BUND CONSTRUCTION TECHNICAL FIELD

This invention relates to a method of and apparatus for forming earth filled embankments commonly and hereinafter referred to as bunds.

Bunds are widely used in the mining industry alongside haul roads as a safety precaution to prevent mining vehicles from running off the road or into the path of an oncoming vehicle and along the edges of cuttings as safety barriers. Bunds are also utilised as levee banks for flood mitigation and for forming containment ponds and dams and the like. However for illustrative purposes, this invention will be described with reference to mine sites.

On mine sites, roadside bunds are required to be built to a height of at least one-half the diameter of the largest mining vehicle wheels which will traverse the road. Many mines utilise haul trucks with 4.2 metre diameter wheels and thus the bunds on these sites must be built to a height of 2.1 metre above the haul road. Such haul roads are also utilised by smaller vehicles and thus the height of the bunds are reduced approaching intersections to enable the drivers of smaller vehicles to have visibility over the bunds as they approach the intersection.

Typically, these bunds are built from removed overburden by operators using excavators to place, then shape the earth banks to the desired upwardly tapered form. The required overburden is mostly dumped adjacent the roadside by large loaders and if excess material is delivered it has to be removed. This double handling of the overburden is common and increases the cost of forming such bunds. Achieving a well shaped and conforming bund requires initial placement of the fill, trimming the top to the desired height followed by passes along each side to shape the side walls thereof. This is a time consuming process and typically an experienced operator utilising a large excavator may form a 2.1 metre high bund at the rate of between 150 to 200 metres per day. As there may be many kilometres of bunds utilised on a typical mine site this is a significant cost in developing the mine site.

This Invention aims to provide an improved method of and apparatus for forming bunds.

SUMMARY OF INVENTION

With the foregoing in view, this invention in one aspect resides broadly in a method of forming a bund including:- providing a bund mould which may be placed on the ground to receive material for confinement in the cross-sectional shape of the required bund;

positioning the bund mould on the ground and feeding material in the bund mould to form a bund portion;

removing the bund mould from the or a portion of the formed bund portion; repositioning the bund mould for forming a further bund portion as a continuation of the formed bund portion;

using this method would consist of a series of closely spaced bund portions. feeding further material into the bund mould to form the continuation of the bund, and

repeating the bund forming steps until the desired bund is formed.

In another aspect this invention resides in a bund mould for use in the method defined above and including a mould having opposed side walls configured to form the desired cross-sectional shape of the bund, feeding means for feeding material into the mould, and said mould being arranged to form a bund portion therein and then be advanced to form a further bund portion as a continuation of the formed bund portion.

The feeding means for the bund mould may be a conveyor such as a screw conveyor or a belt conveyor. Preferably however the feeding means is an open top which is suitably associated with a loading chute or hopper to facilitate feeding of material into the bund mould by placement of material into the bund mould through the open top. The loading chute, if utilised, may have transverse barriers to either strengthen the chute and/or to form a grate to prevent oversize rocks from entering the chute or passing through the open top.

The bund mould may have side walls and end walls and an open base and be lifted from a bund portion formed therein for repositioning to form a continuation of the formed bund portion and for this purpose all internal walls of the bund mould may diverge upwardly to assist removal from the formed bund portion. A bund produced using this method would consist of a series of closely spaced bund portions. Preferably however the bund mould has side walls, a front end wall and an open rear end whereby the bund mould may be dragged forward along the or a portion of the bund portion formed therein for placement of further material therein as a continuation of the formed bund portion to form a continuous bund. The longitudinal internal side walls of the bund mould are suitably planar and they may be maintained transversely equidistant from one another or they may diverge away from the closed front end to assist in freeing of the mould from the formed portion as it is moved forward along the ground. Alternatively the side walls may converge toward the open end so as to squeeze the formed bund portion as the bund mould is drawn along the formed bund portion to its next filling position. This squeezing action will compact or dress the formed bund portion in the process. In this configuration the bund mould may be provided with means for supporting ballast which may be required to resist lifting of the bund mould by the compaction forces.

The configuration of the bund mould, including its cross-sectional configuration and the longitudinal convergence or non-convergence of the side walls, may be varied to suit the properties of the material being used to construct the bund and the method of shifting the bund mould between the bund forming steps. Further, the rear open end may have an outwardly flared end portion to assist in repositioning the bund mould at an angle to the previously formed bund portion for forming a curved bund or for enabling the bund mould to be pushed back toward a formed bund portion and be readily aligned with and engaged about an end of the formed bund portion. In one form the bund mould has a maximum width which enables it to be transported by road transport and it is made relatively lightweight for economical transport and provided with ballast supporting means for weighting the bund mould or a rear portion thereof on site to assist in maintaining its ground supported position during filling and repositioning operations. The bund mould may be formed with opposite side portions which may be adjustably bolted together to form a bund mould of the desired cross-sectional configuration. The walls of the bund mould may be formed as box sections to achieve the necessary strength stiffness and/ or lightness.

The bund mould may also have a base wall or base wall portion or an intermediate floor or floor portion which may underlie material placed therein to assist in preventing the bund mould from lifting during filling and/or as it is dragged along the formed bund portion and/or to provide structural support for the open end of the mould.

Maintenance of its ground supported position in use may also be assisted by providing a towing connection at the front end of the bund mould as close as possible to the base thereof for towing by a substantially horizontal towing force so as not to provide a lifting action at the front of the bund mould during towing or rotation about the front lower end of the bund mould tending to lift the rear end of the bund mould during towing. Preferably the bund mould is supported by longitudinal skids along the base of each side wall and the towing attachment is provided at the front end of these skids. The front end of the bund mould may be lifted prior to sliding the bund mould forward so as to weight bias the rear end of the bund mould as it is dragged along the formed bund portion. This may assist trimming and finishing operations.

The bund mould may have a trimming blade adjacent the open rear end which may be selectively positioned to trim the height of the formed bund wall portion as the bund mould is slid along the ground to its next bund forming position. This blade may be in the form of a door which may be selectively swung into its operative position or it may be a vertically adjustable blade extending across the rear open end or it may be constituted by the back wall of the loading chute. Alternatively it may be in the form of forwardly and downwardly inclined blade which deflects excess material upwardly and away from the formed bund portion and which thus acts to force the rear end of the bund mould downwardly as it Is moved along the formed bund portion. The bund mould may be provided with a relatively large hopper or loading chute whereby filling the hopper prior to dragging the bund mould along the ground to its next operative filling position will increase the effective weight of the bund mould.

The bund mould may have compaction means such as a weighted sheep's foot roller supported adjacent the rear open end in or above the loading chute for compacting the material into the bund mould as it is moved along a formed bund portion or it may be provided with vibration means for assisting compaction of the material in the bund mould. DESCRIPTION OF EMBODIMENTS

In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate preferred embodiments of the invention and wherein:-

Fig. 1 is a side view of one embodiment of the invention;

Fig. 2 is a sectional view of the embodiment illustrated in Fig. 1;

Fig. 3 is a perspective view of the body part of the embodiment illustrated in Fig. 1;

Fig. 4 is an end view of the embodiment illustrated in Fig. 1 ;

Fig. 5 is a underside view of the body part of the embodiment illustrated in Fig. 1 ;

Fig. 6 illustrates a further embodiment of the invention, and

Fig. 7 illustrates one method of building a bund according to this invention,

The bund mould assembly 10 illustrated in Figs. 1 to 5 is ground supported on skids 11 and utilises an open ended mould 12 to form bunds of the desired cross-section by forming a first bund portion or segment within the mould 12 and then sliding the mould assembly 10 forwardly along the ground and partway along the formed bund segment to a position at which the mould assembly 10 is arranged in its selected alignment with the formed bund portion to follow the desired path. For this purpose the bund mould assembly 10 has an open top 13 through which material may be loaded into the mould 12. To facilitate loading a hopper or loading chute 14 extends upwardly from the open top 13. The opposed side walls 15 of the mould 12 diverges downwardly away from the open end 13 and terminate on respective ground engaging skids 11 which extend the full length of the mould 12 and forwardly past the front wall 17 to a cross-member 18 which has an upper returned portion to facilitate locking engagement with the towing means utilised to move the bund mould assembly 10 step by step as each bund portion is formed.

The towing means may be an excavator which may engage its bucket behind the cross member 18 so as to utilise a horizontal pulling action to slide the bund mould assembly 10 along the ground, or it may be a dozer or loader utilising a sling trapped behind the cross member 18. A sling 19 supported partway up the front wall 17 may also be utilised to drag and/or lift the front end of the bund mould assembly 10. The sling 19 is provided with a hanging point 20 from which it may be suspended when not in use.

In this embodiment the skids 11 extend along the lower edges 16 of the side walls 15 and are approximately 200mm high so that a the lower edge 21 of the front wall 17 is held above the ground so that it does not snag on small protrusions which may be in the desired path of the bund. The skids 11 suitably include a leading ramped portion to assist their sliding along the ground. A bracing floor 23 is provided to resist spreading of the side walis 15 at the. open rear end 22. This floor 23 includes a full width floor portion at the front of the mould 12 where the floor 23 is fixed to the side walls 15 and the front wall 17 and rear side portions 24 which taper rearwardly to the rear ends of the side walls 15. The floor area is reduced by this arrangement to reduce the weight of fill which would be supported above the floor and to thereby decrease the pulling load required to move the bund mould assembly 12 beneath a bund portion formed therein while at the same time utilising a portion of the formed bund weight to maintain the mould supported on the ground by the skids 11. The configuration of this floor 23 and its vertical position between the side walls 15 may vary according to the type of fill to be used, the implements available to slide the mould assembly 10 forward and method of operation required by an operator. Furthermore all bracing may be maintained externally of the mould 12 if desired. For example as illustrated in Fig. 4 a ring frame 25 or similar may be utilised to maintain the rear ends of the side walls 15 in their desired spaced configuration.

Furthermore during filling operations, external apparatus may be used to compact the fill in the mould 12. For example an excavator equipped with a sheep foot roller of a width which enables it to be inserted through the open top 13 may be used progressively to compact the fill within the bund mould 12 during filling operations.

In the bund mould assembly 30 illustrated in Figs. 6 and 7, the mould 31 is reinforced by vertical external frames 32 which are spaced apart a distance which will accommodate an excavator bucket therebetween to facilitate loading of material into the bund mould 31.

As illustrated, the lower internal edges 33 of the frames 32 are utilised to trim the top face 34 of each bund portion or segment 35 to the desired height as the mould assembly 30 is dragged across the bund portion formed therein. In addition an operator may only part-fill the mould to achieve a desired bund height.

In use, a bund 40 is formed in discrete segments 35, each moulded to shape in the bund mould and which segments may be aligned in a straight line or angularly to one another to enable the bund 40 to be placed along a desired path whether straight or circuitous, on even terrain or on undulating terrain. This method of forming will provide a bund in which the bund height will be maintained at a consistent height relative to the ground without the necessity to utilise a skilled operator to trim the wall to the desired height.

This mould assembly 30 may be provided with panels, shown dotted at 36, which cooperate with the side walls 37 of the mould 31 to form ballast tanks 38 which may be loaded with fill or other ballast to increase the operative weight of the mould assembly 30. The panels 36 may be hinged at their top end to enable them to be swung out to empty the ballast therefrom.

It is expected that some collapsing of the formed front end of the bund portion will occur during movement of the bund mould assembly to the next filling position. Because of this and as the rear open end of the mould has to be closed by the formed bund portion before filling, the bund mould assembly in use is slid forwardly to its next filling position so as to maintain an overlap with the previously formed bund segment so as to replace the collapsed bund portion. Thus each bund segment 35 is shorter than the length of the mould 31. Of course if such inconsistencies in construction are of no concern, each segment may have a length which is approximately equal to the length of the mould 31.

By way of example only, a bund which is approximately two metres high will have a base width of between three to five metres. If the mould is ten metres long it will require about forty cubic metres of fill to form the bund mould portion within the mould which Is equivalent to twenty-six, 1.5 cubic metre bucket loads by an excavator. This would take approximately 12 minutes if loading from a pile of adjacent fill and mould repositioning operations could take 3 minutes, for example. This would result in a bund wall construction rate in the order of 300 metres per eight hour day which is far in excess of what is presently achieved. Furthermore as the volume of material required for a certain length of wall will be consistent, the correct amount of fill may be dumped at predetermined intervals along the bund path maximising efficiency of construction and materials handling.

In addition the formed bund wall will be of consistent form, meet the height requirements irrespective of the terrain. By utilising a drop-in, bolt-in or fold-down panel associated with say vertical frame 32 adjacent the open end of the mould in the embodiment of Fig. 6, the trimmed height of the formed bund may be reduced to suit the application such as forming reduced height walls at intersections.

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