WO2023164750A1

WO2023164750A1 - Block caving mine configurations and methods

Info

Publication number: WO2023164750A1
Application number: PCT/AU2023/050146
Authority: WO
Inventors: Geoffrey DUNSTAN
Original assignee: Caveman Consulting Pty Ltd
Priority date: 2022-03-04
Filing date: 2023-03-03
Publication date: 2023-09-07

Abstract

A block caving mine configuration including one or more drawbells that each funnel into a respective intersection of drives in an extraction level, such that there are at least four draw points at the base of each of the one or more drawbells.

Description

BLOCK CAVING MINE CONFIGURATIONS AND METHODS

Field of the Invention

[001 ] The present invention relates to block caving mine configurations, block caving mining methods, and methods for developing block caving mines.

Background

[002] Any reference herein to known prior art does not, unless the contrary indication appears, constitute an admission that such prior art is commonly known by those skilled in the art to which the invention relates, at the priority date of this application.

[003] Block caving is an underground mining method whereby an ore body (1 ) is ‘undermined’ or mined from the bottom up. A cavern (or ‘undercut cavity’) (2) is excavated beneath the ore body (or ‘ore column’), and the ore body thereafter collapses into the undercut cavity under its own weight. Funnel type structures known as drawbells (3) are formed beneath the undercut cavity and operate to funnel collapsed rock/ore to draw points (4) within a haulage network (or ‘extraction level’) (8) below. Ore is collected from the draw points by haulage vehicles and transported to the surface. There is usually no need for additional blasting once the rock/ore begins to naturally collapse.

[004] Conventional approaches implement two main drawbell I extraction level configurations (or ‘layouts’). These are the Herringbone and El Teniente configurations as illustrated in Figures 4A and 4B respectively. Both configurations comprise a series of parallel ‘extraction drives’ (5) with intersecting secondary or ‘drawbell drives’ (6) that result in a series of specifically shaped columns (7) therebetween. Figures 4C and 4D illustrate typical drawbell drives for Herringbone (4C) and El Teniente (4D) configurations/layouts. The base of the drawbell typically sits centrally between the ends of the drawbell drive, funnelling ore from above to two opposed draw points (4) (i.e. the first draw point being accessible via entry to the drawbell drive from the extraction drive on one side of the drawbell and the second draw point being accessible via entry to the drawbell drive from the extraction drive on the opposite side of the drawbell, see e.g. Figures 4A-D).

[005] Drawbell shapes vary but often they have the shape of an inverted frustum of a square or rectangular pyramid. This results in ‘pillars’ (9) being provided over the extraction drives, which are commonly referred to as the major apex pillars. It will be appreciated that pillars are also formed between drawbells over the columns (7) and these are commonly referred to as the minor apex pillars.

[006] In both the Herringbone and El Teniente configurations entry to the secondary or drawbell drives from the extraction drives is designed to be angled from the extraction drives such that ore arriving at the draw points does not inadvertently flow into the extractions drives. Further, chamfered sides at the entry to the drawbell drives provide the draw points are more readily accessible by haulage vehicles like Load Haul Dump (LHD) units (110) which are typically used to transport ore a short distance underground from the draw points to a materials handling system (e.g. crusher or ore pass). Other larger haulage vehicles and fixed infrastructure then being responsible for transporting the crushed ore to the surface.

[007] Whilst historically these configurations have been sufficient, they are less effective and less stable in certain rock types, in deeper mines, and/or where there are taller ore columns. In such cases, the rock (e.g. forming the pillars (9)) may be inherently weaker and/or there may be increased weight over the extraction drive pillars such that the extraction drives are unstable and have a larger probability of caving in. Collapse of an extraction drive is highly undesirable as ore from the surrounding drawbells is no longer recoverable unless a secondary extraction level is constructed, below the first extraction level. Obviously, the development of a second deeper extraction level results in increased labour, time and expense, and reduces the efficiency of the mining operation.

[008] To address this, conventional approaches have sought to reduce the size of the extraction drives and/or to increase the size of the columns (7) and pillars, and thus the drawbell spacing. The aim being to increase the amount of stable un-blasted rock/ore around the extraction drives (i.e. forming the major and minor apex pillars). However, extraction drives need to be maintained at a certain size to allow for haulage vehicle access. Furthermore, a by-product of increased drawbell spacing is that upper portions of neighbouring drawbells do not interact, leading to stagnant areas between drawbells where rock/ore does not flow into the drawbells. As fragmentation of the ore body progresses, the stagnant zones build up, again increasing the load on the extraction drive I major apex pillars. In the Herringbone and El Teniente mining layouts for example, the extraction drive and drawbell drive spacing is limited to about 34m and 22m respectively, before the interaction of the drawbells is compromised.

Summary of the invention

[009] In one broad from, the present invention provides a block caving mine configuration including one or more drawbells that each funnel into a respective intersection of drives in an extraction level, such that there are at least four draw points at the base of each of the one or more drawbells.

[0010] In some forms, the intersection of drives in the extraction level is formed by the intersection of two drives such that each of the four draw points is accessible from a different direction.

[0011 ] In some forms, the extraction level comprises a rectangular grid layout. In some forms, the block caving mine configuration includes a plurality of drawbells that each funnel into a respective intersection in the grid. In some forms, the drawbells are spaced from one another by at least one intersection, in the direction of both axes of the grid. In some forms, the grid is a square grid.

[0012] In some forms, the extraction level includes: a first plurality of main drives that are substantially parallel; and a second plurality of main drives that are substantially parallel, wherein the second plurality of main drives are angled with respect to the first plurality of main drives. In some forms, the first plurality of main drives and the second plurality of main drives are angled at about 90 degrees with respect to one another. In some forms, the first plurality of main drives are substantially equi-spaced from one another. In some forms, the second plurality of main drives are substantially equi-spaced from one another.

[0013] In some forms, each of the one or more drawbells is located above a respective drawbell area defined by a pair of adjacent drives from the first plurality of main drives, and a pair of adjacent drives from the second plurality of main drives. [0014] In some forms, within each drawbell area, there are two drawbell access drives that intersect, each respective drawbell funnelling into the intersection of the two drawbell access drives. In some forms, a first of the two drawbell access drives is substantially parallel to the first plurality of main drives and a second of the two drawbell access drives is substantially parallel to the second plurality of main drives. In some forms, the first of the two drawbell access drives is located substantially at a midpoint between the pair of adjacent drives from the first plurality of main drives that in part define the drawbell area, and the second of the two drawbell access drives is located substantially at a midpoint between the pair of adjacent drives from the second plurality of main drives that in part define the drawbell area, such that the intersection of the two drawbell access drives is substantially centrally located within the drawbell area.

[0015] In some forms, the distance between neighbouring main drives of the first plurality of main drives is greater than about 35m. In some forms, the distance between neighbouring main drives of the first plurality of main drives is in the range of about 35m to about 60m. In some forms, the distance between neighbouring main drives of the second plurality of main drives is greater than about 35m. In some forms, the distance between neighbouring main drives of the second plurality of main drives is in the range of about 35m to about 60m. In some forms, the distance between adjacent drawbell centres along a line substantially parallel to the first plurality of main drives is greater than about 35m. In some forms, the distance between adjacent drawbell centres along a line substantially parallel to the first plurality of main drives is in the range of about 35m to about 60m. In some forms, the distance between adjacent drawbell centres along a line substantially parallel to the second plurality of main drives is greater than about 35m. In some forms, the distance between adjacent drawbell centres along a line substantially parallel to the second plurality of main drives is in the range of about 35m to about 60m.

[0016] In some forms, there are no additional extraction levels above the extraction level which is at the base of the one or more drawbells. In some forms, there are no draw points at a depth which is shallower than the draw points which are located at the base of the one or more drawbells. [0017] In some forms, the one or more drawbells comprise an upper cavity that has the shape of inverted frustum of a rectangular pyramid, and a lower cavity that is substantially rectangular prism shaped.

[0018] In a further broad form, the present invention provides a block caving mine including a block caving mine configuration as described in any of the forms herein.

[0019] In a further broad form, the present invention provides a block caving mining method including the step of developing a block caving mine configuration in any of the forms described herein.

[0020] In a further broad form, the present invention provides a block caving mining method including the step of extracting ore from drawbell draw points in a block caving mine with a configuration in any of the forms described herein.

[0021 ] In a further broad form, the present inventions provides use of a block caving mine configuration as claimed in any one forms described herein.

[0022] In a further broad form, the present invention provides a method of developing a block caving mine, the method including: establishing an undercut level beneath ore to be mined; developing an extraction level beneath the undercut level, the extraction level comprising extraction level drives; and developing one or more drawbells that extend between the undercut level and the extraction level, and that each funnel into a respective intersection of extraction level drives, to provide at least 4 draw points at the base of each of the one or more drawbells.

[0023] In some forms, the intersection of extraction level drives is formed by the intersection of two drives such that each of the 4 draw points is accessible from a different direction.

[0024] In some forms, the one or more drawbells is/are developed from undercut level drives and/or the extraction level drives. In some forms, the one or more drawbells is/are developed by drilling and blasting from the undercut level drives and/or the extraction level drives.

[0025] In a further broad form, the present invention provides a block caving mining method including the steps of: developing a block caving mine in accordance with the method of any one of the forms described herein; caving ore into the one or more drawbells; and extracting ore from draw points of the one or more the drawbells.

[0026] In a further broad form, the present invention provides an extraction level layout for a block caving mine comprising: a first plurality of drives that are substantially parallel; and a second plurality of drives that are substantially parallel, wherein the second plurality of drives are angled with respect to the first plurality of drives.

[0027] In some forms, the first plurality of drives and the second plurality of main drives are angled at about 90 degrees with respect to one another. In some forms, the first plurality of drives are substantially equi-spaced from one another. In some forms, the second plurality of drives are substantially equi-spaced from one another. In some forms, the extraction level layout comprises a square grid of drives.

[0028] In a further broad form, the present invention provides a method of developing a block caving mine, including developing an extraction level with a layout as claimed in any one of the forms described herein.

[0029] In a further broad form, the present invention provides a method of developing a block caving mine as claimed in any one of the forms described herein, wherein developing an extraction level comprises developing an extraction level with a layout as claimed in any one of the forms described herein.

[0030] It will be appreciated that when distances between adjacent neighbouring drives or drawbells are referred to generally herein it is assumed that such measurements are taken between like points in the neighbouring drives I drawbells (e.g. centre of drive to centre of drive etc.) [0031 ] It will also be appreciated that the ‘extraction level’ may sometimes be referred to in the art as the ‘production level’. It will also be appreciated to that ‘drives’ may sometimes be referred to as ‘drifts’ or ‘galleries’, and generally refer to underground tunnels or passages.

Brief Description of the Drawings

[0032] Embodiments of the present invention will be described in further detail with reference to the drawings in which:

Figures 1 to 3 illustrate the process of block caving generally, showing progression of ore fragmentation;

Figure 4A is a plan view of the prior art Herringbone block cave layout;

Figure 4B is a plan view of the prior art El Teniente block cave layout;

Figure 4C is a plan view of a drawbell drive and draw points in a Herringbone block cave layout;

Figure 4D is a plan view of a drawbell drive and draw points in an El Teniente block cave layout;

Figure 5A illustrates a post undercutting method for sequencing the formation of a block caving mine layout;

Figure 5B illustrates an advance undercutting method for sequencing the formation of a block caving mine layout;

Figure 5C illustrates a pre-undercutting method for sequencing formation of a block caving mine layout;

Figure 6 is a perspective view (with rock not shown) of a block caving mine configuration according to one example of the invention;

Figure 7 is a side sectional view of a lower cavity of a drawbell and haulage vehicle at a draw point thereof;

Figure 8 is a plan view of an extraction level layout in accordance with one example of the invention;

Figure 9 is a side sectional view of a single drawbell portion of a block caving mine configuration/layout according to one example of the invention;

Figure 10 is a side sectional view of a block caving mine configuration according to one example of the invention, also indicating typical locations for post condition blasting drifts; Figure 11 is a 3-dimensional cut-away view of a block caving mine configuration according to one example of the invention, also indicating typical locations for post condition blasting drifts; and

Figure 12 illustrates an example of method steps for forming a block caving mine with a configuration as described in the present disclosure.

Detailed Description of Preferred Embodiments

[0033] Block caving mine configurations and methods according to the present disclosure include one or more drawbells with at least four draw points each.. This is typically achieved by locating drawbells such that they funnel into a respective intersection of extraction level drives. Providing four draw points provides several advantages over conventional configurations that only have drawbells with two draw points.

[0034] In the first instance the rate of ore removal is increased, as four draw points may be accessed simultaneously as opposed to two. It has also been surprisingly identified that the use of four draw points provides for more uniform rock disturbance I flow across the span of the drawbell, which allows for larger drawbells, and a larger drawbell spacing (e.g. both span across the top of the drawbell and centre to centre spacing of neighbouring drawbells may be greater than 35m). As the drawbells themselves may be enlarged proportionally to the drawbell spacing, the drawbells, although spaced further from one another, still meet or come close to meeting at their upper parts so as to avoid stagnant zones forming therebetween (e.g. over the pillars).

[0035] It is noted that in the case of prior art conventional Herringbone and El Teniente layouts with only two draw points per drawbell, if the drawbell becomes too large, stagnant zones of limited flow more readily form both between the opposing draw points (4), and at the sides of the drawbell that that are not associated with a draw point (i.e. the sides that extend over the columns (7) to form the minor apex pillars). It will also be appreciated to a skilled person that decreasing the slope of the drawbell side walls, in seeking to provide that the tops of neighbouring/adjacent drawbells meet/interact even when there is increased drawbell spacing, is of limited function, as a minimum slope must be maintained that is equivalent to the angle of repose. [0036] The block caving mine configurations as described herein typically have drawbells which funnel into intersections that are formed by the intersection of two drives in the extraction level, such that each of the four draw points is accessible from a different direction. For example, the extraction level may comprise a grid layout, such as a rectangular or square grid layout, and drawbells may be arranged to funnel into some of the drive intersections of the grid. Typically, the drawbells are spaced from one another by at least one intersection, in the direction of both axes of the grid, to allow appropriate passage for haulage vehicles to move around the extraction level and transport ore/rock therefrom to the surface.

[0037] Generally, the block caving configurations as described herein comprise an extraction level that includes a first plurality of main drives that are substantially parallel, and a second plurality of main drives that are substantially parallel. The second plurality of main drives being angled with respect to the first plurality of main drives. Typically, the first plurality of main drives and the second plurality of main drives are angled at about 90 degrees with respect to one another. The main drives typically providing passage for haulage vehicles (e.g. loaders/trucks) to move around the extraction level.

[0038] The first plurality main drives and/or the second plurality of main drives typically comprise drives that are substantially equi-spaced, such that the main drives form a rectangular or square main drive grid. Each drawbell is located above/within a respective drawbell area defined by a pair of adjacent drives from the first plurality of main drives, and a pair of adjacent drives from the second plurality of main drives. It will be appreciated that with a rectangular or square main drive grid, each drawbell is located above a respective rectangular or square unit of the grid.

[0039] Within each drawbell area there are two drawbell access drives that intersect with each respective drawbell being located at the intersection of the two drawbell access drives. Typically, a first of the two drawbell access drives is substantially parallel to the first plurality of main drives and a second of the two drawbell access drives is substantially parallel to the second plurality of main drives. Thus, in the case of a rectangular or square main grid, the drawbell access drives provide a cross shape (when viewed in plan). [0040] Furthermore, it is generally the case that the first of the two drawbell access drives is located substantially at a midpoint between the pair of adjacent drives from the first plurality of main drives that in part define the drawbell area, and the second of the two drawbell access drives is located substantially at a midpoint between the pair of adjacent drives from the second plurality of main drives that in part define the drawbell area. This provides that the intersection of the two drawbell access drives is substantially centrally located within the drawbell area. The drawbell access drives forming subgrids within each unit of main drive gird. The drawbell access drives and main drives together typically forming an overall rectangular or square grid, of smaller rectangular or square units, when compared to the main drive grid.

[0041 ] The above-described configurations, with four draw points, allow the drawbell size and the distance between neighbouring drawbells to be increased beyond the limitations of conventional layouts, which serves to stabilise the extraction level main drives. The extraction level main drives are formed within larger more stable pillars and stagnant zones thereabove are limited as the drawbell upper cavities interact. For example, centre to centre drawbell spacings (of neighbouring/adjacent drawbells either along a line substantially parallel to the first plurality of main drives or along a line substantially parallel to the second plurality of main drives) may be greater than 35m, and drawbell heights (as measured from the floor of the extraction level) may be greater than 35m.

[0042] To further improve stability of the pillars, the drawbells may comprise a lower cavity, with a substantially consistent cross section, before widening begins at an upper cavity with sloping walls. This provides pillars with a larger/wider base, improving the stability thereof and the extraction level drives therein. For example, the drawbells may comprise a substantially rectangular (typically square) prism shaped lower cavity and upper cavity having the shape of an inverted frustum of a rectangular (typically square) pyramid. Other examples may have a cylindrical lower cavity and an upper cavity with the shape of an inverted frustum of a cone.

[0043] The present disclosure also relates to methods for establishing/developing a block caving mine and block caving mining methods. As is generally the case when establishing/developing a block caving mine, the methods include establishing an undercut level beneath rock/ore to be mined, and developing an extraction level beneath the undercut level, wherein the extraction level comprises one or more drives arranged in a particular layout. Typically, establishing the undercut level includes developing one or more undercut level drives/drifts from which explosive charges may be laid (e.g. drilling and blasting) to later advance/form the undercut cavity. One or more drawbells are developed that extend between the undercut level and the extraction level. It will be appreciated that the order/sequence of development the undercut cavity, drawbells and extraction level may vary. For example, some or all of the elements may be developed concurrently or in progressive fashion alternately. For example, undercut level drives and extraction level drives may be developed initially, in any order, or concurrently. As another example, undercut cavity advancement and drawbell establishment may vary. With ‘advance undercutting’, the development/expansion of the undercut cavity advances/progresses ahead of corresponding drawbell establishment, which trails therebehind. In ‘post undercutting’, drawbells are established before the corresponding portion of the undercut cavity thereabove is developed.

[0044] Once the mine configuration is sufficiently developed rock/ore from the body caves/fragments into the one or more drawbells. Caving may be initiated/facilitated using explosive charges, typically during formation of the undercut cavity, but continues naturally thereafter under its own weight.

[0045] The presently disclosed methods are at least differentiated from prior art methods in that one or more drawbells are developed/established that each funnel into a respective intersection of extraction level drives to provide at least 4 draw points at the base of the drawbell. Typically, the intersection of extraction level drives is formed by the intersection of two drives such that each of the 4 draw points is accessible from a different direction.

[0046] Usually also, drawbells are established/developed from undercut level drives and/or extraction level drives, for example by drilling and blasting from either of these drives. It is also noted that usually, no additional production/extraction levels are required above the extraction level that is located at the base of the drawbell/s. There are therefore typically no draw points at a depth which is shallower than the draw points at the base of drawbells. The absence of ‘higher’ additional extraction/productions levels avoid compromising pillar and drawbell stability.

[0047] It will be appreciated that the present disclosure also relates to a novel extraction level layout for a block caving mine. Such layouts comprise a first plurality of drives that are substantially parallel, and a second plurality of drives that are substantially parallel, with the second plurality of drives being angled with respect to the first plurality of drives. The drives thereby forming a grid of repeating units. Typically, the first plurality of drives and the second plurality of drives are angled at about 90 degrees with respect to one another, such that the units of the grid are substantially square or rectangular. For example, the first plurality of drives may be substantially equi-spaced from another and/or the second plurality of drives may substantially equi-spaced from one another. In one example the layout comprises a square grid of drives. The present disclosure also relates to methods of establishing a block caving mine or block cave mining methods, that include developing an extraction level with such layouts.

[0048] One particular example of a block caving mine configuration according to the invention is illustrated in figures 6 to 11 .

[0049] Figure 6 shows an extraction level (101 ) comprising a first plurality of main drives (102) and a second plurality of main drives (103). The first plurality of main drives may otherwise be referred to as the ‘extraction drives’ and form the primary thoroughfare for haulage vehicles. The second plurality of main drives may otherwise be referred to as the ‘link drives’ and serve as linkages between the extraction drives (102). The link drives (103) are angled at 90 degrees with respect to the extraction drives and both the extraction (102) and link drives (103) comprise parallel equi-spaced drives so that the extraction level comprises a main drive grid of square units.

[0050] Each square unit defines a drawbell area (104) such that one drawbell (105) is located within/above (or associated with) one square unit of the of the grid. To access ore from the base of the drawbell (105), each square unit comprises two intersecting drawbell access drives (106, 107). As shown, the base of each drawbell (105) funnels into the intersection of the two drawbell access drives (106, 107) such that there are four draw points for removing rock/ore at the base of the drawbell. [0051 ] A first of the drawbell access drives (106) extends between the link drives (103) and is substantially parallel to the extraction drives (102), and a second of the drawbell access drives (107) extends between the extraction drives (102) and is substantially parallel to the link drives (103). This provides the drawbell access drives (106, 107) form a cross shape (when viewed in plan) within each grid square unit I drawbell area (104). Each drawbell (105) being located at a respective intersection of drawbell access drives (106,107). Furthermore, the first (106) and second (107) drawbell access drives are located substantially at the mid-point between neighbouring extraction and link drives respectively such that the intersection of the drawbell access drives (106, 107) lies generally at the centre of the square unit I drawbell area (104). As shown, the drawbell access drives typically continue to extend across multiple drawbell areas I square units of the grid.

[0052] Having the drawbells (105) funnelling into the intersection of two drawbell access drives (106, 107) provides that there are four draw points from which rock/ore may be collected. As described previously, the provision of four draw point allows for larger drawbells to be formed without compromising rock/ore flow through the drawbells. For example, spacing between link drives (103), spacing between extraction drives (102), and centre to centre drawbell spacings (of neighbouring/adjacent drawbells either along a line substantially parallel to the extraction drives or along a line substantially parallel to the link drives) may be greater than about 35m.

[0053] As shown in figures 6 and 9, the drawbells (105) typically comprise a substantially rectangular (typically square) prism shaped lower cavity (105a) and upper cavity (105b) having the shape of an inverted frustum of a rectangular (typically square) pyramid. The inclusion of the lower cavity postpones widening (i.e. the increase in cross sectional area) provided by the sloping side walls of the upper cavity and thus results in pillars with a wider/larger base, increasing the stability thereof, and of the extraction level drives therebeneath. As shown in figure 6, lower cavity may not be perfectly prism shaped and may have the vertical edges (111 ) thereof tapering inwardly to meet the respective vertical edges or internal corners (112) of the intersecting drawbell access drive (106,107) below. This avoids ledges (that slow rock/ore flow) being formed at the lower corners of the lower cavity (105a). However, it will be appreciated to a skilled person that drawbell shape may vary. [0054] Referring to figures 8 to 10 example layout dimensions achievable with the block caving mine configurations as described herein may be as follows:

- height (A) from the floor of the extraction level to the top of the drawbell may be greater than about 35m, in some examples in the range of about 35m to about 60m, and in one particular example about 50m;

- span across the top of the drawbell (B) may be greater than about 35m, in some examples in the range of about 35m to about 60m, and in one particular example about 50m;

- height (C) of the lower cavity of the drawbell may be about 15m;

- side length (D) of lower cavity of drawbell may be about 12 to about 15m;

- drawbell access drives may have a height (E) of about 5m;

- extraction drives may have a width (F) of about 5m;

- extraction drives may have a height of about 6.5m to about 7m;

- spacing (H) between neighbouring/adjacent drawbell centres (along a line parallel to the extraction drives or along a line parallel to the link drives) may be greater than about 35m, in some examples in the range of about 35m to about 60m, and in one particular example about 50m;

- spacing (I) between extraction drives may be greater than about 35m, in some examples in the range of about 35m to about 60m, and in one particular example about 50m; and

- spacing (J) between link drives may be greater than about 35m, in some examples in the range of about 35m to about 60m, and in one particular example about 50m.

[0055] In respect of block caving mine development, it will be appreciated that typically undercut and extraction drives (108) are initially formed above and below the proposed drawbell level to set explosive charges for the undercut cavity and drawbells. Preferably, each drawbell is blasted prior to advancement of the undercut cavity, however, the undercut cavity may be blasted integrally, or in advance of the drawbells. Figures 5A-5C illustrate various blast sequences that may be applied.

[0056] Figure 5A shows a post-undercutting method wherein the development of the new drawbells from the extraction level is ahead of the development of the undercut cavity. Figure 5B shows an advanced undercutting method wherein the development of the new drawbells follows blasting the rock above the undercut level closely i.e. drawbell establishment is repeatedly brought more or less into line with the undercut front i.e. so as not to trail by the undercut front by more than 1 -2 drawbells. Figure 5C shows a preundercutting method wherein the development of the new drawbells follows blasting the rock above the undercut level less closely (relative to the method as shown in 5B) i.e. where the drawbell establishment trails a few drawbell spacings from the undercut front.

[0057] It will be appreciated as the undercut cavity is advanced, the initial drives (108) for establishing the undercut are destroyed and form part of the greater undercut cavity. Typically for natural caving of the rock/ore to initiate, the undercut cavity must span a certain area, which is dependent of the particular rock/mine environment/characteristics.

[0058] Also shown in figures 8-10 is an optional slot raise 113, which may be bored prior to drawbell blasting to provide a void that allows for expansion of blasted rock assisting fragmentation.

[0059] Figure 10 shows a side sectional view of a block caving mine configuration according to one example indicating the location of optional post condition blast drives/drifts (109). Post conditioning blasts are sometimes implemented to facilitate ore fragmentation and to improve safety by distancing early seismicity from the extraction level. The drifts/drives (109) formed for post condition blasting are typically spaced at 100-200m intervals from the undercut level. In one example, spacing may be 100 m (e.g. in Figure 10, G1 and G2 may each equal 100m). Figure 11 shows a 3 dimensional cutaway view of the configuration as shown in figure 10.

[0060] Figure 12 outlines example method steps for forming a block caving mine, and a block caving mining, according to the present disclosure. In step 200 vertical access is developed including the formation of a shaft and decline. In step 201 , an optional first (upper) post condition blasting horizon is developed with a view to improving early stage fragmentation. In step 202, an optional second (lower) post condition blasting horizon is developed with a view to improving the initial ore fragmentation and the amount of blasted ore during cave establishment. In step 203, the undercut level is formed, and in step 204 the extraction level and haulage loop are formed.

[0061 ] In step 205, infrastructure chambers (e.g. crusher, workshops etc.) are constructed. In step 206, the drawbells are fired / developed. In step 207, a material handling system (e.g. crusher and conveyer/hoist) is installed. In step 208, the undercut is fired. In step 209, production is commenced and ramped up. Step 210 to 212 are optional post conditioning blasts from the blasting horizons as developed in steps 201 and 202.

[0062] Where ever it is used, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of”. A corresponding meaning is to be attributed to the corresponding words “comprise”, “comprised” and “comprises” where they appear.

[0063] While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, and all modifications which would be obvious to those skilled in the art are therefore intended to be embraced therein.

Claims

1. A block caving mine configuration including one or more drawbells that each funnel into a respective intersection of drives in an extraction level, such that there are at least four draw points at the base of each of the one or more drawbells.

2. A block caving mine configuration as claimed in claim 1 , wherein the intersection of drives in the extraction level is formed by the intersection of two drives such that each of the four draw points is accessible from a different direction.

3. A block caving mine configuration as claimed in claim 1 or 2, wherein the extraction level comprises a rectangular grid layout.

4. A block caving mine configuration as claimed in claim 3, including a plurality of drawbells that each funnel into a respective intersection in the grid.

5. A block caving mine configuration as claimed in claim 4, wherein the drawbells are spaced from one another by at least one intersection, in the direction of both axes of the grid.

6. A block caving mine configuration as claimed in any one of claims 3 to 5, wherein the grid is a square grid.

7. A block caving mine configuration as claimed in claim 1 or 2, wherein the extraction level includes: a first plurality of main drives that are substantially parallel; and a second plurality of main drives that are substantially parallel, wherein the second plurality of main drives are angled with respect to the first plurality of main drives.

8. A block caving mine configuration as claimed in claim 7, wherein the first plurality of main drives and the second plurality of main drives are angled at about 90 degrees with respect to one another.

9. A block caving mine configuration as claimed in 7 or 8, wherein the first plurality of main drives are substantially equi-spaced from one another.

10. A block caving mine configuration as claimed in any one of claims 7 to 9, wherein the second plurality of main drives are substantially equi-spaced from one another.

11. A block caving mine configuration as claimed in any one of claims 7 to 10, wherein each of the one or more drawbells is located above a respective drawbell area defined by a pair of adjacent drives from the first plurality of main drives, and a pair of adjacent drives from the second plurality of main drives.

12. A block caving mine configuration as claimed in claim 11 wherein, within each drawbell area, there are two drawbell access drives that intersect, each respective drawbell funnelling into the intersection of the two drawbell access drives.

13. A block cave mining configuration as claimed in claim 12, wherein a first of the two drawbell access drives is substantially parallel to the first plurality of main drives and a second of the two drawbell access drives is substantially parallel to the second plurality of main drives.

14. A block cave mining configuration as claimed in claim 13, wherein the first of the two drawbell access drives is located substantially at a midpoint between the pair of adjacent drives from the first plurality of main drives that in part define the drawbell area, and the second of the two drawbell access drives is located substantially at a midpoint between the pair of adjacent drives from the second plurality of main drives that in part define the drawbell area, such that the intersection of the two drawbell access drives is substantially centrally located within the drawbell area.

15. A block cave mining configuration as claimed in any one of claims 7 to 14, wherein the distance between neighbouring main drives of the first plurality of main drives is greater than about 35m.

16. A block cave mining configuration as claimed in any one of claims 7 to 15, wherein the distance between neighbouring main drives of the first plurality of main drives is in the range of about 35m to about 60m.

17. A block cave mining configuration as claimed in any one of claims 7 to 16, wherein the distance between neighbouring main drives of the second plurality of main drives is greater than about 35m.

18. A block cave mining configuration as claimed in any one of claims 7 to 17, wherein the distance between neighbouring main drives of the second plurality of main drives is in the range of about 35m to about 60m.

19. A block cave mining configuration as claimed in any one of claims 7 to 18, wherein the distance between adjacent drawbell centres along a line substantially parallel to the first plurality of main drives is greater than about 35m.

20. A block caving mine configuration as claimed in any one of claims 7 to 19, wherein the distance between adjacent drawbell centres along a line substantially parallel to the first plurality of main drives is in the range of about 35m to about 60m.

21 . A block caving mine configuration as claimed in any one of claims 7 to 20, wherein the distance between adjacent drawbell centres along a line substantially parallel to the second plurality of main drives is greater than about 35m.

22. A block caving mine configuration as claimed in any one of claims 7 to 21 , wherein the distance between adjacent drawbell centres along a line substantially parallel to the second plurality of main drives is in the range of about 35m to about 60m.

23. A block caving mine configuration as claimed in any one of the preceding claims, wherein there are no additional extraction levels above the extraction level which is at the base of the one or more drawbells.

24. A block caving mine configuration as claimed in any one of the preceding claims, wherein there are no draw points at a depth which is shallower than the draw points which are located at the base of the one or more drawbells.

25. A block cave mining configuration as claimed in any one of the preceding claims , where the one or more drawbells comprise an upper cavity that has the shape of inverted frustum of a rectangular pyramid, and a lower cavity that is substantially rectangular prism shaped.

26. A block caving mine including a block caving mine configuration as claimed in any one of claims 1 to 25.

27. A block caving mining method including the step of developing a block caving mine configuration as claimed in any one of claims 1 to 25.

28. A block caving mining method including the step of extracting ore from drawbell draw points in a block caving mine with a configuration as claimed in any one of claims 1 to 25.

29. Use of a block caving mine configuration as claimed in any one of claims 1 to 25.

30. A method of developing a block caving mine, the method including: establishing an undercut level beneath ore to be mined; developing an extraction level beneath the undercut level, the extraction level comprising extraction level drives; and developing one or more drawbells that extend between the undercut level and the extraction level, and that each funnel into a respective intersection of extraction level drives, to provide at least 4 draw points at the base of each of the one or more drawbells.

31 . A method as claimed in claim 30, wherein the intersection of extraction level drives is formed by the intersection of two drives such that each of the 4 draw points is accessible from a different direction.

32. A method as claimed in 30 or 31 , wherein the one or more drawbells is/are developed from undercut level drives and/or the extraction level drives.

33. A method as claimed in claim 32, wherein the one or more drawbells is/are developed by drilling and blasting from the undercut level drives and/or the extraction level drives.

34. A block caving mining method including the steps of: developing a block caving mine in accordance with the method of any one of claims 30 to 33; caving ore into the one or more drawbells; and extracting ore from draw points of the one or more the drawbells.

35. An extraction level layout for a block caving mine comprising: a first plurality of drives that are substantially parallel; and a second plurality of drives that are substantially parallel, wherein the second plurality of drives are angled with respect to the first plurality of drives.

36. An extraction level layout as claimed in claim 35, wherein the first plurality of drives and the second plurality of main drives are angled at about 90 degrees with respect to one another.

37. An extraction level layout as claimed in claim 35 or 36, wherein the first plurality of drives are substantially equi-spaced from one another.

38. An extraction level layout as claimed in any one of claims 35 to 37, wherein the second plurality of drives are substantially equi-spaced from one another.

39. An extraction level layout as claimed in any one of claims 35 to 38, comprising a square grid of drives.

40. A method of developing a block caving mine, including developing an extraction level with a layout as claimed in any one of claims 35 to 39.

41 . A method of developing a block caving mine as claimed in any one of claims 30 to 33, wherein developing an extraction level comprises developing an extraction level with a layout as claimed in any one of claims 35 to 39.