JPS6367400A - Anchor bolt assembly - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to anchor bolt assemblies. More particularly, the present invention relates to delayed tensioning bolt assemblies for use in boreholes containing hardenable bonding materials.Assemblies of this type are suitable for use in anchor bolting heavy machinery and in construction. Used for construction purposes and to support the roof of the mine.

[Conventional technology]

It is well known in the field of ore roof support and similar anchor bolting devices to tension bolts by using mechanical expansion devices in combination with hardenable bonding materials. ing. Commonly available bonding materials are supplied in the form of compartmentalized packages in which the resin and the catalyst for the resin are separated.

This horizontal device is disclosed in US Pat. No. 4,280,943. Here, the challenge has been to properly mix the catalyst and the resin, and furthermore, to finally apply tension to the anchor bolt. Mixing of catalyst and resin must occur within a very short period of time. The bolt assembly is inserted into the borehole and rotated at high speed to achieve mixing.

In some devices that utilize mechanical telescopic members and curable bonding materials, tensioning begins almost immediately after the bolt begins to rotate. In such devices, a significant amount of tension is applied while the resin is in its soft state. Other devices delay application of tension until the resin begins to cure.

Typically, a mine head bolt consists of an elongated bolt, an anchor bolting device, and a support such as a head plate and a hardened flat washer placed between the bolt head and the head plate. It is composed of members. The use of this hardened washer is addressed in ASTM Standard F432-83 and 30CFR Part 75.

Anchor bolts with various contours have been used to facilitate mixing. One typical illustration of an anchor bolting device is U.S. Pat.
No. 395,638. That is, a tee bolt with a groove with a helical profile and a raised back is said to promote resin mixing and force the resin into the interior end of the borehole.

A bolt with a helical channel adjacent the distal end is disclosed in US Pat. No. 4,564,515.

Such devices require machining or molding,
Moreover, it costs VC money to produce.

Tensioning bolts has been accomplished using a variety of bolt and telescopic shell configurations. U.S. Patent No. 4,
Bolt and shell combinations of the type disclosed in the '930 patent still provide for tensioning by advancing a cam plug threaded onto the bolt through the anchor bolting shell. While the bolt is placed under tension, the telescoping fingers of the shell grip the wall of the borehole to hold the shell in place. Although such mechanical devices are effective in tensioning the bolts, they result in very concentrated loads on the walls of the borehole, which can crack the walls. U.S. Pat. No. 4,655,645 discloses a combination of helically preformed rods attached to bolts. This helical rod is used in combination with a telescoping shell or coupling device. However, preforming the helical rod represents additional expense.

Any member for reducing the friction between the support member and the surface surrounding the borehole, in which a significant portion of the energy used to tension the bolt is due to friction between the support member and the surface surrounding the borehole. can be wasted at the bolt head unless otherwise supplied. This energy loss causes heating in the bolt head, resulting in
This reduces the amount of tensioning that could be achieved without the losses and causes a change in tensioning from bolt to bolt.

[Problem that the invention seeks to solve]

The present invention provides a simplified anchor bolt assembly that combines excellent resin mixing and tensioning properties without the need for cam plugs or telescoping fingers.

[Means and effects for solving the problem] In order to promote mixing, a thread is provided with a head and a support member at one end and adapted to receive a nut at the other end. An essentially straight rod or wire is attached to the bolt, which has a flat section. The rods or needles or other means are attached to the nuts and bolts by welds of different strengths. These attachment points are chosen so that the rod is held in a straight profile or in a slightly helical profile along the length of the bolt. The head of the bolt is pulled into the borehole while under tension.
To prevent jamming, the head of the bolt can be provided with an enlarged shoulder, or a top plate, washer, or combination thereof can be attached to the bolt at the end of the head. It can also be placed. When the anchor bolt assembly is pushed into a borehole containing a compartment package of curable bonding material and the bolt is rotated, the bolt, rod, and nut rotate as a unit to mix the resin and catalyst. It turns out. As the resin hardens, the drag on the rod increases until the rod breaks or pulls apart at its weakest point. The free length spirals around the bolt, forcing the catalyst and resin mixture toward the top of the borehole.

At this point the nuts are free to rotate with respect to each other. When the partially cured resin becomes strong enough to prevent the nut from rotating, the bolt is screwed into the nut. The nut is pulled down through the partially cured resin, putting the resin into compression and causing it to expand against the walls of the borehole.

Once the resin reaches a sufficient hardening strength to stop the nut from moving, the nut moves downward. This hardening of the resin also stops the bolt from rotating. The installation is complete and the bolts are under tension.

In a preferred embodiment, the bolt includes a support member that acts as a thrust bearing when the bolt is fully inserted into the borehole.

The support member may include a combination of members with abutting flat surfaces, such as two washers resting on the shoulders of the bolt head.

The contours of these members should be chosen so that the bolt head is not drawn into the borehole when the bolt is tensioned, and also that the pressure generated by tensioning the bolt is It should be chosen so that it can be distributed over a large area. At least two contacting surfaces of the support members are coated with a potentially lubricating material. The coating can vary in thickness from about 0.1 WM to about 2.0 WM depending on the materials used. The thickness of the coating is not critical. Preferably, the two contacting surfaces are releasably adhered to each other by a lubricating material. When the bolt assembly rotates,
Friction between the bolt head and the support member generates heat within the support member. As the temperature increases, the latent lubricating material becomes activated and melts and functions as a lubricant. The support member now acts as a lubricated thrust bearing when the bolt is tensioned within the borehole.

A preferred latent 1N4iiIlt material is a hot melt adhesive composite. One example is the H,B, Fuller Company.
) and is HM-908, which decomposes at a temperature of about 150°C. Other latent lubricants that adhere well to the face buttons of the support member and are tactile under normal storage and shipping conditions may also be used. Such materials include HM-2047 from H.B.Fowler and United Resin Products.
80-7801 and 80-792! It also encompasses commercially available products such as hot melt adhesives, as well as similar products that additionally function as latent lubricants. The particular material to be selected will depend on factors such as the temperatures encountered during the mixing and tensioning stages, the potential @ melting temperature of the scrap material, as well as the shipping and storage environment for the anchor bolt assembly. Depends on it. The potentially lubricating material also acts as a protective coating to protect against corrosion and other damage to the support member and helps control contamination between the faces of the support member. In some applications, this material may also be applied to other surfaces of the bolt assembly, such as the threads and shank of the bolt. The material will act as a lubricant to the surfaces when the temperature increases due to friction.

EXAMPLES The present invention will be explained in more detail below based on the drawings.

The anchor bolt assembly of the present invention includes an elongated bolt 11 with a flange 13 and a head 15 at one end. The opposite end of the bolt 11 has a threaded portion 2.
It is equipped with 5.

The threaded portion 25 is adapted to receive a nut 29. As shown in FIG. 1, an elongate rod 31 is attached to nut 29 at point 53 and a second attachment to bolt 11 is attached at point 35. The flange of the bolt 11 functions as a support member. The length of rod 31 can be made longer or shorter as desired, depending on the amount of bonding material in the borehole.

Rod 61 must be attached to nut 29 and another point along the length of bolt 11 remote from nut 29. If desired, the rod can be attached at other points on the bolt 11.

FIG. 2 illustrates and illustrates an anchor bolt assembly located within borehole 39.

The assembly including washers 19 and 21 is described in U.S. Pat.
No. 0,943, the threaded end 25 thereof is first inserted into the borehole containing the curable bonding material 41. When fully inserted, the assembly is rotated at a high speed, eg, 300 to 600 revolutions per minute, for about 5 to 10 seconds. During this period, heat builds up inside the support member due to friction and the coating 23 begins to melt. After a pause for a few seconds, e.g. 5 to 25 seconds, bolt 11
rotation is resumed.

As the bolt 11 continues to rotate, the heat within the support member melts the potentially lubricating material 23. Washers 21 and 19 are
It functions as a lubricated thrust bearing until such time as lubricant is forced out between the abutment surfaces of the two washers. The bolt 11, rod 31 and nut 29 rotate as a unit for mixing the curable bonding material 41. As bonding material 41 hardens, the drag on rod 31 increases, causing the rod to disengage from attachment point 65. The rod 31 is then free to coil around the bolt 11 and force the bonding material 41 towards the top of the borehole 39. As the bonding material hardens, the bolt 11 begins to be threaded through the nut 29 as the nut becomes partially secured within the bonding material 41. The threaded portion 25 of the bolt 11, not shown here, is preferably coated with a mold release agent, which allows the curing resin to pull down the nut through the bonding material. Without bonding to the screw, the resin is brought into compression and the bonding material expands against the walls of the borehole 39.

The mold release agent may be a latent lubricant, which is
A nut 29 can be attached to the threaded end 25 of 1 and coated by dipping into hot material.

The tensioning of bolt 11 provides a unitary structure in which washers 19 and 21 uniformly distribute the pressure generated by tensioning that bolt over a large area area adjacent the mouth of the borehole. This continues until the bolt 11 and nut 29 are finally secured in the borehole.

In other embodiments (not shown), the attachment of rod 31 may be intentionally weakened at a point intermediate points 33 and 35. As the bonding material 41 begins to harden, the rod 31 breaks at its weakened point, leaving it with two free ends. The two parts of the rod are free to coil around the bolt when the bolt is rotated and placed under tension.

In a further embodiment (not shown), the rod 31 can be removed from the attachment point 33 and rolled down towards the head 15 in a fill-like manner. Of course, rod 31 can be attached to bolt 11 and nut 29 by methods other than welding, so long as the rod is removable at a point during installation of the anchor bolt assembly.

As shown in FIG. 3, nut 29 has a cut-off shoulder. The shape and diameter of the nut 29 are selected to allow the nut to enter the borehole and to allow passage of the hardenable bonding material between the nut and the wall of the borehole. If the support member has to be placed on the bolt 11 after the nut 29 has been screwed onto the bolt 11, the opening in the support member will
must be large enough to pass through.

FIG. 4 shows another embodiment of the support member for distributing the pressure over a large area around the borehole when tensioning the anchor bolt. The ceiling plate 43 is used in combination with two washers 45 and 47 which are releasably bonded together by coating the latent lubricating material 23.

〔Effect of the invention〕

A comparative test was conducted in the laboratory to determine the friction losses when using a support member of the present invention similar to that shown in FIG. The bolt, nut and rod assembly is now similar to the assembly shown in FIG. 1, with the attachment of the rod on the bolt to include a strong weld to permit selective removal from the point. The curable bonding material was Du Pont's "Fasloc" rock bolt bonding material, which was placed in a compartment package containing a resin and a catalyst. For one, the support member included a standard uncoated flat washer as described in ASTM Standard F432-83. In other tests where potentially lubricating materials were present, two standard uncoated flat washers were included. Galvanized steel washers were used. All washers had an outside diameter of 5a-
．． It had an inner diameter of 9 countries. The latent lubricating material used was H.B. Feuler's =-9OS hot melt adhesive. The adhesive was heated to about 175°C and the support member washer was heated to about 82°C prior to coating. The contacting surfaces of the washers were coated and then the washers were pressed together to adhere to each other.

When carrying out the test, the washer had a diameter of T435 and 1.22
placed on an elongated bolt with a length of m.

For each test, a deposit top plate of the type shown in Figure 4 is placed over the bolt on top of the washer, and then 15 diameter and 1 A round steel backing plate with a thickness of .25,-* and a 2.5G hole in the center was placed. The end opposite the bolt head was inserted into a 2.54 mm diameter test hole made by @4 to simulate a borehole. The entire assembly is then assembled using a vise to hold the test hole vertically and rigidly, a hydraulic motor to rotate the bolt by driving a chuck that engages the bolt head, and a test hole. It was installed in a machine with a thrust mechanism for forcing the bolt into the hole. Thrust is 0 to 3
4,70 Newtons ON), the revolutions per minute of the prime mover is changed from 0 to 50 ORPM, and the torque generated by the prime mover is changed from 0 to 540 N
- changed by m. Parameters were measured by a sensation device and recorded on a strip chart recorder. The application of tension to the bolt was simulated by applying a thrust force to the head of the bolt, which force was then transferred to the washer, deposit top plate, backing plate, and test hole. The bolt was rotated at 450 RPM and the torque required for rotation was measured and a comparison was made for three different values of simulated applied tension. (The torque required for rotation represents the energy loss experienced when the bolt is actually installed and tensioned). In the first test, a single standard hardened washer and a top plate of the type described in ASTM Standard F 432-85 were tested without the use of potentially lubricating materials. However, 13. ! The energy wasted at a bolt applied tension of 100 N is 86 N-m, 17,
The wasted energy at 80ON is 140 N-m
, and the wasted energy at 31,100N!
It was I OON-m. For a given bolt applied tension, energy losses increased over time as the anchor bolt assembly was rotated. The test was repeated using two standard galvanized steel washers in place of the single hardened washer. No latent lubricants were used. The losses recorded were as follows: bolt applied tension was 13,
When the tension is 30QN, it is 76N-m, and when the tension is 17,80ON, it is i4QN-m, and 51. IQON tension is 50ON-m
Met. These losses again increased over time as the anchor bolt assembly was rotated. The test was repeated again, replacing the support member according to the invention shown in FIG. 4 containing a latent lubricating material. The energy loss is 16N-m until the bolt tension is 1st 80ON.
remained constant. And the loss is that the tension is 31
．． At 100 N, it did not become larger than 52 N-m.

A test installation of an anchor bolt assembly was made in a mineral deposit using a support member according to the invention shown in FIG. The anchor bolt assembly was the assembly shown in FIG. 1 modified to include the top plate and washer shown in FIG. WI4. To measure the bolt applied tension, a compressed rubber pad was placed on the bolt adjacent to the top plate. The latent lubricating material is HM-908 hot melt adhesive from H.B.
The adhesive was deposited onto a galvanized steel washer with an outside diameter of 55I, an inside diameter of 1.93 and a thickness of 4mm. All bolts had a length of 1.2 m and a diameter of 143 CI#. The elongated rod attached to the bolt assembly is 50.5
It had a length of tx and a diameter of 3.2 gates. One end of the rod was welded to the nut and the other end to the bolt. The welding was of such strength that the rod could be selectively removed from the point at which it was attached to the bolt. The curable bonding material was DuPont's "7 Aslotsuco" rock bolt bonding material, which was packaged in compartments containing resin and catalyst. The package was nominally 2.5 cm+ in diameter and 405 m long. The mixing time for the resin and catalyst was typically 5-8 seconds.

Gel time was typically 15-20 seconds.

A borehole with a diameter of 2.54G was drilled in the deposit roof to a depth of 1.22m. In each test, a package of bonding material was inserted into the borehole. An anchor bolt assembly was inserted through the packaging containing the bonding material and into the borehole. Mixing of the resin and catalyst was accomplished by rotating the anchor bolt assembly at approximately 56 ORPM for 5-8 seconds. The mixing operation was then stopped for 15-20 seconds to allow the binding material to gel. The bolt was turned again until the machine was brought to a standstill. In order to measure the bolt applied tension, the
A top bolt compression wad and compression wad gauge manufactured by OodyarRubber Co., Ltd. () was used.

Bolt applied tension is determined by measuring the increase in circumference of the Gutdeyer compression wad using a gauge calibrated to display the tension.

The machine used to drill the borehole and insert and tension the bolt was a standard ore top bolting machine capable of drilling the borehole and installing the bolt in a vertical orientation. The machine was calibrated to deliver a maximum torque of 34 ON-m to tension the bolt. The use of the support member according to the present invention has increased the bolt applied tension by a factor of two compared to that previously achieved using a single standard hardened washer and top plate. . Five bolts were tested, and the bolt applied tension was 45,40ON; 52
,0OOON; 56,0OOON; 51,600 N i and 5<5.90ON.

A variety of materials of construction can be used in the manufacture of anchor bolt assemblies in accordance with the present invention. Where high strength applications are involved, such as anchor bolt assemblies used in mine roofs, steel is the preferred material. However, various plastic materials are available for anchor bolting machines and other applications that do not require such high strength. Curable bonding materials include commercially available polyesters, epoxies, and other known synthetic resins and inorganic grouts. A particularly desirable material is manufactured by the DuPont Company (Ll, du Pont de
Nemours apd Company) under the trade name Fa61oc (registered open collar).

[Brief explanation of drawings]

Figure 'S1 is a partial cross-sectional side view of an anchor bolt assembly with a nut disposed at the threaded end of the elongated bolt, an elongated rod attached to said nut and bolt, and a support member. Figure 2 is a partial cross-sectional side view similar to Figure 1 of the anchor bolt assembly placed in the rock formation and ready for final tensioning. The threaded end of the bolt is then advanced through the nut and the rod is pulled away from the nut and coiled around the bolt so that the support member is in abutting relationship with the rock formation. Fig. 3 is a plan view of the nut for the bolt and shows a cutaway part of the shoulder of the nut;
The figure is a partial side view, partially in section, of an anchor bolt assembly showing the bolt head and a support member including a top plate and two washers supported on the shoulders of the bolt head. 11...Elongated bolt, 13...Flange, 15.
...Bolt head, 19.21...Washer, 23...Latent lubricant material, 25...Threaded part, 29.
... Nut, 51 ... Long thin rod, 33.35 ... Mounting point, 39 ... Bore hole, 41 ... Curable bonding material, 43 ... Top plate, 45.47 ...
・Washer. 2 outside figures, 4

Claims (1)

Claims: 1) An anchor bolt assembly for securing a bolt in a borehole with a hardenable bonding material, comprising: (a)
) an elongated bolt having a head and a support member at one end and a threaded portion at the other end; and (b) a nut threaded onto the bolt and extending into the borehole. (c) a nut shaped so that the hardenable bonding material can pass between the nut and the wall of the borehole; and (c) an attachment point to the nut at one end. and a rod having at least one other attachment point along the length of the bolt remote from the nut. 2) the support member includes first and second support members disposed on the bolt, the first support member having a flat surface adjacent to an area surrounding the mouth of the borehole and an opposite side of the surface; a surface releasably adhered to a contacting surface of the second support member by a latent lubricant material, and the lubricant material is applied to the bolt when the bolt is rotated within the borehole. The anchor bolt according to claim 1, characterized in that the anchor bolt acts as a lubricant that is activated in response to the heat generated when the anchor bolt is attached. 3) the rod is essentially straight and has one end welded to a nut and the other end welded to a bolt;
The rod is further characterized in that the rod is selectively releasable from the point of attachment of the rod on the bolt when the bolt is rotated within the borehole and subjected to the drag of a hardenable bonding material on the rod. An anchor bolt according to claim 1. 4) the freedom of said rod to be selectively released from its point of attachment to a bolt such that said rod is free to coil around said bolt as said bolt is rotated; Anchor bolt according to claim 3, characterized in that it comprises an end. 5) In an anchor bolt assembly for securing a bolt in a borehole with a hardenable bonding material, (a
) an elongated bolt; (b) a member for mixing the bonding material in the borehole upon rotation of the bolt;
c) a support comprising first and second support members disposed on the bolt and secured by the bolt for applying a force against an area surrounding the mouth of the borehole; a member, wherein the first support member has a flat surface adjacent to the region and a surface opposite the surface, the surface being released by a latent lubricating material onto the contacting surface of the second support member; a support member having a surface capable of being bonded, and the lubricant material being a lubricant that becomes activated in response to heat generated when the bolt is rotated, and the bonding material is brought into a hardened state; and a member for applying tension to the bolt within the borehole during consolidation. 6) Anchor bolt assembly according to claim 5, characterized in that the latent lubricating material is a hot melt adhesive. 7) the mixing member has a nut screwed onto the bolt and an attachment point to the nut at one end and another attachment point along the length of the bolt at a point remote from the nut; a rod having a point thereon, and the rod is selectively releasable from its attachment point on the bolt when the bolt is rotated within the borehole and subjected to the drag of a hardenable bonding material on the rod. Anchor bolt assembly according to claim 6, characterized in that: 8) In an anchor bolt assembly for securing a bolt in a borehole with a hardenable bonding material, (a
) an elongated bolt having a head at one end and a threaded section at the other end and a nut threaded into the section; (b) for mixing the bonding material in the hole; (c) a first rod disposed on the bolt;
and a second support member, the support member being secured by the bolt to apply a force to an area surrounding the mouth of the borehole, the first support member has a flat surface adjacent the region and an opposite surface releasably adhered to the contacting surface of the second support member by a latent lubricating material. and a support member in which the lubricating material is a lubricant that becomes activated in response to heat generated when the bolt is rotated within the borehole. 9) the freedom of said rod to be selectively released from its point of attachment to a bolt such that said rod is free to coil around said bolt as said bolt is rotated; Anchor bolt assembly according to claim 8, characterized in that it comprises an end. 10) Anchor bolt assembly according to claim 8, characterized in that the ends of the rods are attached by welds. 11) Claim characterized in that the rod wraps helically around the bolt in one direction when the anchor bolt assembly is rotated, pushing the bonding material towards the nut. An anchor bolt assembly according to claim 9. 12) Anchor bolt assembly according to claim 8, characterized in that the surface of the bolt adjacent to the nut is coated with a latent lubricant.