Seismically induced settlement of ground experiencing undrained shaking and laterally constrained compression

摘要

A method is proposed for estimating seismically induced settlement of saturated sands experiencing undrained shaking and laterally constrained compression. An empirical relationship is developed between the seismic coefficient of vertical compression, m(vs), and standard penetration test blow count, N-60, as a function of factor of safety against liquefaction, F-l, based on data interpreted from 18 sets of laboratory cyclic direct simple shear tests and 23 cases of field observations of seismic liquefaction. The proposed method is compared with seismic settlement observed at 78 sites subjected to 7.1-8.0 magnitude earthquakes, and with predictions by the previous well-known methods of settlement analysis for undrained shaking. For silty-clayey sands, the significant effect of the plasticity of fines on seismic settlement is illustrated. The use of pre- or post-earthquake penetration resistance for back-analyses of field seismic settlement observations is examined. A tentative correction factor is suggested for seismic settlement estimated based on the assumption of undrained shaking and laterally constrained compression for liquefied saturated sublayers at small distances from drainage boundaries or under buildings with small breadths, which may experience volumetric compression during ground shaking.