ZA200406802B - A method of dewatering a solid particulate material. - Google Patents

Description

A METHOD OF DEWATERING A SOLID PARTICULATE MATERIAL

THIS INVENTION relates to a method of dewatering a solid par ticulate material. The invention extends to a method of dewatering a solid particulate material contained within a foramirmous container, to a c ontainer for a solid particulate material, to a sub-—terranean ground support installation and to a method of providing ground support. The inveantion further relates to a drainage system for a sport facility and a method of draining water from a surface of a sport facility.

According to one aspect of the invention, there is provided a rmnethod of dewatering a solid particulate material, which method incl udes subjecting the solid particulate material to sub-atmospheric pressure.

The method may include applying a negative pressure to a dra in line having an inlet positioned at a low level within the material.

The solid particulate material may be contained within a . foraminous container, the method including providing @an outlet in a wall of t-he container and applying the sub-atmospheric preessure across the out let.

In a preferred embodiment of the invention, the method . i ncludes accelerating the dewatering of particulate material contained within a backfill bag by supplementing gravitational dewatering of the particulate material by applying a sub-atmosph eric pressure to at least part of the material.

The method may include providing a conduit which leads from the container at or adjacent an operatively lower end thereof, the conduit defining an inlet and the outlet and a flow passage, connecting t he inlet and the outlet in flow communication.

The container may be in the forrm of a backfill bag for containing waste or residue from mining, time bag having an inlet wvhereby the particulate material can be introdueced into the bag.

According to still another aspect of the invention, there is provided a container for a solid particulate material, which container includes a foraminous body and at least one conduit leading from the body, the conduit defining an inlet, an outlet and a flow passage, connecting the inlet and the outlet in flow comrmunication.

The container may include connectimng means for connecting an outlet of the conduit in flow communication with sub-atmospheric pressure supply means, such as, for example, i n the form of a vacuum oT venturi pump.

In a preferred embodiment of the anvention, the container iss in the form of a backfill bag for containing waste or residue from mining, the bag having an inlet whereby the particulate matewrial can be : introduced into the bag and the conduit being positioned at Or towards an operatively | ower end of the bag. The bag may be of a geotextile material, such as, for example, woven polypropylene tapes.

Ac cording to yet another aspect of the inventiom, there is provided a sub-—terranean ground support installation which in cludes at least one container containing particulate material disposed between a foot wall and a hanging wall of an underground e><cavation, the or each container defining at least one drainage outlet; an d sub-atmo spheric pressure supply means connectable to the at least one drainage outlet for draining liquid from particulate material contained in the container.

The at least one container may be in the form of a foraminous bag of geotextile material, the particulate material being waste mining material and the drainage outlet being positioned at or adjacent an ope ratively lower end of the container.

Ac cording to a further aspect of the inventiora, there is provided a method of providing support in a subterranean excavation, which method imncludes the steps of providing at least one container between a foot w~all and a hanging wall of the subterranean excavation; introducirmg particulate material in suspension into thee or each . container; and subjecting the particulate material to sub-atmosph eric pressure : thereby to facilitate dewatering of the particulate material v ia the at least one drainage outlet.

The at least one container may be in the form of a foraminous bag of a geotextile material, the particulate material being waste mini ng material and at least one drainage outlet may be defined in the cont ainer at or adjacent an operatively lower end thereof.

According to yet a further aspect of the invertion, there is provided a drainage system, which includes at le ast one sub-surface drainage conduit; and sub- atmospheric pressure supply means/vacuum mea ns connected to the conduit for subjecting a sub-surface region to sub -atmospheric pressure.

The system may be installed at a sport facility and may include a n etwork of drainage pipes disposed beneath a playing surface of the sport facility.

According to a still further aspect of the invermtion, there is provided a method of draining water from a surface which method includes subjecting a sub-surface region to sub-atmospher ic pressure.

More particularly, the surface may be that of a sport } facility.

The invention will nowv be described, by way of example, : with reference to the accompanying diagrammatic drawings.

In the drawings,

Figures 1A-D show a series of steps in a method of providing 5 ground support in accordance with the invention;

Figure 2 shows a sectional si de view of a so-called "tailings" dam application of a method of dewat ering a solid particulate material in accordance with the invention; and

Figure 3 shows a schematic wepresentation of a drainage system, for a sport facility, in accordance with the invention.

Reference is made to FEgures 1A-D of the drawings in which reference numeral 10 refers generally to a subterranean excavation in the form of a tunnel or stope in an uanderground mine, more particularly, in a deep-level gold mine.

The tunnel 10 is define d between an overhead hanging wall 12 and lower foot wall 14 comprising mineral material left in place during drilling/blasting of the tunnel 10.

It will be appreciated that it is necessary, in such an underground excavation 10, to provide support for the adjacent ground (usually rock), and, in particular, the hanging wall 12. . There is, accordingly, disposed between the foot wall 14 and the hanging wall 12 a plurality» of containers, one of which 16 is shown in Figures 1A-D of the drawiengs. The container 16 is in the form of a porous bag of a gesotextile material, such as, for example, wovean : polypropylene tapes. The bag 16 has a drainage outlet 18, the outlet 1 8 being defined at an end of a conduit 20 which leads from the bag 16.

The conduit 20 is provieded by a length of pipe and defines an inlet 222, at an end 24 thereof dEsposed within the bag 16, the outlet 18, at i%s end 26 spaced from the end 24, and a flow passage (not shown), which connects the inlet 22 and the outlet 18 in flow communication. Tie conduit 20 is typically made to lead from the bag 16 by forming a receiving opening, for receiving a length of pipe, in a wall of the bag 1 6 at an operatively lower end 26 of the bag 16 and inserting the end 24 of the pipe through thes opening, to be located within the bag 16. A fastener is then received over that part of the material of the bag 1 6 adjacent to the receivin g opening and the pipe, respectively, to secumre the pipe within the opeming.

When it is desired to provide support for the hanging wall 12, waste material from mining operations, so-called "tailings" comprising a slurry of solid particulate material (e.g. soil, small stones and the like) in suspens ion in water, is pumped into the bag 16 so as ®o fill the bag 16 with slurry 28 (Figure 1A). In order for the bagged tailings to render suppo rt to the overhead rock of the hanging wall 122, the tailings are to be de watered and thereby converted from a slurry 238 to solid-state. Under —the influence of gravity, water from the tailings suspension percolates cdownwardly through the particulate material ard drains from the bag 16 wia pores of the woven material of which the bag ; 25 16 is formed and/or the outlet 18. After some time, a region of aeration (i.e. of non-saturatead particulate material) forms in an operative ly upper portion 32 of th e bag 16, above a so-called "phreatic line” X

(which defines the upper level of a zene of saturation with water), and - a zone 34 of particulate material whic his saturated with water is formed in an operatively lower portion 36 of the bag 16 (Figure 1B).

It will be appreciated that, under gravity alone change in the vertical position of the phreatic line X occurs slowly with time and is dependant upon, inter alia, the charac teristics of the particulate material, the volume of the bag 16 and the porosity of the bag 16.

Sub-atmospheric pressure supply means, for example, in the form of a vacuum or venturi pum p (not shown), is connected to an end 26 of the conduit 20 defining thre outlet 18 and a negative gauge pressure {sub-atmospheric pressure) is applied across the end 26 of the conduit 20. The suction effect so-created tends to accelerate the drainage of water from the slurry 28 and the associated descent of the phreatic line X within the bag 16 frorm the operatively upper portion 32 of the bag 16 to the lower portion 36 thereof and eventually to a level of the foot wall 14. At this stage, th e back-fill material contents of the bag are in a solid state and serve to support the hanging wall 12 which settles onto an operatively upper surface of the bag 16 (Figure 1D).

In Figure 2 of the drawings, reference numeral 50 refers generally to a so-called "tailings" dam in which a method of dewatering a solid particulate material in accordance with the invention finds application.

The tailings dam 50 is typically designed to impound slurry waste from mining (tailings) behind a retaining wall 562 of the dam 50.

The retaining wall 52 is typic ally of a solid particulate material 54. In - use, tailings are typically dum ped via a hydro-cyclone 58 on a so-called "beach" 56 of the dam 50. T he tailings slurry comprises solid particles in suspension in water, which water, upon dumping of the tailings on the beach 56, may seep into the particulate material 54 of the adjacent retaining wall 52.

As described above, with reference to Figures 1A-D of the drawings, the water percolatezss downwards under gravity with time. A problem associated with this relatively slow drainage process is weakening of the retaining wall 52 and associated failure thereof.

A conduit 60 ext ends outwardly from the retaining wall 52 at a low elevation, the conduit 60 defining an inlet 62, at an end 64 thereof disposed within the retaining wall 52, and an outlet 66, at an end 68 spaced from the end 6&4 of the conduit 60 and disposed outside of the retaining wall 52. In order to accelerate drainage of water from the particulate material 54 of t he retaining wall 52 via the outlet 66, sub- atmospheric pressure supply means (not shown) is connected to the outlet 66 and the material o¥ the retaining wall 52 is subjected to a negative guage pressure.

Reference is now made to Figure 3 of the drawings in which reference numeral 70 r efers generally to a drainage system for a sport facility in accordance with the invention. The system 70 includes a sub-surface drainage conduit 72 disposed below a surface 74 of a playing field 76 of the sport fa cility, such as, for example, a cricket field.

Typically, a layer of a geotextile material 73, in sheet form, - is inserted between the surface 74 amd the conduit 72.

The system 70 further imcludes sub-atmospheric pressure supply means (e.g. a venturi/vacuum pump) (not shown) connected to the conduit 72 for subjecting a sub-surface region 76 adjacent to the conduit 72 to sub-atmospheric pressure, thereby to enhance drainage of water from the region 76 and in turn f rom the playing surface 74, when required.

The Inventor believes tha t the methods of the invention will facilitate a more rapid drainage of ligu id from a liquid saturated material than would occur under the influence of gravity alone. It is believed that the methods of the invention will in turn allow for more rapid "setting "/solidifying of particulate material in suspension thereby more rapidly to yield a support of the materi al. In its application to the mining industry, this will permit more rapid forward penetration of a seam where support is provided at spaced apart positions in the direction of drilling as progress into the seam is made. Furthermore, it is believed that the invention will alleviate problems associated with the slow drainage of liquids which permeate loa d bearing structures of particulate material (such as, retaining walls of tailings dams), and compromise the integrity thereof, by accelerating the drainage of liquid therefrom. The

Inventor believes that drainage of surface water from playing surfaces of cricket fields, golf courses or other sport facilities may be improved by use of a drainage system of and methods of the invention.

Claims (20)

PCT/IBO3/00-499 CLAIMS:

1. A method of dewatering a solid particulate material, which method includes introducing the solid particulate material into at least one foraminous container; and subjecting the particulate material to sub-atmospheric pressure.

2. A method as claimed in Claim 1, which includes applyieg a negative pressure to a d rain line having an inlet positioned at a low | evel within the material.

3. A method as claimed in Claim 1 or Claim 2, which incltudes providing an outlet in a wall of the container and applying the ssub- atmospheric pressure across the outlet.

4. A method as claimed in Claim 3, which includes providimng a conduit which leads from the container at or adjacent an operati-vely lower end thereof, the conduit defining an inlet and the outlet and a Flow passage, connecting the inlet and the outlet in flow communication .

5. A method as claimed in Claim 3 or Claim 4, in which the J container is in the form of a backfill bag of a geotextile material for containing waste or residue from mining, the bag having an inlet whereby the particulate material can be introduced into the bag. AMENDED SHEET CLEAN COPY

PCT/1IBO3/00499

6. A container for a solid particulate material, which container includes a foraminous body and at least one conduit leading from the body, the conduit defining an inlet, an outlet and a flow passage, connecting the inlet and the outlet in flow communication; and connecting means for connecting an outlet of the conduit in flow communication with sub-atmeospheric pressure supply means.

7. A container as claimed in Claim 6, which is in the form of a backfill bag for containing waste or residue from mining, the bag having an inlet whereby the particulate material can be introduced into the bag and the conduit being positiored at or towards an operatively lower end of the bag.

8. A container as claimed in Claim 7, which is of a geotextile material.

9. A sub-terranean ground support installation which includes at least one container, as claimed in any one of Claims 6 to 8, inclusive, containing particulate material disposed between a foot wall and a hanging wall of an underground excavation; and sub-atmospheric pressure supply means connectable to the at least one outlet for draining liquid from particulate material contained in the container.

10. A method as clai@med in any one of Claims 1 to 5, inclusive, which includes AMEIMNDED SHEET CL EAN COPY .

PCT/IBO3/00499 providing the at least one container between a foot wall and a hanging wall of a subterranean excavation.

11. A drainage system, which includes at least one sub-surface drainage conduit; sub-atmospheric pressure supply means connected to the conduit for subjecting a sub-surface region to sub-atmospheric pressure; and a layer of a geotextile material inserted between the surface and the conduit.

12. A drainage system as claimed in Claim 11, which is instalied at a sport facility and which includes a network of drainage pipes disposed beneath a playing surface of the sport facility.

13. A method of draining water from a surface, which method includes inserting a geotextile material between the surface and at least one sub-surface conduit; and subjecting a sub-surface region to sub-atmospheric pressure.

14. A method as claim ed in Claim 13, in which the surface is that of a sport facility.

15. A method as claimed in Claim 1, substantially as herein described and illustrated. AMENDED SHEET

PCT/IBO3/00499

16. A container as claimed in Claim 6, substantially as herein described and illustrated.

17. An installation as claimed in Claimm 8, substantially as herein described and illustrated.

18. A system as claimed in claim 11, su bstantially as herein described and illustrated.

19. A method as claimed in Claim 13, substantially as herein described and illustrated.

20. A new method of dewatering a sol id particulate material, a new container for a solid particulate material, a new ground support installation, a new drainage system, or a mew method of draining water from a surface, substantially as herein described. AMENDED SHEET