Abstract:
A material and method is provided for lining man-entry sized pipes and securing the lining to the pipe. The lining comprises a plurality of adjacent, unplasticized polyvinyl chloride panel segments circumferentially curved within the pipe, each including an interior channel through which grout may be injected. Upon the grout&#39;s curing, the grout provides strength and support for a second layer of grout injected into an annulus between the pipe&#39;s inner surface and an outer surface of the lining.

Description:
This is a continuation-in-part of U.S. patent application Ser. No. 08/712,408, filed Sep. 11, 1996, now U.S. Pat. No. 5,785,456, issued Jul. 28, 1998. 
    
    
     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&#39;s inner surface and the new liner&#39;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&#39;s plastic panels. Flexural rigidity is expressed mathematically as the product of the material&#39;s flexural modulus of elasticity (E) and its moment of inertia (I). 
     A material&#39;s flexural rigidity may be influenced by the material&#39;s geometric form. For example, a common manner of increasing a material&#39;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&#39;s shape and must be flexible and light enough to be manually deformed. These limitations determine the maximum value of the material&#39;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&#39; 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 interior surface of a pipe incorporates a plurality of elongated panels, each panel having an inner wall, an outer wall, an anterior end, a posterior end and first and second longitudinal edges, the plurality of panels being positioned adjacent one other and circumferentially curved along the interior surface of the pipe such that the plurality of panels form a circumferentially curved surface extending through the pipe and adjacent at least a portion of the interior surface of the pipe; and means for lockingly connecting opposing first and second longitudinal edges of the plurality of adjacent elongated panels. Each one of the panels includes a plurality of channels defined between the inner wall and the outer wall. 
     Other objects and features of the present invention will be apparent from the following detailed description of the preferred embodiment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be further described in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a cross sectional view of a liner panel constructed in accordance with a preferred embodiment of the invention; 
     FIG. 2 is a cross sectional view of a locking mechanism taken along lines  2 — 2 ′ of FIG. 1; 
     FIG. 3 is a cross sectional view of a clip constructed in accordance with a preferred embodiment of the invention; 
     FIG. 4 is a cross sectional view of an assembled locking mechanism constructed in accordance with a preferred embodiment of the invention; 
     FIG. 5 is a side view of a posterior plug constructed in accordance with a preferred embodiment of the invention; 
     FIG. 6 is a bottom view of a posterior plug constructed in accordance with a preferred embodiment of the invention; 
     FIG. 7 is an end view of a posterior plug constructed in accordance with a preferred embodiment of the invention; 
     FIG. 8 is a side view of a manifold constructed in accordance with a preferred embodiment of the invention; 
     FIG. 9 is a bottom view of a manifold constructed in accordance with a preferred embodiment of the invention; 
     FIG. 10 is an end view of a manifold constructed in accordance with a preferred embodiment of the invention; 
     FIG. 11 is an overall perspective view of the first preferred embodiment of the present invention as applied to the interior surface of a pipe; and 
     FIG. 12 is an overall perspective view of a second preferred embodiment of the present invention as applied to the interior surface of a pipe. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the figures, wherein like reference characters indicate like elements throughout the several views and, in particular, with reference to FIG. 1, a panel  10  has an elongated and generally planar body  11 , a smooth inner surface  15  and anterior and posterior terminal ends. A plurality of T-shaped legs  20  extend perpendicularly from an outer surface  25  of body  11 . Upon installation as described below, T-shaped legs  20  stiffen panel  10  by increasing panel  10 &#39;s flexural rigidity and may also anchor panel  10  to a grout layer (not shown). 
     Parallel and adjacent to outer surface  25  is a planar wall  35  having an inner wall surface  36  and an outer wall surface  37 . Planar wall  35  is integrally formed with outer surfaces of T-shaped legs  20  and extends the entire width of panel  10 . In this fashion, a number of interior channels  45  are bounded by outer surface  25 , first and second T-shaped legs  20  and inner wall surface  36 . Interior channels  45  extend the length of panel  10 . 
     With reference to FIG. 2, opposing edges of panel  10  each include a locking mechanism  50 . Locking mechanism  50  includes a retainer  55  having a generally U-shaped cross-section, and a terminal end  60 . Terminal end  60  includes a back-swept retaining flange  65  projecting a short distance toward an opposing sidewall of retainer  55 . Retainer  55  may be offset from a horizontal plane defined by inner surface  15  of panel  10  creating a notch  70 . 
     Upon installation as discussed below, edges of two adjacent panels  10  may be secured with a joiner strip  75 . With reference to FIG. 3, joiner strip  75  is formed into an elongated strip and includes a horizontal member  80  with two vertical members  85  located on opposing sides of a vertical centerline  86  bisecting horizontal member  80 . Each vertical member  85  is generally perpendicular to horizontal member  80  and includes a retaining clasp  90  projecting toward vertical centerline  86 . 
     As illustrated in FIG. 4, installation of two panels  10  is performed by positioning two panels  10  adjacent one another and forcing each vertical member  85  of joiner strip  75  over a retaining flange  65  of a locking member  50 . In this fashion, retaining clasps  90  and retaining flanges  65  cooperate to lock and secure each panel  10 . Additionally, horizontal member  80  of joiner strip  75  fits into notch  70  of inner surface  15  resulting in a smooth and continuous inner surface throughout the length of the pipe liner. 
     In the preferred construction, panel  10 , including body  11 , T-shaped legs  20 , wall  35 , locking mechanism  50  and joiner strip  75  are manufactured from extruded unplasticized polyvinylchloride (uPVC) or high density polyethylene although any suitably flexible and durable material may also be used. 
     Preferably, grout has a low viscosity prior to curing and should be able to flow freely through relatively small channels. Grout should also be chemically compatible with the material from which panel  10  is formed. When cured, grout should have an elastic modulus much higher than the material from which panel  10  is formed (greater than 400,000 psi). Grout should preferably be formed from widely available and low cost materials such as Portland cement, fly ash or line, water and superplasticizer. 
     Pipes may be lined with a layer of panels  10  in a number of different configurations. For example, extensive pipe degradation may require lining a pipe&#39;s entire inner surface. Alternatively, less severe pipe degradation may require lining only a portion of a pipe&#39;s inner surface. These two alternatives are discussed below for illustrative purposes. 
     To line a pipe&#39;s entire inner surface, an elongated length of panel  10  may be passed through a suitable opening in the pipe. Panel  10  may then be curved around the pipe&#39;s interior surface in a continuous spiral such that terminal ends  40  of T-shaped legs  20  (FIG. 1) face the pipe&#39;s inner surface. Adjacent edges of each panel  10  winding are secured together as described above, resulting in a smooth and continuous lining substantially conforming to the pipe&#39;s inner surface (FIG.  11 ). In actual application, an elongated length of panel  10  would normally consist of several  200  foot lengths which are spliced together in the pipe. Such splices must allow the flow of grout to be pumped into the entire lining. Such splices would, therefore, include a plurality of individual couplings shaped as injectors on both ends. (See FIGS. 9,  110 , and FIG. 6,  96 .) 
     Following panel  10 &#39;s installation, exposed ends of interior channel  45  located at a posterior terminal end of panel  10  are closed with a posterior plug  95 . With respect to FIGS. 5 through 7, posterior plug  95  includes projections  96  configured complementary to posterior terminal end of panel  10  and seals the corresponding ends of each interior channel  45 . Posterior plug  95  also includes an air escape valve  100  for allowing air to exit from each interior channel  45  when grout is injected as described below. 
     In a preferred embodiment, air escape valve  100  may be an end-cock allowing air to escape from interior channels  45  and which may be manually closed to prevent grout from escaping when interior channels  45  are full of grout and no air bubbles are observed in the grout flow. Alternatively, air escape valve  100  may be a plug or cap configured complementary to posterior terminal end of panel  10 . This version of air escape valve  100  is installed after grout completely fills each interior channel  45 . 
     Grout is injected into interior channels  45  following the installation of posterior plug  95 . Grout is injected into interior channels  45  by means of a manifold  105 . As shown in FIGS. 8 through 10, manifold  105  includes injectors  110  configured to fit tightly within an anterior terminal end of panel  10  and which communicate with each interior channel  45 . Manifold  105  further includes a receiving tube  115  for coupling with a flexible hose (not shown) through which grout is pumped. 
     Grout is pumped from an external reservoir, through the flexible hose and through manifold  105  into each interior channel  45  until each interior channel  45  has been completely filled with grout. When each interior channel  45  has been completely filled, manifold  105  is then left in place or is replaced with an anterior plug to prevent grout from leaking out of each interior channel  45 . The anterior plug is configured similar to posterior plug  95 , except the anterior plug does not have an air escape assembly. The grout is then allowed to cure, i.e. solidify and harden. 
     In this fashion, the entire pipe is lined with a smooth and continuous uPVC layer having an inner layer of grout. Additionally, an annulus is formed between the pipe&#39;s inner surface and wall outer surface  37  of wall  35 . An additional layer of grout may then be injected into the annulus between the pipe&#39;s inner surface and wall outer surface  37 . T-shaped legs  20  become anchored to this second grout layer and panel  10  is thereby securely positioned. The hydraulic head pressure of this second grout layer is supported by the first grout layer and the first grout layer&#39;s weight also increases the allowable vertical rise of the second grout layer without “floating” the liner. 
     In contrast to lining a pipe&#39;s entire inner surface as discussed above, it may be desirable to line only portions of the pipe&#39;s inner surface. To line a portion of a pipe&#39;s inner surface, as illustrated in FIG. 12, a number of panel segments  10   a  are first cut to a predetermined length. Each segment is then curved circumferentially around the pipe&#39;s inner surface PS such that terminal ends  40  of T-shaped legs  20  face out toward the pipe&#39;s inner surface. The ends of these segments are then secured along the lower surface portions of the pipe by means of fasteners  10   b . Examples of fasteners that may be used to secure the panel segments  10   a  include mechanical anchors, nails, J-hooks or any other conventional means of supporting the segments in place. 
     Adjacent edges of each panel segment  10   a  are secured together as described above, resulting in a smooth and continuous lining inside the pipe. Specifically, opposing edges of two adjacent panel segments  10   a  may be secured with a joiner strip segment  75   a  that is cut to the same predeteremined length as the panel segments  10   a . As with the joiner strip  75  shown in FIG. 3, each joiner strip segment  75   a  is formed into an elongated strip and includes a horizontal member  80  with two vertical members  85  located on opposing sides of a vertical centerline  86  bisecting horizontal member  80 . Each vertical member  85  is generally perpendicular to horizontal member  80  and includes a retaining clasp  90  projecting toward vertical centerline  86 . 
     Installation of two panel segments  10   a  is performed by positioning two panel segments  10   a  adjacent one another and forcing each vertical member  85  of joiner strip segment  75   a  over a retaining flange  65  of a locking member  50 . In this fashion, retaining clasps  90  and retaining flanges  65  cooperate to lock and secure each panel  10 . Additionally, horizontal member  80  of joiner strip segment  75   a  fits into notch  70  of inner surface  15  resulting in a smooth and continuous inner surface between the adjacent panel segments  10   a  and throughout the length of the pipe liner. 
     Following installation of the lining, the posterior terminal end of each panel  10  segment is closed with posterior plug  95  as described above. Grout is then injected into each panel  10  segment and cured as described above. Manifold  105  may also be replaced with the anterior plug. In this fashion, a portion of the pipe&#39;s inner surface is lined with a smooth and continuous uPVC layer. Again, a gap is formed between the pipe&#39;s inner surface and wall outer surface  37 . 
     An additional layer of grout may then be injected between the pipe&#39;s inner surface and wall outer surface  37 . T-shaped legs  20  become anchored to this second grout layer and the liner is thereby securely positioned. The hydraulic head pressure of this second grout layer is resisted by the first grout layer. 
     In this manner, a lining for an inner surface of a pipe is formed having a smooth inner surface, T-shaped legs  20  extending perpendicularly from outer surface  25  and having a number of interior channels  45 . Additionally, a cavity is formed between the inner surface of the pipe and outer wall surface  37 . 
     This liner may have interior channels  45  filled with grout and anterior and posterior terminal ends enclosed by the anterior plug and posterior plug  95  respectively. Additionally, the liner may also have the annulus between the inner surface of the pipe and outer wall surface  37  filled with grout. Finally, the liner may have anterior and posterior terminal ends enclosed by a modification of the anterior plug and posterior plug  95 . 
     Although the present invention has been fully described in connection with the preferred embodiment thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims, unless they depart therefrom.