Gravelly Liquefaction Case Histories after 2008 Wenchuan-China Earthquake Mw=7.9

Gravelly soils were erroneously considered to be non-liquefiable due to their high capacity for pore pressure dissipation, resulting from their larger grain size. However, recent case studies have demonstrated that gravelly soils are susceptible to seismic liquefaction triggering. In particular, investigations performed in the Chengdu Plain following the 2008 Wenchuan earthquake (M-w = 7.9) provided evidence of seismic soil liquefaction in gravelly soil mixtures. Site investigations involved rotary and/or core drilling followed by dynamic cone penetration tests (DPT) and multiple channel analysis of the shear wave velocity (MASW) measurements. In 73 locations, 65 V-s measurements and 47 DPT-N-120 were taken. This paper introduces case histories with gravelly liquefiable critical layers and includes processing details. The assessment procedure includes identifying the critical layer susceptible to liquefaction, estimating the representative in-situ density state, groundwater table depth, intensity and duration parameters of seismic shaking, and gradation characteristics such as D-50 and D-30. The resulting preliminary results were presented in the CSR vs N-120 and V-s domains to enable comparisons with available liquefaction triggering methods.