TRENCHLESS METHOD OF INSTALLING A MONOLITHIC MANHOLE IN A LEVEE FOR PIPE ACCESS

Abstract

A monolithic manhole is formed in a levee without trenching, to provide access to drain pipes within the levee for maintenance and repair of the pipes. The manhole is formed by first forcing an outer tube downwardly into the earth and levee and removing soil from within the outer tube to expose the pipe. An inner tube is lowered into the outer tube, with an annular space maintained between the tubes. The annular space is filled with concrete, which hardens to form a monolithic vertical wall. A concrete floor may be poured at the bottom of the wall and a cover attached to the top of the wall. A hole is cut in the pipe inside the wall to provide internal access to the pipe.

Claims

1: A method of creating a manhole in a soil levee having a drain pipe, comprising: determining a location of the manhole so as to intersect the drain pipe; inserting an outer tube vertically into the levee by vacuum excavation, so as to remove soil from inside the outer tube; inserting an inner tube inside the outer tube so as to provide an annular space between the tubes; and pouring concrete into the space to form a monolith concrete manhole wall.

2: The method of claim 1 further comprising removing the inner tube after the concrete has cured to a non-slump strength.

3: The method of claim 1 further comprising pouring a concrete base in the bottom of the outer tube before the inner tube is inserted.

4: The method of claim 3 further comprising forming a sloped cap on the base after the inner tube is inserted.

5: The method of claim 1 further comprising adding a stabilizer to the soil around the outer tube.

6: The method of claim 1 further comprising providing a cover on top of the manhole wall.

7: The method of claim 6, further comprising attaching a frame to a top of the manhole wall, with the cover being secured to the frame.

8: The method of claim 1 wherein the inner tube includes multiple cylindrical sections stacked one upon another.

9: The method of claim 8 wherein the sections have different diameters to create different diameters along the manhole wall.

10: The method of claim 1 wherein the manhole is formed without digging a trench in the levee.

11: A method of providing access to a pipe in an earthen levee, comprising: forcing an outer tubular member downwardly into the levee until a bottom of the outer tubular member is at least level with the pipe; then removing soil within the outer tubular member; then lowering an inner tubular member into the outer tubular member so as to form an annular space between the outer and inner tubular members; then filling the annular space with material to form an annular wall; and removing an upper piece of the pipe within the annular wall to expose the interior of the pipe.

12: The method of claim 11 wherein the inner tubular member has multiple stacked sections.

13: The method of claim 11 further comprising removing the inner tubular member after the annular wall is solidified.

14: The method of claim 11 further comprising forming a floor inside the outer tubular member before the inner tubular member is lowered.

15: The method of claim 14 further comprising forming a cap on top of the floor sloping downwardly from the annular wall to the pipe.

16: The method of claim 11 further comprising adding soil stabilizer material around the outer tubular member.

17: The method of claim 11 further comprising providing a cover on top of the annular wall above the levee.

18: The method of claim 11 wherein the annular wall is formed without trenching into the levee.

19: The method of claim 11 wherein the soil is removed from inside the outer tubular member by vacuum excavating.

20: The method of claim 11 wherein the soil is removed as the outer tubular member is forced downwardly into the levee.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is an elevation view of the levee with a drain pipe, a collection pipe, and a manhole formed in accordance with the present invention.

[0014] FIG. 2 is an exploded schematic of the components for forming the manhole in the levee.

[0015] FIG. 3 is a sectional view of the monolithic manhole, taken along lines 3-3 of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0016] FIG. 1 shows a levee 10 with at least one perforated drain tile pipe 11 running lengthwise along the levee, and at least one solid collector drain pipe 12, extending transverse to the levee from the drain tile pipe 11 to a pump station (not shown), at the base of the levee on the land side 16. The levee 10 is constructed adjacent a body of water 14 to protect the land 16 from flooding. The pump station is operatively connected to the collector pipe 12 to pump collected water back to the water side 14 of the levee 10. The levee 10 and drain pipes 11, 12 are conventional and may have a variety of constructions.

[0017] The method of installing the new, poured-in-place manhole 20 begins by determining the location that the manhole is to be installed in the levee 10 for intersecting with one or both of the drain pipes 11, 12. One option for selecting or determining the manhole location is to extend a camera with a transmitter, such as a Sonde transmitter, in one end of the pipe 11 or 12 or at a downstream access point. The camera is pushed upstream to view the pipe and to position a transmitter. An above-ground receiver senses a signal from the transmitter within the pipe. The camera is moved through the pipe to a position corresponding to the desired position for the manhole.

[0018] Once the new manhole position is set, a hollow tube 22 is forced downwardly from the upper surface of the levee 10 using a vacuum excavator. In one embodiment, the tube 22 is approximately 60 inches in diameter and made of any suitable material, such as fiberglass. The tube 22 may have other dimensions and may be made of different materials.

[0019] The vacuum excavator removes the levee material or soil from the interior of the tube 22, thereby allowing the tube 22 to be lowered into the levee. The tube 22 is notched 24 at the lower end, which allows the tube 22 to be saddled over the pipe 11 or 12 until the tube is at the desired final elevation, with the bottom of the tube 22 being approximately 6 inches below the pipe. The tube 22 may be position over the perforated pipe 11 or the solid collector pipe 12, or at the T intersection of these pipes.

[0020] Next, concrete, such as ready-mixed concrete, is placed at the bottom of the fiberglass tube 22 and poured to a thickness of approximately 6 inches, or to the lowest pipe invert elevation, so as to form a base or foundation 25. Preferably, the base 25 is sloped downwardly toward the pipe, as shown in FIG. 3, though the base may be horizontal. After the concrete has sufficiently cured, the pipe 11 and/or 12 is opened by cutting and removing the top half of the pipe inside the tube 22. The opening may extend the full diameter of the tube or may be a shorter segment of the pipe.

[0021] The soil surrounding the exterior of the tube 22 that has been disturbed during the vacuum excavation process may need stabilization. One method for stabilizing the soil is by injecting hydrophobic liquid polyurethane to fill voids and fissures. The stabilizing material may be injected through ports drilled through the tube 22 or through probes installed vertically around the exterior of the tube 22. The stabilization step creates a rigid and dense closed soil/grout matrix to solidify soils on the exterior of the manhole 20. Other soil stabilization methods may also be used.

[0022] A cylindrical manhole forming system 26 is lowered into the tube 22 so as to be concentric within the tube 22 and define an annular space 28 between the interior of the tube 22 and the exterior of the forming system 26. One example of a forming system is the Monoform by HydroKlean, LLC used for rehabilitating deteriorated manholes, such as old brick manholes. Preferably, the gap 28 between the tube 22 and the forming system 26 is approximately 10 inches but can vary in thickness based on factors such as buoyancy mitigation calculations. The forming system 26 may include multiple cylindrical sections 30 with various diameters and rise heights, with tapered reducing sections to connect the different diameter straight sections. For example, the initial base or bottom section may have a 40-inch diameter and is set level and plum on the base 25, which serves as the footing for the forming system 26. Preferably, both the drainage pipe 11 and the collector pipe 12 will be slipped or blocked out, with inserts butted to the base and extending slightly into the pipe connections. The additional sections of the forming system 26 are then installed above the base 25, to the final elevation height of the manhole 20. The top of the forming structure 26 includes a conical section 32, which can reduce the diameter of the forming system to approximately 26 inches. The conical section 32 defines an access opening 34 at the top of the manhole 20. The opening 34 may be concentric or eccentric to the center axis of the manhole 20.

[0023] Concrete, such as ready-mixed concrete, or other material is then poured into the annular space 28 between the outer tube 22 and the inner forming tubes 26 so as to create the new monolithic concrete manhole wall 36. The final height or elevation of the wall 36 may be flush with the levee 10 or may extend above the levee. After the concrete has cured or obtained sufficient strength so as to avoid slumping, the forming system 26 is removed to expose the newly poured walls. The pipe slips or block out inserts (not shown) can also be removed from the pipe 11, 12 so that the upper cut out 38 is open.

[0024] A cap 40 may be formed in the bottom of the manhole, on top of the base 25, after the concrete wall 36 is poured. Preferably, the cap 40 has a 1 inch per foot slope from the spring-line of the exposed pipe 11, 12 and extending to the manhole wall. The cap provides a seal at the interface of the base 25 and the wall 36.

[0025] After the concrete wall 36 has cured, the top is provided with a frame 42 and a removable cover 44. The frame 42 may be set on a gasket and fastened or otherwise secured to the top of the wall with stainless steel anchor bolts. The cover 44 is preferably bolted to the frame 42, for example using stainless steel bolts, or may be pivotally connected to the frame for movement between open and closed positions.

[0026] After the manhole 20 is constructed, the site may be cleaned up by disposal of the levee soil and materials removed from inside the tube 22. The soil around the top of the manhole 20 can be finished to eliminate any remaining evidence of the construction process, such as mulching, seeding, or sodding.

[0027] The manhole installation method of the present invention eliminates trenching of the levee and produces a monolithic concrete wall without affecting the integrity of the levee 10. The manhole may be made to any desired height and diameter.

[0028] The invention has been shown and described above with the preferred embodiments, and it is understood that many modifications, substitutions, and additions may be made which are within the intended spirit and scope of the invention. From the foregoing, it can be seen that the present invention accomplishes at least all of its stated objectives.