METHOD AND SYSTEM FOR STABILISING EARTHEN FORMATIONS FIELD OF INVENTION

[0001] The present invention relates generally to the stabilisation of earthen formations, such as the roof or side walls of an underground mine or above ground rock cut.

[0002] In one form the invention relates to the anchoring of rock bolts in earthen formations.

[0003] In particular, the present invention relates to a rock bolt that reduces known difficulties associated with such devices. Further, the present invention provides a method that reduces known difficulties associated with inserting filling material into rock bolts and installation of such filled devices.

[0004] It will be convenient to describe the present invention in relation to man-made underground structures such as tunnels, however it should be appreciated that the present invention is not so limited and can be used to stabilise both above ground and underground earthen structures, whether man-made or naturally occurring. Furthermore, while it will also be convenient to describe the present invention with reference to the mining industry, it should be appreciated that the present invention is not limited to mining applications and can be used by other industries such as civil engineering and geotechnical engineering.

BACKGROUND ART

[0005] The discussion throughout this specification comes about due to the realisation of the inventor and/or the identification of certain related art problems by the inventor and, moreover, any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material forms a part of the prior art base or the common general knowledge in the relevant art in Australia or elsewhere on or before the priority date of the disclosure and claims herein. [0006] It is to be appreciated that any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the present invention. Further, the discussion throughout this specification comes about due to the realisation of the inventor and/or the identification of certain related art problems by the inventor. Moreover, any discussion of material such as documents, devices, acts or knowledge in this specification is included to explain the context of the invention in terms of the inventor's knowledge and experience and, accordingly, any such discussion should not be taken as an admission that any of the material forms part of the prior art base or the common general knowledge in the relevant art in Australia, or elsewhere, on or before the priority date of the disclosure and claims herein.

[0007] Rockbolts and dowels have been used for many years to support earthen formations for mining and civil engineering.

[0008] Rock bolts' are elongate stabilisers for location in drill holes to stabilise earth, rock or other structures including excavations and may alternately be known by names such as /rock stabiliser', 'roof-bolt', friction stabiliser or split-set bolt. Rock bolts transfer load from the unstable exterior of an earthen formation, to the confined and much stronger interior of the rock mass.

[0009] Rock bolts generally consist of steel rods or tubes with a mechanical or chemical anchor at one end and a face plate and nut at the other end. Well known 'split set' rock bolts have an elongate tube that is generally of circular or C-shaped cross- section and having a longitudinal channel or groove along the entire length of the tube. The tube edges that define the groove are typically separated by a gap of approximately 20mm. Split set rock bolts are usually installed into a hole drilled into an earthen formation using an impact tool.

[0010] The diameter of the drill hole is slightly less than the outer diameter of the elongate tube, so that during installation, the elongate tube is subject to radial compressive force. The compressive force causes the channel or groove t.o at least partly close, reducing the diameter of the tube to fit the diameter of the hole. This ensures that there is at least some frictional engagement between the elongate tube and the earthen formation. [0011] Strength is relatively simple to achieve but friction is more difficult, especially for 'split sets'. Rock bolts of the prior art principally rely on mechanical coupling devices, grout, and the spring effect of the C section split set described above and resistance to deformation of a steel section.

[0012] Another type of rock bolt is the 'Swellex' dowel which consists of a tube which is folded in on itself. No pushing force is required during insertion into a drill hole and the dowel is activated by injection of high pressure water (approximately 30 MPa or 4,300 psi) which inflates the folded tube into intimate contact with the wall of the blast hole.

[0013] Rock bolts essentially rely on two physical parameters to provide load support, namely:

1. strength - particularly tensile strength and so some degree, shear strength, and

2. friction between the rock bolt body and the rock.

[0014] Strength is relatively simple to achieve but friction is more difficult. Rock bolts of the prior art principally rely on mechanical coupling devices, grout, and the spring effect and resistance to deformation of a steel section.

[0015] Some commercially available rock bolts are manufactured in a range of diameters, each diameter having a different recommended load carrying capacity. When they are inserted into drill holes, they are distorted to the shape of the drill hole/drill hole wall by application of pushing force or by application of water under high pressure. In order to achieve suitable distortion under pressure, yet maintain high tensile strength it is necessary to use thin walled tubes of expensive steel.

[0016] For example, split set rock bolts used in underground mines are typically about 2.4 meters long, and have an uncompressed diameter of approximately 46mm. This diameter of rock bolt would typically be installed in a drill hole having a nominal diameter of 43.5mm. However the actual diameter of the hole will vary along its length between approximately 43 and 46 mm. In particular, the diameter of the drill hole can vary markedly where the drill hole passes through unstable areas, or soft rock that crumbles, or areas where rocks dislodge from the side of the drilled hole.

[0017] Hence if a 46mm rock bolt is installed into an approximately symmetrical drill hole the width of the channel or groove in the tube will vary with the diameter of the drill hole, conforming to variations in the drill hole diameter. The elongate tube of the rock bolt will be squeezed by the earthen wall of the hole where the diameter is less than 46mm giving good frictional engagement; A rock bolt having a tube of 46mm diameter can be loaded with approximately 4 tonnes per metre of embedment. However, the rock bolt tube will have less frictional contact and lower load capacity in regions where the diameter of the drill hole is greater than 45 mm.

[0018] US reissue patent Re 30,256 (Scott) discloses a rock bolt consisting of a tube of generally 'C shaped cross section, having a slot defined by edges which are separate prior to installation. During the installation process, in those parts of a hole which are narrower than the nominal diameter of the rock bolt, the edges are forced together. If portions of the hole are very narrow, the edges will abut and thus restrict any further radial compression of the rock bolt. This would make installation of the rock bolt very difficult or in some cases impossible. Furthermore the edges and the inner and outer surfaces of the tube are often exposed to water from underground seepage and over time the rock bolt will tend to rust and fail.

[0019] US patent 4,012,913 (Scott) discloses a rock bolt having offset edges which are separated prior to installation. During the installation process, in the narrower parts of the hole, the edges are moved past each other so they overlap. However, this allows further radial compression of the tube after installation, reducing the external surface area of the rock bolt that is subjected to frictional force from surrounding rock. This creates an unsafe situation because the rock bolt can be dislodged, particularly if it is installed in a tunnel roof and sufficient load is applied.

[0020] Just as the rock bolt compresses and expands as is it is inserted into the hole, it can also expand and compress as it is forced out of a hole under the load of the tunnel roof. The effective bond strength due to friction between surrounding material and stabilisers of this type is relatively low. [0021] A further problem with rock bolts of this type occurs when the rock bolt is installed in a hole and the edges are moved past each other. Proximate one edge, there is always a gap (referred to as the tangential gap) which is formed between the rock bolt wall and the wall of the drill hole. There is no frictional engagement along the portion of the rock bolt proximate the gap and it reduces the overall frictional force on the rock bolt.

[0022] Grouting: For short term applications, rock bolts are generally left ungrouted. However for more permanent applications, high load areas, or in rock in which corrosive groundwater is present, the space between the bolt and the surrounding earth can be filled with cement or resin grout. Grouting also provides improved embedding of the rock bolt and increased load carrying capacity. Grouting changes a rock bolt from a ductile object into a stiff object and locks it in place creating a higher friction than is normally achieved. Shear strength is also increased however, grout shrinkage can reduce the stiffness of the rock bolt. The grout is typically a coarse cement or resin composition that can flow along the drill hole and into narrow cavities to fill them. The grout subsequently sets to form a solid that consolidates with the adjoining earth to form a solid mass.

[0023] Introducing grout to a drill hole can increase the load carrying capacity of the rock bolt to approximately 12 to 16 tonnes per meter of embedment. Once it is set the grout substantially reduces the risk of radial deformation of the elongate tube of the rock bolt that may be caused by movement of surrounding rock. Furthermore, any forces that would otherwise push the rock bolt out of the drill hole will be resisted because the larger diameter portions of the rock bolt tube will not pass through narrower portions of the hole.

[0024] However, there are problems associated with the grouting of rock bolts. It can be difficult to pump grout into a drill hole such that the grout travels the entire length of the rock bolt tube. Often air is trapped inside the drill hole and cannot be vented to make way for the flow of grout. Also, rock bolts are often inserted into the vertical drill holes in mine roofs. If grout of low viscosity or slow setting time is used it can tend to fall out of the drill hole under the action of gravity.

[0025] The confined area of a mine tunnel also presents difficult working conditions that make it necessary to install rock bolts in two steps. In the first step the holes are drilled and the rock bolts inserted. Then, due to the limited working space the drilling crew retire and remove their drilling equipment to make way for the large size pumping equipment. In the second step the pumping crew bring their pumping equipment into the tunnel to pump grout into the drill holes.

[0026] The two-step approach to installing and grouting rock bolts has the disadvantage of causing delays as the two separate crews bring in and remove equipment. There is also a requirement for separate drilling and grouting crews. The two-step process is considered costly, cumbersome and time consuming

[0027] In an alternate method, the grout is retained in cartridges that are loaded into the tube of the rock bolt. The cartridges are shaped to substantially conform to the internal dimensions of the tube and can be loaded before or after the rock bolt is installed in the drill hole. The cartridge is at least partly manufactured of fluid permeable material and the grout is activated by exposing the cartridge to an activating fluid such as, water.

SUMMARY OF INVENTION

[0028] An object of the present invention is to improve the speed and efficiency with which a rock bolt may be located and secured in a drill hole.

[0029] A further object of the present invention is to improve the retention and load capacity of a rock bolt in a drill hole.

[0030] A further object of the present invention is to alleviate at least one disadvantage associated with the related art.

[0031] It is an object of the embodiments described herein to overcome or alleviate at least one of the above noted drawbacks of related art systems or to at least provide a useful alternative to related art systems. [0032] In a first aspect, the present invention provides a method of installing a rock bolt, the method including the steps of: a. drilling a hole in the region to be stabilised, b. locating the rock bolt in the drill hole, c. introducing an expanding filler to the drill hole, and d. initiating expansion of the expanding filler.

[0033] Typically the drill hole has a diameter that is less than the diameter of the rock bolt to be installed.

[0034] Other aspects and preferred aspects are disclosed in the specification and/or defined in the appended claims, forming a part of the description of the invention.

[0035] Throughout this specification the term 'expanding filler' is intended to refer to a substance that can be introduced to a drill hole in a fluid form and subsequently expands and transitions to a solid form. It may. include fillers, but typically has little or no adhesive capability. This is in contradistinction to 'grout' which does not expand as it transitions to a solid form. The expanding filler is usually inserted into a drill hole in a fluid form having been activated and requires a period of time to 'set' or 'cure' thereby transitioning to a solid form.

[0036] Where used herein the term 'rock bolt' is intended to refer to any elongate stabiliser for location in drill holes to stabilise earth, rock or other structures including excavations and may alternately be known by names such as 'rock stabiliser', 'roof-bolt', friction stabiliser or split-set bolt. The excavations may include, for example, mining tunnels, open cut mining sites, transport tunnels forming part of a road or rail system, cuttings or cliffs.

[0037] In a preferred embodiment the rock bolt used in the present invention is a 'split set'. In a particularly preferred embodiment the rock bolt used in the present invention is of a type disclosed in International patent application PCT/AU02/01046 (WO 03/014517). This application relates to a stabiliser having a hollow elongate body portion including an opening extending substantially the entire length of the body portion and a closure member aligned to substantially cover the opening of the body portion, the closure member being configured to extend substantially parallel to an inner wall of the body portion in the vicinity of the opening.

[0038] The expansion of the filler exerts force on the inside of the split set, potentially causing radial expansion and other deformation of the rock bolt. It may also be advantageous to have small amounts of expanding filler exude from the interior of the rock bolt into any void space between the rock bolt and drill hole wall.

[0039] Accordingly, in another particularly preferred embodiment the rock bolt use in the present invention is of a type disclosed in Australian provisional application 2013902801 which includes apertures located periodically along at least part of its length.

[0040] In a second aspect of embodiments described herein there is provided a method of stabilising an earthen feature, the method including the steps of: a. drilling a hole in the region to be stabilised, b. locating a rock bolt in the drill hole, c. introducing a fluid expanding filler to the drill hole, and d. initiating expansion and solidification of the expanding filler.

[0041] The fluid expanding filler may be introduced to the drill hole by any convenient means including pumping or insertion of cartridges.

[0042] The fluid expanding filler may be introduced to the drill hole before, after, or simultaneously with location of the rock bolt in the drill hole. In a particularly preferred embodiment the expanding filler is contained within packages, typically cylindrically shaped packages that are initiated and inserted into the rock bolt prior to its location in a drill hole.

[0043] In a third aspect, the present invention provides a system for stabilising an earthen formation, the system comprising: a. a rock bolt for insertion in a drill hole in a formation to be stabilised, and b. an expanding filler that expands after introduction to the drill hole.

[0044] Suitable expanding substances are known in the field, of quarrying as non- explosive demolition agents. They are typically supplied as dry powders and mixed on- site with water to form a fluid in the form of a slurry or suspension. The slurry is pumped into drill holes or fissures in rock or concrete where they expand and split the substrate. The broken rock or concrete can then be easily removed with a pick breaker, pneumatic breaker, excavator or the like.

[0045] In essence, embodiments of the present invention stem from the realisation that expansive properties of certain fluids can be utilised to consolidate an earthen feature instead of fracturing rock. Furthermore, there is the realisation that the expansive properties of these fluids can be used to anchor rock bolts, by increasing friction between the rock bolt and rock, and increase tensile strength. This concomitantly increases the load that can be supported by the rock bolt.

[0046] Suitable commercial expanding fillers include EXPANDO™ from SinoSource Enterprise Co., Ltd, CRACKAMITE™ from Hydraulics & Pneumatics Pty Ltd, BUSTAR™ from Demolition Technologies Incorporated and DEXPAN™ from Archer USA.

[0047] In a fourth aspect, the present invention provides an expanding filler when used in combination with a rock bolt for stabilising an earthen formation, the expanding filler including water and a dry component, the dry component comprising:

• calcium oxide >60 wt%, preferably 80-90 wt%; • ferric oxide 1-5 wt%, preferably 2-3 wt%;

• silicon dioxide 5-10 wt%, preferably 5-6 wt%; and

• aluminium oxide 1-5 wt%, preferably 1-2 wt%.

[0048] When the dry component is mixed with water, the expansion of the filler typically increases in proportional to the time elapsed from mixing. Maximum expansive stress is typically reached at about 12 to 24 hours but can continue to increase for several days depending on temperature, humidity and other conditions. The expansive pressure at a consistent volume preferably exceeds 7,000 Tim ² , more preferably 11 ,200 T/m ² (122 MPa).

[0049] Typically the dry component is combined with water in a ratio of 80:20 to 65:35. The amount of water added will depend on the amount of expansion required. The diameter of the drill hole or rock bolt tube and temperature will also affect. the amount of expansion obtained. If the fluid expanding filler is to be pumped into a drill hole and/or rock bolt it should have sufficient water to make it readily pumpable without being too fluid. Alternatively, if the expanding filler is introduced to the drill hole or rock bolt in one or more cartridges or 'sausages' it will be in dry form. The cartridge can be doused in water prior to insertion, or subjected to water once it is in place in the drill hole or rock bolt.

[0050] Other aspects and preferred forms are disclosed in the specification and/or defined in the appended claims, forming a part of the description of the invention.

[0051] Advantages provided by the present invention comprise the following:

• increased friction between a rock bolt and surrounding rock thus increasing the load capacity of the rock bolt;

• the solid expanded filler has a strong mechanical and/or chemical interaction with the rock bolt and resists forces that would push the rock bolt out of the drill hole; • expanding filler can be introduced to drill holes without the use of external high-pressure pumping devices (as per grout), thus simplifying the process and reducing costs;

• the ratio of the diameter of the rock bolt to the diameter of the drill hole is less critical than when grout is used;

• any coating on the rock bolt is less likely to be damaged because there is less reliance on close conformance between the rock bolt and drill hole diameters; and

• the size of any gap in the rock bolt tube can be minimised allowing more steel to be used for the tube, increasing the friction, tensile strength and shear strength as compared with rock bolts of the prior art.

[0052] Further scope of applicability of embodiments of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure herein will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Further disclosure, objects, advantages and aspects of preferred and other embodiments of the present application may be better understood by those skilled in the relevant art by reference to the following description of embodiments taken in conjunction with the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the disclosure herein, and in which:

• Figure 1 is a drawing depicting the components of a typical rock bolt.

• Figures 2(a), 2(b), 2(c) and 2(d) are cross sectional illustrations of examples of the tubes used in rock bolts of the prior art; 1.2

• Figures 3(a) and 3(b) are cross sectional illustrations of tube used in rock bolts in combination with the use of expanding filler according to the present invention.

• Figure 4 is a perspective view of one embodiment of a rock bolt suitable for use in the present invention; and

• Figure 5 is a perspective view of another embodiment of a rock bolt^suitable for use in the present invention.

DETAILED DESCRIPTION

[0054] Figure 1 is a drawing depicting the components of a typical rock bolt (1). A variety of types of rock bolts are commercially available but the basic principle of operation is the same in all. As shown in Figure 1 the typical components are a tapered cone (9) with an internal thread and a pair of wedges held in place by a bail (13). The cone (9) is screwed onto the threaded end of the elongated body (12) of the rock bolt and the entire assembly is inserted in to a drill hole. The length of the drill hole is usually at least 100mm longer than the bolt otherwise the bail (13) will be dislodged by being forced against the end of the drill hole. Once the assembly is in place a sharp pull on the end of the bolt will seat the rock bolt. Tightening the bolt forces the cone further into the wedge, thereby increasing the anchoring force.

[0055] These rock bolts work well in hard rock but are not very effective in closely jointed rock and soft rock because rock in contact with the wedge grips tends to fail. Grout or resin cartridges (also known as 'sausages') are often inserted to alleviate this problem. .

[0056] At the end of the rock bolt projecting from the drill hole there is a fixed head or threaded end and nut (2). A faceplate (1) distributes the load form the bolt onto the rock face. In addition a tapered washer or conical seat (4) compensates for the fact that the rock face is typically at right angles to the bolt. Tensioning of rock bolts is important to ensure that all the components are in contact and that a positive force is applied to the rock. [0057] Traditionally, grouting is carried out by using a short grout tube (5) to feed the grout into the drill hole. A smaller diameter breather tube (3) to bleed air is taped (7) to the rock bolt and extends to the end of the hole.

[0058] As illustrated by Figure 1 , rock bolts typically have an elongate body (12), comprising a rod or tube. Figures 2(a), 2(b) and 2(c) illustrate in cross-section typical tube conformations of rock bolts of the prior art which can be used with the expanding filler of the present invention. For example, Figure 2(a) illustrates a rock bolt tube having a slot defined by edges (15 and 16) which are uncompressed prior to installation (Figure 2(a)(0). The gap between the edges (15 and 16) is typically about 20 mm.

[0059] During installation, in those parts of the drill hole which are narrower than the nominal diameter of the tube, the edges (15 and 16) are forced together in the direction of arrow (17) (Figure 2(a)(ii)) due to localised compression. In portions of the drill hole that are very narrow the edges (15 and 16) will abut and restrict any further radial compression of the tube, In portions of the drill hole that are comparatively wider, or comprised of softer rock, expansion of the expanding filler will cause localised expansion of the tube, forcing apart the edges (15 and 16) of the tube.

[0060] Accordingly, some parts of the tube will be compressed by the wall of the drill hole while others parts of the tube have been forced to expand until the contact the wall of the drill hole and possibly expand into weaker rock such as that with high clay contents. The greater the amount of metal in contact with the rock wall of the drill hole, the better the frictional engagement with the rock. The tube may thus be very distorted but this contributes to keeping the rock bolt in place.

[0061] Figure 2(b) illustrates a rock bolt tube having offset edges (18 and 19) which are separated prior to installation (Figure 2(b)(i)). During the installation process, in the narrow parts of the hole, the edges (18 and 19) will be moved past each other in the direction of the arrow (10). Further radial compression after installation can result in decreasing the area of contact between the tube and surrounding rock, thus reducing the frictional force acting upon the rock bolt. Furthermore, a gap (10a) can form between the tube wall (19) and the drill hole wall, further reducing the area of contact. However, once the expanding filler of the present invention is pumped into the tube and expanded, the parts of the tube wall (19) in the vicinity of the gap (10a) are expand radially outward until they contact the drill hole wall. This distorts the tube, and concomitantly increases the area of contact and the amount of frictional engagement with the rock.

[0062] Figure 2(c) illustrates a tube of a rock bolt, having a V-shaped portion along its entire length (Figure 2(c)(0). During installation of the rock bolt in a drill hole, the parts of the drill hole which are narrower than the nominal diameter of the tube will force together the edges (22 and 23) (Figure 2(c)(ii)). If portions of the drill hole are very narrow, the edges (22 and 23) will abut and thus prevent any further circumferential deformation of the tube.

[0063] Once the expanding filler of the present invention is pumped into the tube and expanded, the parts of the tube wall ^" (19) that are not abutting the wall of the drill hole will be force to expand radially outward until they contact the drill hole wall. Thus, along the length of the tube some portions have been compressed at the time of installation while other portions have been expanded post-installation. Thus, the proportion of the tube wall that is in contact with the wall of the drill hole is maximised.

[0064] Figure 2(d) illustrates a further conformation of the tube of a rock bolt (25). In this conformation the tube (26) is generally of cylindrical shape, with a step (31) and a closure in the form of a portion (30) that overlaps an edge of the tube (26). The overlapping portion serves to guide the first stop (29) and second stop (28) to abut each other if the tube (26) is strongly radially compressed. Expansion of the expanding filler post-installation may reduce the amount of overlap at the edge of the tube (26) and cause portions of the tube (26) to expand radially outwards until they contact the wall of the drill hole. The tube (26) may be significantly distorted along its length by the expansion and contraction to fit the variable cross sectional shape of the drill hole.

[0065] Figure 2(e) illustrates a further embodiment of the tube (26) of a rock bolt (25) which is similar to the tube depicted in Figure 2(e), but having a smaller step (31) and a gap extending the length of the tube (26). Again, in portions of the drill- hole that are comparatively wider, or comprised of softer rock, expansion of the expanding filler will cause localised expansion of the tube, increasing the gap. Accordingly, some parts of the tube will be compressed by the wall of the drill hole and the gap will be small while others parts of the tube will have been forced to expand and the gap will be comparatively larger.

[0066] Figure 2(f) illustrates a further embodiment of a tube (25) of a rock bolt including a sleeve (32) having a locating protuberance (33) positioned to reside within the slot defined by the edges (34 and 35) of the tube (25). The sleeve (32) substantially reduces and ideally prevents grout escaping from the rock bolt during installation of the rock bolt in a drill hole and while the grout is setting within the stabiliser. With reference to the present invention, expanding filler can be pumped into the tube (25) and as it expands the edges (34 and 35) move apart, sliding along the sleeve (32). Thus, in portions of the drill hole that are comparatively wide, or comprised of soft rock, there is localised expansion of the overall tube diameter. Other parts of the tube will remain compressed by the wall of the drill hole. The tube may thus be distorted and of varied diameter along its length but this contributes to keeping the metal tube adjacent the wall of the drill hole and retains the rock bolt in place.

[0067] Figure 3 is a further illustration of how introduction of an expanding filler to the, tube of a rock bolt forces regional radial expansion of the tube, thus increasing the friction between the tube and the rock. The expansive force is so large that it can deform the rock bolt to at least partly conform to the shape of any crack, fissure or void in the rock. In regions of earth having low strength such as clay or soil, the expanding filler may flow out of the tube and deform the strata in the vicinity of the rock bolt.

[0068] Figure 3(a)(i) illustrates a 45mm diameter rock bolt comprising a tube (55) of C-shaped cross section, the gap being defined by two edges (56 and 57). When the tube (55) is filled with expanding filler as shown in Figure 3(a)(ii) the gap approximately doubles in size, forcing the tube (55) hard against the drill hole wall an the expanding filler being directly in contact with rock in the vicinity of the gap. Thus, the ratio of the diameter of the rock bolt to the diameter of the drill hole is less critical than when grout is used. Furthermore, if the rock bolt includes a coating, such as a galvanised coat or polymer, the coating is less likely to be damaged because there is less reliance on the rock bolt and drill hole diameters being similar. Furthermore, the size of the gap in the tube can be minimised because it relies less on compression by the rock and more on expansion by the expanding filler. Decreasing the size of the gap allows more steel to be used for the tube, increasing the friction, tensile strength and shear strength as compared with rock bolts of the prior art.

[0069] Figure 3(b)(i) illustrates a further conformation of rock bolt (60) including a closure member (66) positioned to substantially cover the slot defined by the edges (62 and 64) extending substantially the entire length of the hollow elongate body portion (25). As shown in Figure 3(b)(ii) the closure member (66) substantially reduces escape of expanding filler from the rock bolt and presses the closure member (66) against the edges of the tubular body portion (25).

[0070] The expanding filler may be introduced to the drill hole and rock bolt by any convenient means used for introducing grout. For example the expanding filler may be pumped or injected into the rock bolt when it is in position in the drill hole, for example as is presently done with grout, or pre-loaded into the rock bolt hole or inserted into the hole with the rock bolt, for example by inserting expanding filler in cartridge(s) or sausages into the hole prior to or with the rock bolt. One of the advantages of using expanding filler is that the process does not require external high-pressure pumping devices, simplifying the process and reducing costs as compared with the use of grout.

[0071] Figure 4 illustrates, in perspective view, a section of a rock bolt for use according to the present invention for earth stabilisation, comprising a hollow elongate body portion 65 having an opening extending parallel to its longitudinal axis. The elongate closure member 78 is aligned to substantially cover the opening and extending adjacent an inner wall of the body portion, parallel with the edges 74, 75 of the gap of the body portion 65. The closure member 78 has apertures 80 located periodically along its length.

[0072] Figure 5 illustrates, in perspective view, a section of another embodiment of a rock bolt for use according to the present invention. In this embodiment bosses 73 and apertures 80 located periodically along the entire length of the closure member 78.

[0073] The rock bolts as depicted in Figures 4 and 5 are typically filled with bulk or packaged expanding filler. For example, the bulk expanding filler is typically pumped into the rock bolt where it expands. Packaged expanding filler is typically contained within elongate cartridges that are of elongate shaped so that they can be pushed along the interior of the rock bolt.

[0074] The cartridge packaging may be porous to water, and is contacted with water (either before or after it is located in the rock bolt) to initiate expansion of the filler in the cartridge. Alternatively the cartridges may contain a first chemical component and a second chemical component which react together to initiation expansion. The cartridges typically need to be ruptured to bring the first and second chemical components into contact and mix them to initiate expansion.

[0075] When the closure member 78 of the rock bolt includes apertures 80 such as those depicted in Figures 4 and 5, bulk expanding filler can flow out of the apertures 80 as it is being pumped into the rock bolt. Packaged expanding filler can flow out of the apertures 80 after the filler expands and ruptures the cartridges.

[0076] While this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification(s). This application is intended to cover any variations uses or adaptations of the invention following in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth.

[0077] As the present invention may be embodied in several forms without departing from the spirit of the essential characteristics of the invention, it should be understood that the above described embodiments are not to limit the present invention unless otherwise specified, but rather should be construed broadly within the spirit and scope of the invention as defined in the appended claims. The described embodiments are to be considered in all respects as illustrative only and not restrictive.

[0078] Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and appended claims. Therefore, the specific embodiments are to be understood to be illustrative of the many ways in which the principles of the present invention may be practiced. In the following claims, means-plus-function clauses are intended to cover structures as performing the defined function and not only structural equivalents, but also equivalent structures.

[0079] "Comprises/comprising" and "includes/including" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. Thus, unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', 'comprising', 'includes', 'including' and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".