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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