TEST AND CHARACTERIZATION METHOD FOR SHEAR STRENGTH OF SLATE CONTAINING WEAK INTERCALATED LAYER

Direct shearing tests of pre-split structural plane filled with clay films are conducted on the slate specimens using a microprocessor servo-controlled shearing tester under various normal stresses. After that, two experimental phenomena are found as follows. (1)During the process of direct shearing test of structural plane, the areas which bored the shearing force were not the whole structural plane, but were partial structural plane. (2)The values of effective frictional areas which bored the shearing force during every shearing process, could increase with the increasing of normal stress, but the increasing rate decreased gradually. In this paper, to analyze the changing law of shear strength parameters of filled structural plane, the apparent shear strength parameters and effective shear strength parameters were proposed. The apparent shear strength parameters were calculated according to the assumption that the shearing force was borne by the whole structural plane. And then, curves of relation between apparent shear stress and shear displacement were obtained. And apparent shear strength parameters were achieved by fitting the apparent shear stresses under various apparent normal stresses. The effective shear strength parameters were calculated according to the assumption of effective frictional areas. In the same way, the curves of relation between the effective shear stress and the shear displacement, and effective shear strength parameters were obtained. Comparing the apparent shear strength parameters with effective shear strength parameters, we find that:(1)the frictional angle has no relationship with the choice of structural plane which bears the shearing force. But the cohesion is influenced by the choice of structural plane. (2)Comparing with the apparent cohesion, the value of effective cohesion is improved by 95%. This paper may contribute to the assessment and selection of the treatment plan of landslide engineering.