Bacteria Could Steady Buildings Against Earthquakes

Soil bacteria could be used to help steady buildings against earthquakes, according to researchers at UC Davis. The microbes can literally convert loose, sandy soil into rock.

When a major earthquake strikes, deep, sandy soils can turn to liquid, with disastrous consequences for buildings sitting on them. Currently, civil engineers can inject chemicals into the soil to bind loose grains together. But these epoxy chemicals may have toxic effects on soil and water, said Jason DeJong, an assistant professor of civil and environmental engineering at UC Davis.

The new process, so far tested only at a laboratory scale, takes advantage of a natural soil bacterium, Bacillus pasteurii. The microbe causes calcite (calcium carbonate) to be deposited around sand grains, cementing them together. By injecting bacterial cultures, additional nutrients and oxygen, DeJong and his colleagues found that they could turn loose, liquefiable sand into a solid cylinder.

“Starting from a sand pile, you turn it back into sandstone,” DeJong said. Similar techniques have been used on a smaller scale, for example, to repair cracks in statues, but not to reinforce soil.

The new method has several advantages, DeJong said. There are no toxicity problems, compared with chemical methods. The treatment could be done after construction or on an existing building, and the structure of the soil is not changed — some of the void spaces between grains are just filled in.

DeJong and his collaborators are working on scaling the method up to a practical size, and applying for funds to test the method in the earthquake-simulating centrifuge at UC Davis’ Center for Geotechnical Modeling. The centrifuge is part of the national Network for Earthquake Engineering Simulation, funded by the National Science Foundation.

A paper describing the work has been published in the Journal of Geotechnical and Geoenvironmental Engineering. The other authors are Michael Fritzges, a senior engineer at Langan Engineering, Philadelphia; and Klaus Nüsslein, associate professor of microbiology at the University of Massachusetts, Amherst. The work was supported by the National Science Foundation.

4 responses to “Bacteria Could Steady Buildings Against Earthquakes

  1. there are no reportable “toxic” effects, however, could there be a chance that this bacteria could be infectious to the human population? could it use other bacteria or allow viruses to infect humans or animals? we must be very very cautious in using “civil bio bugs” since we are just beginning to completely understand how bacteria and viruses interact with each other to effect and infect human and animal physiology.

  2. you have to inject oxygen??? liquefaction only occurs in saturated soils (i.e. below the groundwater table), no? i guess maybe you could recirculate the bacteria through the ground with some kind of air/liquid injection system. you’d need a grid pattern. hmm, starting to sound expensive.

  3. Amanda: “natural soil bacterium” means it already exists, naturally, in the soil. We are in much more danger from the simple over-prescription of antibiotics and overuse of antibiotic soaps than we will EVER be from a (potential) project like this.

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