AU2005101045A4 - A method and apparatus for testing the strength of a settable material - Google Patents

Description

SA METHOD AND APPARATUS FOR TESTING THE STRENGTH OF A O SETTABLE

MATERIAL

FIELD OF THE INVENTION This invention relates to an apparatus for testing the strength of a settable material. It also extends to a method of testing the strength of a settable Smaterial using this apparatus.

SThis invention relates particularly but not exclusively to a method and apparatus for testing the early stage strength of a cementitious material that is fibrecrete/shotcrete when it is used to line an open rock wall or a rock wall of a passage in a tunnel, eg. of a mine, and it will be convenient to hereinafter describe the invention with reference to this example application. However it is to be clearly understood that the invention is capable of broader application.

Fibrecrete comprises a cementitious material that is a concrete mix together with steel fibres that strengthen the concrete mix. Shotcrete comprises the cementitious mix without the fibres contained therein.

For example the invention is not limited to application on mines and could be applied to rock walls and tunnels in any other civil engineering application. For example tunnels are often cut for roads and rail and this invention could be used in this application. Further open rock walls are found wherever a cutting is cut in the natural land topography to create a level piece of land for whatever purpose and the invention could also be used in this application.

Further this invention can also be applied to settable materials other than fibrecrete. For example it could be applied to any cementitious material such as cement, concrete or the like.

BACKGROUND TO THE INVENTION Underground mining is carried out on a large scale in Australia and indeed many other countries of the world. In underground mining operations mine shafts and tunnels are excavated in the rock and these are used to provide 2 access to a mine face. During mining operations people and mine vehicles, including vehicles for transporting the mine ore, move though these tunnels and passages on a regular basis.

The rock defining these passages can crack and degenerate over time. This poses a risk of rocks falling down from a wall or roof of the passage onto a worker passing below. This clearly poses risks to the safety of mine workers _passing through the passages. Accordingly good mining practice requires these passages to be screened or lined after they have been formed, eg blasted, to prevent falling rock and the like from injuring persons passing through the passages during normal mining activities.

Currently there are two ways of performing the screening of these passages.

One such way involves placing mesh over the exposed rock of the passage.

The mesh then catches any pieces of rock that might fall down and stops them landing on someone. However this method has some shortcomings. The mesh has fairly large openings and a piece of rock could still fall through such an opening. Further the mesh tends to rust and then needs to be replaced. This is a difficult and messy job and is a dangerous operation in itself.

Another recognised method of screening the mine-shaft involves spraying fibrecrete onto the exposed rock to line the passage with fibrecrete. This method is preferred because fibrecrete is durable and lasts for 10 years or more without deteriorating.

This screening of a rock wall is also generally a well used civil engineering practice to line a rock wall with a cementitious material, eg fibrecrete or shotcrete in cuttings, tunnels and the like. This assists in stabilising the rock face and resists discrete rocks from breaking off from the main rock body and falling off the rock face.

When such a layer of cementitious material is laid down it would be advantageous if engineers could get an idea or a measure of the strength of the n 3 fibrecrete or shotcrete. This is particularly so in the initial hours after the Sfibrecrete has been laid down onto the rock surface, known as the early strength of the concrete.

This would enable mine managers to know with confidence when personnel could safely re-enter the area of the mine that has been screened. At the same time these managers would not have to wait longer than necessary to re- enter 0the screened area. In mines it is particularly desirable that access to the work n area be regained as soon as possible to reduce the downtime and keep the productivity of the mine at a high level.

In addition to the early strength it would also be advantageous if a way could be devised of measuring the strength of the layer of fibrecrete once it is fully set.

This is important to get a general idea of the safety of the area beneath the rock wall.

Currently engineers and contractors do not have an easy method and apparatus for measuring the strength of the fibrecrete and shotcrete. One way they currently measure the early strength of the fibrecrete and/or shotcrete is to use a soil penetrometer. This is a device that has a sharp needle that is designed to measure the hardness of ground. The needle measures the force required to penetrate the ground when it is pressed into the ground. In use to measure the strength of shotcrete the needle is stabbed into the concrete randomly at certain points over a certain area of fibrecrete. Each stab produces a reading of the force required to penetrate the cementitious material and these are averaged out thereby a measure of the hardness of and setting of the cementitious material.

The individual readings very widely, eg from 0.5 MPa .3 MPa and the measure of the hardness of the cementitious material is obtained by averaging out a sample of readings, eg at least 10 such readings.

tf 4 However the fact that individual readings within a small area can vary so much .shows that the system is not very accurate and this fact is widely recognised in this industry.

This is a major shortcoming of existing screening operations. Firstly engineers are not able to verify or test the strength of the fibrecrete once it has set. This leads to a safety risk. Secondly there is no reliable and accurate way of _measuring the early strength of the fibrecrete and/or shotcrete in the first couple of hours after it is laid down. This is important because mine engineers and managers have an economic imperative to permit mine workmen to re-enter the area that has been screened as soon as possible after the screening has been sprayed onto the surface. The mine engineers and managers also have an imperative to provide a safe working environment for their workers.

Clearly it would be highly advantageous if a way of measuring the early strength of fibrecrete and/or shotcrete could be developed. This should enable its strength to be determined in an easy and cost effective manner and as a routine part of laying down the layer of cementitious material in the screening operation.

SUMMARY OF THE INVENTION According to one aspect of the invention there is provided testing apparatus for testing the strength of a cementitious layer applied to a support surface, the apparatus including: a pull out indicator having a base for mounting on the support surface and embedded in said cementitious layer and a shank having one end mounted on and extending to a free end out of said cementitious layer; a jack mounted for movement on machinery including a support member having securing means operable to engage said free end, jacking legs disposed on said support member about said securing means and operable to urge said support member away from said layer, and is associated with alignment means for aligning said securing means with said pull out indicator; and measuring means responsive to the force applied to the pull out indicator by the jack.

O

The machinery may be a simple support or may be machinery already associated with the environment in which the testing apparatus is expected to work. In tunnelling and other applications where sprayable cementitious N mixtures are contemplated, the machinery may for example comprise the spraying or drilling boom. The machinery may include a robotic boom such as a robotic spraying boom.

0 The alignment means may be manual, automatic or semiautomatic alignment means. For example the alignment may comprise a probe-and-collar mechanical alignment. Alternatively the alignment means may comprise a laser-based guidance system manually co-operable with the machinery to guide the securing means to the pull out indicator. In a yet further alternative, the alignment means may comprise a laser-based guidance system automatically co-operable with the machinery to guide the securing means to the pull out indicator.

The jacking legs may be hydraulically operable to apply linear force along said shank, such as by hydraulic pressure equalization or independent control in response to strain or pressure measurements in each leg. The measuring means may be responsive to a load sensor in operative communication with the hydraulic system of the jacking legs.

In a further aspect there is provided an apparatus for testing the strength of a layer of cementitious material applied to a support surface, the apparatus comprising: a pull out indicator having a base for mounting on a support surface and a shank having one end mounted on the base and extending away from the base to a free end, the base extending laterally outwardly of the shank such that when the indicator is pulled in a direction away from the support surface it urges against a part of the layer of settable material and offers resistance to being withdrawn from the layer; a jack comprising a support member, a plurality of legs of adjustable length rigidly mounted on the support member and projecting away there from 6 for mounting on a support surface, the legs including means for extending and contracting the legs on demand whereby to move the support member towards or away from the support surface to effect a jacking action, a means on the (support member for securing the pull out indicator there to such that when the length of the legs is extended then force is transmitted through to the pull out n indicator to tend to pull it out of the settable material, and a means for _measuring the force applied to the pull out indicator by the jack.

Thus the pull out indicator is mounted on a support surface, eg a rock surface, before the settable material is laid down and then the base of the element is covered by the settable material as it is laid down. After the material has been laid down a jack is mounted in operative relation to the pull out indicator and the support member of the jack is secured thereto. Thereafter the jack is jacked away from the support surface and a force will eventually be reached when the pull out element is pulled away from the support surface and the settable material starts cracking. Thereafter further jacking will pull the element fully away from the settable material and it will fail.

The support member of the jack may comprise a flattened body having two major surfaces. An upper surface of the support member may be substantially planar.

The indicator may include a jack engagement formation. The jack engagement formation may comprise at least one shoulder formation, eg towards the free end of the shank thereof. The shoulder formation/s may project laterally outward on opposed sides of the shank, eg at positions diametrically opposed on the shank.

The jack engagement formation may be formed by an enlarged free end of the circumferential shank. In one form the jack engagement formation may be a discrete element separate from the shank that is mounted on the shank, eg by complementary screw thread formations on each of the shank and shoulder S7 formation/s. In another form the jack engagement formation is integral with the O shank.

(Thus the jack engagement formation, eg in the form of shoulder formation/s provides a surface against which the securing means can engage whereby to n apply force to the indicator element.

SThe base of the pull out indicator may extend laterally out of the shank on at n least two diametrically opposed sides of the shank.

The base may be bilaterally symmetrical about a plane passing through a full diameter of the base. The diameter of the base may be at least three times the diameter of the shank, preferably at least 5 times the diameter of the shank.

In one form the base may be circular. In another form the base may be square.

The base may define a contact surface for contacting a support surface and an opposed surface facing away from the support surface.

The contact surface may define a recess, eg a shallow recess, for receiving adhesive therein. Further the base may define apertures therein for permitting adhesive to pass from the contact surface through to the opposed surface, eg when it is pressed up against a contact surface.

The shank may have a non-circular cross-sectional shape. Specifically the cross-section of the shank may comprise a plurality of linear sides. In one form the cross-sectional shape of the shank may be a cruciform shape.

The shank will have a sufficient length such that the jack engagement formation projects outwardly proud of a layer of cementitious material that is applied to the support surface, eg after the full gauge or design thickness has been applied to the support surface.

8

O

The pull out indicator will naturally have to be sufficiently strong to withstand the forces applied to it when it is pulled out of the layer of cementitious material.

Conveniently the indicator may be made of a metallic material, eg mild steel.

However other high strength materials such as composites and other synthetic materials may conceivably also be used.

The legs of the jack may be extended and retracted by hydraulic power. Each Sleg may comprise a piston received within a hydraulic cylinder and be movable, eg telescopically, relative thereto by an increase or reduction in the hydraulic fluid within the cylinder.

Each leg may include a support surface portion that extends to a support surface in use and a support member portion that engages the support member. Conveniently the piston may be fast with the support surface portion and the cylinder may be fast with the support member portion.

The support surface portion may further include a foot at the free end thereof for mounting on the support surface. The support surface portion may be mounted on the foot such that it is pivotal there to. The support surface portion may be joined to the foot by means of a universal joint that permits pivoting in all directions. In one form the universal joint may be in the form of a ball and socket joint.

The jack may include means for adjusting the legs to accommodate any unevenness in the surface on which they are mounted, eg the surface of material that has been laid down. The length of each leg may be capable of accommodating for an uneven surface. Further the angle of the foot on the support surface may be adjusted by means of the universal joint to accommodate an uneven support surface.

The legs of the jack maybe moved relative to the support member by means of a hydraulic ram and associated hydraulic circuit.

S9 X The hydraulic circuits of each of the legs may be interconnected so that the opressure of the hydraulic liquid in each of the legs is the same. This equalises the pressure applied by all the legs to the support surface.

This ensures that the same force is applied to the pistons of each leg and the Ssame force is applied across all legs. Again this helps to ensure that all legs _apply the same force notwithstanding unevenness in the surface of _cementitious material on which they are mounted. This helps to pull the indicator directly out away from the support surface.

This ensures that the jacking force is applied in an axial, eg strictly axial direction or a direction that is perpendicular to the support surface on which the pull out indicator is mounted. That\way the jack element always pulls away from the support surface even though the support surface is perfectly horizontal or perfectly even.

The jack may have three or more side legs of adjustable length. In a preferred form the jack has four said legs.

The means for securing the pull out indicator to the support member may comprise a pair of clamping formations on diametrically opposed sides of the indicator. Each clamping formation defines a shoulder that engages the shoulder, eg described above, on the jack engagement formation of the pull out indicator.

Each clamping formation may comprise a longitudinal portion having one end mounted on the support member and extending away there from to a second end and a transverse flange portion extending away from the longitudinal portion towards said second end, the transverse flange portion defining said shoulder.

V

O

The flange portions are designed to have sufficient width such that when they engage said shoulder on the indicator the longitudinal portion is spaced away from the radially outer edge of the shoulder on the pull out indicator.

The reason for this is to make sure that only a purely axial force is applied to the pull out indicator and no shear or bending force.

_Each clamping formation may have its longitudinal formation pivotally mounted to the support member, eg towards the first end of the longitudinal formation.

The longitudinal portion may be pivoted from a disengaged position spaced away from where the indicator is positioned into an upright locked position where the transverse flange portion engages the shoulder of the indicator.

Each clamping formation may further include locking means for locking it in the engaged position. The locking means may comprise a hydraulic cylinder that pivots the clamping formation upwardly from the released position into the upright locked position in which it locks the clamping formation for use.

In one form the hydraulic fluid for this cylinder may be in fluid communication with the fluid for the hydraulic cylinders of the legs and thereby at the same hydraulic pressure as these legs.

The jack engaging formation, eg shoulders, on the indicator may be sized such that the longitudinal portions of the clamping formations are spaced away there from when fitted around the shoulder on the indicator.

The jack may further include an alignment means mounted on the jack for aligning the centre of the support member with the centre of the indicator.

The alignment means may comprise a laser mounted on the support member, eg centrally with respect to the legs of the jack and directed broadly in a direction parallel with the legs of the jack.

~n 11 The laser may be mounted in a recess within the support member and be .aligned to direct a beam exactly perpendicularly to the surface of the support member.

The function of the laser is to centralise the securing means, eg the clamping n formations, and thereby also the legs of the jack, relative to the pull out indicator _such that the jacking force that is applied to the pull out indicator is applied _evenly to diametrically opposed sides of the indicator and this pulls it Perpendicularly off the support surface.

The means for measuring the force applied to the indicator may comprise a load sensor in operative communication with the hydraulic fluid associated with the hydraulic pistons of the legs. This provides a measure of the force applied to the indicator.

The force measuring means may further include a visual indicator of the force applied to the indicator. The visual indicator may record the highest force applied to the indicator before it starts cracking and is displaced off the rock support surface and also the force being applied at any given time, ie in real time. It may also record the force at\which the indicator is finally pulled fully away from the support surface.

The jack may further include a stroke sensor for measuring the length of the stroke of the jack each time it is used to pull an indicator out of a layer of cementitious material.

The support member may also have a formation defining an opening for receiving a nozzle of an apparatus for spraying cementitious material. This way a jack can be lifted into position in use by a nozzle of a concrete spraying apparatus. Thus the jack is able to be mounted on a nozzle without difficulty by simply receiving the nozzle within the formation or vice versa such that it is safely supported thereon in a stable fashion.

V 12

O

This enables the jack to be carried on a boom, eg a robotic boom that has been developed for the spraying operations and this makes it easier to use and gives it a greater reach.

According to another aspect of this invention there is provided a pull out 0 indicator for use together with a jack for testing the strength of a layer of cementitious material applied to a support surface, the pull out indicator having a base for mounting on a support surface and a shank having one end mounted on the base and extending away from the base to a free end, the base 0 10 extending laterally outwardly of the shank such that when the indicator is pulled in a direction away from the support surface it urges against a part of the layer of settable material and offers resistance to being withdrawn from the layer; The indicator may have any one or more of the optional or preferred features of the indicator escribed above in the first aspect of the invention.

According to another aspect of the invention there is provided a jack for use together with a pull out indicator for testing the strength of a layer of cementitious material applied to a support surface, the jack comprising: a support member, a plurality of legs of adjustable length rigidly mounted on the support member and projecting away there from for mounting on a support surface, the legs including means for extending and contracting the legs on demand whereby to move the support member towards or away from the support surface to effect a jacking action, a means on the support member for securing the pull out indicator there to such that when the length of the legs is extended then force is transmitted through to the pull out indicator to tend to pull it out of the settable material, and a means for measuring the force applied to the pull out indicator by the jack.

The jack may have any one or more of the optional or preferred features of the jack described above in the first aspect of the invention.

S13 This invention also extends to a method of testing the strength of a layer of Scementitious material that has been applied to a support surface, the method comprising: (Ni providing an indicator as described above according to one of the preceding aspects of the invention; applying the indicator to a support surface, eg by adhering the indicator Sto the surface; _applying a cementitious material to the surface, eg by spraying the material onto the surface through a nozzle of a concrete spraying apparatus; allowing some time for the cementitious material to harden; providing a jack as described above according to the preceding aspects of the invention; mounting the jack on the surface of the cementitious material in a superimposed relationship to the indicator mounted within the material with the legs resting on the support surface; pivoting the clamping formations from a release position up into a locked position where they engage a jack engagement formation on the indicator; progressively increasing the force applied to the legs to lengthen the legs and thereby jack the indicator out of the layer of material and noting the force indicated by the force measuring means until the layer cracks.

The method may include any one or more of the subsidiary features described above in any of the preceding aspects of the invention.

Thus the indicators are mounted on the rock wall before a cementitious layer(s) of, for example, fibrecrete and/or shotcrete is laid down over the base of the anchor and at least part of the shank thereof. Thereafter in order to test the strength of the cementitious layer(s), a jacking means of a jack is operatively coupled to the shank and then the jacking element is axially displaced in a direction away from the support surface. The force progressively builds up in the jacking element and the anchor as a result of the displacement of the jacking element and at some point the cementitious layer(s) will crack and displace away from the support surface. The force indicating means provides 14 an indication of when this occurs and thereby an indication of the strength of the cementitious layer(s).

N The base of the INDICATOR may comprise a flattened body with two major surfaces, eg. extending parallel to the support surface. One of the major surfaces may be mounted on the support surface in use and the other major surface may face away from the support surface in use.

The flattened body may have a circular configuration. Alternatively the flattened body may have a rectangular configuration, eg. a square configuration.

The shank may extend substantially perpendicularly away from the other major surface of the base and the shank may be at least as long as the depth or thickness of settable material that will be laid on the support surface.

The indicator may be made of a metallic material, eg. steel, so that it does not deform or break when the jack is used to pull it off the wall. The indicator may be cast or moulded as an integral article.

It is important that the indicator is stronger than the settable material that is laid over the indicator so that it is the settable material with cracks and then fails when the indicator is pulled off the support surface by the jack.

DETAILED DESCRIPTION OF THE PREFERRED

EMBODIMENTS

An apparatus for testing the strength of a settable material such as fibrecrete forming a screening on a rock wall may manifest itself in a variety of forms. It will be convenient to hereinafter describe in detail at least one preferred embodiment of the invention with reference to the accompanying drawings.

The purpose of providing this detailed description is to instruct persons having an interest in the subject matter of the invention how to put the invention into practical effect. It is to be clearly understood however that the specific nature of this detailed description does not supersede the generality of the preceding bore description. In the drawings: n Fig. 1 is a schematic front view of a jack suitable for testing a layer of Scementitious material; Fig. 2 is a sectional view of part of the jack of Fig. 1 showing some of the internal components; Fig. 3 is a top plan view of the jack of Fig. 1; Fig. 4 shows an apparatus for testing the strength of a cementitious _material comprising the jack of Fig. 1 mounted on a boom and a pull out _indicator that is mounted on a support surface before the cementitious material is applied thereto and which is pulled out of the layer of cementitious material whereby to test the strength of the cementitious material; Figs. 5 through to 9 show the apparatus for testing the strength of the material comprising the jack of Fig. 1 and a pull out indicator in various stages of use; Fig. 10 is a schematic view of a jack in accordance with a second embodiment of the invention; Fig. 11 is a sectional view of part of the jack of Fig. 10 showing some of the internal components; Fig. 12 is a top plan view of the jack of Fig. 10; and Fig. 13 is a table showing the information gathered during testing of the strength of the indicator.

In Figs. 1 to 3 reference numeral 1 refers to an apparatus in accordance with the invention for testing the strength of a settable material. The apparatus comprises broadly a jack 2 and an indicator 3.

The jack 1 comprises a support member 5 and a plurality of legs 7 that are mounted on the support member 5 and projecting away there from. In the illustrated embodiment there are four said legs 7 although this number can vary.

The main thing is that there are sufficient legs 7 for mounting the jack 2 in a stable fashion of the surface on which it is to be used. Each leg 7 comprises a support member portion 10 and a support surface portion 12 which is telescopically adjustable relative to the support member portion 10. The support surface portion 12 is operatively coupled to the piston 14 of a hydraulic cylinder V16 and the support member portion 10 is associated with the cylinder part 16 of the hydraulic cylinder. Thus by pumping hydraulic fluid into the hydraulic cylinder 16 and/or releasing the hydraulic fluid the piston 14 can be moved relative to N the cylinder 16. Each leg 7 has a foot 20 at the free end thereof and the foot is operatively mounted to the leg 7 by means of a universal joint that is a ball and socket joint. This ball and socket joint permits movement and particularly 0 pivoting of the foot 20 in all directions relative to the leg 7.

In the illustrated jack 2 each leg 7 also includes a ratchet and pawl mechanism 28 for moving the support surface portion 12 relative to the support member portion 10 roughly into position before the hydraulic circuit is used to exert a strong jacking action. Thus the ratchet mechanism is used to place the leg portions 10, 12 at approximately the right length for any given application.

The jack 2 also includes clamping formations 30 for passing over shoulders on the pull out indicator 3 to secure the support member 5 to the indicator 3 to enable it to be pulled out. Each clamping formation comprises a longitudinal portion 32 that has a first end 33 that is pivotally mounted to the support member 5 and a second end 34 that has a transverse flange portion extending outwardly away there from. The transverse flange portion 35 forms a shoulder that engages the indicator 3.

The transverse flange portions 35 have greater width than the adjacent part of the indicator (to be described in more detail below) such that the longitudinal portion 32 there of is spaced away from the indicator 3 and does not make contact with it.

The clamping formations 30 further include locking means in the form of hydraulic cylinders 38 that pivot the clamping formations 30 upwardly into a vertical position engaged over the indicator 3 and also lock them in this position while the indicator 3 is being pulled out.

Vt 17 The jack 2 further includes an alignment means in the form of a laser 40 that is mounted on the support member 5 in a central position. The laser 40 is positioned to direct a laser beam perfectly perpendicular to the support surface and this is used to centralise the indicator 3 with respect to the jack 2.

The jack 2 also includes a force measuring means mounted on or in the support _member 5 for measuring the force that is applied to the legs 7 of the jack 2 and _thereby also the indicator 1. The force measuring means comprises a load sensor 50 that senses the pressure of the hydraulic fluid in the hydraulic cylinders that are supporting the legs 7 which in turn is a measure of the force being applied to the indicator. The sensor 50 is exposed to the hydraulic fluid within the hydraulic circuit and there by it can measure the pressure of the fluid.

The force measuring means has a gauge operatively coupled to the sensor that visually indicates to a user the force that is being applied to the indicator at that particular time. The gauge also records the highest force that is recorded before the layer of material starts cracking for use later on in calculating the strength of the material.

The support member also includes means for supporting it on the end of a nozzle as shown in Fig 1 in the form of a support formation 55. The support formatio is on the rear of the support member and is sized to receive a nozzle with a small amount of clearance. The nozzle in turn may be mounted on robotic arm as shown in Fig 4. This way it can be lifted up to reach the ceiling of a passage and the like.

The indicator 3 comprises a base 60 and a shank 62 that extends away from the base 62 to a free end 64. The base 60 extends laterally outwardly beyond the width of the shank 62 by a considerable distance. The diameter of the base is more than five times the diameter of the shank 62. In the illustrated embodiment the base 62 is circular. While it is convenient for the base 62 to be this shape other shapes such as rectangular, including square are not excluded.

'n 18 The shank 62 has a sufficient length such that it projects out above the layer of material whatever the layer of this material is.

NThe shank 62 further includes a jack engaging formation 66 at the free end 64 of the shank. 62. The jack engaging formation 66 comprises an enlarged end of the shank 62 that defines shoulders or shoulder formations all around the shank 62 for engaging the flange portion 35 of the clamp formations In the embodiment illustrated in Fig. 10 the jack engaging formation 66 defines a bore with a screw thread formation and the shank 62 also defines an external screw thread formation towards its free end. The jack engaging formation 66 is screwed onto the shank 62. It is thus attached to the rest of the indicator 3 prior to the indicator 3 being placed in position. In Figs. 1 and 2 the jack engaging formation 66 is integral with the shank of the indicator 3.

In use as shown in Figs. 4 to 9 an indicator 3 is mounted on a support surface that is a rock surface 70 of a wall that is required to be screened. The base of the indicator 3 is adhered to the support surface 70 using an adhesive to stick it to the rock surface 70 before any cementitious material is applied there to.

Thereafter a cementitious material, e.g. fibrecrete, is applied to the surface using a nozzle and spraying apparatus in the usual way. A layer 72 of this material is progressively built up on the surface 70 in the usual way until a layer having a design gauge or thickness, eg. of 50 mm, has been achieved.

By this point the indicator 3 will be largely covered by the cementitious material 72 that has been applied to the surface 70. All that will be visible will be the jack engaging formation 66 at the free end of the shank 62 of the indicator 3.

The cementitious material will then be left for a while to set. After some time has elapsed say, 1 or 2 hours, then a jack 2 will be brought into position just below the indicator 3. This is accomplished using the robotic boom 76 shown in V 19 Fig. 4. The jack 2 and specifically the support member 5 thereof is supported on a nozzle 78 that otherwise is used to spray the cementitious material.

NThe support member 5 of the jack 2 is centralised relative to the indicator 3 by the laser 40 mounted on the support member 5. The laser 40 radiates a beam that defines a point image on the end of the indicator 3 and this enables an _operator to centralise the jack 2 relative to the indicator 3 (Fig. Thereafter the legs 7 of the jack 2 are placed in position on the surface of the applied material 72 (Fig. The legs 7 are extended if necessary so that the feet 20 rest on the surface. Specifically the ball and socket joints linking each foot 20 to the legs 7 enable each foot 20 to be angled other than perpendicular to the leg 7 and also for different feet 7 to be angled differently from each other (Fig. The ratchet and pawl mechanism 28 is used to get the legs 7 to approximately the right length and then the hydraulic fluid is used to do the rest.

The next step is for the clamping formations 30 to be clamped over the jack engaging formation 66 on the indicator 3 (Fig. To do this the longitudinal portions 32 of each said clamping formation 30 are pivoted upwardly by their associated hydraulic cylinders. This engages the transverse flange portions behind the shoulder of the jack engaging formation 66 such that jacking force from the jack 2 is transmitted through to the indicator 3.

The jacking process is then commenced. Hydraulic fluid is pumped into the hydraulic cylinders causing the pressure to rise and applying a force that tends to cause the legs 3 to lengthen. Specifically the surface portions associated with the pistons are displaced out of the cylinders away from the support member portions. This applies a pull out force to the indicator 3 and when a sufficiently high enough force is reached then the indicator 3 will crack the layer of material 70 and pull away a bit from the rock surface. This is shown in Figs.

4 and 9.

tn The gauge of the force measuring means indicates the force at any time being U applied to the indicator 3 and also records the highest force that was applied to the indicator 3 before it started cracking. Thus the force applied to the indicator 3 at the point that it starts to fail gives a very good indication of the strength, eg the early strength of the cementitious material, and this can be used to assess whether an area that has been screened can be safely re-entered.

The jack also includes a stroke sensor mounted on the support member in proximity to the gauge that measures the length of the stroke or displacement of the support member before the indicator is pulled fully out of the layer of material Figs. 10 to 12 illustrate another embodiment of the invention that is a minor variation on the embodiment in Figs. 1 to 9.

As this embodiment has many functional and structural similarities with the earlier embodiment the same reference numerals will be used to refer to the same components unless otherwise illustrated.

The description below will focus on the differences between this embodiment and the earlier one. In Figs. 10 to 12 the jack has three legs 7 instead of four.

The legs 7 are arranged in the corners of an equilateral triangle when viewed in plan view as shown in Fig. 12. The three legs provides stability when mounted on a support surface much like a tripod for a camera. Some times depending on the terrain of the surface of material the three legs may be more convenient to use than the four legged embodiment. Clearly a similar level of stability could not be provided by two legs.

Otherwise the structure and functioning of this jack is the same as that in Figs. 1 to 9.

V 21

O

Fig. 13 shows the information that might typically be collected and analysed by U contractors and/or mine managers to measure early strength and determine re entry times.

An advantage of the apparatus described above is that it can be used to get an accurate measure of the strength of a layer of cementitious material.

This enables mine managers and engineers to predict with confidence when they may safely allow workers to re -enter an area that has been screened off.

It takes the guess work out of the process.

Applicant also believes that because this apparatus provides engineers and managers with a substantially better tool for measuring the strength of the settable material as it sets when compared with the crude techniques that were previously used there is the prospect of fine tuning this calculation and shortening the re-entry times. This has the potential to create huge savings and increases in productivity on mines if this is the case. The time workers have to wait before they can re-enter a section of a mine is essentially down time and is lost.

Yet further applicant believes that this apparatus and method is easy to implement. All that it requires is for the indicators to be adhered to the rock wall at spaced intervals before the material is sprayed onto the surface so that the indicators are encased in the layer of material as it is laid down. Then later on when the material has been fully laid down and has had some time to strengthen then the jack can be moved into position and the strength of the settable material determined.

A further advantage of this apparatus is that the jack can be placed on a robotic boom that is currently used to support a nozzle for spraying the material on the surface. This enables the jack to be placed up high at points on the rock wall more then 8 foot above the floor of the passage.

nm 22 It will of course be realised that the above has been given only by way of illustrative example of the invention and that all such modifications and Svariations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as defined in the claims appended hereto.

Claims (3)

1. 2. Testing apparatus according to claim 1, wherein said machinery includes a robotic boom.
2. 3. Testing apparatus according to claim 1 or claim 2, wherein said alignment means comprises a laser-based guidance system co-operable with said machinery to guide said securing means to said pull out indicator.
3. 4. Testing apparatus according to any one of the preceding claims, wherein said jacking legs are hydraulically operable to apply linear force along said shank, and wherein said measuring means is responsive to a load sensor in operative communication with the hydraulic system of the jacking legs. Testing apparatus substantially as hereinbefore described, with reference to the accompanying drawings. DATED THIS TWENTY-SECOND DAY OF DECEMBER 2005 ALBERT JOHN LONCARIC BY PIZZEYS PATENT AND TRADE MARK ATTORNEYS