36 DECEMBER 2021 WorldWide Drilling Resource® RENEW - SUBSCRIBE NOW! because explosions cause P waves thought to be unrepresentative of earthquakes dominated by S waves, or shear waves. In a quake, P waves, also known as compressional waves, travel much faster than the S waves, that follow, and each type of wave causes the ground to oscillate in a different direction. “We showed that the P waves the explosions generated didn’t matter at all and that the secondary waves we generated were a lot closer to quake motion than had been previously thought,” said Stuedlein. “This is as good an analogue for quakes as possible.” Stuedlein suggested a couple of methods for ground improvement. One is called vibro-compaction, which densifies the soil, and the other is deep soil mixing, which involves injecting water and a cement slurry into the ground through heavy equipment resembling a giant drill. The Port of Portland is planning to employ deep soil mixing. “You essentially solidify the ground by turning sand into sandstone to raise the strength of the material,” he said. Wharton said the port has completed 30% of the design work needed for ground improvement. When the design is complete, or close to it, the port will pursue federal funding, and hopes to begin deep soil mixing on a 6000-foot stretch at the east end of the south runway within ten years. “We’ve shown that blasting experiments can be used to determine fundamental dynamic properties of any kind of soil and are particularly well-suited for soils that are not easily sampled,” he said. “And they can be conducted at any depth, opening up a new avenue for learning vital dynamic characteristics of geological materials.” Oregon State University cont’d from page 35
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