Prime Machine Case Study

Here you can find information on the Prospector – Micropile Tiebacks Process, as well as get an account from the Rhino himself Troy. 

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Troy :

This project was done in Salt Lake City, Utah. The customer wanted to add space to his property so he could build a garage. The terrain was very sloped, and as the general contractor started to dig out the hillside, the soils just kept caving in, so we were contacted to go take a look and see if there was a way we could pull back the soil.

We went and looked, and they actually had a plan to install soil mills, also known as tiebacks, where we would drill into the side of the hill, and then, as the bar goes into the ground, grout is pushed through the rod (the rod is hollow). These are also called hollow bar micropiles. As the grout goes through the rod, it comes out into the earth, and it merges the soil with a structural grout. Once that’s done, we usually work in a 10 foot lift, depending on the soil, so we can put 2 or 3 rows of micropiles in (or tiebacks). Once those are installed, the contractor came, and put a wire mesh and sprayed shotcrete, which is just a low aggregate concrete, kind of a stucco, or gunite. He sprayed that over the wire mesh, and it creates what is essentially a concrete wall, tight within the mountain. Our anchors went anywhere from 20 feet to almost 40 feet into the hillside. It was really tied back, and it had a lot of strength. Once they did that, we’d return, and do another row. So while we were gone, they’d go back and excavate another 5 or 10 feet; do another, “cut,” we call it. After they were done with that, we’d go back and install another 2 or 3 rows of micropile tiebacks.

We went and looked, and they actually had a plan to install soil mills, also known as tiebacks, where we would drill into the side of the hill, and then, as the bar goes into the ground, grout is pushed through the rod (the rod is hollow). These are also called hollow bar micropiles. As the grout goes through the rod, it comes out into the earth, and it merges the soil with a structural grout. Once that’s done, we usually work in a 10 foot lift, depending on the soil, so we can put 2 or 3 rows of micropiles in (or tiebacks). Once those are installed, the contractor came, and put a wire mesh and sprayed shotcrete, which is just a low aggregate concrete, kind of a stucco, or gunite. He sprayed that over the wire mesh, and it creates what is essentially a concrete wall, tight within the mountain. Our anchors went anywhere from 20 feet to almost 40 feet into the hillside. It was really tied back, and it had a lot of strength. Once they did that, we’d return, and do another row. So while we were gone, they’d go back and excavate another 5 or 10 feet; do another, “cut,” we call it. After they were done with that, we’d go back and install another 2 or 3 rows of micropile tiebacks.