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Discussion Starter · #1 ·
heres some pics of a job I've been working on. 30'+ excavation right next to an adjacent building. 1st pic you can see the street side soe. sheet piles with 2 levels of 4 and 5 strand tiebacks. Check out the dewatering as well. Water table is about 10' bgs. 2nd pic you can see the grout underpinning. The building is pretty long so traditional underpinning would have taken way too long to excavate 4' pits, by hand, that deep. To install the grouting, they drill down (from street level before excavation) a regular 5"-6" hole then while withdrawing the drill string, grout and high pressured water and air are pumped into the hole to make a 4 to 5 ft diameter column of cemented soil under the building. The columns are staged as not to undermine a portion of the building and to eventually create a continuous grout wall. All the grout is mixed on site. In the 1st pic, at the top you can see a yellow silo. That is for storage of the dry portland. From there it goes into a hopper where it is measured and mixed with water, then to the mixer and pump house shown in the 3rd pic.
 

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Vagitarian
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Great pics, do you have any more ?
 

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Discussion Starter · #5 ·
Here's a few more for those who are interested. First pic is of the staging area silo, pump house ect. Second is of the powerpac and rig. Had a little problem at this location. The bit must have gotten blocked up or they were chasing a piece of rock down the hole, because once we started digging we found a hole in the grout wall. In this photo the guys are drilling a patch for the hole. Also the wall shown in this pic is a permeant retaining wall. Meaning it's getting finished with something (not sure what) and thats it. No block or concrete is going in front of it. In the photo excavation is at about 2/3 to the bottom.
 

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Discussion Starter · #6 ·
testing program

Before starting production grouting the contractor has to prove they can do the job. First pic show drilling for a test column. The column is at a radomn spot near the building to recieve production underpinning. Next we core the test column. The core is shown in the 2nd pic. Excellent recovey and quality for this type of work. We also do compression testing. Requirement for this job is 500psi.
 

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Discussion Starter · #7 ·
Last thing for the test program is to dig up the test columns to check the diameter. One was too small so they had to use the same installation parameters they used for the larger column for the underpinning. You can see that everthing in the ground gets encapulated in the grout.
 

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Discussion Starter · #8 ·
Thats little more involved than the one I just did. :laughing: Amazing the scope and scale of that work, bet that had a pretty big price tag.
Not sure of the price tag for this job but if I had to guess its in the 7 to 8 figure range:thumbup:
 

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Why not just use sheet piles and tiebacks under building? or drive H piles along the building with timber lagging and tiebacks? was it a siesmeic issue? Basicly it is a secant pile.
 

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Discussion Starter · #10 ·
Sheet piles or soldier piles and lagging are not acceptable as underpinning in most cases because they will deflect too much with that much load behind them, causing unacceptable settlement. Plus just the vibrations from installing the piles so close to the foundations could cause damage to the building or settlement.

Basicly it is the same a secant pile just mixing the soil/cement inplace instead of pouring concrete, and no steal.
 
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