The Relationship between Geological Structure and Failure Type in the Rock Slopes of Parts of Anah Monocline, West of Iraq

Abstract

Field observations and assessment of rock slope stability in selected sites in Anah monocline, West of Iraq, revealed the presence of different types of slope failure. The distribution and abundance of failure types are related to different discontinuity patterns in various structural positions within the asymmetrical Anah monocline. This is the first study that relates failure types to the structural position in a major fold. This relationship was observed all over the monocline area and confirmed by studying four stations along a traverse normal to the fold axis. The study revealed that wedge sliding is relatively common in the northern limb of Anah monocline whose dip angle is(35) with conjugate shear joints (S2) whose intersection lines plunge downdip.The plane sliding is prevailing in the hinge area with conjugate shear joints (S1) whose intersection lines are parallel to the hinge of the fold. Toppling failure is relatively dominant in the southern limb whose dip angle is less than (5)with two pairs of vertical orthogonal joints (F1, F2, and F3, F4) which are normal to the bedding planes. Rockfall was almost equally abundant in all structural positions which indicates no structural position influence on it. The concluded relationships are attributed to the dependence of most failure types on the discontinuity pattern, which is in turn, largely influenced by the structural position, in addition to the relationship between the discontinuities and the slope face.