Abstract:

The 2008 Wenchuan earthquake caused destructive geologic hazard such as mountain landslide, collapse and debris flow in the mountainous area. Meanwhile, the liquefaction occurred extensively in the Chengdu plain that was mainly underlain by gravelly soils. Six typical liquefied sites were selected for drilling and field test in order to understand the features of liquefied soil and verify the feasibility of the liquefaction evaluation method in the Code for Seismic Design of Buildings. The results indicate: (1) The liquefied soils of six typical sites range from sand to gravels, two of which are sand and the rest are gravels. (2) The liquefied soil layers are loose and non-uniform with gently grain size distribution curve and large coefficient of uniformity; and the liquefied sands are well-graded soils and liquefied gravels are not. (3) The liquefaction evaluation method in the seismic code predicts one of the six typical sites as non-liquefaction site. Moreover, the code method is not feasible for gravels liquefaction assessment, because the standard penetration test (SPT) is impeded through the gravelly soils by big cobbles

Key words: Wenchuan earthquake, liquefaction of sand, type of soil layer, grain size distribution, liquefaction distinguish