Can ‘ground improvement’ help reduce earthquake damage?

A group of engineers studying at the University of Texas at Austin (UT) recently presented the preliminary results of their research on "ground improvement" strategies meant to guard against earthquakes in areas with wet, unstable soil. The project, which involved field testing in New Zealand, is ongoing.

New Zealand earthquakes highlighted soil liquefaction risk

The government of New Zealand began funding a series of field experiments after a cluster of earthquakes hit the Canterbury region during 2010-2011. This seismic activity proved devastating for the city of Christchurch and surrounding suburbs because the underlying soil is naturally wet and loose, causing the ground to liquefy during the quake.

More than 20,000 properties were affected by earthquake-induced liquefaction, with some of the greatest damage along the banks of the winding Avon River. Total economic losses exceeded 15 percent of New Zealand's gross domestic product.

Researchers highlight need to improve earthquake resilience

The UT engineers emphasized the risk of liquefaction during future earthquakes, writing that "effective engineering solutions must be developed to increase the resilience of homes and low-rise structures." Looking ahead, stakeholders need to determine how to adapt to their heightened awareness of this risk.

Officials in New Zealand have designated a "Red Zone" in Christchurch where structures will not be rebuilt, which contains more than 6,000 residential properties. The government also provided funding for research into various ground improvement methods, such as soil compaction, grouting and installation of stabilizing "piers" beneath buildings.

UT became involved because it operates a 64,000-pound "T-Rex" mobile shaker truck as part of the National Science Foundation's Network for Earthquake Engineering Simulation. The T-Rex was in the right place at the right time, having been sent to Christchurch previously for a seismic profiling project.

Using the T-Rex, underground explosions, and advanced motion sensors, researchers tested four ground improvement methods at two sites. They are still analyzing the test data, but say that the most effective methods have already been differentiated by their performance during the trials.

Interested parties can read this overview of the ground improvement research on the UT website.

Is large-scale 'ground improvement' feasible?

Boston Globe correspondent Kevin Hartnett notes that "the idea of changing the composition of the earth to ward against something as massive as an earthquake sounds a little futile. At the same time, there are other areas — like planting trees to prevent erosion — where we've successfully used home remedies to staunch tremendous natural forces."

What the ground improvement research emphasizes above all is the importance of being proactive in disaster preparation. To that end, insurance carriers need to keep valuations accurate and up to date for all properties in their portfolio.