Liquefaction-Induced Movements of Buildings with Shallow Foundations

Seismically induced settlement of buildings with shallow foundations on liquefiable soils has resulted in significant damage in recent earthquakes. In Adapazari, Turkey multi-story buildings punched into, tilted excessively, and slid laterally on softened ground. The state-of-the-practice still largely involves estimating building settlement using empirical procedures developed to calculate postliquefaction consolidation settlement in the free-field. This approach cannot possibly capture shear-induced and localized volumetricinduced deformations in the soil underneath shallow mat foundations. Geotechnical centrifuge experiments were performed recently to identify the dominant mechanisms involved in liquefaction-induced building settlement. The centrifuge tests revealed that considerable building settlement occurs during earthquake strong shaking. Volumetric strains due to localized drainage in response to high transient hydraulic gradients and deviatoric strains due to shaking-induced ratcheting of the buildings into the softened soil are important effects that are currently not captured in current procedures. The relative importance of each mechanism depends on the characteristics of the earthquake motion, liquefiable soil, and building. The initiation, rate, and amount of liquefaction-induced building settlement depend greatly on the shaking intensity rate (SIR) of the ground motion. Preliminary recommendations for estimating liquefaction-induced movements of buildings with shallow foundations are made. However, additional work is warranted