Hydraulic and earth engineering – Underground passageway – e.g. – tunnel – Lining
Reexamination Certificate
1998-05-06
2001-04-03
Lillis, Eileen D (Department: 3673)
Hydraulic and earth engineering
Underground passageway, e.g., tunnel
Lining
C405S146000, C405S155000
Reexamination Certificate
active
06210074
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a method and material for lining underground pipes such as sewer pipes. More particularly, the present invention relates to a method and material particularly suitable for, but not limited to, man-entry sized circular and oviform pipes.
2. Description of the Prior Art
Sewer pipes often become obstructed or structurally deteriorated due to pipe corrosion by hydrogen sulfide, general degradation, organic growth, and root infiltration. As a result, the flow of sewage can become obstructed or the sewer pipe may collapse. A degraded sewer pipe, even if not obstructed, may allow ground water to infiltrate, thus unnecessarily increasing fluid flow to a treatment plant.
The cost associated with replacing sewer pipes can be prohibitively high, and disruption to above ground traffic may not be feasible. Therefore, sewer pipes are often relined rather than replaced. In order to minimize above ground disruption during sewer pipe relining, sewer pipes are often relined using technology that does not require digging a trench above the sewer pipe.
Relining sewer pipes can be accomplished by installing a layer of unplasticized/rigid polyvinylchloride (uPVC) to form a new inner surface in existing pipes. An annular gap may be created between the existing pipe's inner surface and the new liner's outer surface. Grout may then be injected into this annular gap to strengthen and support the new liner as discussed in U.S. Pat. Nos. 5,388,929, 5,145,281 and 4,678,370.
When a relining and grouting process is carried out in man-entry sized pipes, for example pipes having diameters of 36″ and larger, the plastic liner must resist the hydraulic head pressure of the grout as it is being pumped into the annulus between the pipe and the plastic liner. Additionally, because gravity forces the grout to the bottom of the annulus, the liner may float on top of grout collected at the bottom of the annulus.
In order to prevent deflection of the liner due to hydraulic head pressure and to prevent floating, grout is usually injected in successive stages or “lifts”. Individual grout lifts cannot be injected until the previous lift is sufficiently cured to not transmit the hydraulic pressure to that portion of the PVC liner that it is in contact with. Furthermore, the previous grout lift anchors the PVC liner and resists the hydraulic pressure trying to deflect the liner which could result in the liner pulling out of the partially-cured lower grout layer or pulling the liner and grout together away from the pipe wall by overcoming the bond between the grout and pipe wall. Adequate curing may take as much as 12 to 24 hours. This limits the rate at which grout may be injected during the grouting process and increases the total time for the lining process.
Another method to prevent liner deflection due to excessive hydraulic head pressures is to increase the stiffness of the liner. The ability of the plastic liner to withstand hydraulic head pressure without significant deflection is dependent on the flexural rigidity or stiffness factor of the liner's plastic panels. Flexural rigidity is expressed mathematically as the product of the material's flexural modulus of elasticity (E) and its moment of inertia (I).
A material's flexural rigidity may be influenced by the material's geometric form. For example, a common manner of increasing a material's flexural rigidity is to locate a large amount of the material at a distance from a neutral axis, e.g., as in “I” beams.
Liner material is usually manufactured and shipped to a job sight in flat strips or standard size circular coils. The lining material must then be formed to fit the pipe's shape and must be flexible and light enough to be manually deformed. These limitations determine the maximum value of the material's flexural rigidity. For example, a liner measuring 12″ wide with ½″ high profile, made from rigid PVC has an EI value of 1600. For this material, it is estimated that grout lifts must be limited to about 6 to 12″ of vertical rise to avoid excessive panel deflection. The limited size of these lifts significantly increases the grouting process' total time and cost.
Because of the limitations discussed above, a need exists for a method and material which may be used to line man-entry sized pipes allowing faster and more economical lining and grouting by reducing the number of successively cured lifts.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method and material for lining relatively large diameter sewer pipes.
It is a further object to provide a method and material for lining relatively large diameter sewer pipes employing grout installed with or without successively cured lifts.
It is yet another object to provide a method and material for lining relatively large diameter sewer pipes employing an inner layer of grout which provides support for an outer layer of grout.
It is yet another object to provide a method and material for lining relatively large diameter sewer pipes employing an inner layer of grout for reducing the susceptibility of a sewer liner from floating on, and being displaced by, a second layer of grout.
According to one broad aspect of the invention, there is provided a structure for lining an interior surface of a pipe, incorporating an elongated panel having an inner wall, an outer wall, an anterior end, a posterior end and first and second longitudinal edges, and means for lockingly connecting at least one the first and second longitudinal edges of the elongated panel with an opposing longitudinal edge of an adjacent elongated panel. The panel is circumferentially curved along the interior surface of the pipe, wherein the panel includes a plurality of channels defined between the inner wall and the outer wall. A plurality of lockingly connected elongated panels form a circumferentially curved surface adjacent at least a portion of the interior surface of the pipe.
According to another broad aspect of the invention, there is provided a method of lining an interior surface of a pipe, including the steps of providing an elongated panel having an inner wall, an outer wall, an anterior end, a posterior end, first and second longitudinal edges and a plurality of channels defined between the inner wall and the outer wall; curving the elongated panel so as to fit circumferentially along the interior surface of the pipe; lockingly connecting at least one of the first and second longitudinal edges of the circumferentially curved elongated panel with opposing longitudinal edges of adjacent circumferentially curved panels such that a plurality of circumferentially curved adjacent panels forms a circumferentially curved surface extending through the pipe; and positioning the plurality of circumferentially curved adjacent panels to form the circumferentially curved surface adjacent at least a portion of the interior surface of the pipe.
According to yet another broad aspect of the invention, there is provided a method of lining an interior surface of a pipe that includes the steps of providing a plurality of elongated panels, each panel having an inner wall, an outer wall, an anterior end, a posterior end, first and second longitudinal edges, and a plurality of channels defined between the inner wall and the outer wall; curvedly forming each of the plurality of panels so as to be circumferentially positionable along the interior surface of the pipe; positioning the plurality of panels adjacent one another so as to form a circumferentially curved surface extending through the pipe; lockingly connecting correspondingly opposing first and second longitudinal edges of the plurality of adjacent panels; and positioning the plurality of adjacent panels to form the circumferentially curved surface adjacent at least a portion of the interior surface of the pipe.
According to a further broad aspect of the invention, a system for lining an inter
Danby of North America
Lillis Eileen D
Mayo Tara L.
Reed Smith Hazel & Thomas LLP
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