Settling grain bin in hands of world reknowned compaction grouter
Wed, 10/28/2015 - 2:43pm admin
Earlier this summer, Midwest Cooperative in Philip had completed the construction of two new massive grain bins. Through routine examination, it has been discovered the west side of the western bin is settling more than projected.
According to Jay Baxter, western group manager, Philip location, when workers were done with the original construction, engineers periodically “shoot” the bins with surveying equipment to check how many feet and inches above sea level the bins are, and if they are straight, true and plumb. Among other reasons, this periodic checking is to make sure the bins were put in correctly.
Baxter said different engineers worked together, geological, concrete, structural, bin and geopier (ground improvement). The completed bins were to be loaded one-third full, allowed to settle, reshot, loaded another third, reshot, etc. It was anticipated both bins would settle approximately four inches. The east bin settled properly. The west bin settled close to proper, but its west side continued to drop further than projected.
It was determined that structurally everything is still sound, with no structural damage to the concrete work or the metal. Engineers requested that Midwest Cooperative raise the west side of the bin to ensure continued structural soundness.
“Within a couple of weeks the bin-jacking should be complete,” said Baxter. “So, we should have long-time use of this large investment. We should be able to have maximum use of it for decades to come. Professionally, we are ensuring that we are protecting our farmers’ investment and equity in their local co-op.”
Consultant Sam Bandimere, Denver, is in charge of the compaction grouting that will raise and stabilize the west side of the bin. “I do this work all over the world,” he said. He is working for Sparks Concrete Lifting, Rapid City, owned by Mark Erickson. “I kind of developed this system,” said Bandimere. He sold a “mud-jacking” business back in 1996, and now consults, working with any contractor who wants to learn to do the work.
Compaction grouting treats the symptom of settling buildings, and also the cause. “We’ve never found a structure that can’t be lifted,” said Bandimere. He has done mid-rises in Rapid City, and corrected high-rises in Korea. The grain bin in Philip, loaded with 37 percent of its holding capacity and with its lowest point currently at 10-5/8 inches from where it should be, should not be a problem.
It is a very slow process. The ratio of solids, water and air determines the solidness of something, from soupy mud to rock. Grout pushed in under a structure makes the surrounding soils give up water and air. But, that grout may just push away and not lift up the structure.
Bandimere and his five person crew first drilled 16 containment holes circling around the west side of the bin, and about three and one-half feet from the base. These 25 foot plus deep PVC pipe have a 15 degree batter (angle toward the bin). Grout is slowly forced in so the area around the outside of each pipe is compacted, thus pretty much connecting and filling in the soil area to make an underground “wall” of grout.
Another 16 lift holes are drilledwithin the first arc, almost touching the bin’s base, with a 25 degree batter. When grout is forced through these, the grout cannot go through the outer wall, thus is slowly forced upward. This results in increased heaving capacity and a column support around each pipe for the building.
Each job is different. The bin has underground electrical lines near its base which had to be found and addressed. The loading tower’s foundation is just feet from the bin’s foundation. Bandimere has three strain gauges on the tower’s underground wall, wire gauges that, he said, can detect a split-hair’s difference in movement on the pressure against the tower’s base.
Last week his crew set and filled the containment wall. This week they began the lift. He uses a specially converted concrete pump that has been put on a former military truck. Though it can produce 2,000 pounds of pressure per square inch of almost solid grout, its usual working pressure is around 600 psi. Bandimere said it is not the volume of grout, but pressure and control. You cannot pump very fast, and must allow the water to get away.
There are a lot of things that can cause problems with building foundations. Bandimere seems to be the man to handle them all. With no previous formal education, he has written a paper, “Compaction Grouting: a Half Century Review” (Geotechnical Institute Document 53-10), for the American Society of Civil Engineers. He is also currently the chairman of a ASCE committee.