Bore and Jack of water line in sand with cobbles
Bore and Jack of water line in sand with cobbles
(OP)
Does anyone have experience with bore and jack of pipes (24 inch water line)in conditions with cobles and occasional boulders? I reviewed most of the posts on the board on this subject but they were a little different than the sittuation I have.
I have a project with a 24 inch wateline that needs to cross under 48 inch RCP storm drains for about 100 feet. The civil does not want to cut the storm drains and do an open cut, he believes it would still be cheaper to do some pipe jacking. Storm drains are dry 99 percent of the year so diversion of storm water would not be of much concern.
The bottom of the storm drains are about 10 feet below the roadbed. The soils are sand with gravel, cobbles and the occasional boulder. Cobles are about 5 to 15 percent by volume, and the occasional boulder was encountered in my borings. I drilled 3 borings near the location and one terminated at 12 feet on a boulder, and the other 2 were able to get to 30 feet depth with some difficulty. The borings caved to about 7 feet after pulling the augers. There is not groundwater. Most of the borings I drilled for this project terminated on a large cobble or boulder at some point before the planned depth.
I am concerned about groundloss around the bore and jack operation, and how to get past any cobbles or boulders without to much expense, any guidance or experiences anyone could share would be appreciated. I am thinking about grouting first, but if it could be done without?? Any ideas.
Thanks
I have a project with a 24 inch wateline that needs to cross under 48 inch RCP storm drains for about 100 feet. The civil does not want to cut the storm drains and do an open cut, he believes it would still be cheaper to do some pipe jacking. Storm drains are dry 99 percent of the year so diversion of storm water would not be of much concern.
The bottom of the storm drains are about 10 feet below the roadbed. The soils are sand with gravel, cobbles and the occasional boulder. Cobles are about 5 to 15 percent by volume, and the occasional boulder was encountered in my borings. I drilled 3 borings near the location and one terminated at 12 feet on a boulder, and the other 2 were able to get to 30 feet depth with some difficulty. The borings caved to about 7 feet after pulling the augers. There is not groundwater. Most of the borings I drilled for this project terminated on a large cobble or boulder at some point before the planned depth.
I am concerned about groundloss around the bore and jack operation, and how to get past any cobbles or boulders without to much expense, any guidance or experiences anyone could share would be appreciated. I am thinking about grouting first, but if it could be done without?? Any ideas.
Thanks





RE: Bore and Jack of water line in sand with cobbles
The best way to test something is to squeeze it, slowly, until it breaks!
RE: Bore and Jack of water line in sand with cobbles
RE: Bore and Jack of water line in sand with cobbles
RE: Bore and Jack of water line in sand with cobbles
The conditions you discuss with collapsing holes and refusal on boulders pretty much say to me that you shouldn't even think about jack and bore.
Does the waterline definitely have to go under the storm drains with no potential to route it over those lines (I realize frost concerns might prevent that)? And even if it does cross under, why would you have to cut the storm drains for open trench.....couldn't they just be temporarily supported? I'd agree that if trenchless was required you're probably talking signficantly oversized casing with human entry to chip out boulders and some sort of face stabilization. Wouldn't even want to think of the costs related to that type of work.
RE: Bore and Jack of water line in sand with cobbles
I have tried to talk the civil out of it but have not been suscesful so far. I will still recommend open cut as my first recommendation, but will need to put in as a secondary option parameters for the bore and jack. The civil does have some experience but I am not sure how much, or maybe he has to much.
There is not enough room over the storm pipes to get the water line and stay below the pavement with any cover. I had not thought about temporary support, that might work.
What is the minimum size cassing you would use if you are going to send a man into it?
RE: Bore and Jack of water line in sand with cobbles
htt
http://www.asce.org/bookstore/book.cfm?book=4561
http://www.nastt.org/
RE: Bore and Jack of water line in sand with cobbles
RE: Bore and Jack of water line in sand with cobbles
What was the strenght of the grout? less than 500 PSI
How large of a grout bulb did they create to be sucessful with the 36 in casing? The caseings top was 48 inches or more below the top most elevation of the ballast bed. we did observe some of the grout coming through the ballast. (ballast is very porous after all.)
How much area around the evenutal casing is needed for support? That was not something that I was asked to determine. (my function was to take elevations of the tracks to ensure there were no elevation changes.)
The best way to test something is to squeeze it, slowly, until it breaks!
RE: Bore and Jack of water line in sand with cobbles
RE: Bore and Jack of water line in sand with cobbles