JPS6140998A - Method of lock anchor construction - 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 relates to a rock anchor construction method for preventing collapse and peeling of surrounding ground after tunnel excavation.

<Background of the Invention> In general, the rock anchor method involves artificially inserting and burying rock bolts with axial tensile strength around a tunnel to form a ground arch and greatly improving the physical properties of the ground. This is a construction method that prevents the surrounding ground from collapsing and peeling. To fulfill this role, materials used as rock bolts generally include steel bars, deformed steel bars, and fiber-reinforced plastic rods, which have high compressive elasticity when inserted into boreholes. These rod-shaped materials are bent to allow insertion into the borehole when the ground is uneven, and the borehole itself is often bent when the borehole is long, and cannot be bent to accommodate this bending. In particular, when inserting a rock bolt after filling a self-hardening material into a drilled hole, it is impossible to confirm the axis of the hole filled with the self-hardening material, so check the bending, displacement, etc. of the drilled hole in advance. In consideration of this, the rod must be inserted at an eccentric angle of about 30 degrees with respect to the axis of the hole being drilled, but the conventional rod-shaped materials cannot be used in such a construction method. Also, if you forcefully insert the lock bolt with its tip touching the hole wall, a large insertion resistance will occur, and even if it is inserted aligned with the axis of the hole, its own weight will cause the tip to touch the hole wall. If the hole gets stuck, the insertion resistance becomes excessive, and if the drilled hole itself is curved, the insertion resistance becomes even more excessive, making construction difficult. For this reason, in many cases, the rear end of the lock bolt is inserted by hitting it with a large mechanical force, but it is not possible to insert it sufficiently.
It takes time to insert. In the worst case, an excessive layer of stress may be applied to the rock bolt, causing damage and making construction impossible.

On the other hand, after rock bolts have been buried to reinforce the ground, as the diameter of the tunnel expands, the rock bolts may be cut along with the ground during excavation. It is difficult to do so, and there is a risk of cutting sparks flying around. From this point, easy to cut,
Synthetic fiber rope rock bolts have been proposed as rock bolts, but these synthetic resin rope rock bolts have extremely low compressive elasticity and cannot be inserted into the borehole against the self-hardening material filled in the borehole. Not only is this impossible, but it also cannot be inserted due to the curvature of the hole itself.

<Object of the invention> The present invention has been made in view of the above background, and
In order to solve the drawbacks of the conventional rock anchor construction method, a new flexible rock bolt is used instead of a rigid rod-shaped rock bolt, and this method is used to insert it into a drilled hole. It is.

<Structure of the Invention> The gist of the present invention, which was made to achieve the above object, is a first step of filling a hole drilled in the ground with a self-hardening material that will become an anchor body; A rock anchor construction method comprising a second step of inserting a rock bolt as a tension part into the drilled hole, and in the second step, the drilled hole is inserted against the self-hardening material filled in the drilled hole. Synthetic resin with a rope-like structure made of a fiber-reinforced thermosetting resin composite material that has compressive elasticity that allows it to be inserted into the borehole, and has bending elasticity that corresponds to the bending that allows it to be inserted into the borehole and the bending of the borehole itself. A rock anchor construction method characterized by inserting a manufactured rock bolt. In other words, the rock anchor construction method of the present invention involves drilling a rock bolt hole of approximately 1.5 to 2D relative to the diameter of the rock bolt in the ground using a rock drill such as a leg drill or a trilifter, and then drilling the rock bolt hole with mortar. Alternatively, a self-hardening adhesive such as unsaturated polyester resin or epoxy resin is filled into the drilled hole using a compressor or pump, and a synthetic resin lock with a rope-like structure made of fiber-reinforced thermosetting resin composite material as described below is used. The feature is that the bolt is inserted using a feed roller or the like.

The synthetic resin rock bolt made of fiber-reinforced thermosetting resin composite material used in the construction method of the present invention has a core material made of reinforcing fiber bundles impregnated with thermosetting resin, and the outer periphery of this core material is made of thermoplastic resin. It has a rope-like structure made of a fiber-reinforced thermosetting resin composite material made by twisting or braiding resin-coated composite slants and then heating and curing uncured thermosetting resin.

To explain in more detail, the above-mentioned synthetic resin rock bolt is made of high-strength, low-elongation reinforcing fiber bundles such as glass fiber, aromatic polyamide fiber, carbon fiber, polyester fiber, vinylon fiber, and unsaturated polyester resin. A core material impregnated with a thermosetting resin such as an epoxy resin and shaped into a circular shape is heated using various polyethylenes, ethylene-vinyl acetate copolymers, polypropylene homopolymers or copolymers, various nylons, various ABS, etc. A composite strand is formed by coating a plastic resin in an annular shape, and a plurality of uncured composite strands, for example eight, are braided to create an eight rope (hereinafter referred to as an eight rope) or one rope as the axis and its outer periphery. A rope-like structure such as a 1×6 type rope is formed by twisting six strands together, and then heated to harden the thermosetting resin to form a rope-like structure made of a fiber-reinforced thermosetting resin composite material. There is.

In particular, in this synthetic resin rock bolt, the thermoplastic resin of each adjacent strand of the composite strand that forms a rope-like structure after curing is partially or entirely fused in the longitudinal direction at the contact area. The structure satisfies compressive elasticity and bending elasticity, and as described later, the compressive elastic modulus is 150 kg/rrn2 or more1
The bending elastic modulus is set in the range of 15 kg/mm" to 100 kg/mu" to facilitate insertion into a drilled hole filled with a self-hardening material.

In addition, the tensile force of the synthetic resin rock bolt of the present invention varies depending on the required value based on the construction conditions, but is approximately 5.
The dimensions of the core material of the composite strand to obtain this strength are, for example, eight rope or 1 x 6 type rope, the reinforcing fiber bundle is glass roving, and the thermosetting resin is unsaturated polyester. In the case that
Its cross section is assumed to be approximately circular, with a diameter of approximately 3.5 rm, and its outer periphery is covered with a thermoplastic resin having a thickness of approximately 0.5 ra.

As mentioned above, when inserting the synthetic resin bolt into a drilled hole filled with a self-hardening material, the compressive elastic modulus is preferably 150 kg/mn2 or more to facilitate insertion work.
If the value is below this value, the composite strand of the rope-like structure will be displaced independently, for example, the rope-like structure will expand in diameter, and the insertion resistance will become large, making it difficult to insert the entire length of the hole. The rate is 15 kg/rrrn2 to 100 depending on the form factor of the synthetic resin rock bolt.
A range of 100 kg/mm2 is desirable, and in this range, the flexibility characteristics can be taken advantage of, but if it is over 100 kg/mm2, the elasticity of the rock bolt becomes poor and the construction method according to the present invention becomes impossible. If the weight is less than 1 kg/mm2, the tip bends greatly due to its own weight, causing problems such as difficulty in smooth insertion.

Furthermore, whether the above-mentioned thermoplastic resin fusion bond is applied to a part or all of the longitudinal direction may be determined depending on the conditions required for the rock bolt, but for example, as a self-hardening material for drilling holes, When using mortar, if there is no fusion bonding at all or only some fusion bonding, the gaps between the composite strands will filter and separate the components of the mortar upon insertion, selectively removing the cement milk. Since there are obstacles such as discharge, it is necessary to cover the entire surface in the longitudinal direction.

It is preferable to fusion-bond them vertically. Furthermore, in the composite strand of the synthetic resin lock bolt of the present invention,
The bonding surface between the fiber-reinforced thermosetting resin cured core material and the coating thermoplastic resin is one in which the thermosetting resin and the thermoplastic resin have mutual chemical affinity or have similar solubility factors. Although it is possible to select a combination of materials and join them using adhesive force, it is also possible to combine them with non-contact materials.

If the thermoplastic resin coating is in close contact with the core material due to its shrinkage force, combined with the characteristics of the rope-like structure, it can fully function as a lock bolt.

The anchor anchoring force of the rock bolt is achieved through the adhesive force between the rock bolt and the self-hardening material filled in the hole.
Although it depends on the adhesive force between the self-hardening material and the ground, in the present invention, the bonding between the self-hardening material and the synthetic resin rock bolt is achieved by bonding the self-hardening material and the synthetic resin rock bolt to the uneven surface of the rope-like structure made of braided or twisted composite strands. The degree of twist of the composite strands in the rope-like structure is also important, since it depends on at least the anchoring effective adhesion with the material. The degree of twist of the synthetic resin lock bolt used in the present invention is determined by the fixing force required for the lock bolt, but it is preferably approximately 600+n+n or less. In addition, the thermoplastic resin of the composite strand described above, the thermoplastic resin of the core material, and the thermoplastic resin of the composite strand and the self-hardening material to be filled in the drilled hole are combined by selecting materials that have similar solubility factors to each other. For example, the adhesive force at each bonding interface becomes strong, and the reinforcing force of the core material can be expressed with high efficiency.

<Embodiments> Hereinafter, preferred embodiments of the construction method of the present invention will be described in detail with reference to the accompanying drawings.

Example 1 A hardened mortar with a flow value of 190 nn was injected into a drilled hole 1 with a hole diameter of 36 m++ and a hole length of 4 m as the self-hardening material 2 using a pump, and then a synthetic resin having the structure described in detail below was used as the rock bolt 3. Manufactured rock bolt with eccentric angle 0
were inserted by the feed roller 4 every 10 degrees in the range of 06 to 40', and the insertion resistances were compared. As a result, complete construction was possible with a small insertion resistance of up to 70° at an eccentric angle, that is, within a range of 30° from the axis of the hole being drilled.

The synthetic resin rock bolt used in this example uses glass fiber as the reinforcing fiber 7 for the core material 6 of the composite strand 5, unsaturated polyester resin as the thermosetting resin 8, and the outer coating 9 for the core material 6 of the composite strand 5. is a composite strand made of ethylene-vinyl acetate copolymer, braided into an 8-rope shape, and heat-cured.The volume content of glass fiber in the core material is 49%, and the composite has a roughly circular cross section. Strand core diameter: 5.5 rru, outer diameter of covering: 6.7 ml
The coating resin of the eight composite strands has a maximum diameter of 24.3 nm and a minimum diameter of 16 nm, in which the adjacent strands are fused and bonded almost to each other in the longitudinal direction.
．． It has a size and shape of 8im. The compressive modulus of this synthetic resin rock bolt is 588 kg/mn2, the bending modulus is 24.3 kg/+am2, and the tensile strength is 13
．． It was 4 tons.

In addition, in the present invention, the compressive elastic modulus and the bending elastic modulus are
It was measured by the following method. That is, the compression modulus is 3
A sample with a length of 00 mm was compressed in the axial direction at a speed of 10 mm/min, a compressive load-strain diagram was automatically recorded, and the tangential slope was determined to be the compressive modulus of elasticity. The bending elastic modulus was measured by performing a three-point bending test on a sample having a length of 150 nn+ at a distance between fulcrums of 10,100 l and a loading rate of 10 mm/min, and measuring the tangential slope of the load-strain curve as described above.

Note that this method of measuring the bending modulus of elasticity yields a value that also reflects the morphological deformation behavior of the rope-like structure. It is not a universal value like .

Example 2 Construction was carried out under the same conditions as in Example 1, except that the synthetic resin lock bolt had a 1×6 type rope-like structure and had a configuration described in detail below.

That is, the synthetic resin rock bolt used in this example is composed of composite strands with the same composition as in Example 1, but the dimensions and shape of the composite strands are such that the diameter of the core material is 6.
．． On the 5th side, the diameter of the covering part is 7.7 m, and six composite strands are twisted around the outer circumference with one of the composite strands as the axis, and the covering parts of each composite strand are mutually arranged on the entire surface in the longitudinal direction. 1×6 type rope structure fused across the length, maximum diameter 24mm, minimum diameter 21mm, compression modulus 840 kg/mm”, bending modulus 73 kg/mm”
rtn2, tensile strength 14Ton.

This synthetic resin lock bolt has eccentric angles up to 306.
Complete construction was possible with a maximum insertion resistance of about 70 kg.

Comparative Example 1 Compared to Example 1, a sample having the same structure as Example 1 except that low-density polyethylene was used for the covering portion of the composite strand, and the covering portion was not fused and bonded to each other along its length. When a synthetic resin rock bolt with an eight-rope structure was press-fitted into the same hole as in Example 1 using a feeding row, it was inserted at an insertion depth of 1.2 m even when inserted at an eccentric angle of 0°, that is, in the horizontal direction. Resistance increased rapidly and insertion over the entire length was impossible.

The dimensions and shape of this synthetic resin lock bolt were the same as in Example 1, but the compression modulus was 35 kg/mu2 and the bending modulus was 11 kg/mm2, both of which were low.

Comparative Example 2 The outer periphery of the synthetic resin rock bolt of Comparative Example 1, that is, the rope-like structure in which the covering portion of the composite strand has a non-adhesive structure, is coated with adhesive polypropylene to a thickness of approximately 1 m to form a composite A construction test similar to that described above was conducted using a coated eight-rope rock bolt designed to restrain the strands. In this case, the insertion resistance is 4 at an eccentric angle of 0°, that is, at an insertion depth of 3.5 m when inserted in the horizontal direction.
It weighed 60 kg, which made it difficult to insert it.

The compressive elastic modulus of the coated eight-rope rock bolt used in this comparative example was 122 kg/2, and the bending elastic modulus was 12 kg/in''.

As a guideline for the structure, physical properties, workability, and bending elasticity of the synthetic resin rock bolts of the above examples and comparative examples, the seventh
Table 1 summarizes the results of measuring the chord length Lmn when a rock bolt with a beam length of 1000 mm is cantilever supported as shown in the figure and a load of 5 kg is applied to its free end.

The relationship between string length and flexibility is such that the smaller the length of L, the more flexible the string is.

(The following is a blank space) <Effects of the Invention> As explained in detail below, according to the rock anchor construction method of the present invention, the angle of up to about 30 degrees from the fine hole can be
A maximum of 70 kg can be completely installed with any small insertion force. In addition, the rock bolt used in the construction method of the present invention has a rope-like structure made of fiber-reinforced thermosetting resin composite material,
It has both compressive elasticity and bending elasticity, as well as high tensile strength comparable to that of steel. Due to these physical characteristics, the method of the present invention allows for easy eccentric insertion and the ability to follow the bending of the hole itself. The rock bolt itself can be supplied in an endless drum-shaped state, and therefore it can be cut to any length, it is lightweight and easy to handle, and it is corrosion resistant. In addition, it can bring many benefits in construction, such as ease of cutting when tunnel diameter is expanded after rock bolts are buried.

These numerous effects of the present invention are particularly due to the fact that when tunnel excavation is carried out, the ground is poor and the stress release after excavation is large and there is a fear of collapse. This is particularly effective when a method is adopted in which rock bolts are driven to reinforce the ground and then cut during the next cutting and spreading. That is, according to the construction method of the present invention, after excavating an advanced tunnel with a relatively small cross section, a hole is drilled in the ground to be reinforced, and then a self-hardening resin material is injected and filled into the hole. The flexible lock bolt of the present invention has an eccentric angle of O~
It can be inserted with a relatively small insertion force within the range of 30', and the lock bolt can follow the deformation of the drilled hole, so it can be inserted over the entire length of the drilled hole, and when enlarging the tunnel cross section afterward, the lock bolt can be inserted with a relatively small insertion force. Bolts can be easily and safely cut, and workability is significantly improved compared to conventional construction methods that use rigid metal rock bolts, etc., making excavation work safer, reducing construction costs, and shortening construction time. It is measured.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a state in which rock bolts are inserted according to the construction method of the present invention, and FIGS. 2 and 3 are ropes made of fiber-reinforced thermosetting resin composite material used in the construction method of the present invention. 4 and 5 are cross-sectional views of FIGS. 2 and 3, respectively, and FIG. 6 is a perspective view showing the structure of the composite strand of the synthetic resin rock bolt in the present invention. 7 are schematic diagrams of a method for measuring physical properties as a measure of bending elasticity in the present invention. 1. Hole drilling, 2. Self-hardening material, 3. Rope-like structure rock bolt made of fiber-reinforced thermosetting resin composite material.

Claims (2)

[Claims] (1) A first step of filling a hole drilled in the ground with a self-hardening material that will become an anchor body, and a second step of inserting a rock bolt as a tension part into the hole filled with the self-hardening material. A rock anchor construction method comprising: in the second step, the material has compressive elasticity that can be inserted into the borehole against the self-hardening material filled in the borehole, and can be inserted into the borehole opening. A rock anchor construction method characterized by inserting a synthetic resin rock bolt with a rope-like structure made of a fiber-reinforced thermosetting resin composite material that has bending elasticity according to bending and bending of the hole itself. (2) A synthetic resin rock bolt made of fiber-reinforced thermosetting resin composite material has a core material made of reinforcing fiber bundles impregnated with thermosetting resin, and the outer periphery of this core material is covered with thermoplastic resin. After twisting or braiding the composite strands, the uncured thermosetting resin is cured by heating, and the thermoplastic resin of the adjacent composite strands is partially or completely fused and bonded at the contact part to form a rope-like structure. It becomes more,
This rope-like structure has a compressive elastic modulus of 150 kg/mm^2 or more so that it can be inserted against the self-hardening material filled in the hole, and can be inserted into the hole opening by bending and drilling. 15kg/m as bending elasticity according to the bending of itself
The rock anchor construction method according to claim 1, characterized in that the rock anchor has a bending modulus in the range of m^2 to 100 kg/mm^2.