Pipe Jacking
Pipe Jacking
(OP)
I have a project that would benefit from a pipe jacking solution. In order to construct a tunnel section for a new rail project we must relocate a 30" sewer overflow. The only feasible alignment runs below a masonry retaining wall which ranges in height from 4' to 15'. to avoid having to temporarily support the surcharge, remove the wall, and reconstruct, I would like to jack the pipe beneith the wall. This would require a 325' jack length to optimize the alignment. Some questions come to mind. Is this feasible? What type of pipe is most suited, RCC, steel, or other? How big must the jack pit be? Should the pipe size be increased to 42 or 44 to allow hand removal at the face? Their are numerous near by potential obstrctions, how much percition can be anticipated in the line and grade over the distance? What range of cost per foot is appropriate for an order of magnitude estimate. The soil is sand and clay mix with little to no rocks/bolders.





RE: Pipe Jacking
RE: Pipe Jacking
Their process utilized a "pilot tube microtunneling system" which was very accurate in grade. I know some of the systems are limited in pipe size they can handle, but, you might check into it. An internet query will give a lot of info.
The jacking process can easily get off course if it encounters a large object in it's path. Most contractors around here oversize the steel casing so that the carrier pipe can be set to grade within it.
RE: Pipe Jacking
http://www.microtunneling.com/
This technology was developed in Europe where it is used under heavily developed urban areas. There should be no settlement problems when the tunnel is completed.
RE: Pipe Jacking
RE: Pipe Jacking
There are several jacking systems available for smaller pipe sizes which usually utilize some kind of drill head to loosen the ground and a screw to transport the displaced soil to the start excavation. A pressing station in the start excavation pushes the jacking pipes gradually forward. Pipes are usually steel or reinforced concrete. They need to be designed and calculated for the stresses. These systems work fine and we have used them several times successfully. For bigger pipe sizes (44" and up) you could employ somebody at the face for hand removal if the ground is stable and save (safety caution). Minor curves can be done if you get an experienced contractor, however, ususally you are fix. Start excavation for your pipe size: assume 10'x 7'
Microtunneling
A lot more expensive due to the machinery involved. Maybe overkill for your pipe lenght. Sizewise no problem. Could consider full or part cutting head. Remote steering allows for pretty flexible alignments. Start excavation 10x10'. Pipes as above. Very elegant way to built but truly expensive.