WO2007053895A1

WO2007053895A1 - Structural cavity

Info

Publication number: WO2007053895A1
Application number: PCT/AU2006/001674
Authority: WO
Inventors: Andrew Van Der Meer; Gavin Thomas
Original assignee: Andrew Van Der Meer; Gavin Thomas
Priority date: 2005-11-09
Filing date: 2006-11-09
Publication date: 2007-05-18

Abstract

A method for constructing a structural cavity (10) and also a structural cavity (10), constructed in accordance with such a method. The method involving providing a form (12) establishing the profile of at least the upper portion of the cavity. A settable material (16) is applied to the upper side of the form (12), which upon setting provides load support. An overlay of stabilised granular material (18) is applied above the settable material. The structural cavity (10) is particularly suitable for use as an in-ground tunnel.

Description

"Structural Cavity"

Field of the Invention

The present invention relates to a structural cavity. The invention has been devised particularly, although not solely, as a structural cavity in the form of a tunnel. A tunnel in accordance with the invention is particularly suitable as an in- ground tunnel.

Background Art

In-ground tunnels are constructed for various purposes. A tunnel can be constructed to provide an overpass above a location. A tunnel may also be constructed in the establishment of a material loading system involving a stockpile of particulate material above the tunnel, with provision for loading material from the stockpile into load carrying vehicles located at a loading zone within the tunnel. Typically, such a tunnel is constructed at ground level and earth material built up around the tunnel structure thereby forming an in-ground tunnel.

There are various known ways of constructing such tunnels. One construction method involves use of a robust metal arch to define the interior profile of the tunnel and form a supporting frame over which select material is backfilled. The select backfill typically comprises a sand or other granular material which must match strict quality and specifications.

Another method involves a heavy duty metal arch which acts as formwork against which a load supporting concrete structure can be constructed.

Perhaps the most common method for an in-ground tunnel construction is to use pre-cast concrete sections to assemble an arch defining the interior profile of the tunnel, and then backfilling with select backfill material.

All of these methods require heavy cranage (equipment) due to the nature of the materials (to be handled), which can be quite cumbersome and costly. In addition, the construction personnel are generally required to work from scaffolding a number of metres off the ground, creating safety issues.

The present invention seeks to address these problems through construction of a stable structure using relatively lightweight and readily available materials. Further, safety problems are overcome or at least reduced because construction personnel can work on a solid ground surface at all times.

Reference to cited material or information contained in the text should not be understood as a concession that the material or information was part of the common general knowledge or was known in Australia or any other country.

Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Disclosure of the Invention

In accordance with the present invention there is provided a method for constructing a structural cavity comprising;

providing a form establishing the profile of at least the upper portion of the cavity;

applying a settable material to the upper side of the form, which upon setting provides load support; and

applying an overlay of stabilised granular material above the settable material.

The form preferably remains as a permanent feature of the structural cavity, in which the inner surface of the structural cavity is defined by the form. Alternatively, the form may be removed such that the inner surface of the structural cavity is defined by the inner surface of the settable material. A continuous arch of metal sheeting is particularly convenient for constructing the form, although a range of materials may be used, for example, plywood.

Preferably, the metal sheeting extends continuously between opposite sides of the cavity.

In one form of the invention the form is anchored at the ends thereof. Where the structural cavity is constructed on the ground, the ends of the form are typically anchored to footings in the ground.

The settable material preferably comprises a conglomerate construction material, for example, concrete. Preferably, the concrete is applied by spraying, in which case it may comprise shot-crete.

Preferably the settable material is reinforced, typically by means of metal reinforcement such as mesh.

Preferably, the settable material is applied in a layer.

The layer formed by the settable material is preferably of adequate thickness to provide either the required stability for the structural cavity, or such that the strength of the layer of settable material is at least 15MPa.

The stabilised granular material may be of any grade or specification, making earth material quite suitable for this purpose, whereby the earth material is stabilised by a suitable stabilising agent, for example, cement or lignosulphonates.

The quantity of stabilising agent required is variable, depending on the type of earth material and the desired design strength upon stabilisation. Construction of the structural cavity by the addition of both the settable material and the stabilised granular material is preferably conducted in stages, building from the ground up.

Where the cavity comprises a tunnel, there may be a plurality of forms joined to one another in succession along the length of the tunnel.

In accordance with the present invention there is provided a structural cavity, comprising;

a load supporting structure establishing the profile of at least the upper portion of the cavity; and

an overlay of stabilised granular material.

The load supporting structure may comprise a layer of settable material which has set.

The load supporting structure preferably comprises a form to which the settable material was applied during construction of the tunnel.

Preferably, the form comprises metal sheeting extending continuously between two opposed sides of the cavity.

In one form of the invention the structural cavity may be constructed on mine sites underneath ore stockpiles. In such circumstances chutes are preferably incorporated into the upper portion of the cavity to allow access to the stockpile from the cavity.

Brief Description of the Drawings

The present invention will now be described, by way of example only, with reference to several embodiments thereof and the accompanying drawings in which: Figure 1 is a cross sectional view of the structural cavity in accordance with the first embodiment;

Figures 2 to 9 are a sequence of diagrams showing the stages of construction of the structural cavity; and

Figure 10 is a cross sectional view of the structural cavity in accordance with the second embodiment.

Best Mode(s) for Carrying Out the Invention

In Figures 1 to 9 there is shown a first embodiment of a structural cavity 10, in accordance with the present invention, in the form of an in-ground tunnel. The structural cavity 10 comprises a form 12 establishing the profile of the structural cavity 10, a layer of settable material 16, and an overlay of stabilised earth material 18. Retention of the stabilised earth material is aided by backfilling using a compacted backfill material 20. The form 12 is supported by a temporary support structure 14 (as shown in Figures 4 to 9) prior to placement of the settable material 16, the stabilised earth material 18 and the backfill material 20. The form 12 is initially established from durable material, such a sheet metal, anchored at its ends to the ground using concrete footings 22. The sheet metal can be fitted as one continuous sheet, or by connecting pieces together in sections to form an arch. The settable material 16 comprises a construction conglomerate material, such as shot-crete and is sprayed onto the upper surface of the form 12 and allowed to set. The thickness of the layer of settable material 16 is adjusted such that the strength is adequate to support the height of the arch. Preferably, the strength of the settable material exceeds 15MPa. The settable material 16 is reinforced by attaching mesh 24 to the upper surface of the form 12 and spraying the settable material 16 thereon. The overlay of stabilised granular material 18, such as earth stabilised with cement, is applied to the form 12 and settable material 16. - Q -

Construction is typically performed in stages as shown in Figures 2 to 9. The form 12 is constructed and anchored to cement footings 22 as shown in Figure 2. The reinforcing mesh 24 is attached to the upper surface of the form 12 (Figure 3) and the settable material 16 is then applied in sections close to ground level and allowed to set according to Figure 4. Stabilised earth material 18 is then laid around the upper surface of the settable material 16, such that the stabilised earth material 18 extends outwards from the layer of settable material 16. The stabilised earth material 18 is then backfilled with compacted backfill material 20 (Figure 5). The stabilised earth material 18 gains enough strength when stabilisation is complete such that construction personnel can stand on it, thus allowing access to the upper portion of the form 12 without the requirement for scaffolding. The first section of stabilised earth material 18 as shown in Figure 6 therefore provides a ground surface upon which construction personnel can stand in order to apply the next section of settable material 16. The process as hereinbefore described is repeated, as shown in Figures 7 and 8, until the entire form 12 is covered in settable material 16 and encompassed in stabilised earth material 18, to form a tunnel as seen in Figure 9. The temporary support structure 14 can then be removed once the tunnel 10 has gained its own strength. In this embodiment, the form 12 remains in place to form part of the completed tunnel 10, as shown in Figure 1. In another embodiment, the form 12 can also be removed, leaving the settable material 16 as a load supporting structure.

In Figure 10 there is shown a cross sectional view of a structural cavity 30 according to a second embodiment. The structural cavity 30 is of a construction similar to the structural cavity 10 according to the first embodiment and corresponding reference numbers are used to identify similar parts. The structural cavity 30 may be fitted with one or more loading chutes 26, which allow for efficient loading of ore from the stockpile onto trucks and/or trains. In use, a truck may pass into the structural cavity 30, pausing underneath the chute 26. The chute 26 is then opened and ore 28 allowed to pass through and land in the vehicle. This eliminates a variety of ore handling problems in that the ore only has to be lifted and dropped once into the stockpile. From this description it can be seen that this new method of building a structural cavity 10 is both cost and time effective. This method can be applied in a number of different industrial areas including but not limited to ore stockpiles, vehicular underpasses and overpasses.

The present invention is not to be limited in scope by any of the specific embodiments described herein. These embodiments are intended for the purpose of exemplification only. Functionally equivalent products and methods are clearly within the scope of the invention as described herein.

Claims

The Claims Defining the Invention are as Follows:

1. A method for constructing a structural cavity comprising;

applying a settable material to the upper side of the form, which upon setting provides load support;

2. A method according to claim 1 , wherein the form remains a permanent feature of the structural cavity.

3. A method according to claim 1 , wherein the form is later removed such that the inner surface of the structural cavity is defined by the inner surface of the settable material.

4. A method according to any one of claims 1 to 3, wherein the form is constructed from sheet-like material.

5. A method according to any one of the preceding claims, wherein the sheeting material extends continuously between opposite sides of the cavity to define an arch.

6. A method according to any one of the preceding claims, wherein the form is anchored at the ends thereof.

7. A method according to any one of the preceding claims, wherein the form is anchored to footings in the ground.

8. A method according to any one of the preceding claims, wherein the settable material comprises a conglomerate construction material.

9. A method according to any one of the preceding claims, wherein the settable material is applied by spraying.

10. A method according to any one of the preceding claims, wherein the settable material is reinforced.

11. A method according to any one of the preceding claims, wherein the settable material is applied in a layer.

12. A method according to claim 12, wherein the layer of settable material is of adequate thickness to stabilise the structural cavity.

13. A method according to claim 12, wherein the strength of the layer of settable material is at least 15 MPa.

14. A method according to any one of the preceding claims, wherein the stabilised granular material is stabilised by a suitable stabilising agent.

15. A method according to claim 1 , wherein the addition of settable material and stabilised granular material is conducted in stages.

16. A method according to claim 1 , wherein a plurality of forms join in succession to define the length of a tunnel.

17. A structural cavity constructed in accordance with a method according to any one of claims 1 to 16.

18. A structural cavity comprising;

an overlay of stabilised granular material.

19. A structural cavity according to claim 18, wherein the load supporting structure comprises a form and settable material.

20. A structural cavity according to any one of claims 18 or 19, wherein the form is constructed from a sheet-like material.

21. A structural cavity according to at least one of claims 18 to 20, wherein the sheet-like material extends continuously between two opposed sides of the cavity to define an arch

22. A structural cavity according to at least one of claims 18 to 21 , wherein a chute is incorporated into the upper portion of the cavity.

23.A method for constructing a structural cavity substantially as hereinbefore described with reference to Figures 1 to 9.

24.A structural cavity substantially as hereinbefore described with reference to Figures 1 to 9.