Hydraulic and earth engineering – Fluid control – treatment – or containment – Flow control
Reexamination Certificate
2000-08-22
2003-03-18
Pezzuto, Robert E. (Department: 3671)
Hydraulic and earth engineering
Fluid control, treatment, or containment
Flow control
C405S124000
Reexamination Certificate
active
06533498
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to headwall structures and in particular to improved lightweight headwall structures used with standard culvert or drainage pipes in infrastructure water management system. Because they are lightweight while having adequate strength, headwall structures according to the invention are easily transported and installed. They may be largely prefabricated. They are intended to be used in substitution for standard heavy concrete headwalls.
BACKGROUND OF THE INVENTION
Headwalls are structures that attach to the end of a culvert or drainage pipe and support the surrounding earth or fill, thus preventing or impeding local erosion and undercutting of the bank around the culvert, thereby minimising the risk of serious washout. These structures also facilitate the attachment of auxiliary components, e.g., trash gates for debris and animal control, security grids for prevention of entry into culvert or pipe, weir boards for use in control of water flow and levels in agricultural installations, etc. Such structures include a back wall having an orifice to receive a culvert or pipe, and often include a tray joined to the lower edge of the back wall and extending outwards therefrom and may have two outwardly flared (diverging) wings or sidewalls joined to the back wall and to the tray to retain and stabilize the surrounding earth or fill side wings for earth bank stabilization. The wings and tray when present as part of a headwall structure used as an outflow (exit) structure downstream of the culvert or pipe, direct the outflow received from the pipe or culvert away from the headwall. If used as entrance structures upstream of the pipe, such headwall structures receive water from a source such as an open ditch or drain and direct the water into the orifice and thence into a connected pipe if such is present.
Conventionally such headwall structures are made of relatively heavy concrete either formed in place or precast. It is well known that structures formed in place are labour-intensive and may also require prolonged traffic diversion if they have to be erected in association with a road in use. Because of their heavy weight, precast concrete structures require heavy-duty equipment to transport, handle and install. Additionally, concrete has several disadvantages. It is rigid and prone to cracking in the event of earth movement due to seismic events or subsidence or due to permafrost conditions in northern areas. Concrete is not environmentally friendly due to leaching of material into the ground water. It is also highly porous and subject to spalling and salt absorption.
A representative conventional culvert with associated concrete headwall can be found in U.S. Pat. No. 4,993,872 to Lockwood; this patent discloses a prefabricated headwall but without a pipe. A concrete headwall for use with a connected pipe is disclosed in U.S. Patent No. 3,779,021 to Green. An alternative concrete structure for connection to a pipe is disclosed in U.S. Pat. No. 5,551,798 to Goodreau. On occasion the use of plastics materials for coupling pipe to another structure has been proposed; see for example U.S. Pat. No. 5,971,663 to Brothers.
The Green patent discloses headwalls manufactured by pouring concrete into a light plastic prefabricated form. This method substantially reduces the amount of labour required to build the headwall, but still requires considerable time and effort, because the concrete has to be transported to the site. Poured-in-place concrete is increasingly unacceptable because of potential negative environmental and ecological impact on wildlife habitats and drinking water quality. Note that the Green design, because of the complexity of surface detail, would not readily accommodate after-market add-on auxiliary devices such as trash gates, security grids and weir boards.
Goodreau's disclosed structure embodies two prefabricated end walls of the culvert with a specific retainer system; his structure suffers from the inherent disadvantages of using concrete slabs. Goodreau does not disclose the use of sidewalls or wings that retain the adjacent earth bank, so there could be a tendency for the earth bank to spill over the flat bottom portion of the headwall outlet area. Goodreau's design does not retain side bank slope material nor minimize ingress into pipe opening, nor does it provide complete retention of the integrity of the side slope. His headwall may not be suitable for permafrost or boggy areas without some modification, because his footings appear to be inadequate for the weight of the precast concrete unit. The structural stability of the Goodreau design is reliant on the stability of the backfill material, as no other means of supporting the headwalls to remain vertical is apparent other than the pipe connection itself.
Other patents disclosing prefabricated concrete headwall structures, mostly for use with box culvert systems or other channel constructions, include U.S. Pat. Nos. 2,041,267 to Schroeder, and 5,836,717 to Bernini.
An inexpensive headwall constructed from material other than concrete was proposed in U.S. Pat. No. 4,723,871 by Roscoe. This headwall for culverts consists of a substantially monolithic plastics shell structure, filled with a granular material or a flowable material capable of solidifying. This specific headwall is simpler and lighter than many known before it; however, it does not provide reliable performance in use. Roscoe's design does not offer full bank retention nor prevent undermining of the structure from water flow, as it does not provide wing walls nor an extended base. Further, Roscoe's design does not permit rapid installation under adverse weather conditions; yet once installed, it cannot be readily removed if need be. The manufacture in place of the Roscoe structure may not be economically viable in remote areas nor environmentally acceptable in maintaining non-contamination of water systems from poured-in-place materials during installation.
In short, while various previously known designs have utility, they all suffer from disadvantages. A strong, reliable, lightweight, easily transported and easily installed structure is needed that will provide adequate bank stabilization and adequate downstream water diversion away from the surrounding earth or fill. Such structure should be readily connectable to associated pipe and should be readily capable of receiving auxiliary devices such as trash gates, security grids and weir boards for attachment thereto. A problem to overcome is that while reinforced concrete structures are sufficiently heavy to tend to stay in place and sufficiently strong and rigid to maintain structural stability under load, a lightweight unit designed to serve the same purpose as a given concrete headwall may lack inherent structural stability and may not readily withstand the forces imparted to it in use.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide a headwall structure that meets the foregoing need and overcomes the disadvantages of conventional headwalls. Such structure should facilitate the control of water flow, erosion, flooding, silt and debris and should be readily attachable to any culvert pipe of any type, size or style, used in an infrastructure water management system.
Another object of the present invention is to provide a headwall that is economical, efficient, easy to install, and also easy to remove to accommodate the possibility of future reclamation of areas to their natural state.
Another object of the present invention is to provide a headwall structure with earth-stabilizing sidewalls and a bottom plate or tray providing in combination with the sidewall configuration (including associated reinforcing elements preferably integrally formed therewith) a suitable water flow channel that serves either as an outlet chute defining a satisfactory exit channel configuration for water outflow, or when used in reverse (entrance) orientation, a satisfactory inlet flow channel configuration.
Yet another object
Barrigar Robert H.
Pechhold Alexandra K.
Pezzuto Robert E.
LandOfFree
Reinforced composite material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reinforced composite material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reinforced composite material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3051094