WO2021212182A1

WO2021212182A1 - Dynamic drop testing apparatus

Info

Publication number: WO2021212182A1
Application number: PCT/AU2021/050368
Authority: WO
Inventors: David William Evans; Adam Amos
Original assignee: Dywidag-Systems International Pty Limited
Priority date: 2020-04-23
Filing date: 2021-04-23
Publication date: 2021-10-28
Also published as: CA3180675A1

Abstract

A system (100) for dynamically testing a ground support element (102) for use in strata control in civil engineering and mining operations, the system including: a buffer (104); a frame (114) to be moved in a direction towards the buffer (104) from a first position, in which the frame (114) is spaced from the buffer (104), to a second position, in which the frame (114) is in contact with the buffer (104) so that movement of the frame (114) in the direction is at least slowed by the buffer (104), the frame (114) having an attachment portion (158) to be coupled to the element (102) so that the element (102) is movable with the frame (114); and a load mass (172) arranged for relative movement with respect to the frame (114) and operatively associated with the element (102) such that contact between the buffer (104) and the frame (114) causes the load mass (172) to move in the direction of movement relative to the frame (114) to load the element (102) thereby causing displacement of a portion of the element (102) in the direction of movement as the movement of the frame (114) is at least slowed, wherein the frame (114) has an end portion (148) to contact the buffer (104), with the load mass (172) spaced further from the buffer (104) in the direction of movement than the end portion (148), prior to contact between the end portion (148) and the buffer (104), such that the load mass (172) continues to move toward the buffer (104) in the direction of movement after the contact between the end portion (148) and the buffer (104).

Description

DYNAMIC DROP TESTING APPARATUS

Field

[0001] The present invention relates to a system for dynamically testing a ground support element for use in strata control in civil engineering and mining operations, and a method of dynamically testing the ground support element.

Background

[0002] One known method of stabilizing the roof or wall of mines, tunnels or other ground excavations is to utilise a ground support element, commonly a rock bolt, mesh, or shotcrete panel, secured to the face of the rock to be stabilised.

[0003] Such ground support elements are typically designed to withstand dynamic loading induced by seismic events within the rock mass and dynamic rock failures encountered at the excavation boundary.

[0004] It is therefore desirable to experimentally assess and determine the dynamic response and energy dissipation performance of various ground support elements to ensure effective and safe operation of the ground support element under dynamic loading.

[0005] Various means have previously been proposed to simulate such seismic events to assess the dynamic performance of ground support elements. Disadvantageously, such means are typically large-scale complex facilities requiring relatively high capital costs to setup and the provision of large testing areas.

Object

[0006] It is an object of the present invention to substantially overcome, or at least ameliorate, one or more of the above drawbacks. Summary of Invention

[0007] In a first aspect, the invention provides a system for dynamically testing a ground support element for use in strata control in civil engineering and mining operations, the system including: a buffer; a frame to be moved in a direction towards the buffer from a first position, in which the frame is spaced from the buffer, to a second position, in which the frame is in contact with the buffer so that movement of the frame in the direction is at least slowed by the buffer, the frame having an attachment portion to be coupled to the element so that the element is movable with the frame; and a load mass arranged for relative movement with respect to the frame and operatively associated with the element such that contact between the buffer and the frame causes the load mass to move in the direction of movement relative to the frame to load the element thereby causing displacement of a portion of the element in the direction of movement as the movement of the frame is at least slowed, wherein the frame has an end portion to contact the buffer, with the load mass spaced further from the buffer in the direction of movement than the end portion, prior to contact between the end portion and the buffer, such that the load mass continues to move toward the buffer in the direction of movement after the contact between the end portion and the buffer.

[0008] Preferably, the frame includes one or more frame members extending in the direction of movement from an upper portion to a lower portion, with the lower portion providing the end portion, and wherein the load mass is movably arranged between the upper and lower portions.

[0009] Preferably, the one or more frame members, the upper portion, and the lower portion at least partly surround a loading region in which the load mass is located.

[0010] Preferably, the buffer includes a contact surface being generally planar in configuration and extending in a widthwise direction and a lengthwise direction, with the widthwise and lengthwise directions being transverse to the direction of movement.

[0011] Preferably, the end portion has a contact surface being generally planar in configuration and extending in a widthwise direction and a lengthwise direction, with the widthwise and lengthwise directions of the contact surface of the end portion being parallel with the widthwise and lengthwise directions, respectively, of the contact surface of the buffer.

[0012] Preferably, the contact surface of the buffer has a width dimension and a length dimension, and wherein the contact surface of the end portion has a width dimension and a length dimension, with the width and the length dimensions of the contact surface of the buffer being equal to or greater than the width and the length dimensions, respectively, of the contact surface of the end portion.

[0013] Preferably, the load mass is entirely located over the contact surface of the buffer when the frame is in both the first and second positions.

[0014] Preferably, the contact surface of the buffer is formed of a compliant medium.

[0015] Preferably, the compliant medium is formed of particulate matter.

[0016] Preferably, the particulate matter is sand.

[0017] Preferably, the ground support element is a rock bolt, a mesh, a shotcrete panel, a polymeric panel, or combination thereof.

[0018] In a second aspect, the invention provides a method for dynamically testing a ground support element, the method including: providing the above described system according to the first aspect; providing the ground support element to be tested; coupling the ground support element to the attachment portion of the frame; moving the frame in the direction of movement from the first position to the second position; measuring relative displacement of the attachment portion and the load mass simultaneously with the load on the element as the movement of the frame is at least slowed; and generating test data based on measurements of the relative displacement and the load. [0019] Preferably, moving the frame includes releasing the frame from a predetermined height relative to the buffer so that the frame is accelerated freely in the direction of movement by gravitational force towards the buffer.

[0020] Preferably, the method further includes simultaneously measuring the relative displacement and the load as a function of time.

[0021] Preferably, the method further includes: providing an optical detector; and providing a processor, wherein measuring the relative displacement as a function of time includes capturing the relative displacement at predetermined time intervals using the optical detector and subsequently generating image data for processing by the processor.

[0022] Preferably, the optical detector is a digital camera with a frame rate in the range of about 6000 to 10000 frames per second.

[0023] Preferably, the method further includes providing a first optical target fixed relative to the load mass and a second optical target fixed relative to the frame, the optical targets to be recognised by the processor when processing the image data and generating the relative displacement measurements.

[0024] In a third aspect, the invention provides a method for assessing one or more mechanical properties of a ground support element at high loading rates; the method including: receiving the test data generated by the above described method according to the second aspect; processing the test data to calculate an energy value for the element; and classifying the element based on the calculated energy value.

[0025] Preferably, the method further includes processing the test data to determine displacement and force values relative to time prior to processing the test data to calculate the energy value.

[0026] In a fourth aspect, the invention provides a method for quality assurance of a ground support element, the method including: obtaining the test data generated by the above described method; and evaluating the test data to determine whether the ground support element satisfies one or more parameters.

[0027] In a fifth aspect, the invention provides a process including supplying a ground support element which is equivalent to the ground support element which has been assessed for its mechanical properties based on the above described method.

Brief Description of Drawings

[0028] Exemplary embodiments of the present disclosure will now be described, by way of examples only, with reference to the accompanying description and drawings in which:

[0029] FIG. 1 is an isometric view of a system according to a first embodiment, shown in a first position;

[0030] FIG. 2 is a front elevation view of the system of FIG. 1;

[0031] FIG. 3 is a top plan view of the system of FIG. 1;

[0032] FIG. 4 is a cross-sectioned, front elevation view of the system taken along line A-A of FIG. 3;

[0033] FIG. 5 is an enlarged detail view of portion B of FIG. 4;

[0034] FIG. 6 is a cross-sectioned, front elevation view of an attachment portion of the system of FIG. 1, shown with a rock bolt anchored therewithin;

[0035] FIG. 7 is an enlarged detail view of portion C of FIG. 6;

[0036] FIG. 8 is an isometric view of the system according to the first embodiment, shown in a second position;

[0037] FIG. 9 is a front elevation view of the system of FIG. 8;

[0038] FIG. 10 is a top plan view of the system of FIG. 8; [0039] FIG. 11 is a cross-sectioned, front elevation view of the system taken along line A-A of FIG. 10;

[0040] FIG. 12 is an enlarged detail view of portion B of FIG. 11;

[0041] FIG. 13 is an isometric view of a system according to a second embodiment, shown in a first position;

[0042] FIG. 14 is a front elevation view of the system of FIG. 13;

[0043] FIG. 15 is a top plan view of the system of FIG. 13;

[0044] FIG. 16 is a cross-sectioned, front elevation view of the system taken along line A-A of FIG. 15;

[0045] FIG. 17 is an enlarged detail view of portion B of FIG. 16;

[0046] FIG. 18 is an isometric view of the system according to the second embodiment, shown in a second position;

[0047] FIG. 19 is a front elevation view of the system of FIG. 18;

[0048] FIG. 20 is a top plan view of the system of FIG. 18;

[0049] FIG. 21 is a cross-sectioned, front elevation view of the system taken along line A-A of FIG. 20;

[0050] FIG. 22 is an enlarged detail view of portion B of FIG. 21;

[0051] FIG. 23 is a cross-sectioned, isometric view of the system taken along line A-A of FIG.

20;

[0052] FIG. 24 is an isometric view of a system according to a third embodiment;

[0053] FIG. 25 is a front elevation view of the system of FIG. 24; [0054] FIG. 26 is a vertically cross-sectioned, front elevation view of the system of FIG. 24; and [0055] FIG. 27 is an enlarged detail view of portion A of FIG. 26.

[0056] FIG. 28 is a high-level diagram showing the components for generating test data using the system according to the first and second embodiments.

Description of Embodiments

[0057] Referring to FIGs. 1 to 12 of the accompanying drawings, a system 100 according to a first embodiment is depicted. The system 100 is configured for dynamically testing a ground support element, in particular a rock bolt 102 (shown in FIG. 6) for use in strata control in civil engineering and mining operations. It will, however, be appreciated that the system 100 may be utilised for dynamically testing other structural support elements.

[0058] With particular reference to FIG. 1, the system 100 includes a buffer 104. The buffer 104 has a body 106 being generally cuboidal in configuration. The body 106 extends in a widthwise direction W and a lengthwise direction L. The body 106 includes a first pair of opposing parallel sidewalls 108a extending in the widthwise direction W, and a second pair of opposing parallel sidewalls 108b extending in the lengthwise direction L. Each of the sidewalls 108a are joined at their ends to respective adjacent ends of each of the sidewalls 108b so as to form a rectangular or square profile of the body 106. It will be appreciated that the shape of the body 106 may be varied. For example, the body 106 may be circular, hexagonal or other polygonal in configuration. In the embodiment depicted, the sidewalls 108a, 108b are formed of structural steel to form a rigid frame structure of the body 106.

[0059] The body 106 includes a contact surface 110 surrounded by the sidewalls 108a, 108b.

The contact surface 110 is generally planar in configuration so as to provide a level surface (i.e. horizontal). Other embodiments may use contact surfaces that are not horizontal, or indeed contact surfaces that are not planar. Preferably, the contact surface 110 has a width dimension in the range of about 2m to 4m, more preferably 3m, and a length dimension in the range of about 2m to 4m, more preferably 3m. The contact surface 110 is preferably formed of a compliant medium contained by the sidewalls 108a, 108b. In the embodiment depicted, the compliant medium is particulate in nature and is preferably sand 111 (shown in FIG. 11). It will be appreciated, however, that the contact surface 110 may be formed of any suitable energy- dissipating material or structure. For example, the contact surface 110 may be formed of a solid material, such as a metallic impact plate, or a fluid, such as a dilatant non-Newtonian fluid, or combination thereof. In other embodiments, the buffer 104 may simply be provided in-ground or by a level ground surface. For example, a portion of the ground may be excavated and back filled with the sand 111 to provide the contact surface 110. It will be appreciated, however, that containing the medium of the buffer 104 within a framed structure, such as the sidewalls 108a, 108b, allows for a more homogenous or consistent media to be used. Optionally, the buffer 104 may be provided with a cover or lid to keep out precipitation and/or contaminants so as to ensure the properties of the medium or sand 111 remain generally consistent.

[0060] The buffer 104 includes a vertical axis 112 centrally located on the body 106 and extending perpendicularly to the contact surface 110, that is, the axis 112 extends perpendicularly to both the widthwise and lengthwise directions W, L.

[0061] The system 100 also includes a frame 114 having a longitudinal central axis 116 to be generally aligned with the axis 112 of the buffer 104 during use of the system 100. As will be explained in greater detail below, the frame 114 is configured to be moved along its axis 116 in a direction D towards the buffer 104 from a first position (see FIG. 1), in which the frame 114 is spaced from the buffer 104, to a second position (see FIG. 8), in which the frame 114 is in contact with the buffer 104 so that movement of the frame 114 in the direction D is at least slowed by the buffer 104.

[0062] The frame 114 includes a plurality of elongate frame members 118 extending longitudinally in the direction D from an upper portion 120 to a lower portion 122 of the frame 114. The frame members 118 are symmetrically spaced from the axis 116 by a perpendicular distance measured relative to the axis 116. In the embodiment depicted, the plurality of elongate frame members 118 includes a first pair 118a of diametrically opposing parallel frame members 118 relative to the axis 116, and a second pair 118b of diametrically opposing parallel frame members 118 perpendicularly offset from the first pair 118a with respect to the axis 116. Although, it will be appreciated that the frame 114 may have any suitable number of frame members in other configurational arrangements. The frame 114 also includes a circular web 124 extending circumferentially relative to the axis 116 of the frame 114 and connecting each of the elongate frame members 118 together. The web 124 is typically formed of structural grade steel and is welded to each of the frame members 118 to provide enhanced rigidity to each of the frame members 118.

[0063] As shown in FIG. 2, each of the frame members 118 are joined at their respective upper ends 126 to the upper portion 120 of the frame 114, and at their respective lower ends 128 to the lower portion 122 of the frame 114.

[0064] The upper portion 120 of the frame 114 includes a hub portion 130 arranged with its centre located on the axis 116 of the frame 114. The hub portion 130 includes a hub opening 131 (shown in FIG. 3) formed axially through the centre of the hub portion 130. The upper portion 120 also includes a plurality of strut segments 132 (shown in FIG. 2) projecting laterally from the hub portion 130 to each of the upper ends 126 of the frame members 118, with lateral ends of the strut segments 132 secured to the upper ends 126. A lifting brace 136 extends between an opposing pair of strut segments 132 to facilitate lifting of the frame 114 by a crane (not shown), or other lifting mechanism, to a predetermined height from the contact surface 110 of the buffer 104.

[0065] The upper portion 120 also includes a plurality of bracing elements 138 mounted to, and extending between, the hub portion 130 and each of the strut segments 132 to provide enhanced rigidity to the upper portion 120. The strut segments 132 and the bracing elements 138 are typically formed of structural grade steel and are welded to each other to form a rigid frame structure. The upper portion 120 further includes a plurality of rails 140 mounted to, and extending between, adjacent strut segments 132. It will be appreciated that the rails 140 may serve to facilitate the attachment of personnel equipment, such as ladders or platforms, while working on the frame 114.

[0066] The hub portion 130 includes an upper anchor flange 142 surrounding the hub opening 131, and a lower support flange 144 surrounding the hub opening 131. The lower support flange 144 is axially spaced from the anchor flange 142. The support flange 144 is fixed to each of the strut segments 132. Located between the flanges 142, 144 are a number of load cells 146 configured to output a load response between the flanges 142, 144. Optionally, strain gauges or the like may be utilised to output the load response.

[0067] The lower portion 122 of the frame 114 includes an end portion in the form of an annular disc 148 circumferentially extending with respect to the axis 116. The disc 148 has an outer diameter which is less than the width dimension of the contact surface 110 of the buffer 104 when measured in the widthwise direction W. Similarly, the disc 148 has an outer diameter which is less than the length dimension of the contact surface 110 of the buffer 104 when measured in the lengthwise direction L. By virtue of this arrangement, the disc 148 is entirely located over the contact surface 110 of the buffer 104 when the frame 114 is in both the first and second positions. In other embodiments, the outer diameter of the disc 148 may be equal to the width and length dimensions of the contact surface 110 of the buffer 104 when measured in the widthwise and lengthwise directions W, L, respectively.

[0068] In the embodiment depicted, the disc 148 preferably has an inner diameter in the range of about 1100mm to 1500mm, more preferably 1310mm, an outer diameter in the range of about 1700mm to 2100mm, more preferably 1910mm, and a constant thickness in the range of about 30mm to 70mm, more preferably 50mm. The disc 148 has a contact surface 150 (shown in FIG. 2) formed on the underside of the disc 148 which is generally planar in configuration. The contact surface 150 of the disc 148 provides the leading surface of the frame 114 with respect to the direction D of movement. The contact surface 150 of the disc 148 directly opposes the contact surface 110 of the buffer 104 in the first position. In the second position, the contact surface 150 of the disc 148 is in contact with the contact surface 110 of the buffer 104. More specifically, in the embodiment depicted, the disc 148 is embedded into the sand 111 when in the second position (as shown in FIG. 11). It will be appreciated that the dimensions and properties of the buffer 104 may be varied to alter the surface area of the contact surface 110 to in turn control the energy capture efficiency or energy dissipation through the system 100. It will also be appreciated that the contact surface 150 may be varied, by changing its profile or by increasing or decreasing its surface area for example, to change the impact response with the buffer 104.

[0069] The circular or annular configuration of the disc 148 may at least aid in minimising any imbalance upon contact with the buffer 104. This is based on having a constant radial distance from the circular periphery of the disc 148 relative to the axis 116. That is, the distance to the first point of contact with the buffer 104 is consistently at the same distance from the axis 116, thereby minimising the potential for variation between tests. It will, however, be appreciated that the end portion of the frame 114 may not necessarily have an annular configuration but instead have a square, rectangular, or other polygonal configuration, whilst having a width dimension and a length dimension equal to or less than the width and length dimensions, respectively, of the contact surface 110 of the buffer 104.

[0070] The lower portion 122 of the frame 114 also includes a plurality of frame spacers or stubs 152 projecting from the disc 148 in a direction opposite to the direction D of movement. The stubs 152 serve to attach each of the lower ends 128 of the frame members 118 to the disc 148. The stubs 152 are attached to the disc 148 and to the lower ends 128 by fasteners 154 but may alternatively be secured by welding or other fixation techniques. The stubs 152 can be removed or replaced with other stubs to change the overall height of the frame 114 as required and therefore facilitate the testing of rock bolts of varying lengths.

[0071] Together, the upper portion 120, the lower portion 122, and the frame members 118 partly surround or enclose a loading region 156 of the frame 114.

[0072] With particular reference to FIGs. 4 and 6, the frame 114 further includes an attachment portion in the form of a collared pipe 158 for coupling the rock bolt 102 to the frame 114 so that the rock bolt 102 is movable with the frame 114. The pipe 158 extends longitudinally along the axis 116 of the frame 114 through the loading region 156 between an upper end portion 160 and a lower end portion 162 of the pipe 158. The upper end portion 160 is configured to be fixed to the anchor flange 142, whilst the lower end portion 162 terminates within the loading region 156. The pipe 158 is filled with a cured cementitious grout 166 through which a borehole 168 is drilled and the rock bolt 102 subsequently anchored therewithin. Optionally, the rock bolt 102 may be point anchored, mechanically anchored (such as with an expansion shell) and/or may be embedded or partially embedded within a cured load transfer medium such as resin, cementitious grout or the like. The rock bolt 102 may further optionally be inserted into the borehole 168 with a friction Tight interference’ fit or by any other suitable means of anchoring the rock bolt 102 to enable load transfer with the interior surface of the borehole 168. A notch 164 (shown in FIG. 7) is formed around the outer circumference of the pipe 158 and partially through the grout 166 to form an annular discontinuity separating the pipe 158 into the upper and lower end portions 160, 162. The axial location of the notch 164 on the pipe 158 may vary depending on particular design criteria. [0073] A collar flange 170 is fixed to an end extremity of the lower end portion 162 of the pipe 158 and extends radially from the lower end portion 162 with respect to the axis 116 of the frame 114.

[0074] The system 100 further includes a load mass 172 secured to the collar flange 170 and locating within the loading region 156 of the frame 114. In the embodiment depicted, the load mass 172 is formed of several mass plates 172a. Each plate 172a has a central bore 174 formed therethrough with a central axis to be aligned with the axis 116 of the frame 114. The bore 174 is sized so that the collared pipe 158 may pass therethrough so that each of the plates 172a can be stacked and aligned on the axis 116 along the lower end portion 162 of the pipe 158. Each of the plates 172a are configured to be releasably secured to the collar flange 170 by a plurality of tie rods 176. In this way, the combined weight of the plates 172a is transferred to the collar flange 170 which in turn is transferred to the lower end portion 162 of the pipe 158.

[0075] In other embodiments, the rock bolt 102 may be unembedded and directly anchored to the anchor flange 142 and the collar flange 170 at each end of the rock bolt 102 or at various points along the length of the rock bolt 102.

[0076] By virtue of this configuration, the load mass 172 is spaced further from the buffer 104 in the direction D of movement than the contact surface 150 of the disc, prior to contact between the disc 148 and the buffer 104. In this way, the load mass 172 is entirely located over the contact surface 110 of the buffer 104 when the frame 114 is in both the first and second positions.

[0077] A method for dynamically testing the rock bolt 102 will now be described. The method firstly includes providing the system 100 and the rock bolt 102 to be tested. The rock bolt 102 is anchored within the borehole 168 of the pipe 158. The weight of the load mass 172 can be adjusted by adding or removing the plates 172a as desired.

[0078] The frame 114 is then hoisted to a predetermined height from the buffer 104, facilitated by the lifting brace 136. The frame 114 may be hoisted by a crane or other hoisting device and by using a quick-release hook 177 of the crane or hoisting device coupled to the lifting brace [0079] The frame 114 is then released from the crane or hoisting device so that the frame 114 accelerates under gravity in the direction D of movement towards the buffer 104 from the first position to the second position.

[0080] After contact is made between the contact surface 150 of the disc 148 and the contact surface 110 of the buffer 104, the load mass 172 continues to move toward the buffer 104 in the direction D of movement due to momentum of the load mass 172. To minimise lateral movement of the load mass 172 within the loading region 156 upon contact between the frame 114 and the buffer 104, the frame 114 is provided with a pair of opposing guide rails 178 fixed to one of the pairs of frame members 118. Each of the mass plates 172a has a lateral male profile to be loosely received or contained within a corresponding female profile of each of the guide rails 178 such that there is negligible frictional resistance to the travel of the load mass 172 in the direction D of movement.

[0081] As the load mass 172 continues to move toward the buffer 104, the momentum of the load mass 172 is transferred to the collar flange 170 which in turn transfers the momentum to the lower end portion 162 which in turn transfers the momentum to the region of the notch 164 of the pipe 158 causing the upper and lower end portions 160, 162 to axially separate, as shown in FIG. 11. Separation of the upper and lower end portions 160, 162 causes a portion of the anchored rock bolt 102 to elongate in the direction D of movement as the momentum, and therefore force, is transferred to the rock bolt 102, as shown in FIG. 12. Depending on the amount of force transferred, the rock bolt 102 will yield elastically, then plastically and may ultimately fracture from tensile overload.

[0082] To facilitate measuring the elongation of the rock bolt 102, first and second optical targets 180, 182 are provided and positioned on the pipe 158 proximate the notch 164 prior to hoisting the frame 114. The first optical target 180 is positioned on the upper end portion 160 of the pipe 158, and the second optical target 182 is positioned on the lower end portion 162 of the pipe 158 and aligned with the first optical target 180. In this way, the first optical target 180 is fixed relative to the frame 114 and the second optical target 182 is fixed relative to the load mass 172.

[0083] With particular reference to FIG. 28, an optical detector, preferably a digital camera 184, is also provided to capture images of the first and second optical targets 180, 182 over a predetermined event time interval and to subsequently generate image data. Preferably, the digital camera 184 has a frame rate in the range of about 6000 to 10,000 frames per second. A processor 186 is also provided to process the image data by recognising the optical targets 180, 182. The processor 186, for each individual image, is configured to firstly digitally identify a known distance on the targets 180, 182 to be used as a measurement calibration reference and to subsequently measure relative displacement between the optical targets 180, 182 over the predetermined time interval, specifically at the timepoint of each image. Optionally, the relative displacement may be measured using a laser distance gauge, accelerometer or the like. The processor 186 also receives load data from the load cells 146. The processor 186 is configured to firstly measure the relative displacement of the optical targets 180, 182 and subsequently match or pair this measurement with the load data as a function of time. Test data may then be generated based on measurements of the relative displacement and the load and displayed on an image display 188. The test data may be processed to calculate an energy value for the rock bolt 102. The rock bolt 102 may be classified based on the calculated energy and total displacement values. In this way, the present disclosure provides a method for assessing the mechanical properties of a ground support element at high loading rates.

[0084] Referring to FIGs. 13 to 23 of the accompanying drawings, a system 200 according to a second embodiment is depicted. The system 200 is of a similar configuration to the system 100 of the first embodiment. Accordingly, features of the system 200 that are identical to those of the system 100 are provided with an identical reference numeral. For features that are identical between the system 100 and the system 200, it will be appreciated that the above description of those features in relation to the system 100 is also applicable to the corresponding identical features found in the system 200.

[0085] The system 200 is configured for dynamically testing a ground support element, in particular a mesh 202, for use in strata control in civil engineering and mining operations. It will, however, be appreciated that the system 200 may be utilised for dynamically testing other structural support elements such as a shotcrete panel, a polymeric panel, a combined mesh and shotcrete panel, or a combined bolt, mesh and shotcrete panel, resin media, or other ground support elements, ground material or simulated ground material, or any combination thereof.

[0086] The system 200 includes the above described buffer 104. [0087] The system 200 also includes a frame 214 having a longitudinal central axis 216 to be generally aligned with the axis 112 of the buffer 104 during use of the system 200. As will be explained in greater detail below, the frame 214 is configured to be moved along its axis 216 in a direction D towards the buffer 104 from a first position (see FIG. 13), in which the frame 214 is spaced from the buffer 104, to a second position (see FIG. 18), in which the frame 214 is in contact with the buffer 104 so that movement of the frame 214 in the direction D is at least slowed by the buffer 104.

[0088] The frame 214 includes a plurality of first frame members 218 extending longitudinally in the direction D from an upper portion 220 to a lower portion 222 of the frame 214. The frame members 218 are symmetrically spaced from the axis 216 by a perpendicular distance measured relative to the axis 216. In the embodiment depicted, the plurality of frame members 218 includes a first pair 218a of diametrically opposing parallel frame members 218 relative to the axis 216, and a second pair 218b of diametrically opposing parallel frame members 218 perpendicularly offset from the first pair 218a with respect to the axis 216.

[0089] The upper portion 220 of the frame 214 includes a plurality of second frame members 224. The frame members 224 are symmetrically spaced from the axis 216 by a perpendicular distance measured relative to the axis 216. In the embodiment depicted, the plurality of second frame members 224 includes a first pair of opposing parallel frame members 224a extending in the widthwise direction W, and a second pair 224b of opposing parallel frame members 224 extending in the lengthwise direction L. Each of the frame members 224 of the first pair 224a are joined at their ends to respective adjacent ends of each the frame members 224 of the second pair 224b so as to form a rectangular or square profile of the upper portion 220.

[0090] The upper portion 220 of the frame 214 includes a hub portion 230 arranged with its centre located on the axis 216 of the frame 214. The hub portion 230 includes a hub opening 231 (shown in FIG. 15) formed axially through the centre of the hub portion 230. The upper portion 220 also includes a plurality of strut segments 232 projecting laterally from the hub portion 230 to each of the frame members 224, with lateral ends of the strut segments 232 secured to a mid-portion of the respective frame member 224.

[0091] The lower portion 222 of the frame 214 includes an end portion 247 formed of a plurality of third frame members 248. The plurality of frame members 248 includes a first pair 248a of opposing parallel frame members 248 extending in the widthwise direction W, and a second pair 248b of opposing parallel frame members 248 extending in the lengthwise direction L. Each of the frame members 248 of the first pair 248a are joined at their ends to respective adjacent ends of each the frame members 248 of the second pair 248b so as to form a rectangular or square profile of the end portion 247. It will be appreciated that the profile or configuration of the end portion 247 may be varied. For example, the end portion 247 may have a circular, hexagonal or other polygonal configuration. In the embodiment depicted, the frame members 218, 224, 248 and the strut segments 232 are formed of structural steel to form a rigid frame structure.

[0092] In this way, the frame 214 forms a generally cuboidal configuration. Although, it will be appreciated that the frame 214 may form other suitable configurations.

[0093] The end portion 247 has a width dimension which is less than the width dimension of the contact surface 110 of the buffer 104 when measured in the widthwise direction W. Similarly, the end portion 247 has a length dimension which is less than the length dimension of the contact surface 110 of the buffer 104 when measured in the lengthwise direction L. By virtue of this arrangement, the end portion 247 is entirely located over the contact surface 110 of the buffer 104 when the frame 214 is in both the first and second positions. In other embodiments, the width and length dimensions of the end portion 247 may be equal to the width and length dimensions of the contact surface 110 of the buffer 104 when measured in the widthwise and lengthwise directions W, L, respectively.

[0094] The end portion 247 has a contact surface 250 formed on the underside of each of the frame members 248 which is generally planar in configuration. The contact surface 250 of the end portion 247 provides the leading most surface of the frame 214 with respect to the direction D of movement. The contact surface 250 of the end portion 247 directly opposes the contact surface 110 of the buffer 104 in the first position. In the second position, the contact surface 250 of the end portion 247 is in contact with the contact surface 110 of the buffer 104.

[0095] The lower portion 222 of the frame 214 also includes a plurality of stubs 252 projecting from the end portion 247 in a direction opposite to the direction D of movement. The stubs 252 serve to attach each of the lower ends 228 of the frame members 218 to the end portion 247. The stubs 252 are secured to the end portion 247 and the lower ends 228 by welding but may alternatively be secured by fasteners or other fixation techniques.

[0096] Together, the upper portion 220, the lower portion 222, and the frame members 218 partly surround or enclose a loading region 256 of the frame 214.

[0097] The frame 214 further includes an attachment portion 258 fixed to each of the stubs 252 for coupling the mesh 202 to the frame 214 so that the mesh 202 is movable with the frame 214. The mesh 202 is coupled to the attachment portion 258 so that the mesh 202 is normal to the direction D of movement. In the embodiment depicted, the attachment portion 258 includes a base 259 (shown in FIG. 16) extending normal to the axis 216 and axially spaced from the mesh 202. Located between the base 259 and the mesh 202 are a number of load cells 246 configured to output a load response between the base 259 and the mesh 202. Strain gauges or the like may be utilised to output the load response.

[0098] The frame 214 further includes a shaft 271 slidably received within the hub opening 231 and longitudinally extending along the axis 216 between an upper shaft end 271a and a lower shaft end 271b (shown in FIG. 22). The upper shaft end 271a (shown in FIG. 14) includes a lifting engagement means such as a shackle 273 to facilitate lifting of the frame 214 by a crane (not shown), or other lifting mechanism, to a predetermined height from the contact surface 110 of the buffer 104.

[0099] The lower shaft end 271b terminates within the loading region 256 of the frame 214.

[0100] The system 200 further includes a load mass 274 mounted to the lower shaft end 271b so as to be movably arranged within the loading region 256 with respect to the frame 214 between a first position (see FIG. 14), in which the load mass 274 is spaced from the mesh 202, and a second position (see FIG. 21), in which the load mass 274 is in contact with the mesh 202 so as to axially load the mesh 202. In FIG. 14, the load mass 274 is shown spaced but close to the mesh 202. However, the spacing may be arbitrarily varied to suit different test circumstances. Optionally, the base of the load mass 274 may be bolted (with a bolt and plate, for example) through to the underside of the mesh 202 to ensure that the load mass 274 and the centre of the mesh 202 remain coupled together during testing displacement or shock vibration throughout the test event. As shown in FIG. 17, a collar 275 is fixed to the hub 230 around the hub opening 231 within the loading region 256 to engage a portion 276 of the load mass 274 so as to restrict axial movement of the shaft 271 in a direction opposite the direction D of movement thereby confining the load mass 274 to move within the loading region 256.

[0101] By virtue of this configuration, the load mass 274 is spaced further from the buffer 104 in the direction D of movement than the contact surface 250 of the end portion 247, prior to contact between the end portion 247 and the buffer 104. In this way, the load mass 274 is entirely located over the mesh 202 which in turn is entirely located over the contact surface 110 of the buffer 104 when the frame 214 is in both the first and second positions.

[0102] A method for dynamically testing the mesh 202 will now be described. The method firstly includes providing the system 200 and the mesh 202 to be tested. The mesh 202 is coupled to the frame 214 by way of coupling to the attachment portion 258.

[0103] The frame 214 is then hoisted to a predetermined height from the buffer 104, facilitated by the shackle 273. The frame 214 may be hoisted by a crane or other hoisting device and by using a quick-release hook 177 of the crane or hoisting device coupled to the shackle 273.

[0104] The frame 214 is then released from the crane or hoisting device so that the frame 214 accelerates under gravity in the direction D of movement towards the buffer 104 from the first position to the second position.

[0105] After contact is made between the contact surface 250 of the end portion 247 and the contact surface 110 of the buffer 104, the load mass 274 continues to move toward the buffer 104 in the direction D of movement due to momentum of the load mass 274. Movement of the load mass 274 within the loading region 256 is facilitated by appropriately sizing the hub opening 231 relative to the diameter of the shaft 271.

[0106] As the load mass 274 continues to move toward the buffer 104, the momentum of the load mass 274 is transferred to the mesh 202 to cause the mesh 202 to locally deform in the direction D of movement (as shown in FIG. 21).

[0107] To facilitate measuring the deformation of the mesh 202, first and second optical targets 280, 282 are provided (see FIG. 17). The first optical target 280 is positioned on the collar 275. The second optical target 282 is positioned on the portion 276 of the load mass 274. In this way, the first optical target 280 is fixed relative to the frame 214 and the second optical target 282 is fixed relative to the load mass 274.

[0108] The digital camera 184 is also provided to capture images of the first and second optical targets 280, 282 over a predetermined event time interval and to subsequently generate image data. The processor 186 is also provided to process the image data by recognising the optical targets 280, 282. The processor 186, for each individual image, is configured to firstly digitally identify a known distance on the targets 280, 282 to be used as a measurement calibration reference and to subsequently measure relative displacement between the optical targets 280,

282 over the predetermined time interval, specifically at the timepoint of each image.

Optionally, the relative displacement may be measured using a laser distance gauge, accelerometer or the like. The processor 186 also receives load data from the load cells 246.

The processor 186 is configured to firstly measure the relative displacement of the optical targets 280, 282 and subsequently match or pair this measurement with the load data as a function of time. Test data may then be generated based on measurements of the relative displacement and the load and displayed on the image display 188. The test data may be processed to calculate an energy value for the mesh 202. The mesh 202 may be classified based on the calculated energy and total displacement values. In this way, the present disclosure provides a method for assessing the mechanical properties of a ground support element at high loading rates. Similarly, the present disclosure provides a method for quality assurance of a ground support element whereby the method firstly includes obtaining the test data, and subsequently evaluating the test data to determine whether the ground support element satisfies one or more parameters; that is, the test data may be used to determine if the ground support element is suitable for sale or supply. Also disclosed is a process including supplying a ground support element which is equivalent to the ground support element which has been assessed for its mechanical properties based on the testing methods of the present disclosure.

[0109] Referring to FIGs. 24 to 26 of the accompanying drawings, a system 300 according to a third embodiment is depicted. The system 300 is of a similar configuration to the system 100 of the first embodiment. Accordingly, features of the system 300 that are identical to those of the system 100 are provided with an identical reference numeral. For features that are identical between the system 100 and the system 300, it will be appreciated that the above description of those features in relation to the system 100 is also applicable to the corresponding identical features found in the system 300. [0110] The system 300 is configured for dynamically testing the rock bolt 102 (shown in FIG.

6) and the mesh 202 in a combined method of testing as will be discussed below.

[0111] The system 300 includes the above described buffer 104 and frame 114. With particular reference to FIGs. 25 and 26, the mesh 202 is secured to the frame 114 adjacent the lower ends 128 of the frame members 118 so that the mesh 202 extends normal to the direction D of movement. The height of the mesh 202 relative to the disc 148 may be adjusted depending on the application. Optionally, the mesh 202 may be constrained at distinct points relative to the frame 114 or may be fully constrained around a perimeter of the mesh 202.

[0112] A load mass 374 is mounted to the collar flange 170 of the lower end portion 162 of the pipe 158. The load mass 374 is of a similar construction to the load mass 172 of the system 100. The load mass 374 preferably has a domed base 376 to minimise localized stress concentrations imparted to the mesh 202. Although, other rounded or reduced profiles of the base 376 may be utilised. The base 376 is secured (by way of bolts and a plate 375, for example) through to the underside of the mesh 202 to ensure that the load mass 374 and the centre of the mesh 202 remain coupled together during testing displacement or shock vibration throughout the test event.

[0113] In the embodiment depicted, the mesh 202 is constrained within a mesh frame 303 which is configured to attach to each of the frame members 118 adjacent the lower ends 128. A plurality of discrete sub-frames or supports 378 are affixed to the mesh frame 303 and spaced from the underside of the mesh 202. Located between each of the supports 378 and the mesh 202 is a load cell 346 (FIG. 27) configured to output a load response between the respective support 378 and the mesh 202. Strain gauges or the like may be utilised to output the load response. Optionally, the mesh 202 may be held by each of the load cells 346 by way of spigot attachments (not shown).

[0114] A method for dynamically testing the rock bolt 102 and mesh 202 using the system 300 is similar to the methods for dynamically testing the rock bolt 102 and the mesh 202 using the system 100 and the system 200, respectively.

[0115] After contact is made between the contact surface 150 of the disc 148 and the contact surface 110 of the buffer 104, the load mass 374 continues to move toward the buffer 104 in the direction D of movement due to momentum of the load mass 374. [0116] As the load mass 374 continues to move toward the buffer 104, the momentum of the load mass 374 is transferred to the collar flange 170 which in turn transfers the momentum to the lower end portion 162 which in turn transfers the momentum to the region of the notch 164 (FIG. 7) of the pipe 158 causing the upper and lower end portions 160, 162 to axially separate. Separation of the upper and lower end portions 160, 162 causes a portion of the anchored rock bolt 102 to elongate in the direction D of movement as the momentum, and therefore force, is transferred to the rock bolt 102. As the portion of the anchored rock bolt 102 elongates, the momentum of the load mass 374 is further transferred to the mesh 202 to cause the mesh 202 to locally deform in the direction D of movement. In this way, momentum of the load mass 374 is transferred to both the rock bolt 102 and the mesh 202 in a single operation. To facilitate measuring the deformation of the rock bolt 102 and the mesh 202, optical targets such as those utilised in the system 100 and the system 200 may be provided in the system 300.

[0117] It will be appreciated that the systems 100, 200 and 300 may provide a relatively cost- effective, compact and simple means of dynamically testing a ground support element.

[0118] A person skilled in the art will appreciate various modifications and alternatives to individual aspects of the systems described, along with alternate uses of the systems.

List of Reference Numerals

100 System according to a first embodiment 150 Contact surface of disc 102 Rock bolt 152 Stubs

104 Buffer 154 Fasteners

106 Body 156 Loading region of frame

W Width wise direction 158 Collared pipe

L Lengthwise direction 160 Upper end portion of pipe

108a First pair of sidewalls 162 Lower end portion of pipe

108b Second pair of sidewalls 164 Notch

110 Contact surface of buffer 166 Grout

111 Sand 168 Borehole

112 Axis of buffer 170 Collar flange

114 Frame 172 Load mass

116 Axis of frame 172a Mass plates

D Direction of movement 174 Central bore

118 Frame members 176 Tie rods

118a First pair of frame members 177 Quick-release hook 118b Second pair of frame members 178 Guide rails 120 Upper portion of frame 180 First optical target

122 Lower portion of frame 182 Second optical target

124 Web 184 Digital Camera

126 Upper ends of frame members 186 Processor

128 Lower ends of frame members 188 Image Display

130 Hub portion

131 Hub opening 200 System according to a second embodiment

132 Strut segments 202 Mesh

136 Lifting brace 214 Frame

138 Bracing elements 216 Axis of frame

140 Rails 218 First frame members

142 Upper anchor flange 218a First pair of first frame members

144 Lower support flange 218b Second pair of first frame members

146 Load cells 220 Upper portion of frame

148 Disc 222 Lower portion of frame Second frame members a First pair of second frame membersb Second pair of second frame members

Lower ends of first frame members

Hub portion

Hub opening

Strut segments

Load cells

End portion of frame

Third frame members a First pair of third frame members b Second pair of third frame members

Contact surface of end portion

Stubs

Loading region of frame Attachment portion Base of attachment portion Shaft a Upper shaft end b Lower shaft end Shackle Load mass Collar

Portion of load mass First optical target Second optical target

System according to a third embodiment

Mesh frame

Load cell

Load mass

Plate

Domed base Support

Claims

1. A system for dynamically testing a ground support element for use in strata control in civil engineering and mining operations, the system including: a buffer; a frame to be moved in a direction towards the buffer from a first position, in which the frame is spaced from the buffer, to a second position, in which the frame is in contact with the buffer so that movement of the frame in the direction is at least slowed by the buffer, the frame having an attachment portion to be coupled to the element so that the element is movable with the frame; and a load mass arranged for relative movement with respect to the frame and operatively associated with the element such that contact between the buffer and the frame causes the load mass to move in the direction of movement relative to the frame to load the element thereby causing displacement of a portion of the element in the direction of movement as the movement of the frame is at least slowed, wherein the frame has an end portion to contact the buffer, with the load mass spaced further from the buffer in the direction of movement than the end portion, prior to contact between the end portion and the buffer, such that the load mass continues to move toward the buffer in the direction of movement after the contact between the end portion and the buffer.

2. The system of claim 1, wherein the frame includes one or more frame members extending in the direction of movement from an upper portion to a lower portion, with the lower portion providing the end portion, and wherein the load mass is movably arranged between the upper and lower portions.

3. The system of claim 2, wherein the one or more frame members, the upper portion, and the lower portion at least partly surround a loading region in which the load mass is located.

4. The system of any one of the preceding claims, wherein the buffer includes a contact surface being generally planar in configuration and extending in a widthwise direction and a lengthwise direction, with the widthwise and lengthwise directions being transverse to the direction of movement.

5. The system of claim 4, wherein the end portion has a contact surface being generally planar in configuration and extending in a widthwise direction and a lengthwise direction, with the widthwise and lengthwise directions of the contact surface of the end portion being parallel with the widthwise and lengthwise directions, respectively, of the contact surface of the buffer.

6. The system of claim 5, wherein the contact surface of the buffer has a width dimension and a length dimension, and wherein the contact surface of the end portion has a width dimension and a length dimension, with the width and the length dimensions of the contact surface of the buffer being equal to or greater than the width and the length dimensions, respectively, of the contact surface of the end portion.

7. The system of claim 6, wherein the load mass is entirely located over the contact surface of the buffer when the frame is in both the first and second positions.

8. The system of any one of claims 4 to 7, wherein the contact surface of the buffer is formed of a compliant medium.

9. The system of claim 8, wherein the compliant medium is formed of particulate matter.

10. The system of claim 9, wherein the particulate matter is sand.

11. The system of any one of the preceding claims, wherein the ground support element is a rock bolt, a mesh, a shotcrete panel, a polymeric panel, or combination thereof.

12. A method for dynamically testing a ground support element, the method including: providing the system of any one of the preceding claims; providing the ground support element to be tested; coupling the ground support element to the attachment portion of the frame; moving the frame in the direction of movement from the first position to the second position; measuring relative displacement of the attachment portion and the load mass simultaneously with the load on the element as the movement of the frame is at least slowed; and generating test data based on measurements of the relative displacement and the load.

13. The method of claim 12, wherein moving the frame includes releasing the frame from a predetermined height relative to the buffer so that the frame is accelerated freely in the direction of movement by gravitational force towards the buffer.

14. The method of claim 12 or 13 further including simultaneously measuring the relative displacement and the load as a function of time.

15. The method of claim 14 further including: providing an optical detector; and providing a processor, wherein measuring the relative displacement as a function of time includes capturing the relative displacement at predetermined time intervals using the optical detector and subsequently generating image data for processing by the processor.

16. The method of claim 15, wherein the optical detector is a digital camera with a frame rate in the range of about 6000 to 10000 frames per second.

17. The method of claim 16 further including providing a first optical target fixed relative to the load mass and a second optical target fixed relative to the frame, the optical targets to be recognised by the processor when processing the image data and generating the relative displacement measurements.

18. A method for assessing one or more mechanical properties of a ground support element at high loading rates; the method including: receiving the test data generated by the method of any one of claims 12 to 17; processing the test data to calculate an energy value for the element; and classifying the element based on the calculated energy value.

19. The method of claim 18 further including processing the test data to determine displacement and force values relative to time prior to processing the test data to calculate the energy value.

20. A method for quality assurance of a ground support element, the method including: obtaining the test data generated by the method of any one of claims 12 to 17; and evaluating the test data to determine whether the ground support element satisfies one or more parameters.

21. A process including supplying a ground support element which is equivalent to the ground support element which has been assessed for its mechanical properties based on the method of any one of claims 12 to 17.