Abstract: It is improved that there is staged characteristics of lateral pressure coefficient K0 of soft clay. When the test load P is less than sample’s remaining structure strength , the value of is small, and when , the value of K0 is increased. It’s the reflection of the staged characteristics of soft clay’s mechanical property. When , the structure of soil sample is undamaged, the sample is similar to a rigid material, the value is small; When , soils microstructure is damaged, the sample is changed to be elastoplastic material, the value is increased. In geotechnical practices, the sample is disturbed during drilling and sampling, the microstructure of under-consolidated or normal-consolidated soft clay is destroyed, the staged characteristics of index is disappear.

Key words: lateral pressure coefficient, residual structure strength, staged characteristics