Shaking Ground: Gabions in Earthquake Country

Retaining walls in seismically active regions face a double burden: they must hold back static earth pressure day to day, and survive violent, unpredictable shaking during an earthquake without collapsing. For decades, the standard engineering approach treated gabion walls the same way it treated rigid concrete ones — as essentially solid bodies analyzed with pseudo-static methods borrowed from concrete gravity-wall design. More recent research suggests that approach may undersell what gabions can actually do.

Because a gabion wall is built from many discrete, individually stacked units rather than a single monolithic pour, it behaves differently under dynamic loading than a rigid wall does. Laboratory shake-table studies — in which scaled or full-scale wall models are mounted on a platform and subjected to simulated earthquake motions —have repeatedly found that gabion-faced walls can undergo noticeable displacement and settlement during strong shaking without catastrophic collapse. The flexibility that helps a gabion wall tolerate ordinary ground settlement appears to serve a similar protective function during an earthquake, allowing the structure to absorb and dissipate seismic energy through small movements between units rather than concentrating stress until something fractures.

That does not mean gabion walls are somehow immune to seismic risk, or that conventional design methods translate perfectly. Full-scale shake-table testing conducted by Japan's National Research Institute for Earth Science and Disaster Resilience, using a model representative of vertically stacked gabion walls common in Nepal, found that standard slip-surface design calculations underestimated the depth at which severe deformation actually occurred during testing — prompting researchers to propose adjusted methods that explicitly account for gabion flexibility rather than treating the wall as rigid.

Real-world construction has not waited for the research to fully catch up. In Sikkim, in India's seismically active Himalayan foothills, engineers building Pakyong Airport faced the challenge of supporting an airfield carved into steep mountainside terrain, with cut-and-fill retaining structures reaching roughly 70 to 80 meters in height along parts of the site — among the tallest reinforced-soil structures built anywhere. The solution combined geogrid soil reinforcement with gabion facing units, chosen partly for exactly the properties this article describes: the assembly's flexibility and free-draining nature, valuable in a region where both earthquakes and heavy monsoon rainfall are recurring hazards.

Researchers studying gabion seismic behavior are candid that the field remains younger, and the underlying body of evidence thinner, than the equivalent research on rigid concrete-faced walls. But the available shake-table and case-study evidence points in a consistent direction: in earthquake country, a gabion wall's willingness to bend rather than break is not just a construction convenience. It may be one of its most valuable structural properties.