Grid Type Deep Mixing Applications to Liquefaction Mitigation-Paper

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The paper reviews the use of grid-type deep mixing to mitigate soil liquefaction during earthquakes. The deep mixing method, developed in Japan in the 1970s, stabilizes soil in place by mixing it with cement-based binders. In grid-type applications, stabilized walls form cells around loose, saturated soil. These stiff walls restrain soil movement and shear deformation, limiting excess pore-water pressure and reducing liquefaction risk while using less treated soil than a solid block.<br /><br />Research since the late 1980s—including centrifuge and shaking-table tests and numerical analyses—has informed design guidance. Key considerations include grid spacing, wall thickness and strength, and the depth and overall stability of the improved ground. Earlier guidance recommended a grid-spacing-to-liquefiable-layer-thickness ratio below about 0.8; later procedures refined design for infrastructure and buildings.<br /><br />Field performance demonstrates the method’s effectiveness. At a Kobe port building during the 1995 Hyogoken-Nambu earthquake, untreated surrounding ground liquefied and quay walls suffered major displacement, while the improved ground showed no surface cracking and the building piles and floor remained largely undamaged. After the 2011 Tōhoku earthquake, a building in Urayasu and improved road and river embankments showed no significant damage, despite widespread liquefaction nearby and severe damage to an adjacent untreated road.<br /><br />The paper concludes that grid-type deep mixing has been successfully applied to building foundations, roads, and embankments. Its design, construction, and quality-control practices have advanced through research and earthquake experience. The need for liquefaction mitigation has grown, including plans to apply the method to many residential properties damaged in Urayasu.

Keywords

grid-type deep mixing

soil liquefaction

earthquake mitigation

deep mixing method

cement-based binders

stabilized soil walls

excess pore-water pressure

centrifuge tests

shaking-table tests

liquefaction resistance