Post-liquefaction settlement analyses based on the volume change characteristics of undisturbed and reconstituted samples

Available data on post-liquefaction volumetric strain were collected from the results of tests conducted in several laboratories on both undisturbed samples and reconstituted samples. The volume change characteristics were found to depend significantly on the degree of disturbance during the undrained cyclic loading preceding the drainage. Its effect was shown to be expressed quantitatively by way of the maximum shear strain, γmax, as an index parameter. Charts were prepared for the volumetric strain as a function of the ranges in relative density and void ratio considering two levels of disturbance, as expressed by γmax=4.13% and 10%. These charts were provided for each post-liquefaction volumetric strain in association with the reconstituted and undisturbed samples. By postulating the former to represent the performance of recent man-made fills and the latter to represent that of alluvial or diluvial deposits, simple analyses were conducted to estimate the settlements of the ground surface at five sites which were affected by liquefaction during the 2011 East Japan Earthquake. A comparison of these estimated values with those actually observed indicated a reasonable level of agreement. Four sites where compaction piles had been installed were also chosen for similar analyses. Both the observed and the estimated settlements were small, namely, in the order of a few centimetres, which also indicates mutual coincidence as a whole.