SHEETING PANELS FOR TRENCH SHORING
A substantially rectangular trench shoring sheeting panel made primarily of polyethylene includes at least one pair of hand holes. In some embodiments, the sheeting panel includes a plurality of buttons protruding outwardly from one of the sheeting panel's surfaces. As compared to three-quarter inch FinnForm, the polyethylene sheeting panel typically has (i) equivalent or superior structural properties and (ii) a significantly lower useful-life cost.
This application claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 61/508,154, filed Jul. 15, 2011, in the U.S. Patent and Trademark Office. This application incorporates the earlier provisional application by reference in its entirety.BACKGROUND OF THE INVENTION
The present invention relates to the field of shoring systems for supporting the sides of a trench or hole in the ground and, in particular, sheeting panels for hydraulic shoring techniques.
Various shoring techniques have been employed for supporting the sides of a trench or hole in the ground during excavation. One shoring technique, called “aluminum hydraulic shoring,” employs hydraulic jacks, aluminum shoring rails, and shoring sheeting panels to support the sides of the trench. After a portion of the trench is excavated, two sheeting panels may be placed substantially parallel to one another on opposite side of the trench. The shoring rails, typically already connected by the hydraulic jacks, are then placed on the faces of the two sheeting panels. The hydraulic jacks extend perpendicularly from the face of one sheeting panel to the face of the second sheeting panel. After proper placement of the shoring rails and hydraulic jacks, the hydraulic cylinders within the jacks are pressurized. Alternatively, the hydraulic shoring rails may be fastened to the sheeting panels, and then the assembly of rails and panels may be placed in the trench.
In 1989, the Occupational Safety and Health Administration (OSHA) adopted federal standard 29 CFR 1926, Subpart-P establishing safety requirements for excavation work-sites. In particular, Regulation 1926, Subpart-P, Appendix D includes item (g)(7) identifying the types of shore sheeting that may be used for aluminum hydraulic shoring for trenches. Item (g)(7) states: “Plywood shall be 1.125 inch thick softwood or 0.75 inch thick, 14 ply, arctic white birch (Finland form). Please note that plywood is not intended as a structural member, but only for prevention of local raveling (sloughing of the trench face) between shores.”
The OSHA Subpart P standard also requires (i) manufacturers of shoring equipment to develop their own tabulated data for the aluminum hydraulic shoring equipment they develop, and (ii) users of the equipment to adhere to the data developed for the shoring rails and sheeting panels they are using. To afford themselves of broader liability protection, most manufacturers of hydraulic shoring have tried to stay as close as possible to the data developed by OSHA. Other types of sheeting such as steel plate and plywoods with performance equivalent to and even less than three-quarter-inch, 14 ply, Artic White Birch (Finland form or “Finnform”) have been allowed. Finnform plywood is a relatively difficult standard to meet or exceed so it is used as the calibration standard within the industry.
To date, plywood has primarily been used for shoring sheeting panels. Although plywood performs well as a shoring panel, the material also has a number of drawbacks. In particular, water, mud, and drying cause the plywood panels to gray and eventually delaminate. The handling and installation of plywood panels also breaks the corners of the plywood panels. Thus, the useful life of plywood sheeting panels is approximately one to two years.
Additionally, plywood breaks and punctures relatively easily. If a plywood sheeting panel is punctured or an edge of the panel is broken, the overall area of restraint provided by the panel is reduced. Unrestrained areas of soil and rock may shift and move creating potential safety hazards.
As noted, plywood sheeting panels can be damaged during handling, which may include dragging the panel. Over time, the panel becomes bent in the face plane, and breaking and splintering occurs on the face of the panel. As the deterioration progresses the coverage and effectiveness of the sheeting becomes less than intended. Furthermore, splintering on the edges and face of the plywood present a safety hazard to workers handling the shores (e.g., the assembly of shore rails and sheeting panels). Even with gloves on, large plywood splinters can penetrate the hands and other parts of the body. Workers inside the trench that are not handling the shores can still brush up against the shore receiving puncture wounds. Working at the trench level exposes the upper body and head to the surrounding shoring sheeting.
To combat these issues, metal edge protectors may be installed on plywood sheeting panels, and the shores may be cleaned and refurbished after each use. The cost and time associated with replacing the plywood panels, installing metal edge protectors, and cleaning the shores can be excessive.
Therefore, a need exists for an improved sheeting panel that meets or exceeds the OSHA regulations for aluminum hydraulic shoring for trenches. More particularly, there exists a need for a sheeting panel that reduces the long-term cost of maintaining and installing shoring systems and is durable, easy to handle and maintain, and safe for both shore installers and workers inside the trench.SUMMARY OF THE INVENTION
In one aspect, the present invention embraces a substantially rectangular trench shoring sheeting panel made primarily of polyethylene. The sheeting panel includes a front surface, a rear surface, and four edges.
In an exemplary embodiment, the sheeting panel includes at least one pair of hand holes extending through the front surface and the rear surface. Each of the hand holes is separated a lateral distance from the other along one of the sheeting panel's four edges.
In another exemplary embodiment, the sheeting panel includes four pairs of hand holes extending through its front surface and rear surface. Each pair of hand holes is typically located along a different edge of the sheeting panel. Within each pair of hand holes, each hand hole is separated a lateral distance from the other along one of the sheeting panel's four edges.
In yet another exemplary embodiment, at least one side of the sheeting panel includes buttons protruding outward from a majority of the sheeting panel's surface.
In yet another exemplary embodiment, a strip of area extending centrally across the length of the sheeting panel's surface is free of buttons.
In yet another exemplary embodiment, the sheeting panel includes four corner holes located in each of the shoring panel's corners.
The foregoing and other objects and advantages of the invention and the manner in which the same are accomplished will become clearer based on the following detailed description taken in conjunction with the accompanying drawings in which:
The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which multiple embodiments of the invention are shown. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.
The present invention embraces a sheeting panel made primarily of polyethylene. As depicted in
The sheeting panel 10 typically includes four pairs of hand holes 14, 15, 16, and 17 to facilitate safe handling. The hand holes 14, 15, 16, and 17 may be molded into the polyethylene sheeting panel 10 during manufacturing. Alternatively, the hand holes 14, 15, 16, and 17 may be cut out of the sheeting panel 10. For a given pair of hand holes 14, 15, 16, or 17, the hand holes are typically separated a lateral distance from each other (i.e., spaced apart) along one of the four edges of the sheeting panel.
As depicted in
As noted, the sheeting panel typically includes pairs of hand holes. That said, the sheeting panel 10 may include individual hand holes. For example, if the width of the sheeting panel is relatively small, a single hand hole may be sufficient to facilitate safe handling.
The sheeting panel 10 may also include four corner holes 31, 32, 33, and 34. As depicted in
As depicted in
Alternatively, the side of the sheeting panel 10 facing the trench wall may include buttons 22. In such an arrangement, the buttons 22 increase the frictional force (i.e., provide extra traction) between the vertical face of the trench, thereby reducing the risk of sliding or slipping.
As previously noted, the sheeting panel is made primarily of polyethylene, which provides significant advantages in terms of both convenience and structural performance as compared to typical FinnForm plywood sheeting panels. The polyethylene sheeting panel may be manufactured in a variety of colors (e.g., black or white), and is easily cleaned by spray washing. Furthermore, the polyethylene sheeting panels can be cut and drilled with the same tools that are used for plywood sheeting panels.
From a structural standpoint, the polyethylene sheeting panels provide additional benefits. For example, the polyethylene sheeting panels do not splinter or delaminate on the panel-face or edges. Furthermore, the polyethylene sheeting panels deflect rather than breaking when loaded excessively. A 44.5-inch-wide, 96-inch-long, and half-inch-thick polyethylene sheeting panel weighs approximately seventy-eight pounds. The polyethylene sheeting panels also meet or exceed the structural properties of three-quarter inch FinnForm.
Table 1 (below) is a comparison of physical and structural properties of polyethylene sheeting panels to the plywood panels allowed in OSHA Regulation 1926, Subpart-P, Appendix D, item (g)(7).
Despite the fact that OSHA Regulation 1926 does not consider sheeting to be a structural member, from an engineering standpoint, a structural comparison is an appropriate way to compare the panels. In a structural sense, 1.125-inch-thick softwood is inferior to both polyethylene sheeting panels and FinnForm. Maximum bending moment is a particularly notable value in Table 1 because, if a panel were to fail by trench wall collapse, bending would be the failure mode of the sheeting. Although the FinnForm panel has a higher maximum bending moment than the polyethylene sheeting panel, the overall analysis indicates that the polyethylene sheeting panel is technically equivalent to the FinnForm panel.
The modulus of elasticity is much lower for polyethylene sheeting panels. Although this indicates that the panel will deflect more when loaded, for the purpose of preventing local raveling, it is considered an advantage because it allows the shore and sheeting to conform to the trench wall without breaking the sheeting. The higher modulus of elasticity associated with plywood and FinnForm is an indication that it is more brittle and will break, delaminate, or puncture more easily. A complete structural analysis of the sheeting panels of Table 1 can be found in Appendix 1, wherein the polyethylene sheeting panel is referred to as the “SHOR-MAT Panel.”
Additional mechanical tests were performed on polyethylene sheeting panels in accordance with some embodiments of the present invention. The results of those tests can be found in Appendix 2.
The polyethylene sheeting panel of the present invention also facilitates a reduction in the cost associated with maintaining and installing shoring equipment. In this regard, the following exemplary cost comparison between polyethylene sheeting panels and FinnForm sheeting panels demonstrates that the inventive sheeting panels can facilitate a substantial cost savings.EXAMPLE
The use of sheeting with hydraulic shoring applications is dependent on depth of excavation and soil type. In general sheeting is required in excavations over 10 feet deep in OSHA type B and C soils. The sheeting may be attached to the shoring or set inside the excavation before the shore (i.e., the shore rails and hydraulic jack) is set and pressurized. Generally, on the West Coast and South Coast, sheeting is attached to the shore, and, on the East Coast, it is set independently from the shore.
Shoring panels become damaged on the corners by rigging, dragging on the surface during installation, and removal. Plywood also becomes bent and broken due to raveled and uneven trench walls. Plywood is often cut to fit around pipes and other obstructions. Weather and ground water table conditions also have an effect on the quantity of plywood used and the life expectancy of the sheeting panels. Wet weather and coastal regions will utilize more shoring sheeting than arid and central states. The purchase and installation of shoring sheeting panels is done at the local supplier level rather than at the manufacturer's level.
Table 2 (below) presents the summarized results of a cost estimate of a useful life cost comparison between polyethylene sheeting panels and FinnForm sheeting panels.
In a major municipality on the West Coast a shoring supplier installs 300 sheets of 4-foot×8-foot FinnForm on 150 hydraulic shores every two years. The useful life of the FinnForm sheeting is two years. The typical soils that the sheeting is used in are either coarse sands and gravels or medium stiff sandy clays. Rainfall is heavy in the winter and water tables are high, within 8 feet of the surface.
The useful life of polyethylene sheeting panels is assumed to be over 10 years. This useful life assumption is supported by experience using polyethylene materials in other harsher construction applications. The cost of polyethylene sheeting panels is double (i.e., 2×) the cost of FinnForm. The analysis includes the cost of purchasing the panels, installing them on the shores, removing the panels from the shores and disposing of the dilapidated sheeting, and maintaining the shores after each use. Labor cost is assumed to be from the shoring supplier's general warehouse and yard maintenance workforce.
As shown in Table 2, the cost of operating and maintaining a trench shoring operation can be significantly reduced by using the polyethylene sheeting panels of the present invention. The complete cost analysis used to generate Table 2 can be found in Appendix 3, wherein the polyethylene sheeting panel is referred to as the “SHOR-MAT Panel.”
In the drawings and specification, there have been disclosed typical embodiments on the invention and, although specific terms have been employed, they have been used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.
1. A trench shoring sheeting panel, comprising:
- a substantially rectangular sheeting panel made primarily of polyethylene, said sheeting panel having a front surface, a rear surface, and four edges; and
- at least one pair of hand holes extending through said front surface and said rear surface, each of said hand holes being separated a lateral distance from each other along one of said sheeting panel's four edges.
2. A trench shoring sheeting panel according to claim 1, wherein said sheeting panel is made primarily of polyethylene having a modulus of elasticity of less than 1000 ksi.
3. A trench shoring sheeting panel according to claim 1, comprising four pairs of hand holes extending through said front surface and said rear surface, wherein:
- each of said pairs of hand holes is located along a different edge of said sheeting panel than each of said other pairs of hand holes; and
- within each of said pairs of hand holes, each of said hand holes is separated a lateral distance from the other along one of said sheeting panel's four edges.
4. A trench shoring sheeting panel according to claim 1, comprising buttons on at least one of said sheeting panel's surfaces, said buttons protruding outward from a majority of said sheeting panel's surface.
5. A trench shoring sheeting panel according to claim 4, wherein a strip of area extending centrally across the length of said sheeting panel's surface is free of buttons.
6. A trench shoring sheeting panel according to claim 1, comprising four corner holes extending through said front surface and said rear surface, wherein said corner holes are located in each of the shoring panel's corners.
7. A trench shoring sheeting panel, comprising:
- a substantially rectangular sheeting panel made primarily of polyethylene, said sheeting panel having a front surface, a rear surface, and four edges; and
- four pairs of hand holes extending through said front surface and said rear surface, each of said hand holes located along a different edge of said sheeting panel than each of said other pairs of hand holes; and
- buttons on at least one of said sheeting panel's surfaces, said buttons protruding outward from a majority of said sheeting panel's surface;
- wherein each of said pairs of hand holes is separated a lateral distance from the other along one of said sheeting panel's four edges.
Filed: Jul 13, 2012
Publication Date: Jan 17, 2013
Inventor: Arthur L. Price (Charlotte, NC)
Application Number: 13/548,729
International Classification: E02D 17/00 (20060101);