US3797254A - Consolidation of rock strata - Google Patents

Consolidation of rock strata Download PDF

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Publication number
US3797254A
US3797254A US00229844A US3797254DA US3797254A US 3797254 A US3797254 A US 3797254A US 00229844 A US00229844 A US 00229844A US 3797254D A US3797254D A US 3797254DA US 3797254 A US3797254 A US 3797254A
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United States
Prior art keywords
borehole
reinforcing member
tubular
end portion
tubular reinforcing
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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
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US00229844A
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English (en)
Inventor
A Askey
J Murphy
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Explosives & Chem Prod
EXPLOSIVES AND CHEM PROD LTD GB
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Explosives & Chem Prod
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Priority claimed from GB572971*[A external-priority patent/GB1329905A/en
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Publication of US3797254A publication Critical patent/US3797254A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK 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
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK 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
    • E21D21/0026—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection characterised by constructional features of the bolts
    • E21D21/0033—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection characterised by constructional features of the bolts having a jacket or outer tube

Definitions

  • This invention relates to the consolidation of rock strata and is concerned with a method of consolidating rock strata, particularly but not exclusively underground rock strata of a friable condition such as those often found in underground roadways and tunnels en countered in mining and civil engineering, and with a reinforcing member suitable for use in said method.
  • the consolidating rod is formed from a tube filled with a stiffening material such as cement and has a conformation at its outward facing end such as to seal the end of the borehole.
  • a stiffening material such as cement
  • Such consolidating rods require a mechanically exerted pressure of the order of 900 kg. for insertion and therefore canonly be installed with relatively sophisticated machines not conventionally available in most underground mines.
  • smooth consolidating rods can be withdrawn from the borehole at a load close to the yield point of the material used for the tube.
  • a tubular reinforcing member having enlarged end portions-in a borehole having a diameter such that there is an annular clearance between the wall of the borehole and the body portion of the reinforcing member of at least 2 mm., perferably from 3 to 5 mm., the reinforcing member being secured in the borehole, preferably over substantially its full length, by means of a polyester-based resin composition.
  • a bearing plate is secured to said enlarged end portion so as to be in contact with the rock adjacent to the mouth of the borehole.
  • said enlarged end portion may be provided with means for securing a bearing plate to the end portion of the reinforcing member.
  • An unexpected advantage of the use of a tubular reinforcing member in accordance with the invention is that when a tensile stress is imposed on the tubular member, no significant movement occurs up to the yield point of the material from which the tubular member is made, normally a metal or alloy such as steel, but beyond that point the material draws down uniformly over its whole length between the two enlarged end portions, in contrast to a solid rock bolt which is mechanically or resin anchored at only its inner end portion which on being 'tensioned beyond the yield point will normally neck down at one point and ultimately fail at this point with relatively small extension of the bolt.
  • the tubular reinforcing member is provided with a solid indicator rod extending lengthwise thereof and secured, when in use, to the inner end portion of the member, the rod projecting from the other end portion of the member so as to be capable of indicating any extension of the member when in use.
  • the reinforcing member of the invention which will generally be formed from a metal or alloy, preferably steel, will advantageously be used! in conjunction with a polyester-based resin composition preferably pack aged in a multi-component single compartment cartridge such as that described in, for example, our earlier U.K. Specification No. 1,127,913 or the specification of our copending application Ser. No. 49606/70.
  • the tubular reinforcing member may be installed with other bonding materials, for example portland cement, gypsum or a resin reinforced hydraulic composition, which may be injected into the borehole in premixed form.
  • the reinforcing member When the reinforcing member is used in conjunction with a bonding material packaged in a cartridge, the member must be rotated during insertion in the borehole to ensure destruction of the cartridge casing and adequate mixing of the reactive contents thereof.
  • rotation may be effected with handheld drilling machines at a relatively low mechanically exerted pressure of from 20 50 kg.
  • the reinforcing member 10 consists of a length of steel tube which is slotted at each end and then expanded by driving in a steel conical wedge 12. This is advantageous in that in use the expansion of the outer end of the tube in this manner may be carried out at the same time as the fixing of a bearing plate.
  • the reinforcing member consists of a steel tube 14 the ends of which have been expanded by hot working the metal on a suitable forming die.
  • one end of a steel tube 16 has been expanded by hot working in a manner such as to provide a means of securing a captive threaded stud 18 to which in use a bearing plate can be secured.
  • the other end of the tube may be expanded in the manner shown in FIG. 1.
  • FIG. 5 illustrates a further embodiment of the reinforcing member of the invention in which a conical wedge 24 at one end of the tube 25 is extended and fitted with a coarse thread 26.
  • a short length of thick walled plastic tubing is inserted in the borehole ahead of the resin cartridge(s) and the member is then inserted with rotation in the normal way.
  • the threaded end of the bolt engages with the plastic sleeve thereby expanding it against the wall of the borehole and providing immediate support for the member before gelation of the resin has commenced.
  • Such a supporting sleeve serves to retain the reinforcing member in the borehole and permits immediate removal of the drilling machine.
  • a bearing plate may subsequently be attached by any of the means outlined below.
  • FIG. 6 illustrates how a bearing plate 28 can be used in conjunction with a tubular reinforcing member such as the embodiment of FIG. 1, Whilst FIG. 7 illustrates the use of a bearing plate 28 in conjunction with a tubular reinforcing member 16 such as the embodiment of FIG. 3.
  • FIG. 8 there is illustrated a reinforcing member similar to that shown in FIG. 1 but having an axially extending rod 30 secured by a screwthread to a threaded socket in the conical wedge 32 at one end and projecting from the other end through an axial bore in the conical wedge 34 at that end, so as to provide an indication of an extension of the tubular member 10 when in use.
  • FIG. 9 illustrates an arrangement for testing the effectiveness of tubular reinforcing members in accordance with the invention.
  • FIG. 1 The simplest method of fixing a bearing plate to the reinforcing member involves the use of the embodiment of FIG. 1, which is expanded at its inner end be fore insertion in the borehole.
  • a close fitting bearing plate 28 having a central aperture 36 is then placed over the protruding end of the tube 10 and a tapered conical wedge 12 is hammered or pushed with a hydraulic ram (not shown) into the open end of the tube to expand the end adjacent the aperture in the plate.
  • FIG. 6 illustrates this method of fixing the bearing plate 28.
  • An alternative method of attaching a bearing plate 28 consists in the use of a tubular reinforcing member 16 having a captive steel threaded stud 18 at its outer end as shown in FIG. 3.
  • this reinforcing member 16 is inserted in the usual fashion and a standard roofbolt bearing plate 28 subsequently applied to the protruding captive stud l8 and tensioned by conventional means, as illustrated in FIG. 7.
  • tubular reinforcing members of the invention are of use for full or supplementary support in mine roadways.
  • tubular members of adequate length up to 4 metres, can be inserted into the strata surrounding the rock opening and spalling of the immediate surface rock minimised by attachment of suitable bearing plates to the exposed ends of the rein- I forcing members.
  • it is important to monitor the movement of the supported strata beds so that adequate warning of impending failure of the supported structure can be given.
  • various devices have hitherto been used to measure bed separation in the roof of a mine roadway. Such devices measure only the movement of the ground and do not indicate the stress developing within the individual reinforcing members.
  • the tubular reinforcing member of the invention offers the advantage of a means of measuring actual bolt stress by means of an inner calibrated rod located within the tube bolt itself, as previously described with reference to FIG. 8.
  • an inner calibrated rod located within the tube bolt itself, as previously described with reference to FIG. 8.
  • the exposed free end of the rod 30 will be observed to withdraw within the open end of the tubular member.
  • Such a situation indicates that the tubular member 10 is already bearing stress in excess of its yield load and provides a valuable-warning of serious movement within the supported roof structure.
  • FIG. 7 in which a bearing plate 28 is attached to the tubular member 16 by means of a captive stud 18, is of particular value in that it allows a high degree of flexibility in the use of the system, for example, it may not always be desirable or necessary to fully bond the tubular member over its whole length, so that in a 6 ft. borehole adequate performance may be achieved by bonding only the upper 4 ft. of the tubular member into the borehole.
  • Making use of this method of plate fixing it is possible to vary the lengths of the tubular member 16 and solid captive stud 18 so that in the instance above, a 4 ft. tubular member could be fitted with a 2 ft. captive stud.
  • reinforcing systems designed for use in rippings or to counteract floor movement in mines, can be devised where the tubular member 16 is inserted deep into the rock and a removable extension piece attached to the captive stud 18. Immediate support is therefore available when the tubular member 16 is installed and subsequent removal of the extension piece permits ripping or dinting of the floor and re-use of the reinforcing member by using an extension piece of a shorter length.
  • tubular reinforcing member is also of value when buried relatively deep into the strata.
  • significant improvement may be achieved by installing tubular members deep into the strata ahead and above the coal seam.
  • a 12 ft. borehole may be bored at an angle through the coal and into the overlying rock and a 6 ft. tubular member then installed in the inner end of the borehole.
  • the total length of the tubular member is kept well clear of the track of the coal cutting equipment but nevertheless provides valuable support to the ground before removal of the underlying support coal.
  • EXAMPLE 1 Three concrete blocks were arranged as illustrated in FIG. 9 of the accompanying drawings.
  • the blocks A and B were each 24 inches in length and 18 inches in diameter and the block C was 10 inches in length and 6 inches in diameter.
  • Blocks A and B were heavily reinforced with steel mesh and cast from concrete of 5,000 lbs p.s.i. compressive strength.
  • a centre hole 43 mm. in diameter was bored in the blocks as illustrated.
  • Cartridges 40 mm. in diameter and having a total weightof l 10 g., containing a reactive filled polyester resin grouting composition, were inserted into the hole, followed by a tubular member as illustrated in FIG. 1.
  • the bolt was rotated at a speed of 500 r.p.m. and thrust through the resin cartridges to release and mix the reactive contents.
  • Example 2 A tubular reinforcing member as illustrated in FIG. 4 was manufactured from mild steel welded tube, having an external diameter of 37 mm, and an internal diameter of 31.5 mm. A rolled thread was formed over a length of mm. at either end of the tube so as to increase the diameter of 38.6 mm. The tube was closed with a pressed steel cap which was tack welded in place. The tube, of 1.8 m. overall length, was installed in a 43 mm. diameter borehole in the laminated shale roof of a mine roadway. Sufficient. resin cartridges were inserted into the borehole before installation of the tube to ensure that the annular space between the tube and the hole would subsequently be filled with resinous composition. The borehole was drilled approximately 40 mm.
  • a steel plate approximately 200 mm. square and 10 mm. thick, was centrally bored with a 39 mm. diameter hole so that it fitted smoothly over the protruding rolled thread end of the tube.
  • the plate was secured in firm contact with the roof of the roadway by means of a tapered steel wedge, approximately 30 mm. in length having a minimum diameter of 30 mm. and maximum diameter of 37 mm. After sliding the plate over the protruding end of the tube the wedge was inserted within the end of the tube and forced home with a hydraulic ram providing a thrust of 1 ton, thereby expanding the tube end within the plate.
  • a pattern of reinforcing tubes was installed in this manner along a length of roadway to give a tubing density of one tube per square metre of exposed roof surface.
  • the pattern was installed progressively along the roadway as soon as possible after exposure of fresh roof.
  • a total length of roadway of 50 m. was reinforced in this. way using a total of 250 tubular reinforcing members.
  • the convergence of this supported roadway was measured in comparison with a similar length of the same roadway before and after the reinforced section. From the results it was evident that the support provided bythe bonded tubular members had effectively limited convergence to only about one-tenth of that observed in the unreinforced portions of the roadway.
  • Example 3 Tubular reinforcing members of the type illustrated in FIG. 4 and described in Example 2 were installed into the overlying strata above a coal face to provide support prior to extraction of the coal.
  • the use of wood dowels alone had proved to be insufficient to restrain movement of the overlying strata and the wood dowels were observed to fail in shear.
  • Angled holes 43 mm. in diameter were, therefore, drilled through the coal face up into the overlying shale to a total depth of 3.5 m.
  • the tubular members were then installed with resin cartridges positioned in the inner end of these holes, adequate resin being used to fill the annular space between the tubular member and the hole.
  • the tubular members were 1.7 m.
  • a method of consolidating friable rock strata characterized in that a tubular reinforcing member having preformed enlarged end portions is secured with a bonding material in an oversized borehole drilled in the friable rock strata with one enlarged end portion of said tubular member being positioned adjacent the inner end of said borehole and the other enlarged end portion being retained in a position adjacent the mouth of said borehole by means of a bearing plate, the diameter of the borehole being such that there is an annular clearance between the wall of the borehole and the body portion of the reinforcing member of at least 2 2.
  • tubular reinforcing member is formed from a metal or alloy.
  • tubular reinforcing member is formed from steel.
  • tubular reinforcing member is provided with a solid indicator rod extending lengthwise thereof, the rod being secured to the inner enlarged end portion of said tubular member and projecting from the other end portion of said member so as to be capable ofindicating any longitudinal extension of the tubular member when in use.
  • tubular reinforcing member is secured in the borehole by means of a bonding material consisting of a polyesterbased resin composition.

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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)
  • Excavating Of Shafts Or Tunnels (AREA)
  • Piles And Underground Anchors (AREA)
US00229844A 1971-03-01 1972-02-28 Consolidation of rock strata Expired - Lifetime US3797254A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB572971*[A GB1329905A (en) 1970-12-16 1971-03-01 Screening machine

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US3797254A true US3797254A (en) 1974-03-19

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US (1) US3797254A (es)
CA (1) CA944966A (es)
DE (1) DE2209821A1 (es)
ES (1) ES400968A1 (es)
FR (1) FR2170357A5 (es)
GB (1) GB1337015A (es)
IT (1) IT952068B (es)
ZA (1) ZA721168B (es)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4114384A (en) * 1975-11-05 1978-09-19 Imperial Chemical Industries Limited Method of securing fixing elements in rock
US4289426A (en) * 1979-09-14 1981-09-15 Ingersoll-Rand Company Friction rock stabilizer and method of forming same, and a method of stabilizing an earth structure
US4378180A (en) * 1980-11-05 1983-03-29 Scott James J Yieldable mine roof support fixture
US4444529A (en) * 1981-04-22 1984-04-24 Neste Oy Bolt-like fixing assembly for reinforcing rock structure
US5112160A (en) * 1988-07-26 1992-05-12 Delkor Technik Limited Rock anchor
US5387060A (en) * 1993-03-26 1995-02-07 F. M. Locotos Equipment & Design Co. Tubular mining bolt
US6033153A (en) * 1994-08-30 2000-03-07 Industrial Rollformers Pty. Limited Rock bolt and method of installing a rock bolt
US6447228B1 (en) 1998-05-22 2002-09-10 Industrial Roll Formers Pty Ltd. Rock bolt and method of forming a rock bolt
US7037058B2 (en) 2001-03-21 2006-05-02 Industrial Roll Formers Pty. Ltd. Resin embedded rock bolt
US20130156510A1 (en) * 2011-12-14 2013-06-20 Johann Steyn Rock bolt
US20140119839A1 (en) * 2011-06-30 2014-05-01 Hakan Krekula Expandable mine bolt
US10370968B2 (en) * 2015-11-30 2019-08-06 Sandvik Intellectual Property Ab Friction bolt
CN116104549A (zh) * 2022-11-11 2023-05-12 国能神东煤炭集团有限责任公司 防护装置

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11759293B2 (en) * 2009-08-26 2023-09-19 Joaquin T. Ariza Orthodontic system and method of use

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1696861A (en) * 1927-03-21 1928-12-25 Locke Insulator Corp Insulator-supporting pin
US2492164A (en) * 1946-07-25 1949-12-27 Carlton G Lutts Elastic proving bar
US2682152A (en) * 1950-04-15 1954-06-29 Bierer Joseph Method of and apparatus for reinforcing and supporting mine roofs and the like
US2879686A (en) * 1952-10-31 1959-03-31 Ohio Brass Co Anchor bolt having test rod to indicate tension changes
DE1178815B (de) * 1961-02-28 1964-10-01 Erich Fritz Dipl Ing Ankerausbau fuer Untertageraeume
US3430449A (en) * 1965-11-27 1969-03-04 Rudolf Novotny Anchor bolts and method for fixing same in drill holes especially in friable rock

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1696861A (en) * 1927-03-21 1928-12-25 Locke Insulator Corp Insulator-supporting pin
US2492164A (en) * 1946-07-25 1949-12-27 Carlton G Lutts Elastic proving bar
US2682152A (en) * 1950-04-15 1954-06-29 Bierer Joseph Method of and apparatus for reinforcing and supporting mine roofs and the like
US2879686A (en) * 1952-10-31 1959-03-31 Ohio Brass Co Anchor bolt having test rod to indicate tension changes
DE1178815B (de) * 1961-02-28 1964-10-01 Erich Fritz Dipl Ing Ankerausbau fuer Untertageraeume
US3430449A (en) * 1965-11-27 1969-03-04 Rudolf Novotny Anchor bolts and method for fixing same in drill holes especially in friable rock

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4114384A (en) * 1975-11-05 1978-09-19 Imperial Chemical Industries Limited Method of securing fixing elements in rock
US4289426A (en) * 1979-09-14 1981-09-15 Ingersoll-Rand Company Friction rock stabilizer and method of forming same, and a method of stabilizing an earth structure
US4378180A (en) * 1980-11-05 1983-03-29 Scott James J Yieldable mine roof support fixture
US4444529A (en) * 1981-04-22 1984-04-24 Neste Oy Bolt-like fixing assembly for reinforcing rock structure
US5112160A (en) * 1988-07-26 1992-05-12 Delkor Technik Limited Rock anchor
US5387060A (en) * 1993-03-26 1995-02-07 F. M. Locotos Equipment & Design Co. Tubular mining bolt
US6033153A (en) * 1994-08-30 2000-03-07 Industrial Rollformers Pty. Limited Rock bolt and method of installing a rock bolt
US6447228B1 (en) 1998-05-22 2002-09-10 Industrial Roll Formers Pty Ltd. Rock bolt and method of forming a rock bolt
US7037058B2 (en) 2001-03-21 2006-05-02 Industrial Roll Formers Pty. Ltd. Resin embedded rock bolt
US20140119839A1 (en) * 2011-06-30 2014-05-01 Hakan Krekula Expandable mine bolt
US9051831B2 (en) * 2011-06-30 2015-06-09 Hakan Krekula Expandable mine bolt
US20130156510A1 (en) * 2011-12-14 2013-06-20 Johann Steyn Rock bolt
US8876436B2 (en) * 2011-12-14 2014-11-04 Rsc Mining (Pty) Ltd. Rock bolt
US10370968B2 (en) * 2015-11-30 2019-08-06 Sandvik Intellectual Property Ab Friction bolt
US20190316467A1 (en) * 2015-11-30 2019-10-17 Sandvik Intellectual Property Ab Friction bolt
US10837280B2 (en) * 2015-11-30 2020-11-17 Sandvik Intellectual Property Ab Friction bolt
CN116104549A (zh) * 2022-11-11 2023-05-12 国能神东煤炭集团有限责任公司 防护装置

Also Published As

Publication number Publication date
FR2170357A5 (es) 1973-09-14
IT952068B (it) 1973-07-20
ES400968A1 (es) 1975-02-01
CA944966A (en) 1974-04-09
GB1337015A (en) 1973-11-14
DE2209821A1 (de) 1972-09-21
ZA721168B (en) 1972-11-29

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