Geological Characteristics' Structural Indication of Weak Intercalated Layer in Consequent Bedding Rock Slope

摘要

Baitupo slope at new county-site town of Badong in Three Gorges reservoir region is a consequent bedding rock mass slope, the cutting of yangtze river and gullies provided free faces for rock mass creep. For analyzing tectonic deformation feature of weak intercalated layers of the 3rd Member of Badong Formation in Baitupo slope, intercalated layers can be divided into consequent fracture cleavage type and intercalated fracture cleavage type from deformational degree by analyzing outcrop. Analyzed by X-ray diffraction (XRD), intercalated layers show that their protolyte is calcareous mudstone. Rock slab, scraping trace, shear joints and extension joints are thrusting which are formed by intercalated layer's shearing originated from buckle fold, the conjugate shear joint show that the maximum tectonic principal stress is approximately SN-direction. By analyzing scraping trace on bedding surface of oriented sample by scanning electron microscope, the mode of line type scraping traces' movement is stick slip formed by prophase thrusting shearing, the direction of linear scraping traces are consistent with thrusting scraping trace on the super face, the mode of arciform scraping traces' movement is creeping slip and their direction is in accord with bedding plane dip, which indicates deep-seated rock mass creeps along the surface of weak intercalated layer by gravity action during anaphase slope development.