AU2012244376B2

AU2012244376B2 - One piece box culvert with headwall

Info

Publication number: AU2012244376B2
Application number: AU2012244376A
Authority: AU
Inventors: Phil Thomas
Original assignee: Precast Civil Ind Pty Ltd
Current assignee: Precast Civil Industries Pty Ltd
Priority date: 2011-11-09
Filing date: 2012-11-07
Publication date: 2016-09-29
Anticipated expiration: 2032-11-07
Also published as: AU2012244376A1

Abstract

The present invention is a one piece precast box culvert with headwall unit having a culvert portion, back wall and an apron. In one preferred embodiment there are side 5 walls extending outwardly from the end wall. The one piece precast box culvert with headwall unit can form a module and a plurality of modules can be positioned next to each other to provide a wider passageway for stormwater. Figure 1

Description

ONE PIECE BOX CULVERT WITH HEADWALL

FIELD OF INVENTION

The present invention relates to box culverts. In particular the invention relates to a precast one piece concrete box culvert with a headwall. The present invention has particular but not exclusive application for installation under a road for directing water flow.

BACKGROUND OF THE INVENTION

Box culverts are typically used in drainage applications and as an alternative to pipes. Box culverts are often used beneath roadways where the ability to cover the upper surface of the pipe is limited. Box culverts are available in a variety of dimensions and used in various diverse applications including drainage of stormwater from roads, bridging, subways, foreshores and redirecting water from creeks and streams. A headwall is typically installed at an open end of a box culvert, particularly where water discharges from a culvert. Typically a headwall unit directs the water as it exits the culvert and protects the surroundings from erosion and scouring.

Headwalls may be formed in situ from a multi-part construction requiring onsite assembly. On-site casting requires transportation of premix concrete to the site, and skilled labour to construct the headwall. The installation process can be protracted and this incurs high labour costs. Furthermore, the in situ headwall requires time to cure in order to obtain the required strength.

Alternatively a precast concrete headwall can be attached to the installed culvert on site. Even with the use of precast concrete headwalls there is a need for high quality, skilled labour to ensure that correct construction and installation is carried out to provide a durable headwall unit. Consequently headwalls attached to a culvert in situ are not robust and are prone to failure or dislodgement. This is a particular problem when water flow exceeds the volume of water that can be handled by the culvert. With flooding, the volume of water is sometimes greater than the capacity of the culvert and over the top flow causes dislodgement. Furthermore hydrostatic pressure can disrupt and or dislodge the culvert and headwall.

Consequently there is a failure of the headwall and culvert and the surrounding areas are eroded.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a headwall unit that overcomes at least in part one or more of the abovementioned disadvantages.

SUMMARY OF THE INVENTION

In one aspect the present invention broadly resides in a one piece precast box culvert with headwall unit including a box culvert portion including a roof, a base and two side walls; a headwall portion including a back wall and an apron forming a floor extending from the back wall; wherein said headwall and box culvert are integrally formed and are in communication with each other.

Preferably said headwall portion is substantially at one end of the box culvert portion.

In another aspect the present invention broadly resides in a one piece precast box culvert with headwall unit including a back wall with at least one side wall which extends outwardly from an end of the back wall; an apron forming a floor extending between the back wall and the at least one side wall; and a box culvert including a roof, a base and two culvert side walls; wherein the box culvert is integral with and extends from the rear of the back wall and said back wall has an aperture which forms an opening to the box culvert.

In one embodiment the back wall has one side wall extending outwardly from an end of the back wall. In another embodiment the back wall has two side walls, each of which extends outwardly from an end of the back wall.

Preferably a side wall extends outwardly at an obtuse angle from the back wall. Preferably the side walls extend at an angle of 120 to 150 degrees from the back wall.

Preferably the headwall unit is fitted with one or more soil outlets to allow seepage of water from the soil to facilitate release of water pressure that can build up behind the headwall during heavy rainfall. A build up of water pressure can dislodge headwall units. Preferably soil outlets are located in the side walls of the headwall unit. Preferably a soil outlet is located towards the lower end of a side wall.

In one preferred embodiment, the apron is at a level approximately 100mm lower than the level of the base of the box culvert and the back wall extends upwardly by approximately 250mm above the roof level of the box culvert, where the box culvert dimensions are approximately 1200mm wide and 600mm high. The dimensional relationship between the box culvert, back wall and apron are preferably substantially similar irrespective of the size of the box culvert.

The box culvert is proportional to the apron and back wall where the box culvert is substantially 1200mm wide and 600mm high, the apron is at a level approximately 100mm lower than the level of the base of the box culvert and the back wall extends upwardly by approximately 250mm above the roof level of the box culvert.

Preferably the aperture is rectangular in shape. Preferably the aperture is of similar dimensions to the cross sectional dimensions of the box culvert.

In another aspect, the present invention resides in a plurality of box culverts located adjacent each other to provide a wider passage for the flow of stormwater.

Preferably the box culverts are located so to provide a continuous apron section.

Preferably there are one or more side walls extending outwardly from one or both sides of the continuous apron section.

Preferably any suitable arrangement of a plurality of box culverts can be formed where each box culvert is a module. Preferred embodiments include two box culverts where each box culvert has an outwardly extending wall, three or more box culverts where the middle box culvert or culverts do not have any outwardly extending walls.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the present invention can be more readily understood and put into practical effect, reference will now be made to the accompanying drawings wherein:

Figure 1 is a diagrammatic view of a one piece precast box culvert and headwall unit according to a first embodiment of the present invention;

Figure 2 is a diagrammatic top view of the one piece precast box culvert and headwall unit of Figure 1;

Figure 3 is a diagrammatic view of a multi-cell embodiment of a one piece precast box culvert and headwall unit according to another embodiment of the present invention; and

Figure 4 is a diagrammatic side view of the one piece precast box culvert and headwall unit of Figure 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to Figures 1, 2 and 4, there is shown a one piece precast box culvert and headwall unit 10. The unit 10 has a back wall 11 and two side walls 16. Each side wall 16 extends outwardly from the back wall 11 at an obtuse angle (preferably approximately 120° angle). An apron 15 forms a floor extending between the back wall 11 and the two side walls 16.

The back wall 11 has a rectangular aperture 12 which forms an opening to the box culvert portion 14. The dimensions of the aperture 12 are similar to the dimensions of the box culvert. The box culvert 14 is integral with and extends from the rear of the back wall 11 and includes a roof 17, a base 18 and two culvert side walls 19.

The apron 15 is located at a level approximately 100mm lower than the level of the base of the box culvert. The back wall extends upwardly by approximately 250mm from the roof level of the box culvert. The box culvert of the present embodiment has a span of 1200mm and a height of 600mm.

The headwall unit 10 is fitted with an outlet 13 on each of the side walls 16. The outlets 13 are located towards the lower end of the side walls 16. The outlets 13 allow excess water to seep from the soil and thus ease the water or hydrostatic pressure that can build up behind the headwall during heavy rainfall. A build up of hydrostatic pressure may cause the headwall unit to dislodge or destabilize.

The precast headwall unit 10 is made off-site. With prefabrication, the headwall unit can cure and subsequently increase in integrity before being subjected to operational loads. With a precast headwall unit, no formwork is required at the site of installation, and the on-site construction work is limited to connecting the headwall unit 10 to other portions of box culvert as necessary. Consequently the time taken to install the headwall unit and the need for workers with specialist skills is reduced.

The preferred embodiment described above relates to a one piece single cell headwall unit. The present invention also includes two, three, four and multiple cell headwall units.

With reference to Figure 3 there is shown an alternative embodiment of the present invention. Head wall unit 30 includes three one piece precast box culvert with headwall units 40, 50 and 60 which may be installed side by side to form a three-cell headwall unit 30. Headwall unit 40 is similar to headwall unit 10 and includes a back wall 41 and a side wall 46 extending outwardly from one end of the back wall 41 at an obtuse angle. An apron 45 extends from the back wall 41. The back wall 41 has a rectangular aperture 42 which forms an opening to the box culvert portion 44. The box culvert 44 is integral with and extends from the rear of the back wall 41. The headwall unit 40 is fitted with an outlet 43 in side wall 46 to relieve build up of hydrostatic pressure.

Headwall unit 60 is similar to headwall unit 40, except that wing wall 66 extends from the opposite end of the back wall 61 to give the opposite configuration to that of headwall unit 40.

In a further alternative embodiment headwall units 40 and 60 may be used together and laid side by side to form a two cell headwall unit.

In a yet further embodiment headwall units 40 and 60 may be used in conjunction with two or more headwall units 50 to form a multi-cell headwall unit.

Headwall unit 50 is also similar to headwall unit 10, but has no side walls. Headwall unit 50 includes a back wall 51 with an apron 45 extending forwards from the back wall 51. The back wall 51 also has a rectangular aperture 52 which forms an opening to the box culvert portion 54. The box culvert 54 is integral with and extends from the rear of the back wall 51.

It will be appreciated that the dimensions of the box culvert will change depending on the requirements for the situation.

ADVANTAGES

An advantage of the preferred embodiment of the present invention is that the precast one piece headwall integral with the box culvert has the benefit of quick installation. The time required for installation of a one piece precast headwall unit is greatly reduced, and the construction of formwork at the construction-site is also no longer needed. This eliminates any safety risk associated with the need for components of existing units to be supported during construction. The installation process is quick and minimal skill is required.

The one piece construction of the unit also eliminates the possibility of failure of multi-piece constructions due to dislodgement or misalignment.

Another advantage of the preferred embodiment of the present invention is that the unit is stronger since it is formed as a single piece. It is formed off site and can be allowed to cure fully before installation. This gives a better performance and a longer lifetime product. A further advantage of the preferred embodiment is that subsoil outlets allow dissipation of hydrostatic pressure behind the headwall and prevent the build-up of hydrostatic pressure which can lead to dislodgement of the headwall. A further advantage of the preferred embodiment of the one piece precast box culvert with headwall unit is that it can form a module and a plurality of modules can be positioned next to each other to provide a wider passageway for stormwater.

VARIATIONS

It will of course be realized that while the foregoing has been given by way of illustrative example of this invention, all such and other 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 herein set forth.

Throughout the description and claims this specification the word “comprise” and variations of that word such as “comprises” and “comprising”, are not intended to exclude other additives, components, integers or steps.

Claims

1. A one piece precast box culvert with integrated headwall unit including a back wall, an apron and at least one side wall wherein the apron and at least one side wall extends forwardly from the back wall; and a box culvert including a roof, a base and two culvert side walls; wherein the box culvert extends rearwardly from the back wall and said back wall has an aperture which forms an opening to the box culvert to allow the passage of water; wherein there are one or more soil outlets to allow seepage of water from the soil to facilitate release of water pressure from behind the back wall; wherein in use the integral one piece form of the unit and the presence of the one or more soil outlets work together to maintain the integrity of the placement of the unit.

2. A one piece precast box culvert with integrated headwall unit as claimed in claim 1, wherein there are two or more side walls extending outwardly from an end of the back wall.

3. A one piece precast box culvert with integrated headwall unit as claimed in claim 1 or 2, wherein said one or more side walls extend at an obtuse angle from the back wall.

4. A one piece precast box culvert with integrated headwall unit as claimed in claim 1 or 2, wherein said one or more side walls extend at an angle of 120 to 150 degrees from the back wall.

5. A one piece precast box culvert with integrated headwall unit as claimed in any one of the above mentioned claims, wherein there are one or more soil outlets in the one or more side walls.

6. A one piece precast box culvert with integrated headwall unit as claimed in any one of the above mentioned claims, wherein the box culvert is proportional to the apron and back wall where the box culvert is substantially 1200mm wide and 600mm high, the apron is at a level approximately 100mm lower than the level of the base of the box culvert and the back wall extends upwardly by approximately 250mm above the roof level of the box culvert.

7. A plurality of one piece precast box culvert with integrated headwall units wherein each of the one piece precast box culvert with integrated headwall units are as claimed in any one of the above mentioned claims, wherein the box culvert with integrated headwall units are located adjacent each other to provide a wider passage for the flow of stormwater.

8. A plurality of one piece precast box culvert with integrated headwall units as claimed in claim 7, wherein the one piece precast box culvert with integrated headwall units are located adjacent each other to provide a continuous apron section.

9. A plurality of one piece precast box culvert with integrated headwall unit as claimed in claim 7 or 8, wherein there are two box culvert with integrated headwall units where each unit has an outwardly extending side wall that substantially oppose each other.