Pipe Jacking 1

[BMulqueen]

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.

 

[cvg]

It may be feasible. sewer lines are generally installed in a casing pipe which would be welded steel pipe. casing diameter should be at least 4 inches greater than the outside diameter of the sewer pipe at the bells. Other types of pipe can be direct jacked, however at increased cost. grouting may be needed to fill voids around the pipe. Add the cost of the casing pipe, jacking and then installing the sewer in the casing. jacking pit needs to be large enough to fit 1 joint of pipe, jacking frame and the hydraulic ram, plus some sort of backstop/thrust block on the back wall. Often the thrust block is reinforced concrete. You will also need to pour a foundation slab to mount a pair of guide rails on. Receiving pit only needs to be big enough to remove the shield and construct a manhole or other junction to tie the new pipe into the old.

 

[semo]

Have you given any consideration to Microtunneling. One of our local contractors has performed some of this in one of the nearby communities to install gravity lines in the middle of the streets. It was done to speed construction and not require street surface replacement.

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.

 

[bimr]

Semo is correct. Microtunneling is the correct solution for your application. Don't think jacking would be suitable for this.

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.

 

[dicksewerrat]

Akkerman, Inc has a pilot tube jacking tunneling system that will work for you. Pure microtunneling may be too expensive. Horizontal boring may not be accurate enough over that length. I think TT Technology has a pilot tube system also. Akkerman is in Minnesota and TT Tech is in Illinois.

 

[Chris73]

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.