alcaligenes strains.
The Rockbolt method according to claim 1, 2 or 3, which is a dry powder composed of a polysaccharide of microbial origin produced by aerobically fermenting ATTC 31555 cells.