ABSTRACT
In the area under study gently dipping intrastratal and interstratal fractures are main discontinuities that influence the stability of engineering site. This paper, on the basis of field observation, presents the basic characteristics of the two kinds of fractures, discusses their mechanism and assesses their influence on the engineering. It is thought that the majority of both the intrastratal and interstratal fractures was formed by shearing during flexural folding and developed further under the action of shearing caused by the subsequent tectonic stress field. According to the geometric relations between the fractures and orientations of the slopes and constructions, they have little influence on the stability of the rock mass at the dam site.
