液状化抵抗を原位置から推定する方法についての一試案  [in Japanese] A proposal to evaluate liquefaction resistance by development of new in-situ testing technique  [in Japanese]

Based on measurements of strain dependence on dynamic rigidity under drained condition for some kind of soils, the following equation have been derived. G_0/G=1=α・γ^β; where, G is rigidity at strain, γ, G_0 is at very small strain and α and β are constants. It has been confirmed that this relation holds for very wide strain range of various soil types. Based on the laboratory test for various soil types from soft to hard clay and loose to dense sand, these parameters α and β have been found as material constants. These parameters have been further found to have the following relationship, in generally. β=0.2・logα+0.3; A simple plasto-elastic model, meta serial parallel spring, MSPS model, was appd to simulate stress-strain relation of the soil. Weibull's distribution function was used the distribution of yield strength for each slider elements of MSPS model. As a result of the computation, above former equation was, also, obtained by theoretical model simulation. Both parameters of α and β are clarified to be defined by the characteristic parameters of Weibull's distribution, and also to indicate the structural grade related the compliance of the shear deformation. The increase of the value of these parameters leads to the increase of the structures ensitivity. Loose clean sand which is likely to be liquefied has extra structure sensitivity and if the sensitivity of sand is estimated by α and β, the liquefaction resistance shall be evaluated. A special in-situ S wave logging which gives two these parameters α and β is proposed to identify susceptibility of soils against liquefaction in the field condition.