For the model of soil layers with weak pane or zone, the triaxial tests were performed with the specimen which had a discontinuous plane by cutting.
From these experiments, the following results are obtained.
(1)For sandy soil, the cohesion c' must be zero in case which the discontinuous plane overlaps one another with shearing plane(sliding plane). But even in this case, internal angle of friction φ' can be used the value of standard test results.
(2) In case of cohesive soil, the discontinuous plane is adhered easily by consol idation. So, the influence of the discontinuous plane is only recognized on the secant modulus E_<50>.
(3) The influence of the discontinuous plane grows great as the consolidation pressure is lower.