NZ721749B2 - Improved o-ring drill hole plug - Google Patents

Abstract

plug (10) for blocking off mining exploration drill holes. The plug (10) comprises an elongate body (12) of solid impervious material, and an engineered surface (14) is provided on an external circumference of the elongate body (12). The engineered surface (14) comprises an annular anchoring groove (16) having a ramp (18) extending from a maximum diameter to a minimum diameter of the engineered surface (14) in a braking direction, in which it is intended to prevent movement of the plug (10) in the drill hole. The plug (10) also comprises an O-ring (20) received in the anchoring groove (16) and having a thickness whereby it protrudes slightly above the maximum diameter of the engineered surface (14) and engages with a wall (22) of the drill hole. In use, when the plug (10) is moved in the braking direction in the drill hole, the O-ring (20) rolls up the ramp (18) and wedges between the engineered surface (14) and the wall (22) of the drill hole to provide a braking action for the plug (10) against the wall (22) of the drill hole. e (16) having a ramp (18) extending from a maximum diameter to a minimum diameter of the engineered surface (14) in a braking direction, in which it is intended to prevent movement of the plug (10) in the drill hole. The plug (10) also comprises an O-ring (20) received in the anchoring groove (16) and having a thickness whereby it protrudes slightly above the maximum diameter of the engineered surface (14) and engages with a wall (22) of the drill hole. In use, when the plug (10) is moved in the braking direction in the drill hole, the O-ring (20) rolls up the ramp (18) and wedges between the engineered surface (14) and the wall (22) of the drill hole to provide a braking action for the plug (10) against the wall (22) of the drill hole.

Description

IMPROVED O-RING DRILL HOLE PLUG TECHNICAL FIELD The present invention relates to mining and exploration drilling, and more specifically to a drill hole plug for ng off mining exploration drill holes. The ion has particular application for blocking off underground diamond drill exploration holes, however the product may also be applied to e drill holes.

BACKGROUND ART Once underground access is commenced through a portal or shaft for a new mine, diamond drill crews begin drilling from the first available underground location to allow ists to better define the ore body so that the design of the mine can be optimised. Therefore exploration drilling usually occurs in advance of the mine development, and typically the exploration drill holes range from horizontal to downward dipping to delineate the ore body h and to the side of the main access.

When these exploration drill holes are abandoned, they leave an open hole between the main access and the ore body location which will at some stage be advanced upon. In some cases high pressure water may be encountered during mining, and it is therefore ary to block these abandoned drill holes to prevent the high pressure water from entering the mine.

Commonly-owned, co-pending Australian Patent Application No 2011301781 discloses a clay plug for sealing water flow from a drill hole.

The clay plug 40 of AU2011301781 ses an elongate sleeve 42 of porous material containing a volume of clay material 44 which in this instance is bentonite clay (although other clays may also be suitable). The clay plug 40 further includes a liner 46 of water-soluble material, and a substantially solid central core 48 running substantially the length of the plug. The advantage of using bentonite clay as the “grouting” material in this plug is that bentonite clay slowly expands and seals when in contact with water. The contents of AU2011301781 are incorporated herein by reference.

Diamond drill holes are d by rotation only drill rigs, and as a result drill a hole through hard rock which only varies slightly in er with drill bit wear. Due to this small ion in diameter, it is possible to 1O use close tolerances when designing and installing tools or implements into a d drill hole.

The present invention was developed with a view to providing a plug for plugging a drill hole that exploits this close tolerance by using an O-ring to provide a g action t the wall of the diamond drill hole. The plug is prevented from being pushed out of the diamond drill hole by the braking action of the O-ring. Whilst the plug is designed to resist significant water pressure and water flow when installed into a diamond drill hole, it will be understood that the O-ring plug may also have wider application.

References to prior art in this specification are provided for illustrative purposes only and are not to be taken as an admission that such prior art is part of the common general dge in Australia or elsewhere.

SUMMARY OF INVENTION According to one aspect of the present invention there is provided,.a plug for blocking a drill hole in a rock mass, the plug comprising: an elongate body made of solid impervious material; an engineered surface provided on an external circumference'of the elongate body, the engineered surface comprising an annular anchoring groove having a ramp extending from a maximum diameter of the elongate body to a minimum diameter of the engineered surface in a g direction in which it is intended to prevent movement of the plug in the drill hole in the rock mass when the plug is ed in the drill hole; and, an O-ring received in the anchoring groove of the engineered surface and having a thickness whereby the O-ring protrudes above the maximum diameter of the elongate body and engages with a wall of the drill hole wherein, in use with the plug inserted in the drill hole in the rock mass, when the plug is moved in the braking direction in the drill hole the O-ring rolls up the ramp and wedges n the engineered surface and the wall of the drill hole to provide a braking action for the plug against the wall of the drill hole; wherein the anchoring groove is one of a plurality of anchoring grooves of the engineered surface, and the O—ring is one of a plurality of O—rings received in each of the anchoring grooves respectively in series, and a braking function of the O-rings in the anchoring grooves is separated from the sealing function by providing one or more sealing s in addition to the O-rings in the anchoring grooves, and one or more annular g grooves of rectangular cross-section are provided in the engineered surface that receive the sealing O-rings therein.

In one embodiment the engineered surface is formed integral to the material of the body of the plug. In an ative ment the engineered surface is formed on a hollow collar which is fixed to the external circumference of the elongate body. In the latter ment the elongate body may be a clay plug similar to that described in co-pending AU2011301781. 3O [0010] ably the anchoring groove also has a shoulder located opposite to the ramp, the O-ring abutting the er when the plug is inserted into the drill hole in an installation direction opposite to the braking direction. in one embodiment the shoulder extends in a plane substantially perpendicular to a longitudinal axis of the te body. In an alternative ment the shoulder extends in a plane angled to a longitudinal axis of the elongate body at an angle 9 of n about 25° to 75°. Preferably the anglee is selected so that when the O—ring is seated t the shoulder there is some clearance between the O-ring and the wall of the drill hole wherein, in use, when the plug is moved in the installation direction any friction between the O-ring and the wall of the drill hole is minimized. Preferably the anchoring groove also has a base of substantially constant diameter 1O provided between the shoulder and the ramp, the base containing the O— ring during movement of the plug in the drill hole in the installation direction.

The ramp is preferably angled at substantially 30° to a udinal axis of the plug, but may vary from between 10° to 60°.

[0011]Typically a plurality of annular sealing grooves is provided in front of the anchoring grooves and/or behind the anchoring grooves.

Advantageously a fluid port is provided across each anchoring groove to provide fluid ication and therefore pressure ing across each anchoring O-ring. In one embodiment a plurality of fluid ports extend through the body of the plug, from an outer circumference at each fluid port location to a central port.

In another embodiment a reversed ramped O-ring is received in a groove, which has a reversed ramp extending from a maximum diameter to a minimum diameter of the engineered surface in the installation direction wherein, in use, the plug can also be anchored in the installation ion. ably one or more positioning rods are provided to hold the reversed ramped O—ring during installation, keeping it on a' sufficient angle and clearance distance from the reversed ramp so that it does not interact with the ramp during installation.

In a still further embodiment a second O-ring is received in the anchoring groove and ts the first O-ring in a position at a ing of the ramp as it contacts the wall of the drill hole during installation whereby, in use, the two O-rings engage with each another by frictional contact and rotate together like a geared pair, rotating in te directions, so that as the first O-ring rotates in a direction to roll down the ramp during installation it is held in place at the beginning of the ramp by a spring action of the second O-ring. Typically the first and second O-rings are of substantially the same size.

Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. Likewise the word “preferably” or variations such as “preferred”, will be understood to imply that a stated integer or group of integers is desirable but not ial to the working of the invention.

BRIEF PTION OF THE DRAWINGS

[0016] The nature of the ion will be better understood from the following detailed description of several specific ments of an O-ring plug, given by way of e only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a first embodiment of an O-ring plug according to the present invention prior to assembly of the O-rings; Figure 2 is a perspective view of the O-ring plug of Figure 1 with 0— rings, showing the position of the O-rings during installation; Figure 3 is a perspective view of the O-ring plug of Figure 1 with 0- 3O rings, showing the position of the O-rings after placement of the plug; Figure 4 is a side elevation of the O—ring plug of Figure 1 showing the on of the O-'rings in section view during installation; Figure 5 is a side elevation of the O-ring plug of Figure 1 showing the position of the O-rings in section view after ent of the plug; Figure 6 is a graph showing a comparison of the force ed for installation compared to the sliding ance in the braking direction of an O-ring plug according to the present invention; Figure 7 illustrates an O-ring diameter compared to a drill hole diameter; Figure 8 is a side elevation and an end elevation of part of a second embodiment of an O-ring plug according to the present invention; Figure 9 illustrates the clearance between the O-ring of the O-ring plug of Figure 8 and a wall of the drill hole during installation; Figure 10 is a udinal section view of a third embodiment of an O- ring plug according to the present ion, (O-rings not shown) in which the sealing and anchoring functions are separated; Figure 11 is a longitudinal section view of a fourth embodiment of an O-ring plug according to the present invention, (O-rings not shown) in Which fluid ports are provide to balance the pressure across anchoring O-rings; Figure 12 is a longitudinal section view of a fifth embodiment of an O- ring plug according to the present invention, in which a reversed ramped O-ring is provided; Figure 13 is a side elevation of a sixth embodiment of an O—ring plug according to the present invention, showing the position of a pair of 0- rings in section view during installation; and, Figure 14 is an ed View of the pair of O-rings in Figure 13 g how they rotate like a geared pair during installation.

DESCRIPTION OF EMBODIMENTS [OO17]A first embodiment of an O-ring plug 10 in accordance with the invention for blocking a drill hole, as illustrated in Figures 1 to 5, comprises an elongate body 12 of solid impervious material. An engineered surface 14 is provided on an external circumference of the elongate body 12, the engineered surface comprising an r anchoring groove 16. The anchoring groove 16 has a ramp 18 extending from a maximum diameter D1 to a minimum diameter D2 of the ered surface 14 in a g direction, indicated by arrow ‘A’ in Figure 1. The braking direction is the ion in which it is intended to prevent movement of the plug in the drill hole.

[0018] The plug 10 further comprises an O-ring 20 received in the annular groove 16 of the engineered surface 14. The O-ring 20 has a thickness whereby it protrudes slightly above the maximum diameter D1 of the engineered surface 14, as can be seen in Figures 2 and 4, and engages with a wall 22 of the drill hole. in use, when the plug 10 is moved in the braking ion ‘A’ in the drill hole, the O-ring 20 rolls up the ramp 18 and wedges between the ered surface 14 and the wall 22 of the drill hole to provide a braking action for the plug 10 against the wall 22 of the drill hole. in the rated embodiment the engineered surface 14 is formed integral to the material of the body 12 of the plug 10, which may be machined from steel or a hard plastics material, such as nylon. r in an alternative embodiment the engineered surface may be formed on a hollow collar which is fixed to the external circumference of the elongate body. In the latter arrangement the elongate body may be a clay plug similar to that described in co—pending AU2011301781 or it may be a solid core made of some other material.

Preferably the annular groove 16 also has a shoulder 24 d opposite to the ramp 18, the O—ring 20 ng the shoulder 24 when the plug is inserted into the drill hole in an lation direction, indicated by arrow ‘B’ in Figure 2. The lation direction ‘3’ is opposite to the braking direction ‘A’. Typically the shoulder 24 extends in a direction substantially perpendicular to a longitudinal axis ‘X’ of the elongate body 12, as can be seen most clearly in Figure 4. Preferably the annular groove 16 also has a base 26 of substantially constant diameter provided between the shoulder 24 and the ramp 18. The base 26 contains the O-ring 20 within the groove 16 during movement of the plug 10 in the drill hole in the installation direction ‘B’, as shown in Figures 2 and 4. During nt of the plug 10 in the installation direction ‘B’ there will be a small degree of resistance to movement as the outer circumference of O-ring 20 rubs against the wall 22 of the diamond drill hole. The O-ring 20 itself is prevented from moving from base 26 within the groove 16 by shoulder 24.

However, once the plug 10 is correctly positioned in the drill hole, the direction of movement is reversed to the braking direction ‘A’, as shown in Figures 3 and 5. In this direction of movement of the plug 10, the O-ring 20 is free to move within the groove 16 and will roll from its rest position on the base 26 ‘up’ the ramp 18 as its outer circumference engages with the wall 22 of the drill hole. The more force is applied to the body 12 of the plug 10, the more the O-ring 20 will try to roll further ‘up’ the ramp 18, and therefore the more firmly wedged it will become between the ramp 18 and the wall 22 of the drill hole, as can be seen most clearly in Figure 5. This increases both the on and the force the plug 10 exerts on the drill hole, both of which create the holding y within the drill hole, locking the plug 10 in that position.

[0022] It will be seen that in this ment the O-ring 20 performs two tasks: the primary task is that of a brake, which allows the plug 10 with the ered surface 14 to be installed in one direction, but not to be reversed; a secondary task is to act as a seal, albeit a necessarily imperfect one due to the imperfections in the rock surface of the wall 22 of the diamond drill hole t which it is “sealing”.

In the illustrated embodiment of the plug 10, the annular groove 16 is one of a plurality of annular grooves 16a, 16b and 16c of the engineered surface 14, and the O-ring 20 is one of a plurality of O-rings 20a, 20b and 200 received in each of the annular grooves 16 respectively. Whilst a single O-ring 20 may suffice in some drill holes, the use of multiple O-rings 20 multiplies the braking effect.

In this manner it is possible to uct a plug that will install into a diamond drill hole one way, t significant water pressure and water flow, or air blast pressure from rifling explosives. The device is prevented from being pushed out of the diamond drill hole by the braking action of the O-ring 20, or multiple s, interacting with the wall 22 of the diamond drill hole.

Pushing the plug 10 in the al installation direction ‘B’ again will allow it to once again move freely in the installation direction. The O—ring will roll ‘down’ the ramp 18 to the initial rest position against the square shoulder 24, at which point the plug 10 will then be free to slide further into the drill hole.

The ramp 18 is preferably angled at approximately 30° to the longitudinal axis ‘X’ of the plug 10, but may vary from between 10° to 60° depending on circumstances. The construction of the plug 10 with multiple, identical ramps 18, each within its respective annular groove 16, is relatively simple with conventional lathe equipment or a CNC machine. The plug construction is ted by placement of one O-ring 20 in each of the grooves 16. The plug 10 can then be led into a diamond drill hole.

In use, the O-rings 20 are designed to interfere with the wall 22 of the drill hole slightly during installation, when in the rest position on bases 26, providing (a) frictional drag on the wall 22 of the diamond drill hole, and (b) an imperfect seal. The plug 10 is pushed into the hole with the diamond drill rig feed pressure, with l force. When the feed from the drill rig is retracted, the O—rings 20 will roll in place due to the frictional contact with the wall 22 of the hole, and the plug 10 will be forced slightly back toward the drill rig due to the water re upon the plug. This causes each 0— ring 20 to roll ‘up’ its tive ramp 18, creating both a circumferential force and a frictional resistance on the wall 22 of the diamond drill hole, locking the plug 10 in place and holding fast against the water pressure.

Figure 6 is a graph illustrating the difference in force required during installation of an O-ring plug in a 60mm diameter drill hole, ed to the braking force when the O-ring plug is withdrawn from the drill hole. In Figure 6 fon/vard cement (installation) is shown as positive displacement on the horizontal axis and pressure holding ability (braking resistance) is shown as negative on the horizontal axis.

From Figure 6 it can be see that there is some force required to install the O-ring plug, (shown by the two positive displacement lines), dependant on bit wear. In the reverse direction the force required to withdraw the plug from the drill hole is an order of magnitude higher or more (shown by the negative displacement line). In on to the force required to install the O-ring plug, this method of installation can, over large distances, cause excessive wear to the (s).

[0030] There are circumstances where it is important to be able to install a plug with O-ring plugs more easily, for example, ly rather than with a machine. Therefore it is desirable for the O—ring to form an interference fit in the drill hole once in position, but to be able to minimise interference during installation. Since an O-ring is flexible, this can be achieved geometrically. 3O If the O-ring is pushed, in at an angle greater than 25° or thereabouts, and additionally if the O-ring has clearance to the seat perpendicular to the angle imposed and perpendicular to the direction of the drill hole, it is then le to push in a ly larger O-ring to the final resting position with comparatively little resistance. Once at the resting on, the O-ring may be manipulated back into a perpendicular orientation to perform the anchoring task. Alternatively it may be used at the inclined orientation.

Figures 7 to 9 will be used to describe a second embodiment of an O—ring plug 30 according to the t invention that incorporates this feature. As this embodiment shares many of the same features as the first embodiment of the O—ring plug 10, the same reference numerals will be used to identify the similar parts and will not be described again in detail. As shown in Figure 7, when the O-ring 20 is substantially perpendicular to the longitudinal axis (Z-axis) of the O-ring plug, the outside diameter of the O- ring is slightly larger than the diameter of the drill hole so that it interferes with the drill hole wall 22 in both the X-axis and Y—axis directions. However if the O—ring is angled to the longitudinal axis of the elongate body at an angle 6 of between about 25° to 75°, as shown in Figure 8, then there will some clearance n the O—ring 20 and the drill hole wall 22, at least in the direction of the Y-axis. ln order to achieve this geometry, the annular groove 16 in the engineered surface 14 of the elongate body 12 is formed with a shoulder 34, inclined at an angle 6 to the longitudinal axis of the elongate body, as shown ‘ in Figure 8. The angle 9 is selected so that when the O-ring 20 is seated against the er 34 there is some clearance between the O-ring 20 and the wall 22 of the drill hole wherein, in use, when the plug 30 is moved in the installation direction any friction between the O—ring 20 and the wall 22 of the drill hole is zed. Due to the flexibility of the O-ring and the clearance to the base 26 of the , this geometry also gives sufficient clearance in the direction of the X-axis during installation, as shown in Figure 9.

[0033] Once the O—ring plug 30 is in the rest position, in order to bring the O- ring 20 back to a more perpendicular orientation, the body 12 may be rotated at the same time as the direction of linear movement in the drill hole is reversed to the braking direction, as with the us embodiment shown in Figures 3 and 5. In this direction of movement of the plug 30, the O-ring is free to move within the groove 16. At the same time, the inclined surface of er 34 will force the O—ring to a more perpendicular orientation to increase the erence with the drill hole wall 22. The O-ring will roll then from its rest position on the base 26 ‘up’ the ramp 18 (not shown in Figure 8) as its outer circumference engages with the wall 22 of the drill hole. The more force is d to the body 12 of the plug 30, the more the O—ring 20 will try to roll further ‘up’ the ramp 18, and therefore the more firmly wedged it will become between the ramp 18 and the wall 22 of the drill hole.

By incorporating this geometry in the design of an O-ring plug, the installation process of the O-ring becomes one and the same as the lation process of the plug, albeit with one le additional step, namely rotation of the plug at the end of the process. Additionally, in some situations a plug may be required to be pushed into a drill hole by a drill rig over hundreds of , and the wear on the O-rings would then be a significant factor that may detract from their ability to provide an adequate 2O braking action. However if the O-rings are angled forward until placement it will prevent excessive wear of the O-rings from occurring.

The original ramped O-ring configuration of the first embodiment (illustrated in Figures 1 to 5) combined a braking action as the primary task with a sealing action as a secondary task. ing drives the O-ring up the ramp; yet because the pressure from the fluid within the drill hole acts in the opposite direction, there is a danger that the O—ring seal may be compromised at higher pressures. Accordingly the maximum pressure to failure that can be held by one O—ring is limited to around 250 psi (17 Bar).

While this is just sufficient for some applications, it does not allow any room 3O for a Factor of Safety. ageously the braking (anchoring) and sealing functions can be separated by ing standard piston-type g glands with additional O-rings on a plug, positioned before and/or after the anchoring O—rings.

Because a rock surface is not smooth to the extent of forming a perfect seal (eg. the inside of a drill hole as opposed to a machined cylinder), there is always a very small amount of leakage past any of the O—rings 20 on the O- ring plug 10. Normally in a standard O-ring used for sealing in machined metal components, O—rings in series are ant since the first O-ring seals with ible leakage past it. Further O-rings downstream therefore 1O are unwarranted in that instance. However, in rock, where there is always inherent leakage past s due to imperfect sealing, (albeit with very small flows), the more sealing O—rings provided in series the more rs are present to resist the leakage and ore lower the amount of leakage.

A third embodiment of a high pressure water sealing O-ring plug 40 for a diamond drill hole, in which the braking (anchoring) and g functions are separated, is illustrated in Figure 10 (shown in_long section without the O-rings). As this embodiment shares many of the same features as the first embodiment of the O-ring plug 10, the same reference numerals will be used to identify the similar parts and will not be described again in detail. As shown in Figure 10, there are four annular ing grooves 16 in the engineered surface 14 on the body of the plug 40, each of the grooves 16 providing a seat for one of the braking O-rings 20 (not shown).

There are also two pairs of annular sealing grooves 42 provided in the engineered surface 14, the first pair provided in front of the ramped anchoring grooves and the second pair provided behind the anchoring grooves (when viewed in the direction of installation). The sealing grooves 42 are of rectangular shape in cross—section, as shown in Figure 10, similar to standard piston—type sealing glands, for receiving respective g 0- rings seated therein. The provision of multiple sealing O-rings means that the pressure drop across each O—ring is shared, making the task easier than it would be for a single O—ring.

The provision of the sealing O-rings can reduce the re on the anchoring O-rings to the extent where one O-ring will hold 700-800 psi (48— 55 Bar). For an NQ 76mm plug this is approximately 2 tonne per O—ring, so four ing O-rings gives a potential anchoring force of 8 tonne, which has since been confirmed in a hydraulic press. To allow for drill bit wear, and hence variations in drill hole diameter, these pressure sealing O-rings seat heights. may be on successively larger diameter From the explanation given above of the third embodiment of the O— ring plug 40, the pressure on anchoring O-rings in the presence of sealing O—rings is now approximately one half or even less than that without sealing s. Yet there is still a pressure drop across each of the anchoring 0- rings. Ideally, for m anchoring performance, the pressure differential on each side of the anchoring O-rings should be removed completely.

[0041]Figure 11 illustrates a fourth embodiment of the O-ring plug 50 in which a fluid port 52 is provided across each anchoring groove 42, providing fluid communication that allows free water flow and therefore pressure balancing across each anchoring O—ring 20 (not shown). This could be in the form of a l scored into the side of the plug across each ramp 18.

However this would be potentially problematic in that sharp edges on the ramps could then cut into the anchoring O-rings while they perform the anchoring task.

A better approach is to drill the ports 52 through the body 12 of the plug 50, from the ference at each port location to a central port 54, as shown in Figure 11. This then removes any pressure drop across the anchoring O-rings and ensures that all of the pressure sealing is carried out by the sealing O—rings. Note the central port 54 should be blocked off during manufacture on tion of the porting of the plug.

There is on occasion a requirement to l a plug which, when installed, will no longer easily slide fonNard (in the installation direction).

This may be, for example, when the drilling crew wish to grout behind the plug, and therefore one of the tasks of the plug is to hold a column of grout behind it. This can be achieved by having one or more reversed ramped 0- rings. Figure 12 illustrates a fifth embodiment of the O-ring plug 60 ing to the present invention with provision for a reversed ramped O- ring 62. The reversed ramped O-ring 62 is received in a groove 66, which has a reversed ramp 68 extending from a maximum diameter to a minimum diameter of the engineered surface in the installation direction.

The difficulty with this arrangement is to stop the ed ramped O- ring 62 from g up the ramp 68 and wedging n the engineered surface and the wall of the drill hole during installation. This can be achieved by using one or more positioning rods 64 to hold the reversed ramped O- ring 62 during installation, keeping it on a sufficient angle and clearance distance from the reversed ramp 68 so that it does not interact with the ramp during installation (as illustrated in Figure 12).

With this arrangement, when the drill bit (or other installation tool) is removed from the plug, together with the oning rods, the O-ring 62 is then free to move and to perform its task of anchoring the plug in the fonNards (installation) direction. This may be a standalone reversed ramp O-ring, or it may be combined with normal braking s and ramps which will anchor a plug in the braking direction (as shown in Figure 12), and/or combined with sealing O-rings depending on the task.

A need was also identified for an O-ring plug to provide quick, simple, and routine capping—off of diamond drill holes. Such a plug would protect from rifling if the hole happens to intersect an active mining area, i.e. the plug will block any air blast as well as lower water res. Figures 13 and 14 illustrate a sixth embodiment of an O—ring plug 70 designed to meet this need. This kind of plug is used ely in diamond drill holes that don‘t have significant amounts of water, which is the majority. This plug works by having two O-rings in each ing groove, as described in more detail below. The anchoring feature is essentially the same as in the embodiments previously described. The advantage with two s is that it reduces wear during installation on the O-ring contacting the wall of the drill hole. It also provides a reliable forward resistance which means the plug will support a grout column behind it if the mine wishes to install one.

As the O—ring plug 70 illustrated in s 13 and 14 shares many of the same features as the first embodiment of the O-ring plug 10, the same reference numerals will be used to identify the similar parts and will not be described again in detail. In this embodiment the first O-ring 20 is partnered in the anchoring groove 16 with a second trailing O-ring 72 of substantially the same size. This second O—ring 72 acts as a spring support, and supports the first O-ring 20 in a on at the beginning of the ramp 18 as it contacts the wall 22 of the drill hole during installation. The first O-ring 20 s in the direction to roll down the ramp 18 during movement of the plug 72 in the installation direction B, as shown in Figure 14, but is held in place by the spring action of the second O—ring 72.

The two O-rings 20, 72 engage with each another by onal contact and rotate together like a geared pair, rotating in te directions.

This combined on and spring action acts to (a) reduce the frictional the plug wear on the first O-ring 20, and (b) provide a forward resistance on 70 of approximately 100kg. A fonzvard resistance is desirable in some stances because it allows the plug to support a grouted column placed behind the plug after installation. Without this, the plug may slide fon/vard due to the weight of the grout column behind it. With duplicated anchoring grooves and pairs of O—rings the fonNard resistance can be tailored to suit the requirements and to support, for example, a grout column behind the plug 70. In other respects the plug 70 operates in substantially the same way as the first ment described above.

Now that several embodiments of the O-ring plug have been described in detail, it will be apparent that the described embodiments provide a number of advantages over the prior art, including the following: (i) The plug is simple to manufacture and l, requiring no specialised equipment or tools. (ii) The self—locking, anchoring or braking action of the plug provides a very secure blockage in the drill hole. (iii) The use of multiple O-rings not only increases the braking action, but also improves the seal against the wall of the drill hole, inhibiting the escape of water. (iv) The incorporation of the angled shoulder to reduce the interference of the O-ring with the drill hole wall enables the plugs to be manually installed in a drill hole. (v) Separating the braking function from the sealing function by the addition of one or more sealing O-rings not only improves the sealing but also the ing ance.

It will be readily apparent to persons skilled in the relevant arts that various modifications and improvements may be made to the foregoing ments, in addition to those y described, without departing from the basic inventive concepts of the present ion. For example, the thickness of the O-rings and the corresponding depth of the grooves, relative to the er of the body of the plug, may vary substantially from that shown in the illustrated embodiments. Therefore, it will be appreciated that the scope of the invention is not limited to the specific embodiments described.

Claims (18)

1. A plug for blocking a drill hole in a rock mass, the plug comprising: an elongate body made of solid impervious material; an engineered surface provided on an external ference of the elongate body, the engineered surface comprising an annular anchoring of the elongate groove having a ramp ing from a maximum diameter body to a minimum diameter of the engineered surface in a braking direction in which it is intended to prevent movement of the plug in the drill hole in the rock mass when the plug is inserted in the drill hole; and, 10 an O-ring received in the anchoring groove of the engineered surface and having a thickness whereby the O—ring protrudes above the maximum diameter of the elongate body and engages with a wall of the drill hole wherein, in use with the plug inserted in the drill hole in the rock mass, when the plug is moved in the braking direction in the drill hole the O-ring rolls up 15 the ramp and wedges between the engineered surface and the wall of the drill hole to provide a braking action for the plug against the wall of the drill hole; wherein the anchoring groove is one of a plurality of anchoring grooves of the engineered surface, and the O-ring is one of a plurality of O-rings 20 ed in each of the ing grooves respectively in series, and a braking function of the s in the anchoring grooves is separated from the sealing function by providing one or more sealing O-rings in addition to the O-rings in the anchoring grooves, and one or more annular sealing surface grooves of rectangular cross-section are ed in the engineered 25 that receive the sealing s therein.

2. A plug for blocking a drill hole in a rock mass as d in claim 1, n the engineered surface is formed integral to the material of the body of the plug.

3. A plug for blocking a drill hole in a rock mass as d in claim 1, wherein the engineered surface is formed on a hollow collar which is fixed to the external circumference of the elongate body.

4. A plug for blocking a drill hole in a rock mass as defined in claim 3, wherein the elongate body is a clay plug.

5. A plug for ng a drill hole in a rock mass as d in claim 1, wherein the anchoring groove also has a shoulder located opposite to the when the plug is inserted into the drill ramp, the O-ring abutting the shoulder hole in an installation direction opposite to the braking direction. 1O

6. A plug for blocking a drill hole in a rock mass as defined in claim 5, wherein the shoulder s in a plane substantially perpendicular to a longitudinal axis of the elongate body.

7. A plug for blocking a drill hole in a rock mass as defined in claim 5, wherein the shoulder extends in a plane angled to a longitudinal axis of the 15 elongate body at an angle 9 of between about 25° to 75°.

8. A plug for blocking a drill hole in a rock mass as defined in claim 7, wherein the angle 6 is selected so that when the O—ring is seated t the shoulder there is some clearance between the O-ring and the wall of the drill hole wherein, in use, when the plug is moved in the installation direction 20 wall of the drill hole is minimized. any friction between the O-ring and the

9. A plug for blocking a drill hole in a rock mass as defined in claim 8, wherein the anchoring groove also has a base of substantially constant diameter ed between the shoulder and the ramp, the base containing the O-ring during movement of the plug in the drill hole in the installation 25 direction.

10. A plug for blocking a drill hole in a rock mass as d in claim 1, wherein the ramp is angled at between 10° to 60° to a longitudinal axis of the plug.

11. A plug for blocking a drill hole in a rock mass as defined in claim 10, wherein the ramp is angled at substantially 30° to the longitudinal axis of the plug.

12. A plug for blocking a drill hole in a rock mass as defined in claim 1, wherein a plurality of annular sealing grooves is provided in front of the anchoring grooves and/or behind the anchoring grooves.

13. A plug for blocking a drill hole in a rock mass as d in claim 12, wherein a fluid port is provided across each anchoring groove to provide 1O fluid communication and therefore pressure balancing across each anchoring O-ring.

14. A plug for blocking a drill hole in a rock mass as defined in claim 13, wherein a plurality of fluid ports extend through the body of the plug, from an 15 outer circumference at each fluid port location to a central port.

15. A plug for blocking a drill hole in a rock mass as defined in claim 5, wherein a ed ramped O-ring is received in a groove, which has a reversed ramp extending from a maximum diameter to a m diameter 20 of the engineered surface in the lation direction wherein, in use, the plug can also be anchored in the installation direction.

16. A plug for blocking a drill hole in a rock mass as defined in claim 15, n one or more positioning rods are provided to hold the reversed 25 ramped O-ring during installation, keeping it on a sufficient angle and clearance ce from the reversed ramp so that it does not interact with the ramp during installation.

17. A plug for blocking a drill hole in a rock mass as defined in claim 1, 30 wherein a second O-ring is ed in the anchoring groove and supports the first O-ring in a on at a beginning of the ramp as it contacts the wall of the drill hole during installation whereby, in use, the two O-rings engage with each another by frictional contact and rotate together like a geared pair, rotating in opposite directions, so that as the first O-ring rotates in a direction to roll down the ramp during installation it is held in place at the beginning of the ramp by a spring action of the second O-ring.

18. A plug for ng a drill hole as defined in claim 17, wherein the first and second O—rings are of substantially the same size.