US3849992A - Reinforcing elements for stabilization of rocks - Google Patents

Reinforcing elements for stabilization of rocks Download PDF

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Publication number
US3849992A
US3849992A US36314973A US3849992A US 3849992 A US3849992 A US 3849992A US 36314973 A US36314973 A US 36314973A US 3849992 A US3849992 A US 3849992A
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Prior art keywords
borehole
reinforcing assembly
assembly
reinforcing
bonding composition
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Expired - Lifetime
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English (en)
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J Murphy
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Exchem Holdings Ltd
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Exchem Holdings Ltd
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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D20/00—Setting anchoring-bolts
    • E21D20/02—Setting anchoring-bolts with provisions for grouting

Definitions

  • ABSTRACT Gilliam Assistant ExaminerAlexGrosz Attorney, Agent, or Firm-Larson, Taylor & Hinds
  • the stabilisation of weak rock formations is effected by inserting into a borehole drilled in the rock formation a reinforcing assembly in which a plurality of Iongitudinally extending annular segments are fixedly disposed in longitudinally staggered relationship about a coaxially arranged inner tube, feeding through the inner tube a bonding composition :so as to cause it to flow back from the closed end of the borehole to the annular space at the mouth of the borehole, and allowing the bonding composition to harden so as to bond the reinforcing assembly to the rock formation.
  • rockbolts typically 5 to 7 feet long, around underground openings to stabilise and reinforce the strata immedi ately adjacent to the openings.
  • rockbolts can achieve anchorage in the rock by means of expanding shells or wedging arrangements, or can be anchored at the inner end by means of a rapid setting cement usually based on an unsaturated polyester resin.
  • end anchored rockbolts are tensioned by means of a nut and plate acting against the rock surface around the borehole containing the rockbolt. The stress within such a tensioned bolt provides a force restraining strata-bed separation or relative movement of adjacent blocks of broken rock and hence the use of such bolts in appropriately spaced locations can provide a stressed zone of reinforcement around a mine roadway or other underground opening.
  • reinforcing element such as a rod of metal, wood or reinforced plastic is fully bonded, over its whole length, into a hole bored to receive it, using a suitable resinous or cementitious bonding composition known in the art.
  • Such reinforcing elements are not tensioned but, since they are intimately bonded to the rock, provide maximum localised restraining forces about any interfaces where stresses tend to cause delamination or parting of the rock.
  • the bonding composition for such reinforcing elements can be pumped into the borehole prior to insertion of the reinforcing element or more usually is contained in one or'more frangible capsules which are placed in the borehole and then ruptured and the contents caused to activate by rotation of the reinforcing element on insertion into the borehole.
  • the length of the reinforcing element is limited to six to eight feet although in special circumstances bolts up to twenty feet in length have been used around underground mine openings.
  • the relatively narrow band of rock which may be reinforced with the conventional reinforcing elements described above is normally adequate around a mine roadway but a much greater depth of temporary reinforcement is necessary to stabilise faulted zones on longwall coal faces.
  • a method of reinforcing an underground rock formation which comprises drilling a borehole in the rock formation; inserting into the: borehole a reinforcing assembly comprising a plurality of longitudinally extending annular segments fixedly disposed in longitudinally staggered relationship about a coaxially arranged inner tube, the insertion of the reinforcing assembly being continued until the inner end thereof lies adjacent to the inner end portion of the borehole and the outer end of the reinforcing assembly lies adjacent the mouth of the borehole; feeding a bonding composition through the inner tube of the reinforcing assembly so as to cause the bonding composition to flow out of the inner end of the reinforcing assembly and back along the annular space between the assembly and the wall of the borehole; continuing the feeding of the bonding composition until the said annular space is substantially full of bonding composition; and thereafter allowing the bonding composition to harden so as to bond the reinforcing assembly to the rock formation.
  • the reinforcing assembly comprises a plurality of tubular members arranged in series, each formed from a plurality oflongitudinally extending annular segments fixedly disposed in longitudinally staggered relationship about a coaxially arranged inner tube, the inner tubes of adjacent tubular members communicating by means of a connecting memberjoining the end portions of said adjacent tubular members.
  • the reinforcing assembly is formed from a continuous inner tube about which are fixedly disposed a plurality of longitudinally extending annular segments in longitudinally staggered relationship with respect to the inner tube.
  • the annular segments present in the reinforcing assembly may be formed from any suitable material, for example wood, metal, synthetic thermoplastics or thermosetting material, asbestos cement or resin-bonded glass fibre, whilst the inner tube may be formed, for example, from a synthetic plastics material such as, for example, polyethylene.
  • the annular segments present in the reinforcing assembly are in the shape: of semi-cylindrical annular segments.
  • the annular segments may have cross-sections other than semi-cylindrical.
  • the connecting member joining together adjacent tubular members in the aforementioned first embodiment of the invention may be, for example, a tubular sleeve into which the tubular members are push-fit, or
  • a spigot extending from the inner tube at one end of a tubular member and which is inserted into one end of the inner tube of the adjacent tubular member.
  • the inner end of the assembly with a tubular perforated ejection head having a closed front end.
  • the head preferably has a generally cylindrical body which tapers towards the closed front end, to assist insertion of the reinforcement assembly into irregular boreholes.
  • the ejection head is formed with a plurality of exit apertures through which the bonding composition can be ejected into the annular space surrounding the reinforcing assembly in the borehole, the exit apertures advantageously being substantially symmetrically disposed around the body of the ejection head.
  • FIG. I is a view of the end portion of a tubular member from which one embodiment of a reinforcing assembly can be produced;
  • FIG. 2 is a part longitudinal cross-section of a second embodiment of a reinforcing assembly
  • FIG. 3 is a view of an ejection head for a reinforcing assembly.
  • a tubular member from a plurality of which can be formed a reinforcing assembly for use in the method of the invention comprises two longitudinally extending annular segments 2 of semi-cylindrical shape which are disposed in staggered relationship about a coaxially arranged inner tube 1.
  • FIG. 2 there is shown a preferred reinforcing assembly for use in the method of the invention formed from a continuous inner tube 1 which is surrounded by a plurality of semi-cylindrical annular segments 2 which are in staggered locations with respect to the tube 1 so that at any point at least half of the ultimate tensile strength of the reinforcing assembly is available.
  • the inner tube 1 may be formed from, for example, a flexible or semi-rigid plastics material or metal and fed from a coil thereof into the borehole in an unbroken length.
  • the semi-cylindrical annular segments 2 can be supplied in convenient lengths, for example I to 2 metres, and can be positioned around the tube 1 by means of, for example, adhesive tape or metallic or plastics clips.
  • FIG. 3 shows an ejection head which can be attached to the reinforcing assembly of FIG. 1 or 2.
  • the ejection head has a tubular body 1 which is tapered to form a closed front end 2.
  • a plurality of apertures 3 are disposed substantially symmetrically over the surface of the body 1.
  • the bonding composition employed in the method of the invention may be a cementitious composition or preferably a resinous composition, advantageously one based on an unsaturated polyester resin.
  • Tubular members as illustrated in FIG. 1 were made using a high density polyethylene tube ofinternal diameter 16 mm. and external diameter 19 mm. as the inner tube 1, and semi-circular section annular wooden strips of 19 mm. internal diameter and 36 mm. external diameter prepared from Kerning timber as the annular segments 2.
  • the plastics tube and the timber strips were cut to 66 inches in length and then assembled with a longitudinal displacement so that the overall length of the assembled tubular member was 72 inches and each end of the inner tube was positioned midway between the respective ends of the two semi-circular wooden annular segments.
  • a rapid hardening adhesive based on an unsaturated polyester resin was used to bond the inner tube to the annular segments to form the required tubular member.
  • a borehole 43 mm. in diameter and 44 feet long was drilled horizontally into a faulted area on a longwall coal face.
  • the tubular member as described above was fitted with a tapered ejection head as illustrated in FIG. 3.
  • the ejection head was 36 mm. in diameter, 300 mm. in length and was perforated with 16 apertures, each 10 mm. in diameter, distributed approximately regularly over its surface.
  • the tubular member with the ejection head fitted was inserted into the borehole and another similar tubular member was connected by insertion into the open end of the 36 mm. diameter connecting member.
  • a further six similar tubular members were connected in like manner until the ejection head had reached the inner end of the borehole.
  • the plastics connecting member was then removed from the end of the last tubular member projecting from the mouth of the borehole, which thus contained a reinforcing assembly in accordance with the invention. 1
  • a delivery pipe from a hand operated diaphragm pump was connected to the outer end of the plastics inner tube of the reinforcing assembly and an unsaturated polyester resin based bonding composition was pumped through the reinforcing assembly to the inner end of the borehole.
  • the composition flowed through the ejection head and back along the annular space between the assembly and the wall of the borehole. Pumping was discontinued when the resin bonding composition appeared in the annulus at the mouth of the borehole.
  • the resin based bonding composition contained, in addition to the unsaturated polyester resin, 50 percent by weight of inert filler and 1.0 per cent by weight of pyrogenic silica and was activated by a benzoyl peroxide/amine accelerator system of a type which is well known in the art.
  • a series of longhole reinforcing assemblies was placed as described above at approximately one metre intervals throughout the faulted area of the coalface. After hardening of the injected resinous bonding composition, the coal was cut by conventional mining machinery and very substantial improvement in ground conditions was confirmed due to the stabilisation effect of the reinforcing assemblies.
  • EXAMPLE 2 Coils of high density polyethylene tubing of 16 mm. internal diameter and 19 mm. external diameter were prepared in lengths of 45 feet.
  • a 6 feet length of semicircular annular wooden segment was then attached to a matching position and the composite advanced a further three feet into the borehole.
  • Similar annular wooden segments were added sequentially. with three feet of advance after each addition until the ejection head reached the inner end of the borehole. The projecting portions of the wooden segments were sawn off, i
  • a method of reinforcing an underground rock formation positioned above a coal seam being mined by the longwall system comprises drilling into the rock formation a substantially horizontal borehole having a diameter less than 50 mm. and a length in excess of about feet; inserting into the borehole in stages a reinforcing assembly comprising a plurality of lengths of longitudinally extending annular segments fixedly disposed in longitudinally staggered relationship with respect to each other about a coaxially arranged inner tube, said assembly being made up from a plurality of the lengths of said annular segments while being inserted into the borehole, and the insertion of the reinforcing assembly being continued until the inner end thereof lies adjacent to the inner end portion of the borehole and the outer end of the reinforcing assembly lies adjacent to the mouth of the borehole; feeding a bonding composition through the inner tube of the reinforcing assembly so as to cause the bonding composition to flow out of the inner end of the reinforcing assembly and back along the annular space between the assembly and the wall of the borehole
  • the reinforcing assembly comprises a continuous inner tube about which are fixedly disposed a plurality of lengths of longitudinally extending annular segments in longitudinally staggered relationship with respect to the inner tube.
  • each length of the annular segments is semi-cylindrical in shape.
  • each length of the annular segments is semi-cylindrical in shape.
  • a longhole reinforcing assembly for use in a substantially horizontal borehole formed in an underground formation being mined by the longwall system, said assembly having a length in excess of about 40 feet, and comprising in combination a plurality of lengths of longitudinally extending annular segments fixedly disposed in longitudinally staggered relationship with respect to each other about a co-axially arranged inner tube providing an axial passage throughout the length of said reinforcing assembly for conducting a bonding composition into the annular space between said assembly and the wall of said borehole.
  • each length of the annular segments is semicylindrical in shape.
  • said inner tube is a continuous tube.

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  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Structural Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Geology (AREA)
  • Piles And Underground Anchors (AREA)
  • Devices Affording Protection Of Roads Or Walls For Sound Insulation (AREA)
  • Excavating Of Shafts Or Tunnels (AREA)
  • Lining Or Joining Of Plastics Or The Like (AREA)
  • Adhesives Or Adhesive Processes (AREA)
US36314973 1972-06-05 1973-05-23 Reinforcing elements for stabilization of rocks Expired - Lifetime US3849992A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2610272A GB1384177A (en) 1972-06-05 1972-06-05 Method of and reinforcing elements for stabilisation of rock

Publications (1)

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US3849992A true US3849992A (en) 1974-11-26

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US36314973 Expired - Lifetime US3849992A (en) 1972-06-05 1973-05-23 Reinforcing elements for stabilization of rocks

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US (1) US3849992A (enrdf_load_stackoverflow)
BE (1) BE800497A (enrdf_load_stackoverflow)
CA (1) CA970984A (enrdf_load_stackoverflow)
DE (1) DE2327851A1 (enrdf_load_stackoverflow)
ES (1) ES415818A1 (enrdf_load_stackoverflow)
FR (1) FR2188049A1 (enrdf_load_stackoverflow)
GB (1) GB1384177A (enrdf_load_stackoverflow)
ZA (1) ZA733570B (enrdf_load_stackoverflow)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3987635A (en) * 1975-04-01 1976-10-26 Exchem Holdings Limited Method of reinforcing rock strata
US4092814A (en) * 1974-03-15 1978-06-06 Dyckerhoff & Widmann Aktiengesellschaft Reinforcing rod
US4922679A (en) * 1987-01-13 1990-05-08 Siegfried Fricker Holding and supporting anchor to be cemented-in in a borehole in a mounting base
CN105672240A (zh) * 2016-01-25 2016-06-15 黄河勘测规划设计有限公司 倾倒破坏型危岩体治理方法
US20190040712A1 (en) * 2016-01-29 2019-02-07 Halpa Intellectual Properties B.V. Method for counteracting land subsidence in the vicinity of an underground reservoir
CN115198753A (zh) * 2022-06-20 2022-10-18 上海工程技术大学 一种结构体及其制作模具和应用

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH630438A5 (en) * 1977-02-19 1982-06-15 Bergwerksverband Gmbh Multi-piece sunk resin bolt
DE2827327A1 (de) * 1978-06-22 1980-01-10 Bayer Ag Verankerung von zuggliedern
IT8422466A0 (it) * 1984-08-30 1984-08-30 Fip Ind Procedimento di chiodatura ad aderenza continua per il consolidamento di ammassi rocciosi, disturbati da operazioni di scavo, nonche' apparecchiatura utilizzata.

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2667037A (en) * 1949-08-24 1954-01-26 Edward M Thomas Suspension roof support
DE1182185B (de) * 1961-06-15 1964-11-26 Erich Fritz Dipl Ing Gebirgsanker fuer den Ausbau von Untertageraeumen
US3311012A (en) * 1965-03-11 1967-03-28 Chester I Williams Pressure-actuated expanding anchor
DE1484449A1 (de) * 1964-08-18 1969-10-02 Deutsche Erdoel Ag Verfahren zum Befestigen von Ankern im Erdreich

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2667037A (en) * 1949-08-24 1954-01-26 Edward M Thomas Suspension roof support
DE1182185B (de) * 1961-06-15 1964-11-26 Erich Fritz Dipl Ing Gebirgsanker fuer den Ausbau von Untertageraeumen
DE1484449A1 (de) * 1964-08-18 1969-10-02 Deutsche Erdoel Ag Verfahren zum Befestigen von Ankern im Erdreich
US3311012A (en) * 1965-03-11 1967-03-28 Chester I Williams Pressure-actuated expanding anchor

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4092814A (en) * 1974-03-15 1978-06-06 Dyckerhoff & Widmann Aktiengesellschaft Reinforcing rod
US3987635A (en) * 1975-04-01 1976-10-26 Exchem Holdings Limited Method of reinforcing rock strata
US4922679A (en) * 1987-01-13 1990-05-08 Siegfried Fricker Holding and supporting anchor to be cemented-in in a borehole in a mounting base
CN105672240A (zh) * 2016-01-25 2016-06-15 黄河勘测规划设计有限公司 倾倒破坏型危岩体治理方法
CN105672240B (zh) * 2016-01-25 2017-06-27 黄河勘测规划设计有限公司 倾倒破坏型危岩体治理方法
US20190040712A1 (en) * 2016-01-29 2019-02-07 Halpa Intellectual Properties B.V. Method for counteracting land subsidence in the vicinity of an underground reservoir
CN115198753A (zh) * 2022-06-20 2022-10-18 上海工程技术大学 一种结构体及其制作模具和应用

Also Published As

Publication number Publication date
BE800497A (fr) 1973-10-01
DE2327851A1 (de) 1973-12-20
ZA733570B (en) 1974-04-24
CA970984A (en) 1975-07-15
ES415818A1 (es) 1976-02-01
FR2188049A1 (enrdf_load_stackoverflow) 1974-01-18
GB1384177A (en) 1975-02-19

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