Pumping grout into 300' long conduit run

[thorangle]

Data: 54 inch ID steel casing. A circular pattern of 12x 6 inch diameter PVC conduit with 2 x 4 inch conduit runs inside the casing. A conduit bore spacer installed approximatly every 5 feet, to support the 6 and 4 inch conduit runs, as well as grout injection hose. A 2 inch ID hose will be used to pump grout mix into the steel casing. Casing is underground and approximatly 300 feet long. one end of casing will be blocked off. Grout hose will initialy be at far end of casing. The grout hose will be pulled out of casing as the casing fills with grout. Grout mix weigths approximatly 3 pounds per foot of hose, total initial weight of hose and grout is approximatly 900 pounds.

Question/concern: Drag/friction forces that the grout injection hose will experince on each conduit bore spacer, and could this damage or dislocate the conduit bore spacers?

Anyone have experience with this?

 

[RiBeneke]

I have not had experience with this exact arrangement.
However, some thoughts :
1) Do a friction test with varous types of grout hose/pipe. For example, polypropylene semi-rigid tubing (as used for water supply) will probably have a much lower friction than rubber.
2) From my bitter experience with a pvc conduit that got stuck halfway along a 300 m (1000 ft) steel duct in a tunnel, I can suggest that you make quite sure the spacers cannot dislodge, and that nothing on the hose can snag on them as the hose is withdrawn.

 

[thorangle]

Thanks RiBeneke
I'm using an outside contractor to install the conduit and backfill with grout. So I am somewhat at their mercy as to the type of grout hose/pipe used. Your experience and advice will be helpful when I'm on site. You know how contractors have a tendancy to find a "bigger" hammer when a problem arises.