CA1300940C - Tubular rock bolt - Google Patents
Tubular rock boltInfo
- Publication number
- CA1300940C CA1300940C CA000549771A CA549771A CA1300940C CA 1300940 C CA1300940 C CA 1300940C CA 000549771 A CA000549771 A CA 000549771A CA 549771 A CA549771 A CA 549771A CA 1300940 C CA1300940 C CA 1300940C
- Authority
- CA
- Canada
- Prior art keywords
- rock bolt
- rock
- bolt
- tube
- tubular
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D21/00—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection
- E21D21/008—Anchoring or tensioning means
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D21/00—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection
- E21D21/02—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection having means for indicating tension
Abstract
ABSTRACT
A high tenacity rock bolt system utilizes a cold drawn steel tubular rock bolt construction possessing excellent load bearing and installation characteristics. The bolts are installed in bores drilled in the back, wall or rock face to reinforce the strata against local disturbances, and to maintain the strata in an effectively compressed condition.
The subject tubular rock bolt may incorporate a visual Ground Movement Indicator (GMI) freely suspended as an unloaded rod element within the rock bore, extending through and projecting outside of the rock bolt, to afford visual indication of any axial displacement or elongation of the rock bolt consequent upon loss of anchorage and for settlement of the strata, or movement of the strata, inter alia to cause significant extension in the rock bolt. The hollow construction of the rock bolt greatly assists in economical, effective grouting, if required, to provide an enhanced, economical rock bolting system of high efficiency. The method of manufacture of the rock bolt from continuous weld cold drawn mechanical steel tube is also disclosed.
A high tenacity rock bolt system utilizes a cold drawn steel tubular rock bolt construction possessing excellent load bearing and installation characteristics. The bolts are installed in bores drilled in the back, wall or rock face to reinforce the strata against local disturbances, and to maintain the strata in an effectively compressed condition.
The subject tubular rock bolt may incorporate a visual Ground Movement Indicator (GMI) freely suspended as an unloaded rod element within the rock bore, extending through and projecting outside of the rock bolt, to afford visual indication of any axial displacement or elongation of the rock bolt consequent upon loss of anchorage and for settlement of the strata, or movement of the strata, inter alia to cause significant extension in the rock bolt. The hollow construction of the rock bolt greatly assists in economical, effective grouting, if required, to provide an enhanced, economical rock bolting system of high efficiency. The method of manufacture of the rock bolt from continuous weld cold drawn mechanical steel tube is also disclosed.
Description
~300940 BACKGROUND OF THE INVENTION
This invention is directed to a rock bolt system, and embraces the process of manufacture of the rock bolt, the improved rock bolt thus produced, including a Ground Movement Indicator embodiment and the method of manufacture, and of use of the system.
Rock bolting is practiced in many areas of civil engineering ranging from excavating and tunnelling, to the attachment by anchoring back of fabricated structures to rock masses, and to the use of rock bolts in mining.
A wide range of rock bolts are known. In particular, hollow rock bolts are known, such as:
Canadian Patent 999 762 Williams Nov. 16, 1976 Swiss Patent 631 782 Belloli Aug. 31, 1982 2/25 Velikov April 10, 1986 In the case of the familiar Williams bolt, this hollow rock bolt is manufactured by the pierce-billet method, and initial cost is up to about ten times that of a plain, - :130094~) mechanical rock bolt. The Williams rock bolt is used for specialty bolting, such as anchoring a machine to a cement floor or to rock.
One of the dominant factors in selecting rock bolts is that of cost. One of the most commonly used underground bolts is a mechanical rock bolt, made from solid bar and used in conjunction with an anchoring shell.
In mining, the protection and safety of men and of equipment depends upon the integrity of the strata.
Rock bolts having expansible shell anchors are anchored within extended bores in the back, the wall or the rock face, for the purpose of compressing adja ~ tstrata of the rock so as to enhance ~their strength and stability and to virtually create a rock beam. Rock bolts also are used for the attachment of mine screening mesh in area covering relation primarily with the rock back, for safety purposes, by containment of loose rock.
At certain locations in a mine, under circumstances where greater security is required, such as permanent passages or ways and in certain types of strata, rock bolts are grouted into their respective rock bores.
Grouting is costly, but enhances the security of the rock bolt, and diminishes movement in the strata by filling the , 3 ~300940 residual bore space or a selected portion, with cement or epoxy cement, thus also providing direct load transfer between the rock bolt and the adjoined strata, so as to stabilize the strata.
Grouting is not generally carried out in the working area of a normal stope. However, in areas where acid ground water is encountered, grouting also affords significant corrosion protection to the rock bolts.
The apparent cost of purchasing and setting rock bolts can be readily calculated on a theoretical basis, based on the area to be secured, the recommended density of bolting, and hence, the bores to be drilled and the number of bolts and shells to be procured and set. However, this does not present a true picture of the situation, nor of the costs involved.
Due to a number of factors such as poor initial installation, loss of anchorage due to slippage movement of the shell, including the local effects of blasting and other ground tremors and displacement, experience over many years in the field has revealed a "loss" generally of about 40% of ungrouted rock bo~ts, as initially placed.
i;~00940 This situation can be largely remedied by grouting of the installed bolts with conse~uently increased costs. However, with the solid mechanical bolts in general use, effective grouting requires to be undertaken at the outset, owing to the need to provide a vent tube along the length of the rock bclt, and extending through the bearing plate at the rock surface, as well as the need to provide a grout injection access through the bearing plate. Thus, retroactive grouting cannot be effectively undertaken, being virtually impossible, on a practical basis while the cost of grouting on a routine basis greatly increases rock bolting costs.
One characteristic of all known prior use rock bolts is a total inability for an observer to ascertain from the stope floor what is taking place in terms of loading and displacements behind the rock face.
SUMMARY OF THE INVENTION
The present invention provides a tubular rock bolt that is particularly suited for grouting installations. The subject tubular rock bolt construction lends itself to a family of tubular rock bolts most of which have a nominal load rating closely approximating the load ratings of existing mechanical rock bolts.
.....
i300940 Furthermore, the subject tubular rock bolt incorporates standard rolled threads to enable use thereof with standard sizes of nuts and more particularly, with suhstantially standard shells.
In reviewing the contribution afforded by the present invention over the prior art, in terms both of cost and of load bearing capability performance,the subject tubular rock bolt most closely approximates ~e ox~n mechanical rock bolt of solid bar, and accordingly the latter is herein adopted as the valid basis for prior art comparison. The subject tubular rock bolt (TRB) makes possible the adoption of a visible projecting rod-like ground movement indicator (GMI) for installation with the TRB when in a non-grouted condition, to provide a readily seen visual indicator for indicating relative condition changes having taken place between the TRB and its associated strata subsequent to the placement of the TRB.
Such changes in the relative condition of a rock bolt arise as a consequence of a loss in tension in the rock bolt due to non-gripping of the shell within its bore, or to significant extension of the rock bolt as a consequence of strata displacement, which conditions, in the case of prior art rock bolts, were visually undetectable.
. .~ ., These condition changes, ta~en singly or in combination in the case of the subject TRB tend to cause a relative retraction of the GMI visible outer end inwardly into the interior of the TRB.
It has been found that a TRB incorporating the foregoing enu~erated advantages can be manufactured at an acceptable increase in cost over that of existing mechanical rock bolts, using continuous weld,cold drawn mechanical steel tube.
It has further been found that the fabricated tube can be cold drawn, within very closs tolerances, to an outside diameter (O.D.) particularly suited to the formation of rolled threads thereon, for use with existing standard nuts and shells presently used in rock bolting.
In carrying out the process, a range of sizes of tubular bolts having a range of wall thicknesses has been achieved, so as to provide bolts having a significant range of load capabilities. In view of established rock bolting practice, wherein 3/4 inch and 5/8 inch solid mechanical rock bolts are used, the subject tubular rock bolts have a selected tube O.D. to facilitate the rolling of a predetermined standard thread thereon, and a selected wall thickness, as a function of the tensile strength of the continuous weld cold drawn steel tube, to provide an as installed load bearing capacity equivalent to that of a respective one of the existing equivalent standard mechanical rock bolts. However, it has been found ~at, due bo the material selected, and possibly influenced by the tubular form adopted, the subject tubular rock bolt demonstrates great axial resilience and a capacity for extension under cold working, such that effective longitudinal bolt extensions under working tensile loads are readily achieved. The strength and ductility of the TRB are significant in maintaining the compression load in the rock strata in the event of strata disturbance, such as blasting in the vicinity of the installed bolt, thereby providing acceptable performance, in use.
In addition to the foregoing recited charac-teristics, the subject tubular rock bolt (TRB), by virtue of its larger diameter, presents a larger peripheral "wetted area", to which grouting can bond itself, while the volume of grouting required is significantly diminished.
Also, the required volume of grout, on the basis of a standard bored rock hole, is significantly less for grouting a subject .920 inch diameter tubular rock bolt than for grouting a 3/4 inch diameter equivalent strength ~ .
~' i3009AO
plain rock bolt; and is much less for grouting a subject tubular rock bolt than for grouting a 5~8 inch diameter plain rock bolt. These material reductions represent significant cost savings to off-set the higher initial tubular rock bolt costs.
In addition to making available significant savings in grouting quantities, the subject TRB no longer requires the provision of an air vent tube, being self venting through its centre, thereby assuring more reliable grouting, by avoidance of the air locks frequently experienced with vent tubes, in the prior art.
In the case of a 1_5/8 inch diameter rock bore, a subject TRB effects a worthwhile savings in grout quantity, compared with the corresponding standard 3/4 inch diameter bolt. The present invention thus provides a tubular rock bolt of continuous weld cold drawn steel having a predetermined outside tubular diameter to accept a predetermined rolled thread form. The subject tubular rock bolt has a wall of predetermined thickness, to afford an initial tensile load capacity substantially equal to that of an existing predetermined solid section mechanical rock bolt, wherein the subject tubular rock bolt has a comparable extensibility to that of the referenced solid ~.; , :1300940 section mechanical rock bolt, and provides a si~ilar ability of maintaining an effective load and reliability, in use.
Manufacture of the subject continuous weld, cold drawn tube bolt is effected by first manufacturing a larger diameter cold drawn steel tube. A steel ribbon is roll formed at high temperature into a tube formation, and the closure edges thereof compressed together, generally under airjet or oxyjet heating to form a continuous butt welded tube wall, to provide a high quality continuous butt jointed seamed tube, at comparatively low cost. The thus-formed tube is then cold mandrel-drawn through sizing dies until the required outer diameter (O.D.) and wall thickness are achieved, by cold working. In order to achieve the subject tube bolt, optimized OoD~ ~s have been adopted, wherein, working within the constraints of standard rock bolt practice, threads can be rolled thereon for use with standard sized nuts and shells as used with prior art mechanical rock bolts.
In accordance with the present invention a family of five different tubular rock bolts, TRB 1, 2, 3, 4 and 5 have been evolved to-date and are in course of development:
Product Designation TRB 1TRB 2 TRB 3 TRB 4 TRB 5 Dimensions .690"x.150" .920"x.195".920"x.195".920"x.260" .920x.260"
(OD x ~all thickness) swaged swaged Rock bore size 1-1~4"1-5/8" 1-1~4" 1-5/8" 1-1/4"
Replaces 5/8" bolt5/8" bolt3/4" bolt3/4" bolt Adoption of a 0.26 inch wall thickness with the large .92 inch diameter tube provides a high initial load capacity tubular bolt having substantially the same initial load bearing capacity as a 3/4~inch solid bar mechanical rock bolt, while accommodating standard rolled threads to receive a standard l-inch threaded rock bolt shell, for anchoring purposes.
A further embodiment of the .920 inch diameter tubular bolt having a thinner wall, namely of 0.195-inch thickness, provides an initial applied load bearing capacity approaching that of a 5/8-inch diameter solid rock bolt. This tube size also accepts a nominal 1 inch rolled thread, and exhibits characteristic extensibility under load.
In a further embodiment, it has been established that an end of a tubular rock bolt, such as the 0.92-inch tube, may be swaged, pointed or otherwise reduced to a smaller O.D., to accept a 3/4-inch rolled thread thereon, for use with 3/4-inch nuts and 3/4-inch standard shells.
It will be understood that the subject invention is not limited to the foregoing family of tubular rock bolts, and that different diameters and wall thicknesses may be adopted to meet the needs of the industry.
A further aspect of the present invention is the incorporation, with a tubular rock bolt, of a low cost, effective Ground Movement Indicator (GMI). Thus, an elongated rod-like GMI having the rod portion thereof freely suspended within the bore of the tubular rock bolt has the remote distal end thereof independently secured within the distal end of the strata bore, and the free proximal end of the rod portion initially extending outwardly from the bolt proximal end, as the visible GMI.
Upon initial loading, by tensioning the bolt, in applying a predetermined working load thereto, a viewable portion of the GMI rod can be left projecting at the proximal end.
Upon significant subsequent extension of the subject bolt under load, the projecting length of the GMI rod becomes sensibly and substantially proportionately diminished, to 1~
~;~00940 provide visual indication of significant change in the condition of the rock bolt relative to its strata, in its position at the rock back, wall or face, with a corresponding indication of a possible significant change having taken place in the related rock strata. Thus, the extent or degree of disappearance of the GMI rods in a given area of a stope could indicate to some extent the probable degree of danger of a rock fall occurring.
Generally, low cost wires or plastic rods are adopted in the role of GMI indicator rods.
In the preferred embodiment the GMI includes an indicator rod having its own anchor located above the shell to optimize its integrity, by enabling the rod to be independently anchored in the strata. The bridge portion of the bail of the shell is recessed to accommodate the distal bolt end of the TRB, and has a central aperture therein through which the GMI rod extends, when installed.
The apertured bail bridge serves a valuable purpose in facilitating rupture of the bail in the event that the TRB
tube is accidentally screwed upwardly through the shell, so as to rupture the bridge.
Rock bolts are provided in a range of lengths and sizes, and 5 foot and 6 foot rock bolts are generally considered standard production bolts. The subject GMI rods can be provided as a standard item, having a rod size, diametrically compatible with a range of tube bolt ID's, Zi~ ~.
13~0940 and, being readily shortenable by a simple clipping operation, can be provided in a standard length, such as a 9 foot or longer rod, suitable for use with a 6 foot or longer bolt, and then shortened, if required to be used with 5 foot or shorter bolts. Generally the rod is 3 or 4 feet longer than the tube bolt with which it is used.
When it is recognized that stope roof heights in the range of 12 to 20 feet are commonplace, it will be understood that to be effective the protruding rod end of a GMI rod must be clearly visible, and a significant relative displacement thereof must be plainly evident, preferably when viewed from stope floor level, by suitable colouration, such as fluorescent paint.
In the preferred GMI embodiment, having the rod portion thereof supported independently of the TRB shell, the distal end of the GMI rod can be threadedly disengaged by unscrewing it from its anchor portion, to permit withdrawal of the GMI rod from an installed TRB, so that grouting of the TRB can then proceed without any impedance.
More particularly, this invention provides the method of manufacturing a tubular rock bolt comprising the steps of: forming a steel strip in heated condition into a substantially circular section; joining the adjacent ends thereof in welded relation: cold drawing the section to a predetermined smaller diameter, having a predetermined wall thickness; applying a rock anchor means in secured relation adjacent one end of the rock bolt by rolling threads on a surface portion of the rock bolt, said threads being engageable by said rock anchor means, and providing load transfer means in secured relation with the rock bolt other end by rolling further threads on said rock bolt other end, said load transfer means including nut means secured in threaded adjustable relation with said further threads, and load transfer washer means encompassing said other end, in thrust transfer relation with said nut means.
Further this invention provides a method of forming a tubular rock bolt, comprlsing the steps of:
a) forming a steel strip ha~ing parallel longitudinal edges into a laterally curved shape, abutting the edges, and welding the abutting edges by electric resistance welding, in order to form an oversize, thick-walled tube of substantially annular 5 section, b) cold drawing the tube by elongation through dies to produce a tube with smooth inner and outer walls and an internal diameter of at least about 0.34 inches, c) cutting a portion of the tube to form a bolt 0 having first and second ends, d) rolling threads on both ends of the bolt, e) providing a rock anchor attachment which includes a portion having an internally threaded passage matching the rolled thread on said first end of the bolt, and removably threading said attachment onto said first end, and f) providing load transfer means for said second end, said means comprising an internally threaded member 13b ~3~940 for threadably receiving said second end, and for transferring a load from the bolt, through a suitable means, to the surrounding rock structure.
Still further, this invention provides a hollow, thin walled tubular rock bolt having an axial working load capacity substantially equal to a standard solid mechanical rock bolt of predetermined smaller diameter, said tubular rock bolt providing an axial through passage, in use to facilitate the optional use of a ground movement indicator rod in cooperation with the rock bolt, said rock bolt being fabricated from a steel strip having parallel longitudinal edges by forming the strip into a laterally curved shape, abutting the edges, and welding the abutting edges in order to form an oversize, thick-walled tube of substantially annular section, cold drawing the tube by elongation through dies to produce a tube with smooth inner and outer walls, and cutting a portion of the tube to provide said tubular rock bolt.
Finally, this invention provides, in a rock bolt for use in inserted, tensioned relation within a bore in a rock face, said rock bolt being of predetermined length and including a combination with a shell means having an expansible distal head portion to expand, in use, into gripping relation within a remote inner surface of said bore, and a bearing plate and nut means on the proximal end of the rock bolt for tensioning the rock bolt and pulling the bearing plate in compressed relation against the rock face; the rock bolt having a passage therein extending axially for a major portion of said predetermined length, the improvement comprising ground movement indicator means having a viewable proximal end extending outwardly of the proximal end of the rock bolt, and an elongated support portion extending within the rock bolt passage and supported, in use at substantially said rock bolt distal end, in independently secured relation therein, to provide c,~
~ :
i300940 13c external visual indication of axial extension of said rock bolt.
, .~
. ~..
14 13 ~ 940 BRIEF DESCRIPTION OF THE DRAWINGS
Certain embodiments of the invention are described, reference being made to the accompanying drawings, wherein;
Figure 1 is a side view of a section of rock face, showing an embodiment of the subject tubular rock bolt ~TRB) installed in tensioned, anchored relation therein;
Figure 2 is a like view, showing a tubular rock bolt embodiment incorporating a ground movement indicator (GMI) therewith;
Figure 3 is an end view, from below, showing a TRB
installation having a grouting tube inserted upwardly through the plate washer of the installation;
Figure 4 is a plan view of the GMI rod anchor arrangement;
and Figure 5 is a side view showing a GMI rod and associated anchor, together with bail and leaves portions of the shell, and a portion of the tubular rod bolt.
,~ . ~
i3009A0 DETAILED DESCRIPTION OF THE INVENTION
Referring to Figures 1, 2 and 5, the rock bolt assembly 10 comprises a cold drawn tube portion 12 having threaded end portions 14, 16 with rolled threads 18 thereon, and an axial through passage 19. A standard type of shell 20 has leaves portions 22, having serrated gripping surfaces 24 on the exterior thereof. Shell wedge body portion 26 is threadedly mounted at the distal end, on the rolled threads 18 of the tube end 16.
Referring more particularly to Figures 1 and 2, wi~h the bolt assembly 10 inserted into the rock bore 30, the leaves portions 22 of the shell 20 bear against the rock bore, and upon downward retraction of the tube portion 12, the wedge body 26 is drawn downwards axially into expanding relation with the leaves 22 of shell 20, causing them to engage the gripping serrations 24 thereof with the inner surface of rock bore 30.
The bottom tensioning nut 32 bears against the hardened round washer 34 and bearing plate 36, to draw the tube portion 12 axially outwardly in anchor loading relation. Thus, the tube portion 12 is tensioned, while the associated surrounding roc~ portion is compressed, and thereby strengthened.
1~ ~ 300940 In some instances, grout may be injected upwardly through the bore 19 of tube 12, and the GMI 40 is not used.
It is preferred to grout, using an offset passage 35' through the bearing plate 36 for upward insertion of grouting tube 35 therethrough, with displaced air exiting downwardly through the centre passage 19 of tube 12. In such an arrangement, only a short length of grouting tube 35 requires to be inserted.
Referring to Figures 4 and 5, showing particulars of a first GMI embodiment, the threaded upper (distal) end portion 16 of a subject rock bolt 12 is shown.
The elements of the shell are referred to above.
The rod 40 of GMI 54, having a cruciform anchor portion 60 secured to the rod 40 by threads 58 is inserted downwardly into passage 19 of bolt 12. The bail portion 28 of shell 20 has a central aperture 29 therein, for passage of rod 40 therethrough. The surface 40' of bail portion 28 is recessed to receive the distal end 16 of tubular bolt 12, in the event of misadvertant rotation of bolt 12 causing the bolt 12 to advance axially through wedge body ~)`
17 i300940 26 of shell 20. Upon such an occurrence, with the leaves 22 being set in the rock bore 30, the bail portion 40' ruptures readily, adjacent to aperture 29.
The rod retaining thread 58 being formed in anchor portion 60 is secured against rotation, and it is possible to unscrew and withdraw the GMI, rod portion 40 from out of an installed TRB, so that initial non-grouted installation of a TRB incorporating a GMI can be followed by removal of the GMI rod 40, and completion of normal grouting procedures.
The proximal ends of the GMI rods 40 can be clipped off at a standard exposed length, on initial installation, subsequent to the tubular rock bolt 12 being tensioned to the desired initial value of working load.
In Figures 2 and 5, the GMI rod 40 has the inner end portion 42 thereof supported independently above the distal end 16 of tube portion 12 by way of cruciform spring clip 60 which engages the rock bore 30. This has the benefit of optimizing the independence of GMI 54.
This invention is directed to a rock bolt system, and embraces the process of manufacture of the rock bolt, the improved rock bolt thus produced, including a Ground Movement Indicator embodiment and the method of manufacture, and of use of the system.
Rock bolting is practiced in many areas of civil engineering ranging from excavating and tunnelling, to the attachment by anchoring back of fabricated structures to rock masses, and to the use of rock bolts in mining.
A wide range of rock bolts are known. In particular, hollow rock bolts are known, such as:
Canadian Patent 999 762 Williams Nov. 16, 1976 Swiss Patent 631 782 Belloli Aug. 31, 1982 2/25 Velikov April 10, 1986 In the case of the familiar Williams bolt, this hollow rock bolt is manufactured by the pierce-billet method, and initial cost is up to about ten times that of a plain, - :130094~) mechanical rock bolt. The Williams rock bolt is used for specialty bolting, such as anchoring a machine to a cement floor or to rock.
One of the dominant factors in selecting rock bolts is that of cost. One of the most commonly used underground bolts is a mechanical rock bolt, made from solid bar and used in conjunction with an anchoring shell.
In mining, the protection and safety of men and of equipment depends upon the integrity of the strata.
Rock bolts having expansible shell anchors are anchored within extended bores in the back, the wall or the rock face, for the purpose of compressing adja ~ tstrata of the rock so as to enhance ~their strength and stability and to virtually create a rock beam. Rock bolts also are used for the attachment of mine screening mesh in area covering relation primarily with the rock back, for safety purposes, by containment of loose rock.
At certain locations in a mine, under circumstances where greater security is required, such as permanent passages or ways and in certain types of strata, rock bolts are grouted into their respective rock bores.
Grouting is costly, but enhances the security of the rock bolt, and diminishes movement in the strata by filling the , 3 ~300940 residual bore space or a selected portion, with cement or epoxy cement, thus also providing direct load transfer between the rock bolt and the adjoined strata, so as to stabilize the strata.
Grouting is not generally carried out in the working area of a normal stope. However, in areas where acid ground water is encountered, grouting also affords significant corrosion protection to the rock bolts.
The apparent cost of purchasing and setting rock bolts can be readily calculated on a theoretical basis, based on the area to be secured, the recommended density of bolting, and hence, the bores to be drilled and the number of bolts and shells to be procured and set. However, this does not present a true picture of the situation, nor of the costs involved.
Due to a number of factors such as poor initial installation, loss of anchorage due to slippage movement of the shell, including the local effects of blasting and other ground tremors and displacement, experience over many years in the field has revealed a "loss" generally of about 40% of ungrouted rock bo~ts, as initially placed.
i;~00940 This situation can be largely remedied by grouting of the installed bolts with conse~uently increased costs. However, with the solid mechanical bolts in general use, effective grouting requires to be undertaken at the outset, owing to the need to provide a vent tube along the length of the rock bclt, and extending through the bearing plate at the rock surface, as well as the need to provide a grout injection access through the bearing plate. Thus, retroactive grouting cannot be effectively undertaken, being virtually impossible, on a practical basis while the cost of grouting on a routine basis greatly increases rock bolting costs.
One characteristic of all known prior use rock bolts is a total inability for an observer to ascertain from the stope floor what is taking place in terms of loading and displacements behind the rock face.
SUMMARY OF THE INVENTION
The present invention provides a tubular rock bolt that is particularly suited for grouting installations. The subject tubular rock bolt construction lends itself to a family of tubular rock bolts most of which have a nominal load rating closely approximating the load ratings of existing mechanical rock bolts.
.....
i300940 Furthermore, the subject tubular rock bolt incorporates standard rolled threads to enable use thereof with standard sizes of nuts and more particularly, with suhstantially standard shells.
In reviewing the contribution afforded by the present invention over the prior art, in terms both of cost and of load bearing capability performance,the subject tubular rock bolt most closely approximates ~e ox~n mechanical rock bolt of solid bar, and accordingly the latter is herein adopted as the valid basis for prior art comparison. The subject tubular rock bolt (TRB) makes possible the adoption of a visible projecting rod-like ground movement indicator (GMI) for installation with the TRB when in a non-grouted condition, to provide a readily seen visual indicator for indicating relative condition changes having taken place between the TRB and its associated strata subsequent to the placement of the TRB.
Such changes in the relative condition of a rock bolt arise as a consequence of a loss in tension in the rock bolt due to non-gripping of the shell within its bore, or to significant extension of the rock bolt as a consequence of strata displacement, which conditions, in the case of prior art rock bolts, were visually undetectable.
. .~ ., These condition changes, ta~en singly or in combination in the case of the subject TRB tend to cause a relative retraction of the GMI visible outer end inwardly into the interior of the TRB.
It has been found that a TRB incorporating the foregoing enu~erated advantages can be manufactured at an acceptable increase in cost over that of existing mechanical rock bolts, using continuous weld,cold drawn mechanical steel tube.
It has further been found that the fabricated tube can be cold drawn, within very closs tolerances, to an outside diameter (O.D.) particularly suited to the formation of rolled threads thereon, for use with existing standard nuts and shells presently used in rock bolting.
In carrying out the process, a range of sizes of tubular bolts having a range of wall thicknesses has been achieved, so as to provide bolts having a significant range of load capabilities. In view of established rock bolting practice, wherein 3/4 inch and 5/8 inch solid mechanical rock bolts are used, the subject tubular rock bolts have a selected tube O.D. to facilitate the rolling of a predetermined standard thread thereon, and a selected wall thickness, as a function of the tensile strength of the continuous weld cold drawn steel tube, to provide an as installed load bearing capacity equivalent to that of a respective one of the existing equivalent standard mechanical rock bolts. However, it has been found ~at, due bo the material selected, and possibly influenced by the tubular form adopted, the subject tubular rock bolt demonstrates great axial resilience and a capacity for extension under cold working, such that effective longitudinal bolt extensions under working tensile loads are readily achieved. The strength and ductility of the TRB are significant in maintaining the compression load in the rock strata in the event of strata disturbance, such as blasting in the vicinity of the installed bolt, thereby providing acceptable performance, in use.
In addition to the foregoing recited charac-teristics, the subject tubular rock bolt (TRB), by virtue of its larger diameter, presents a larger peripheral "wetted area", to which grouting can bond itself, while the volume of grouting required is significantly diminished.
Also, the required volume of grout, on the basis of a standard bored rock hole, is significantly less for grouting a subject .920 inch diameter tubular rock bolt than for grouting a 3/4 inch diameter equivalent strength ~ .
~' i3009AO
plain rock bolt; and is much less for grouting a subject tubular rock bolt than for grouting a 5~8 inch diameter plain rock bolt. These material reductions represent significant cost savings to off-set the higher initial tubular rock bolt costs.
In addition to making available significant savings in grouting quantities, the subject TRB no longer requires the provision of an air vent tube, being self venting through its centre, thereby assuring more reliable grouting, by avoidance of the air locks frequently experienced with vent tubes, in the prior art.
In the case of a 1_5/8 inch diameter rock bore, a subject TRB effects a worthwhile savings in grout quantity, compared with the corresponding standard 3/4 inch diameter bolt. The present invention thus provides a tubular rock bolt of continuous weld cold drawn steel having a predetermined outside tubular diameter to accept a predetermined rolled thread form. The subject tubular rock bolt has a wall of predetermined thickness, to afford an initial tensile load capacity substantially equal to that of an existing predetermined solid section mechanical rock bolt, wherein the subject tubular rock bolt has a comparable extensibility to that of the referenced solid ~.; , :1300940 section mechanical rock bolt, and provides a si~ilar ability of maintaining an effective load and reliability, in use.
Manufacture of the subject continuous weld, cold drawn tube bolt is effected by first manufacturing a larger diameter cold drawn steel tube. A steel ribbon is roll formed at high temperature into a tube formation, and the closure edges thereof compressed together, generally under airjet or oxyjet heating to form a continuous butt welded tube wall, to provide a high quality continuous butt jointed seamed tube, at comparatively low cost. The thus-formed tube is then cold mandrel-drawn through sizing dies until the required outer diameter (O.D.) and wall thickness are achieved, by cold working. In order to achieve the subject tube bolt, optimized OoD~ ~s have been adopted, wherein, working within the constraints of standard rock bolt practice, threads can be rolled thereon for use with standard sized nuts and shells as used with prior art mechanical rock bolts.
In accordance with the present invention a family of five different tubular rock bolts, TRB 1, 2, 3, 4 and 5 have been evolved to-date and are in course of development:
Product Designation TRB 1TRB 2 TRB 3 TRB 4 TRB 5 Dimensions .690"x.150" .920"x.195".920"x.195".920"x.260" .920x.260"
(OD x ~all thickness) swaged swaged Rock bore size 1-1~4"1-5/8" 1-1~4" 1-5/8" 1-1/4"
Replaces 5/8" bolt5/8" bolt3/4" bolt3/4" bolt Adoption of a 0.26 inch wall thickness with the large .92 inch diameter tube provides a high initial load capacity tubular bolt having substantially the same initial load bearing capacity as a 3/4~inch solid bar mechanical rock bolt, while accommodating standard rolled threads to receive a standard l-inch threaded rock bolt shell, for anchoring purposes.
A further embodiment of the .920 inch diameter tubular bolt having a thinner wall, namely of 0.195-inch thickness, provides an initial applied load bearing capacity approaching that of a 5/8-inch diameter solid rock bolt. This tube size also accepts a nominal 1 inch rolled thread, and exhibits characteristic extensibility under load.
In a further embodiment, it has been established that an end of a tubular rock bolt, such as the 0.92-inch tube, may be swaged, pointed or otherwise reduced to a smaller O.D., to accept a 3/4-inch rolled thread thereon, for use with 3/4-inch nuts and 3/4-inch standard shells.
It will be understood that the subject invention is not limited to the foregoing family of tubular rock bolts, and that different diameters and wall thicknesses may be adopted to meet the needs of the industry.
A further aspect of the present invention is the incorporation, with a tubular rock bolt, of a low cost, effective Ground Movement Indicator (GMI). Thus, an elongated rod-like GMI having the rod portion thereof freely suspended within the bore of the tubular rock bolt has the remote distal end thereof independently secured within the distal end of the strata bore, and the free proximal end of the rod portion initially extending outwardly from the bolt proximal end, as the visible GMI.
Upon initial loading, by tensioning the bolt, in applying a predetermined working load thereto, a viewable portion of the GMI rod can be left projecting at the proximal end.
Upon significant subsequent extension of the subject bolt under load, the projecting length of the GMI rod becomes sensibly and substantially proportionately diminished, to 1~
~;~00940 provide visual indication of significant change in the condition of the rock bolt relative to its strata, in its position at the rock back, wall or face, with a corresponding indication of a possible significant change having taken place in the related rock strata. Thus, the extent or degree of disappearance of the GMI rods in a given area of a stope could indicate to some extent the probable degree of danger of a rock fall occurring.
Generally, low cost wires or plastic rods are adopted in the role of GMI indicator rods.
In the preferred embodiment the GMI includes an indicator rod having its own anchor located above the shell to optimize its integrity, by enabling the rod to be independently anchored in the strata. The bridge portion of the bail of the shell is recessed to accommodate the distal bolt end of the TRB, and has a central aperture therein through which the GMI rod extends, when installed.
The apertured bail bridge serves a valuable purpose in facilitating rupture of the bail in the event that the TRB
tube is accidentally screwed upwardly through the shell, so as to rupture the bridge.
Rock bolts are provided in a range of lengths and sizes, and 5 foot and 6 foot rock bolts are generally considered standard production bolts. The subject GMI rods can be provided as a standard item, having a rod size, diametrically compatible with a range of tube bolt ID's, Zi~ ~.
13~0940 and, being readily shortenable by a simple clipping operation, can be provided in a standard length, such as a 9 foot or longer rod, suitable for use with a 6 foot or longer bolt, and then shortened, if required to be used with 5 foot or shorter bolts. Generally the rod is 3 or 4 feet longer than the tube bolt with which it is used.
When it is recognized that stope roof heights in the range of 12 to 20 feet are commonplace, it will be understood that to be effective the protruding rod end of a GMI rod must be clearly visible, and a significant relative displacement thereof must be plainly evident, preferably when viewed from stope floor level, by suitable colouration, such as fluorescent paint.
In the preferred GMI embodiment, having the rod portion thereof supported independently of the TRB shell, the distal end of the GMI rod can be threadedly disengaged by unscrewing it from its anchor portion, to permit withdrawal of the GMI rod from an installed TRB, so that grouting of the TRB can then proceed without any impedance.
More particularly, this invention provides the method of manufacturing a tubular rock bolt comprising the steps of: forming a steel strip in heated condition into a substantially circular section; joining the adjacent ends thereof in welded relation: cold drawing the section to a predetermined smaller diameter, having a predetermined wall thickness; applying a rock anchor means in secured relation adjacent one end of the rock bolt by rolling threads on a surface portion of the rock bolt, said threads being engageable by said rock anchor means, and providing load transfer means in secured relation with the rock bolt other end by rolling further threads on said rock bolt other end, said load transfer means including nut means secured in threaded adjustable relation with said further threads, and load transfer washer means encompassing said other end, in thrust transfer relation with said nut means.
Further this invention provides a method of forming a tubular rock bolt, comprlsing the steps of:
a) forming a steel strip ha~ing parallel longitudinal edges into a laterally curved shape, abutting the edges, and welding the abutting edges by electric resistance welding, in order to form an oversize, thick-walled tube of substantially annular 5 section, b) cold drawing the tube by elongation through dies to produce a tube with smooth inner and outer walls and an internal diameter of at least about 0.34 inches, c) cutting a portion of the tube to form a bolt 0 having first and second ends, d) rolling threads on both ends of the bolt, e) providing a rock anchor attachment which includes a portion having an internally threaded passage matching the rolled thread on said first end of the bolt, and removably threading said attachment onto said first end, and f) providing load transfer means for said second end, said means comprising an internally threaded member 13b ~3~940 for threadably receiving said second end, and for transferring a load from the bolt, through a suitable means, to the surrounding rock structure.
Still further, this invention provides a hollow, thin walled tubular rock bolt having an axial working load capacity substantially equal to a standard solid mechanical rock bolt of predetermined smaller diameter, said tubular rock bolt providing an axial through passage, in use to facilitate the optional use of a ground movement indicator rod in cooperation with the rock bolt, said rock bolt being fabricated from a steel strip having parallel longitudinal edges by forming the strip into a laterally curved shape, abutting the edges, and welding the abutting edges in order to form an oversize, thick-walled tube of substantially annular section, cold drawing the tube by elongation through dies to produce a tube with smooth inner and outer walls, and cutting a portion of the tube to provide said tubular rock bolt.
Finally, this invention provides, in a rock bolt for use in inserted, tensioned relation within a bore in a rock face, said rock bolt being of predetermined length and including a combination with a shell means having an expansible distal head portion to expand, in use, into gripping relation within a remote inner surface of said bore, and a bearing plate and nut means on the proximal end of the rock bolt for tensioning the rock bolt and pulling the bearing plate in compressed relation against the rock face; the rock bolt having a passage therein extending axially for a major portion of said predetermined length, the improvement comprising ground movement indicator means having a viewable proximal end extending outwardly of the proximal end of the rock bolt, and an elongated support portion extending within the rock bolt passage and supported, in use at substantially said rock bolt distal end, in independently secured relation therein, to provide c,~
~ :
i300940 13c external visual indication of axial extension of said rock bolt.
, .~
. ~..
14 13 ~ 940 BRIEF DESCRIPTION OF THE DRAWINGS
Certain embodiments of the invention are described, reference being made to the accompanying drawings, wherein;
Figure 1 is a side view of a section of rock face, showing an embodiment of the subject tubular rock bolt ~TRB) installed in tensioned, anchored relation therein;
Figure 2 is a like view, showing a tubular rock bolt embodiment incorporating a ground movement indicator (GMI) therewith;
Figure 3 is an end view, from below, showing a TRB
installation having a grouting tube inserted upwardly through the plate washer of the installation;
Figure 4 is a plan view of the GMI rod anchor arrangement;
and Figure 5 is a side view showing a GMI rod and associated anchor, together with bail and leaves portions of the shell, and a portion of the tubular rod bolt.
,~ . ~
i3009A0 DETAILED DESCRIPTION OF THE INVENTION
Referring to Figures 1, 2 and 5, the rock bolt assembly 10 comprises a cold drawn tube portion 12 having threaded end portions 14, 16 with rolled threads 18 thereon, and an axial through passage 19. A standard type of shell 20 has leaves portions 22, having serrated gripping surfaces 24 on the exterior thereof. Shell wedge body portion 26 is threadedly mounted at the distal end, on the rolled threads 18 of the tube end 16.
Referring more particularly to Figures 1 and 2, wi~h the bolt assembly 10 inserted into the rock bore 30, the leaves portions 22 of the shell 20 bear against the rock bore, and upon downward retraction of the tube portion 12, the wedge body 26 is drawn downwards axially into expanding relation with the leaves 22 of shell 20, causing them to engage the gripping serrations 24 thereof with the inner surface of rock bore 30.
The bottom tensioning nut 32 bears against the hardened round washer 34 and bearing plate 36, to draw the tube portion 12 axially outwardly in anchor loading relation. Thus, the tube portion 12 is tensioned, while the associated surrounding roc~ portion is compressed, and thereby strengthened.
1~ ~ 300940 In some instances, grout may be injected upwardly through the bore 19 of tube 12, and the GMI 40 is not used.
It is preferred to grout, using an offset passage 35' through the bearing plate 36 for upward insertion of grouting tube 35 therethrough, with displaced air exiting downwardly through the centre passage 19 of tube 12. In such an arrangement, only a short length of grouting tube 35 requires to be inserted.
Referring to Figures 4 and 5, showing particulars of a first GMI embodiment, the threaded upper (distal) end portion 16 of a subject rock bolt 12 is shown.
The elements of the shell are referred to above.
The rod 40 of GMI 54, having a cruciform anchor portion 60 secured to the rod 40 by threads 58 is inserted downwardly into passage 19 of bolt 12. The bail portion 28 of shell 20 has a central aperture 29 therein, for passage of rod 40 therethrough. The surface 40' of bail portion 28 is recessed to receive the distal end 16 of tubular bolt 12, in the event of misadvertant rotation of bolt 12 causing the bolt 12 to advance axially through wedge body ~)`
17 i300940 26 of shell 20. Upon such an occurrence, with the leaves 22 being set in the rock bore 30, the bail portion 40' ruptures readily, adjacent to aperture 29.
The rod retaining thread 58 being formed in anchor portion 60 is secured against rotation, and it is possible to unscrew and withdraw the GMI, rod portion 40 from out of an installed TRB, so that initial non-grouted installation of a TRB incorporating a GMI can be followed by removal of the GMI rod 40, and completion of normal grouting procedures.
The proximal ends of the GMI rods 40 can be clipped off at a standard exposed length, on initial installation, subsequent to the tubular rock bolt 12 being tensioned to the desired initial value of working load.
In Figures 2 and 5, the GMI rod 40 has the inner end portion 42 thereof supported independently above the distal end 16 of tube portion 12 by way of cruciform spring clip 60 which engages the rock bore 30. This has the benefit of optimizing the independence of GMI 54.
Claims (17)
1. The method of manufacturing a tubular rock bolt comprising the steps of: forming a steel strip in heated condition into a substantially circular section;
joining the adjacent ends thereof in welded relation;
cold drawing the section to a predetermined smaller diameter, having a predetermined wall thickness;
applying a rock anchor means in secured relation adjacent one end of the rock bolt by rolling threads on a surface portion of the rock bolt, said threads being engageable by said rock anchor means, and providing load transfer means in secured relation with the rock bolt other end by rolling further threads on said rock bolt other end, said load transfer means including nut means secured in threaded adjustable relation with said further threads, and load transfer washer means encompassing said other end, in thrust transfer relation with said nut means.
joining the adjacent ends thereof in welded relation;
cold drawing the section to a predetermined smaller diameter, having a predetermined wall thickness;
applying a rock anchor means in secured relation adjacent one end of the rock bolt by rolling threads on a surface portion of the rock bolt, said threads being engageable by said rock anchor means, and providing load transfer means in secured relation with the rock bolt other end by rolling further threads on said rock bolt other end, said load transfer means including nut means secured in threaded adjustable relation with said further threads, and load transfer washer means encompassing said other end, in thrust transfer relation with said nut means.
2. A method of forming a tubular rock bolt, comprising the steps of:
a) forming a steel strip having parallel longitudinal edges into a laterally curved shape, abutting the edges, and welding the abutting edges by electric resistance welding, in order to form an oversize, thick-walled tube of substantially annular section, b) cold drawing the tube by elongation through dies to produce a tube with smooth inner and outer walls and an internal diameter of at least about 0.34 inches, c) cutting a portion of the tube to form a bolt having first and second ends, d) rolling threads on both ends of the bolt, e) providing a rock anchor attachment which includes a portion having an internally threaded passage matching the rolled thread on said first end of the bolt, and removably threading said attachment onto said first end, and f) providing load transfer means for said second end, said means comprising an internally threaded member for threadably receiving said second end, and for transferring a load from the bolt, through a suitable means, to the surrounding rock structure.
a) forming a steel strip having parallel longitudinal edges into a laterally curved shape, abutting the edges, and welding the abutting edges by electric resistance welding, in order to form an oversize, thick-walled tube of substantially annular section, b) cold drawing the tube by elongation through dies to produce a tube with smooth inner and outer walls and an internal diameter of at least about 0.34 inches, c) cutting a portion of the tube to form a bolt having first and second ends, d) rolling threads on both ends of the bolt, e) providing a rock anchor attachment which includes a portion having an internally threaded passage matching the rolled thread on said first end of the bolt, and removably threading said attachment onto said first end, and f) providing load transfer means for said second end, said means comprising an internally threaded member for threadably receiving said second end, and for transferring a load from the bolt, through a suitable means, to the surrounding rock structure.
3. The method claimed in claim 2, in which the step of cold drawing under b) gives the tube an outer diameter between about 0.68 inches and about 0.92 inches, and an inner diameter between about 0.34 inches and about 0.53 inches.
4. The method as set forth in claim 1, including the steps of operating on an end portion of said bolt to reduce the outer diameter thereof, and threading said end portion.
5. A hollow, thin walled tubular rock bolt having an axial working load capacity substantially equal to a standard solid mechanical rock bolt of predetermined smaller diameter, said tubular rock bolt providing an axial through passage, in use to facilitate the optional use of a ground movement indicator rod in cooperation with the rock bolt, said rock bolt being fabricated from a steel strip having parallel longitudinal edges by forming the strip into a laterally curved shape, abutting the edges, and welding the abutting edges in order to form an oversize, thick-walled tube of substantially annular section, cold drawing the tube by elongation through dies to produce a tube with smooth inner and outer walls, and cutting a portion of the tube to provide said tubular rock bolt.
6. The hollow rock bolt as set forth in claim 5, having rolled threads at both ends thereof.
7. The hollow rock bolt as set forth in claim 5, in combination with a shell anchor secured to one end thereof.
8. The hollow rock bolt as set forth in claim 5, having one end thereof reduced to a smaller diameter, and having a correspondingly smaller diameter thread thereon.
9. The hollow rock bolt as set forth in claim 5, said standard solid rock bolt being a 3/4-inch diameter size, said tubular rock bolt having an outside diameter precisely sized for a 1-inch nominal size thread thereon.
10. The hollow rock bolt as set forth in claim 5, said standard solid rock bolt being a 5/8-inch diameter size, said tubular rock bolt having an outside diameter precisely sized for a 3/4-inch nominal size thread thereon.
11. The hollow rock bolt as set forth in claim 5, where n the tube is welded by electric resistance welding.
12. The hollow rock bolt as set forth in claim 5, in combination with ground movement indicator means having a viewable proximal end, an elongated rod portion extending internally of said tubular bolt and having attachment means for securing the distal end of said rod portion, remote from said proximal end, in secured, self-supporting relation whereby, on installation, variations in the effective position of said rock bolt proximal end, in use, under load, are inversely represented by the extent of exposure of said rod proximal end portion outwardly beyond said rock bolt proximal end.
13. The hollow rock bolt and indicator means combination as set forth in claim 12 said attachment means permitting the securement-of, and the removal of said ground movement indicator means from within said rock bolt.
14. The hollow rock bolt as set forth in claim 13, said ground movement indicator means including an elongate cylindrical body.
15. The hollow rock bolt as set forth in claim 14, wherein said cylindrical body comprises a wire.
16. The hollow rock bolt as set forth in claim 14, wherein said cylindrical body comprises a hollow plastic section.
17. In a rock bolt for use in inserted, tensioned relation within a bore in a rock face, said rock bolt being of predetermined length and including a combination with a shell means having an expansible distal head portion to expand, in use, into gripping relation within a remote inner surface of said bore, and a bearing plate and nut means on the proximal end of the rock bolt for tensioning the rock bolt and pulling the bearing plate in compressed relation against the rock face; the rock bolt having a passage therein extending axially for a major portion of said predetermined length, the improvement comprising ground movement indicator means having a viewable proximal end extending outwardly of the proximal end of the rock bolt, and an elongated support portion extending within the rock bolt passage and supported, in use at substantially said rock bolt distal end, in independently secured relation therein, to provide external visual indication of axial extension of said rock bolt.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000549771A CA1300940C (en) | 1987-10-20 | 1987-10-20 | Tubular rock bolt |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000549771A CA1300940C (en) | 1987-10-20 | 1987-10-20 | Tubular rock bolt |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1300940C true CA1300940C (en) | 1992-05-19 |
Family
ID=4136687
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000549771A Expired - Lifetime CA1300940C (en) | 1987-10-20 | 1987-10-20 | Tubular rock bolt |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1300940C (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103061791A (en) * | 2012-12-09 | 2013-04-24 | 山西鑫源机械制造有限公司 | Three-dimensional special type steel belt |
| CN109763850A (en) * | 2019-01-15 | 2019-05-17 | 泰安铭源节能科技有限公司 | A kind of intelligent grouting cable anchor and its detection method |
| CN115030753A (en) * | 2022-05-11 | 2022-09-09 | 中国科学院西北生态环境资源研究院 | Anti-frost-heaving roadway heat-preservation support system and construction method and heat-preservation control method thereof |
-
1987
- 1987-10-20 CA CA000549771A patent/CA1300940C/en not_active Expired - Lifetime
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103061791A (en) * | 2012-12-09 | 2013-04-24 | 山西鑫源机械制造有限公司 | Three-dimensional special type steel belt |
| CN109763850A (en) * | 2019-01-15 | 2019-05-17 | 泰安铭源节能科技有限公司 | A kind of intelligent grouting cable anchor and its detection method |
| CN115030753A (en) * | 2022-05-11 | 2022-09-09 | 中国科学院西北生态环境资源研究院 | Anti-frost-heaving roadway heat-preservation support system and construction method and heat-preservation control method thereof |
| CN115030753B (en) * | 2022-05-11 | 2023-08-08 | 中国科学院西北生态环境资源研究院 | Anti-frost-heaving roadway heat-insulation support system, construction method thereof and heat-insulation control method |
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