Fracturing within anticlines and its kinematic control on slope stability

Anticlinal folding generates both bedding-parallel shear stresses and tensional stresses radial to the fold axis. These stresses typically produce two sets of discontinuities. Discontinuity set S 1 forms coincident with bedding (S 0 ) as a mode II fracture, and discontinuity set S 2 forms perpendicular to bedding and strikes parallel to the fold axis as a mode I fracture. For slopes that strike parallel to the fold axis, these two discontinuity sets may produce three structurally-controlled modes of slope failure. For slopes that are coincident with bedding, planar failures along S 0 /S 1 commonly occur and can be very large. Where bedding dips favorably into the slope, failures along joint set S 2 and across bedding can occur. Toppling failures are common to both of these slope configurations, along S 2 and S 0 /S 1 , respectively. Lastly, flat or shallow dipping S 0 /S 1 fractures, even those favorably oriented, and intersecting S 2 joints define blocks that can be mobilized by high ground-water pressures. An example is presented for each slope configuration to illustrate these kinematic controls on slope stability.