Patent Application
20220243420
The invention relates to a method of repairing or rehabilitating underground structures, such as a manhole, having deteriorating walls by forming a new interior, monolithic concrete wall having an embedded corrosion-resistant barrier anchored in the new wall.
Manholes and other formations provide cavities below the ground level to access sewers, water lines, drains, pipes, electrical wires, cables, and the like. The walls of these structures are often made of brick or concrete and may be subject to very corrosive environments which deteriorate the brick or concrete. Severe deterioration requires the cavity wall to be replaced or repaired. Replacement requires excavation, known as opencut, which is time-consuming and expensive, and may create issues such as community disruption, traffic detours, sewer bypassing, and poor soil compaction following excavation backfilling. Repair requires formation of a new manhole wall inside the existing wall, which may be difficult, though less expensive than replacement and without some of the issues.
The Hydro-Klean Monoform system is one option for repairing a damaged manhole. The monoform system is a no-dig or trenchless rehabilitation process for restoring manholes via installation of a new monolithic concrete wall adjacent the old wall. With the Monoform system, restoration is accomplished by installing a custom-forming system within the existing manhole, leaving an annular space to be filled with a high-strength ready-mix concrete. The system includes various diameters to fit most structures, including those having concentric and eccentric cone configurations. The Monoform system eliminates troubles associated with opencut replacement. The finished, rehabilitated manhole has a similar design and life expectancy to that of installing a new, precast manhole, without excavation. However, the new concrete wall formed by the Hydro-Klean system is still subject to the corrosive environment.
Protective coatings may be sprayed on new or old concrete to minimize or reduce deterioration. Another alternative is a plastic liner mounted on or secured to the concrete, such as the Sure-Grip and Ultra-Grip protective sheets manufactured by Agru America. The Agru liners are used for both new construction and rehabilitation of existing concrete structures in prefabricated and preassembled sections. The Agru liners have not been used for monolithic concrete manhole rehabilitation.
Accordingly, a primary objective of the present invention is the provision of a method of rehabilitating a manhole using custom forms and a protective sheet liner.
Another objective of the present invention is a provision of a process for repairing manholes using the Hydro-Klean Monoform system for forming a new concrete manhole wall with an anchored or embedded plastic liner for corrosion protection.
A further objective of the present invention is the rehabilitation or repair of underground cavities with a new concrete wall having a corrosion-resistant barrier integrally formed thereon.
Still another objective of the present invention is the provision of a method of forming a monolithic concrete wall with a protective plastic barrier below grade without excavation to the full manhole depth.
Yet another objective of the present invention is the provision of a method of repairing manholes and similar underground structures that is relatively simple, economical, safe, and durable.
These and other objectives become apparent from the following description of the invention.
The rehabilitation or repair method for a manhole and other underground walls utilizes a forming system with various sections of which can be assembled so as to correspond to the wall needing repair. The method involves the initial step of assembling sections of a forming system above ground and then applying a plastic liner sheet or barrier on the exterior of the formed sections. The form sections are then removed, leaving the liner in the shape of the assembled forming system. The liner is then collapsed or folded, and moved into the manhole or other underground cavity, and then expanded or unfolded, so as to provide a 3-8 in space between the liner and the wall. The forming system is then reassembled inside the liner to provide structural support of the liner. Concrete is then poured into the space and allowed to cure. After the concrete has cured, at least to a level to avoid slump, the forming sections are removed, leaving the newly formed monolithic concrete wall with the liner sheet or barrier anchored thereto for corrosion protection. The outside seams of the liner are welded above ground, before the forming sections are disassembled, while the inside seams of the liner sheet are welded below ground after the forming system is removed.
The method of the invention produces an in-situ, trenchless monolithic concrete structural relining with a corrosion barrier for the rehabilitation of underground utility components, such as a manhole, vaults, and tanks. The integrated thermoplastic liner provides long-term protection to the newly formed concrete layer from corrosive attack and degradation caused by chemically caustic and/or acidic fluids and gases, such as those present in industrial, municipal wastewater sewer systems and other environments. The benefits of high strength and stiffness of concrete, combined with the benefits of flexible, ductile, corrosion resistant thermoplastics produces a durable internal wall. The protective layer, integrated with the concrete, also prevents clear groundwater infiltration and exfiltration or the outward leaking of industrial and/or municipal wastewater contaminants, so as to protect the environment.
As seen in
The liner 30 of the present invention is shown in
The process for rehabilitating a manhole or similar structure is illustrated in the flow chart of
This form remains in place following construction. A removable form is also acceptable. The reason to remove the chimney is to allow the new liner wall to be constructed at a specified thicknesses without reducing access diameter into the structure after the wall and liner is constructed in place, as described in the following steps.
The form sections 21 to form the cylindrical and conical portions 22, 24 of the forming system 20 are gathered and assembled above ground, apart from the manhole. After the forming system 20 is assembled, one or more sheets of the liner 30 are wrapped around the cylindrical body 22 and the conical portion 24 of the system 20, (and the chimney portion, if present or required), and the exposed outside vertical seams, which preferably overlap, are welded to secure the shape of the liner sheet. The liner sheets are not attached to the forming sections 21. Then, the forming system sections 21 are disassembled and removed from inside the liner 30, leaving the formed liner with a cylindrical body and conical upper portion (as well as a chimney portion, if needed). This formed liner body is flexible and can be partially collapsed so as to fit through the open top of the manhole 10 and set upon the floor of the manhole so as to be spaced from the sidewall 12 of the manhole 10. This installation of the formed liner body into the manhole and expansion of the liner body to it full diameter creates an annular space 40 between the liner body and the sidewall 12, with the anchors 34 residing within the annular space 40. Preferably, the annulus space 40 has a radial depth of approximately 3-8″.
Next, the forming system sections 21 are re-assembled inside the liner 30 in the manhole, so that the sections engage the interior of the liner to provide radial support to the liner 30. Then, the pouring hat or lid 26 is secured to the top of the forming system 20 so as to close the interior of the system 20. Then, concrete is poured into the annular space or annulus 40 so as to fill the space from bottom to top to create the new inner concrete wall 42. After the concrete has cured at least sufficiently to preclude slumping, the forming system sections 21 are removed, leaving the new monolithic concrete wall 42 with the liner 30 integrally secured thereto by the anchors 34. Then, the inside vertical and radial seams of the liner 30 are welded, thereby completing the rehabilitation process.
The method described for a manhole rehabilitation can also be used on other underground walls having other shapes, such as tanks or vaults, so as to repair such structures with a new interior wall having an integral anchored protective barrier.
The anchoring system provides a secure, mechanical bond of the liner 30 to the concrete wall 42, even though plastic and concrete have different thermal expansion coefficients. The liner anchoring system also allows for use in areas of high groundwater back pressure. Also, the thickness of the liner base 32 may be increased or decreased, depending on the specific project requirements and local conditions. The height of the anchors 34 may also be increased or decreased, depending on the factors present for each application, such as the hydrostatic pressure. Depending on project requirements, the welding technologies may include butt welding, extrusion welding, and/or hot wedge welding, to provide secure and leak-proof joints and seams in the liner 30.
The embodiment described hereinbefore is merely preferred embodiment of the present invention and not for purposes of any restrictions or limitations on the invention. It will be apparent that any non-substantive, obvious alterations or improvement by the technician of this technical field according to the present invention may be incorporated into ambit of claims of the present invention.
