WO2012056393A1

WO2012056393A1 - Mine support

Info

Publication number: WO2012056393A1
Application number: PCT/IB2011/054749
Authority: WO
Inventors: Lourens Johannes Scheepers; Stephen Ashley
Original assignee: FIRST STRUT Pty Ltd T/A FIRST TECH GROUP; Anglogold Ashanti PLC
Current assignee: FIRST STRUT Pty Ltd T/A FIRST TECH GROUP; Anglogold Ashanti PLC
Priority date: 2010-10-25
Filing date: 2011-10-25
Publication date: 2012-05-03
Anticipated expiration: 2013-04-25

Abstract

This invention relates to a mine support, and more particularly but not exclusively, to a mine prop which is extruded from a plastic material. The mine prop includes a first elongate tubular structure made from an at least partially polymeric material, and a second elongate tubular structure made from an at least partially polymeric material, wherein the first elongate tubular structure is configured and dimensioned to at least partially fit inside the second elongate tubular structure, in order for the mine prop to be displaceable between an expanded position in which at least part of the first elongate tubular structure is located inside the second tubular structure, and a collapsed position in which a larger part of the first tubular structure is located inside the second tubular structure. The mine prop also includes a retaining mechanism for retaining the mine prop in the expanded position, the configuration being such that the mine prop is allowed to be displaced towards the collapsed position when a predetermined load is exerted on the mine prop.

Description

MINE SUPPORT

BACKGROUND TO THE INVENTION

THIS invention relates to a mine support, and more particularly but not exclusively, to a mine prop which is extruded from a plastic material.

A mine prop is a support post that is used as a roof support in the mining environment. In particular, it is often used to support a hanging wall of a stope relative to a foot wall of a stope. Props are traditionally made from timber, but some steel props are also available in the marketplace.

Mine props are often designed to yield when a predetermined axial force is applied thereto, but it is still an imperative design consideration for a prop to be designed not to fail unpredictably due to buckling below the predetermined design loads. It will therefore be appreciated that the weight to strength ratio of a mine prop, especially a timber mine prop, is often difficult to optimize. Timber props suffer from the disadvantage that the strength of the timber is somewhat unpredictable as the strength is influenced by the rate of growth (driven by seasonal changes and rainfall) and the existence of natural weaknesses due to knobs. To overcome these potential weaknesses, larger diameter timber is chosen to ensure sufficient strength despite such weaknesses. It follows that in many cases existing mine props are relatively heavy, which is particularly undesirable in the environment in which they are to be used.

Due to the fact that strength of timber is unpredictable (as discussed above), the support performance from individual support units is unpredictable. This has obvious impact on support design. To overcome this disadvantage it is desirable to use an engineered material to manufacture a support product. It has in the past been proposed to manufacture steel mine props as an alternative to timber mine props, but this is an expensive alternative that does not really address the weight concerns associated with existing mine props. In addition to the above, mining operations are becoming increasingly cost sensitive, and it would be beneficial if lower cost alternative mine props could be designed which would still meet all the stringent safety criteria applicable to the mining industry. The same criteria discussed above also apply to the design and supply of support packs that provide similar support in the mining environment.

Timber mine props are also known to be used in applications where yielding support is required. Yielding timber props are formed by modifying the structure of the prop, for example making cuts in the bottom end (wedge props) or cutting a tapered cone on the bottom section (profiled prop). However, the same disadvantage discussed above still prevails.

It is accordingly an object of the invention to provide a mine prop that will, at least partially, alleviate the above disadvantages. It is also an object of the invention to provide a mine prop which will be a useful alternative to existing mine props.

It is a further object of the invention to provide a mine support structure that will, at least partially, alleviate the above disadvantages, and/or which will be a useful alternative to existing support structures, including support packs.

SUMMARY OF THE INVENTION

According to the invention there is provided a mine prop including:

a first elongate tubular structure made from an at least partially polymeric material;

a second elongate tubular structure made from an at least partially polymeric material, wherein the first elongate tubular structure is configured and dimensioned to at least partially fit inside the second elongate tubular structure, in order for the mine prop to be displaceable between an expanded position in which at least part of the first elongate tubular structure is located inside the second tubular structure, and a collapsed position in which a larger part of the first tubular structure is located inside the second tubular structure;

a retaining mechanism for retaining the mine prop in the expanded position, the configuration being such that the mine prop is allowed to be displaced towards the collapsed position when a predetermined load is exerted on the mine prop.

The retaining mechanism may include at least one pin extending between sidewalls of both the first and the second tubular structure at an overlapping location. The retaining pin may be adapted to shear when a predetermined load is exerted thereon.

There is also provided for the retaining pin to be adapted to act as a shearing device for shearing the sidewalls of the first and second tubular structure when a predetermined load is exerted thereon.

There is furthermore provided for the retaining mechanism to be in the form of a wedge formation located on the first tubular structure, the wedge formation having an outer diameter larger than the inner diameter of the second tubular structure in order for the wedge formation to at least partially flare the second tubular structure when a predetermined load is exerted thereon.

A further feature of the invention provides for the mine prop to include an adjustable extension in the form of a sleeve that is securable to an end of the mine prop.

There is provided for the sleeve to engage the mine prop by way of complementary threads provided in an inner surface of the sleeve, and on an outer surface of the mine prop.

Preferably, the threads are provided on an operatively upper end of the first tubular structure.

Preferably, the first elongate tubular structure is in the form of an extruded tube including a reinforcement formation provided in the inside thereof.

Preferably, a plurality of reinforcing formations extend lengthwise along the tubular structure, and are more preferably in the form of reinforcing ribs extending inwardly or outwardly from the tubular structure. ln a preferred embodiment the ribs extend radially inwardly from a wall of the tubular structure towards a centre of the tubular structure.

There is provided for the ribs to meet at or towards the centre of the tubular structure.

The ribs may be cross-shaped or Y-shaped in cross section, but it will be appreciated that many different configuration would suffice.

Preferably the second tubular structure is in the form of a hollow extruded tube being configured and dimensioned to receive the first tubular structure in a snug fit.

In a preferred embodiment the first tubular structure and the second tubular structure are be made from PVC or a PVC / fiber composite.

There is provided for the wedge formation also to be made from PVC or a PVC / fibre composite, with the wedge formation being secured to the outer surface of the first tubular structure.

Preferably the wedge formation is welded to the first tubular structure.

BRIEF DESCRIPTION OF THE DRAWINGS

Two embodiments of the invention are described by way of non-limiting examples, and with reference to the accompanying drawings in which: Figure 1 is a side view of a mine prop in accordance with the invention as used in a mine stope; and

Figure 2 is a cross-sectional end view of a first tubular structure of the mine prop;

Figure 3 is a perspective view of the first tubular structure of the mine prop of Figure 1 ;

Figure 4 is a cross-sectional side view of the mine prop of Figure 1 ;

Figure 5 is a cross-sectional plane view of the mine prop of Figure 1;

and

Figure 6 is a cross-sectional side view of a further embodiment of the mine prop.

DETAILED DESCRIPTION OF INVENTION

Referring to the drawings, in which like numerals indicate like features, a non-limiting example of a mine prop in accordance with the invention is generally indicated by reference numeral 10. The mine prop 10 is typically used to support the hanging wall 20 in a stope, by transferring loads to the foot wall 30. The mine prop 10 is of a yielding nature, and comprises a first tubular section 40, that slideably fits inside a second tubular structure 50. Retaining means 60 prevents relative displacement between the first tubular structure 40 and the second tubular structure 50 until a predetermined yielding load is reached. ln this particular, non-limiting, embodiment the first tubular structure 40 and the second tubular structure 50 are in the form of tubular, elongate PVC tubes that are manufactured in an extrusion process. More particularly, in this embodiment the first elongate tubular structure 40 is in the form of a pipe having sidewalls 41 defining a circular cross-sectional profile. Reinforcing formations 42, in the form of reinforcing ribs, extend inwardly from the sidewalls 41 towards a center of the tubular structure so as to provide structural rigidity to the mine prop. In this particular case, the reinforcing formations form a cross-shaped structure when viewed in plan, but it will be appreciated that many arrangements will suffice. For example, the reinforcement formations may:

« be Y-shaped;

e be #-shaped;

« may only extend partially towards the centre of the tubular structure; and/or

» may extend radially outwardly from the sidewalls of the tubular structure.

The important common denominator between the various configurations is that the reinforcing formations are substantially elongate relative to the tubular structure, and are typically integrally formed with the sidewalls of the tubular structure.

The second tubular structure 50 is in the form of a hollow tube. The first tubular structure 40 is configured and dimensioned to form a snug fit inside the second tubular structure 50. At least a lower part of the second tubular structure does not include reinforcing formations to enable relative displacement between the first and the second tubular structure between expanded and collapsed positions. The mine prop 10 is designed to yield (i.e. to be displaced from the expanded to the collapsed positions) when a predetermined load is exerted onto the mine prop. This is achieved by providing a yieldable retaining mechanism 60, that will prevent relative displacement under normal operating conditions, but which will allow relative telescopic displacement above a predetermined design load.

In the embodiment shown in Figure 4 and 5, the yielding mechanism 60 includes two shearing pins that extend through overlapping sections of the first 40 and second 50 tubular structures. In this particular example, the shearing pins do not shear, but rather act as a shearing mechanism in that they cut slots into the sidewall of the second tubular structure 50 when the designed load is reached. However, it is also foreseeable that the shearing pins may be designed to shear when the load exerted thereon exceeds a predetermined magnitude. Also, the invention is not limited to the use of two shearing pins, as any number of shearing pins could be used depending on the structural design of the system.

In the embodiment shown in Figure 6, the yielding mechanism is in the form of a wedge formation 65 that is secured to the first tubular structure 40, and which is configured and dimensioned to flare open the end 66 of the second tubular structure 50 when a predetermined load is applied thereto, thus allowing displacement of the first tubular structure 40 relative to the second tubular structure 50. The wedge formation 65 is preferably made from PVC, and is welded to the tubular structure 40.

The prop 10 shown in Figure 6 also includes an extension arrangement in the form of a sleeve 70 having internal threads 71 adapted to engage complementary external threads 45 provided on the first tubular structure 40. Although the sleeve 70 in itself constitutes an extension, it is also adapted to receive a further extension in the form of required length of a tubular structure 75 which also has external threads 76 for engaging the sleeve 70. In this way the length of the prop 10 can effectively be adjusted to any required length. Although not shown in the drawings, the extension arrangement can also be applied to the embodiment of Figures 4 and 5.

Further, the above are but two embodiments, and the retaining mechanism is not limited to shearing pins and/or a wedge formation. Any retaining mechanism that allows relative displacement between the two tubular structures can be used.

In one specific design the first tubular structure 40 is about 1000mm in length, and has an outer diameter of about 180mm, with a wall thickness of about 10.5mm. The second tubular structure 50 is about 1300mm in length, and has an inner diameter only slightly larger than the outer diameter of the first tubular structure 40 so as to enable a snug slide fit. The wall thickness of the second tubular structure is about 7mm, and no internal reinforcing is provided. The shear pins 60 are located about 300mm from the bottom of the first tubular structure 40. This is, however, but one example, and it will be appreciated that many configurations can be arrived upon through the application of sound engineering principles.

The tubular structures of the mine prop will typically be manufactured in an extrusion process from a suitable plastic material, which may for example be PVC, or alternatively a PVC / fibre glass composite.

The inventors foresee that a mine prop in accordance with the invention will be cost-effective to manufacture and light weight, whilst still being structurally strong enough to withstand the loads required to provide support in the mining environment.

It will be appreciated that the above is only one embodiment of the invention and that there may be many variations without departing from the spirit and/or the scope of the invention.

Claims

CLAIMS:

1. A mine prop including:

2. The mine prop of claim 1 in which the retaining mechanism comprises at least one pin extending between sidewalls of both the first and the second tubular structure at a position where the first and second tubular structures overlap, in order for the retaining pin to act as a shearing device for shearing the sidewalls of the first and second tubular structure when a predetermined load is exerted thereon.

3. The mine prop of claim 1 in which the retaining mechanism is in the form of a wedge formation located on the first tubular structure, the wedge formation having an outer diameter larger than the inner diameter of the second tubular structure in order for the wedge formation to at least partially flare the second tubular structure when a predetermined load is exerted thereon.

4. The mine prop of any one of the preceding claims including an adjustable extension in the form of a sleeve that is securable to an end of the mine prop.

5. The mine prop of claim 4 in which the sleeve is adapted to engage the mine prop by way of complementary threads provided in an inner surface of the sleeve, and on an outer surface of the mine prop.

6. The mine prop of claim 5 in which the threads are provided on an operatively upper end of the first tubular structure.

7. The mine prop of any one of the preceding claims in which the first elongate tubular structure is in the form of an extruded tube including a reinforcement formation provided in the inside thereof.

8. The mine prop of claim 7 in which a plurality of reinforcing formations in the form of reinforcing ribs extending inwardly or outwardly from the tubular structure extend lengthwise along the tubular structure.

9. The mine prop of claim 8 in which the ribs extend radially inwardly from a wall of the tubular structure towards a centre of the tubular structure.

10. The mine prop of any one of the preceding claims in which the second tubular structure is in the form of a hollow extruded tube being configured and dimensioned to receive the first tubular structure in a snug fit.

11. The mine prop of any one of the preceding claims in which the tubular structures are made from PVC or a PVC / fiber composite.

12. The mine prop of claim 3 in which the wedge formation is made from PVC or a PVC / fiber composite.

13. The mine prop of any one of the preceding claims substantially as herein described with reference to the accompanying figures.