Development of a novel vibratory cone probe for in-situ liquefaction assessment

抄録

The liquefaction assessment method in Japan has been developed based on the standard penetration test (SPT). A drawback of SPT is that the number of blows (N-value) is influenced sensitively by particle size and fines content. This caused underestimation of liquefaction resistance of sandy soil with non-plastic fines during the 2011 off the Pacific coast of Tohoku Earthquake (Tohoku) Earthquake. On the other hand, the cone penetration test (CPT) is also used worldwide where cone-tip resistance, skin friction and pore water pressure can be measured. A potential drawback of CPT for the purpose of liquefaction assessment is that the undrained cyclic resistance of soil, which is a dynamic property of soil, is measured indirectly in a static manner. To overcome these limitations, this contribution proposes a vibratory cone penetration test (VPT) for in-situ liquefaction assessment using a novel vibratory cone probe that vibrates horizontally with varying amplitudes of acceleration. The vibratory cone probe can be driven at a constant rate in the same manner with CPT, and the horizontal vibration of the probe can be conducted at any depth in which horizontal acceleration, cone-tip resistance and pore-water pressure can be measured. This contribution presents a case study of VPT using the novel vibratory cone probe, and demonstrates representative field test data where the cone-tip resistance drops sharply when the horizontal acceleration exceeds a threshold value in liquefiable subsoil, while such drop does not occur in non-liquefiable subsoil.