Shear failure mechanism and strength criteria of a dislocated mudded intercalation

The foundation rock of the first stage construction of Gezhouba project belongs to the lower Gretaceous series strata of land facies and rocks are sedimentary siltstones, argillaceaus siltstones with medium-fine grained sandstones. The rock strata have strikes of N20-40 degrees E, forming an angle of 70 degree with the axis of the dam, inclining slightly downstream and to the left bank, dip of SE and dip angles of 4-8 degrees. In the strata numerous weak intercalations parallel to beds are distributed, which are the control factor of the dam stability. Among them, the dislocated mudded intercalations (shear zone) resulting from tectongenesis are of lowest mechanical strength. Ever since the early 70s., a great deal of scientific researches have been conducted by Yangtze Water Conservancy and Hydro-electric Power Research Institute, with both rock and soil mechanical methods in various sample sizes in labs and in situ. Numerous scientific data for engineering design and construction have been prowided.