JPH04281999A - Lock bolt - Google Patents

Abstract

PURPOSE:To reduce weight and improve processability, creeping characteristics, shearing strength, toughness, and shear breaking resistance by a method in which fibers having a given tensile breaking strength are mixed with a synthetic resin having a given bending elasticity and molded. CONSTITUTION:A bundled fiber of polyvinyl alcohol filaments for example, having a tensile breaking strength of 8g/denier, as reinforcing fibers, is dipped in a resin composition such as epoxy resin or unsaturated polyester resin, having a Young's modulus in fracture of 150kg/mm<2> or more (after hardened), in an impregnation tank. The fibers so treated are molded by heating, wound with fibers of a fineness corresponding to 1-5wt.% of the bundled fiber assemblage, and cured. The bar-like molding is subjected to a cutting process to form grooves and then to a finish treatment such as heat treatment.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rock bolt made of bundles of synthetic fibers and synthetic resin.

0002

[Prior art] Conventionally, lock bolts were JIS G311.
It is made by processing iron specified in 2. Recently, a rock bolt construction method using a rock bolt made of fiber bundles and resin has been proposed. For example, a core material obtained by impregnating a reinforcing fiber bundle with high strength and low elongation such as glass fiber, carbon fiber, or aromatic polyamide fiber with a thermosetting resin such as unsaturated polyester resin or epoxy resin can be used as a core material such as polyester. JP-A-62-182400 proposes a construction method using a spiral rope-shaped rock bolt coated with a thermoplastic resin and obtained by fusing and bonding a plurality of strands thereof.

0003

[Problems to be Solved by the Invention] Conventional iron lock bolts are heavy, so they are not only unfavorable in terms of workability and safety, but also have problems with durability due to the formation of rust. In addition, molded products obtained by impregnating fiber bundles of highly rigid fibers such as glass fibers and carbon fibers with epoxy resin and curing them are lighter and more durable than iron products, but they also suffer from compressive shear stress. The tensile shear stress is small, and buckling points (shear failure) occur due to the compression shear method, and it is not strong enough to withstand bending, making it hard and brittle, and it can only be inserted straight into the soil or rock, so it cannot be used for long periods of time. There was also a problem with its durability.

The necessary conditions for rock bolts are NATM (N
ew Austrian Tunneling M
It is used for tunnel excavation technology called method (method) and to prevent landslides on slopes, so (1) Suspension effect of rock: it binds rock and mud blocks that are likely to fall off to healthy ground deep in the ground. (2) Layer aggregation effect: Sewing and supporting rock and mud blocks (3)
This is said to have a reinforcing effect on the seamed portion, but in addition to the conditions (1) to (3), the present invention has found a rock bolt that has the effect of alleviating tensile and shear stress caused by ground deformation as (4). It is. This is a feature that the lock bolt of the present invention has flexibility.

[0005]

[Means for Solving the Problems] The present invention has a tensile cutting strength of 8
A rod-shaped object or a rod-like object with a tensile cutting strength of 8 g/ This rock bolt is made of a molded body in which a synthetic resin having a bending elastic modulus of 150 kg/mm2 or more after solidification or hardening is applied to a braid-like material made of synthetic fibers of denier or more. The rock bolt of the present invention has a tensile cutting strength of 60
kg/mm2 or more, initial tensile modulus is 1000-600
0 kg/mm2 and a bending elastic modulus of 150 to 4
000kg/mm2, does not produce buckling points (shear failure) by compression shearing method, has a tensile shear stress of 2kg/mm2 or more, is capable of bending loading, is made of a molded body with improved creep properties, and excellent toughness. It's a bolt.

The fibers used in the present invention have a tensile strength at break of 8 g/denier or more, preferably a tensile strength at break of 13 g/denier.
/denier or more, and preferably has a cutting elongation of 3 to 15.
% synthetic fiber. If the physical properties of the fiber are outside the above range, the cuttability with a saw and processability will be poor, and in particular, the shear fracture strength and creep properties will be poor, and the toughness will be poor. Specific fibers used in the present invention include, for example,
High-strength polyvinyl alcohol fibers, fully aromatic polyesters made from p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, fully aromatic polyesters made from p,p'-bisphenol and terephthalic acid and p-hydroxybenzoic acid, etc. , a wholly aromatic polyester fiber made from a polyester obtained by condensation polymerization of an aromatic dicarboxylic acid and an aromatic dihydroxy compound or an aromatic oxycarboxylic acid;
Or fully aromatic polyester fibers made from polyesters obtained by reacting 2,6-naphthalene dicarboxylic acid, 2,6-naphthalene diol, 6-hydroxy-2-naphthoic acid, and their ester-forming compounds as main components. Can be mentioned.

[0007] The reinforcing fibers of the present invention are rod-shaped fibers in which fibers having a fineness of 1 to 5% of the total fineness of the bundled fibers are wound around bundled fibers that are simply aligned or twisted together. It takes the form of objects or string-like objects. The thickness of the reinforcing fiber aggregate is appropriately set depending on the size of the rock bolt used, but is usually 3 to 30 mm thick. The string-like material itself has irregularities, but when using bundled fibers, it is necessary to create projections on the bar-like surface in the same way as deformed reinforcing bars in order to mechanically provide adhesion to concrete. As a method for providing protrusions, it is necessary to use fibers or fiber bundles with a denier thickness of 1 to 5% of the total fineness at the time of molding the rod-shaped body, and in order to further improve the irregular shape, it is necessary to use fibers or fiber bundles with a denier thickness of 1 to 5% of the total fineness at the time of molding the rod-shaped body.
00 twists of PVA synthetic fibers, aramid synthetic fibers, polyarylate synthetic fibers, etc. are impregnated with the resin used during pultrusion molding, and then the resin and bundled fibers are made by pultrusion molding. 4 in the axial direction on a rod-shaped object
A method may be adopted in which one or more cords are wound so as to form a diagonal seam at an angle of 0 to 50 degrees, and the cords are heat-treated and bonded. The winding pitch is called the diagonal stitch spacing, and the value obtained by dividing the average spacing of the stitches by the diameter of the bar is 0.
The pitch is preferably 6 to 0.8, and most preferably about 0.7.

[0008] The resin constituting the rock bolt is selected from thermoplastic resins or thermosetting resins and has a bending elastic modulus of 150 kg/mm2 or more after solidification or curing, preferably a bending elastic modulus of 180 to 1800 kg/mm2. Synthetic resin, for example, epoxy resin (flexural modulus 700 kg/
mm2 or more), unsaturated polyester resin (800 kg
/mm2 or more), thermosetting resins such as vinyl ester resins, phenol resins, melamine resins, urea resins, polyethylene terephthalate resins (700 kg/mm2 or more)
above), methacrylic acid ester resin, thermoplastic polyester, polyphenylene oxide, polycarbonate, nylon-66, nylon-MXD6 (200 kg
/mm2 or more) is a synthetic resin selected from thermoplastic resins such as The flexural modulus of this synthetic resin can be determined by selecting it based on the resin's original properties, by adding fillers selected from inorganic fillers, organic fillers, short fiber fillers, etc. to the resin, or by adding crosslinking agents, etc. The desired physical properties can be adjusted by a method of mixing two or more types of resins having different elastic moduli, a method of selecting the composition of the curable resin, etc. If the flexural modulus of the synthetic resin is low, the creep property will increase, making it impossible to maintain morphological stability over a long period of time. On the other hand, if the flexural modulus is too large, the synthetic resin itself becomes brittle and is likely to be damaged by impact or shear failure due to high compressive force. Moreover, the rod becomes hard and its flexibility is impaired, which is not preferable.

[0009] Next, in the production method of a rod-shaped molded article using a thermosetting resin, bundled fibers or The string-like material is immersed and passed through a mold to remove excess resin liquid, and the ratio of fibers in the molded product is 50 to 85.
After converting to % by weight, the resin is heat-treated in a heating zone of at least 100°C or higher to harden the resin and obtain a rod-shaped molded body.

[0010] In addition, in the manufacturing method using thermoplastic resin, the synthetic resin melt melted in an extruder is integrated with bundled fibers or string-like materials drawn to the desired thickness in a die section, and forming is performed. It is taken out through a die and cooled to obtain a rod-shaped molded body.

[0011] Next, the rod-shaped molded body may be cut to form grooves as necessary, or a resin-impregnated fabric, non-woven fabric, yarn, etc. may be wrapped around the surface of the rod-shaped body to give the surface an irregular shape, or the surface of the rod-shaped body may be shaped irregularly. The resin is molded in a deformable state to create irregularities on the rod surface to create surface irregularities to improve bonding with concrete. The obtained rod-shaped molded body is subjected to finishing treatment such as heat treatment as necessary to form a rock bolt.

The characteristic values of the rod-shaped molded article of the present invention are as follows:
The tensile cutting strength is 60 kg/mm2 or more, the initial tensile modulus is 1000 to 6000 kg/mm2, and the bending modulus is 150 to 4000 kg/mm2. Stress is 2kg
/mm2 or more shall be satisfied. Molded products that do not satisfy these properties may have poor creep properties and may not be stable enough to withstand long-term use, or may be brittle and cause shear failure under high compressive force. I can't get anything.

[0013] In addition, in molded articles of fibers and synthetic resins that use glass fibers, carbon fibers, fluorine fibers, aramid fibers, etc. alone, the bondability between the fibers and the resin is insufficient, and when high compressive force is applied, the fibers break down. Interfacial peeling occurs between the resin and the resin, easily causing buckling phenomenon (shear failure). Therefore, when these fibers are used together as reinforcing fibers, it is not preferable to use more than 50%.

[0014]

[Function] The present invention consists of a bundle of fibers or a string made of synthetic fibers selected from polyvinyl alcohol fibers and wholly aromatic polyester fibers having specific fiber properties, and a synthetic resin with a specific bending modulus. By using a rod-shaped molded body with specific characteristic values as a rock bolt, it becomes a rock bolt with flexibility, which was not previously available, and has a ground suspension effect, a layer gathering effect, and a reinforcing effect on seamed parts. In addition, it has the effect of alleviating distortion. Furthermore, the rock bolt of the present invention can be freely installed into a mounting hole having a curved portion that is not a straight line when loading the rock bolt, and has improved bondability with resin or a grafting machine when bonding to the ground. Flexibility enhances the stitching reinforcement effect due to the mechanical anchor effect. In addition, the rock bolt of the present invention has a specific gravity of 1.2 to 1.4, which is about 1/1 that of iron.
It has the advantage of being lightweight at 6, making it easy to transport, and being flexible, it can be wound onto a reel and taken out for the required length. In addition, it does not rust and can be cut with a saw or pliers, making it very safe and economical. The physical properties of the rock bolt of the present invention include high tensile strength, improved creep properties, stable form, excellent bending and processing properties, high strength and toughness, and excellent flexibility with high shear fracture strength. It is a high rock bolt.

[0015]

[Examples] Next, the present invention will be explained with examples. In addition, parts and percentages in the examples refer to weight unless otherwise specified.

The flexural modulus of synthetic resins and rod-shaped molded bodies is determined according to JIS K-6911 "General Test Methods for Thermosetting Plastics" Sections 5 and 17, and the tensile cutting strength and initial tensile modulus are determined according to JIS K-7113 "General Test Methods for Thermosetting Plastics". Measurement was performed according to the "Tensile Test Method for Plastics".

[0017] Furthermore, the shear fracture strength can be measured using (1) JI
According to S K-6911 "General Test Methods for Thermosetting Plastics" Section 5.17, a specimen of a certain thickness is placed on a fulcrum with a distance between the fulcrums that is 3 or 4 times the thickness. ,
The short beam method applies a load to the midpoint and measures the final strength from the stress-deflection curve. Since the final point in this method is the buckling point, the shearing force can be determined from the stress at that time and the cross-sectional area of the sample. (2) Cut a specimen of a certain thickness into a length that is four times the thickness, and place it at a position 1.67 times the thickness of the specimen across the center of the specimen. /
A compression shear method in which cuts with a width of 1 mm are made in opposite directions up to 2, a compressive load P is applied from both ends, and the buckling stress is measured from the load-strain curve. In this method, the compressive shear force can be determined from the stress at the buckling point and the cross-sectional area of the sample. (3) Take a specimen of a certain thickness and make a 1 mm wide cut in opposite directions up to 1/2 the thickness of the specimen at a position twice the thickness across the center of the specimen, and A tensile shearing method in which a part is fixed to a fixture and pulled at a constant speed, and the load P at the time of tensile cutting is measured. With this method, the tensile shearing force can be determined by dividing the load P during tensile cutting by the cross-sectional area.

Examples 1 to 3 High strength polyvinyl alcohol fiber (cutting strength 17.3
g/dr, cutting elongation 7.2%, “PVA fiber”)
120 multifilament yarns of 1800 dr/1000 fil were combined to form a fiber bundle. On the other hand, the following three types of resin compositions or resins were prepared as synthetic resins to be applied to the fibers.

(1) Epoxy resin composition (referred to as "EPX"): The characteristic value of the cured resin is a tensile strength of 5.9 kg/m.
m2, cutting elongation 3.2%, bending stress 9.3kg/mm2
, flexural modulus of elasticity is 730 kg/mm2.

(2) Unsaturated polyester resin composition (“
(referred to as "UPE"): The characteristic values of the cured resin are tensile strength 4.
5kg/mm2, cutting elongation 3.5%, bending stress 8.25
kg/mm2, and the bending elastic modulus is 1050 kg/mm2.

(3) Polyamide resin (referred to as "PAM"): The characteristic value of the solidified resin is a tensile strength of 8.1 kg/mm2.
, cutting elongation 48%, bending stress 11 kg/mm2, and bending elastic modulus 270 kg/mm2.

Next, the epoxy resin composition and the unsaturated polyester resin composition are applied by immersing the bundled fibers in a resin composition liquid in an impregnating bath, and then
The fibers are drawn into a round bar through a molding nozzle heated to ℃ and twisted at a rate of 30 times/m to three filaments of 1800 dr, with a pitch of 0.
7 and cured in a room at 120° C. for 7 hours to obtain a rod-shaped molded product with a diameter of 6.3 mm. In addition, the polyamide resin is applied using a melt extruder, and the melt zone temperature is 27
At 5° C. and a molding die temperature of 280° C., a polyamide resin melt was applied to the bundled fibers and taken off, and a filament was wound as described above and cooled to obtain a rod-shaped molded product with a diameter of about 6.3 mm. These rod-shaped compacts were grooved with a die to obtain rock bolts with a diameter of 6 mm.

Comparative Example 1 In place of the polyvinyl alcohol fibers in Example 1, bundled glass fibers made of 110 glass fiber rovings were used and impregnated with an epoxy resin composition. I made a rock bolt with a diameter of 6mm. The physical properties of the obtained rock bolt were measured and shown in Table 1.

[0024]

[Table 1]

That is, the rock bolts of the Examples had excellent shear fracture strength, whereas the rock bolts of the Comparative Examples suffered shear fractures under relatively low loads. When this broken part was observed, it was found that the fibers and resin had separated and it was not an integrally molded product.

Examples 4 to 6 Fully aromatic polyester fibers from p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (cutting strength 25.
7 g/dr, cutting elongation 3.8%, "PES fiber") 12 multifilament yarns of 1500 dr-300 fil were combined, and 10 yarns were knitted to form a rod-shaped object by pultrusion molding. . Each of the three types of synthetic resin compositions used in Examples 1 to 3 was applied to this rod-shaped article, and processed in the same manner as in Example 1 to produce a rock bolt with a diameter of 6 mm. Table 2 shows the physical properties of the obtained rock bolt.

[0027]

[Table 2]

That is, the rock bolt of the example has high strength and excellent shear fracture strength. Furthermore, we made blocks with rock bolts embedded in concrete, and for comparison we made blocks with iron rock bolts embedded in concrete, and immersed them in a 10% aqueous solution of saline at a temperature of 60°C for 5 days. A durability test of leaving the rock bolts in hot air at 60°C for 5 days was repeatedly conducted to compare the durability of the rock bolts. As a result, the concrete blocks in which the iron rock bolts had been embedded suffered rust and morphological changes, but no abnormalities were observed in the test blocks of the examples at that point.

[0029]

[Effects of the Invention] As explained above, the rock bolt of the present invention has flexibility, high cutting strength and toughness, excellent shear fracture force, does not cause buckling fracture, and has improved creep characteristics. It is an excellent rock bolt that has excellent dimensional stability, is lightweight, has excellent workability when cut with a saw, and has no corrosion or rust.

Claims (1)

[Claims] [Claim 1] A fiber or fiber bundle having a fineness of 1 to 5% of the total fineness of the fiber bundle is wound around a fiber bundle made of synthetic fibers with a tensile cutting strength of 8 g/denier or more. A rock bolt made of a rod-shaped article or a braid-like article made of synthetic fibers having a tensile cutting strength of 8 g/denier or more, to which a synthetic resin having a flexural modulus of 150 kg/mm2 or more after solidification or hardening is applied.