Role of Sliding Block Rotation on Earthquake-induced Permanent Displacement of Embankments and Trenches in Roads

Since proper functioning of the transportation system is essential in times of crisis, correct design and accurate prediction of earthquake-induced permanent displacement of embankments and trenches have been considered by many engineers. Different methods are available for estimating earthquake-induced permanent displacement of embankments and trenches in roads, such as pseudo-static, numerical, analytical and semi-analytical. Due to its simplicity, Newmarkian rigid block analogy has received considerable attention from geotechnical researchers and practitioners. Since the conventional Newmarkian analogy has many limitations, conservative and non-conservative estimations of sliding displacement would be possible. Therefore, researchers have proposed many modifications to this method. One of these limitations is the effect of rotation. In fact, it is anticipated that the downward rotational (stabilizing) movement of the soil mass, can significantly affect the yielding acceleration of the presumed slip surface. In this paper, keeping in mind the effect of rotation, the conventional formulation of the Newmark approach is modified numerically. The results are presented and compared for several conditions including the conventional rigid block, decoupled assumption of sliding and slope response, coupled consideration of sliding and slope response, and decoupled assumption with the effect of sliding block rotation. According to the results of this study, the period ratio (ratio of natural period of slope to the mean period of input motion) and the length of slip surface, can significantly affect the permanent displacement of sliding mass.