Through field tests at the gravelly soils sites in Chengdu plain, the characteristics of the massive liquefied gravelly soils sites in Wenchuan earthquake are studied and the general rules governing the liquefaction behaviors are proposed. New interpretations on the conditions of gravelly soils liquefaction are obtained that some previous misunderstandings are corrected. The analysis indicates: the ranges of particle diameters of the liquefied gravelly soils are wide that the gravel contents vary from 5% to 85% or even beyond; the tested shear-wave velocity is 140 m . s(-1) to 270 m . s(-1) and then corrected as 160 m . s(-1) to 314 m . s(-1) , exceeding the previously recorded; one half of the gravelly liquefied sites are located in seismic intensity VIII (Chinese Scale) regions, i. e. , like sand liquefaction to trigger massive gravelly soils liquefaction requires intense ground shaking; however, the scale of gravelly soils liquefaction can only limitedly increase when the ground shaking triggers liquefaction; the dual-structural soil at shallow depth in Chengdu plain consists of gravelly soils layers and overburden soil layers, i. e., the first of the conditions for gravelly soils liquefaction; the overburden soil layers seal the saturated gravelly soils layers, forming a fundamental condition of liquefaction for gravelly soils; the shear-wave velocity of gravelly soils is large yet the most gravels stay actually very loose, i. e., the second essential condition for the massive gravelly soils liquefaction; the surface ejecta during the earthquake are quite different from the actual liquefied soils which lie less than 6 m in depth that judging from the surface ejecta to deduce the underground liquefied soil categories is not appropriate anymore; the traditional senses that gravelly soils is not liquefiable because of its large shear-wave velocity and large permeability cannot hold; the liquefaction conditions of gravelly soils and general sandy soils are different, since the requirements for the former are considerably stringent.
