Trenchless method of installing a monolithic manhole in a levee for pipe access
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.
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.