Definition of liquefaction

Abstract

Different definitions are used for the onset of liquefaction in engineering practice. For example, NCEER, JRA, and AIJ use γ =3 %, DA = 5 %, and γ = 5 %, respectively. The state where the excess porewater pressure becomes equal to the initial confining stress is used to identify the liquefaction in the field during earthquake and laboratory tests such as a shake table test. In addition, the number of cycles causing liquefaction, N_c is 15 in NCEER and AIJ whereas it is 20 in JRA. In total, 44 liquefaction strength tests of soils sampled from the natural deposits are used to evaluate the liquefaction strength under different definitions, and the relationships between various definitions are evaluated and discussed. The liquefaction strength at N_c = 15 is about 4 to 5 % larger than that at N_c = 20. The soil with large fines frequently does not become a zero confining stress state. The liquefaction strength of NCEER and JRA is nearly the same, and that of AIJ is about 7 % larger than them.