Articulated Concrete Block Stability Assessment for Channelized Flow

Abstract

A moment stability analysis method which computes a safety factor using shear stress and flow velocity was previously developed for assessing the stability of articulated concrete block (ACB) systems during overtopping flow. The present study used the shear and velocity stability assessment (SVSA) method to derive safety factor equations for evaluating channelized flow. The stability analysis method for channelized flow excludes several assumptions used in previous methods, including calculating the rotation angle for movement and using a ratio of the boundary shear stress to critical shear stress to account for all hydrodynamic forces. The SVSA channelized flow equations provide a reliable stability assessment approach for ACB systems. Performance of the SVSA method for channelized flow was evaluated using a database that included overtopping tests for three ACB systems with varying embankment slopes and lengths, and channelized tests for one ACB system. The previous design methodology predicted stability for 71% of the tests and the instability threshold for 50% of the installations. The SVSA approach predicted stability for 92% of the tests and the instability threshold for 83% of the installations. Therefore, the SVSA method provides an enhancement for predicting stability of ACB systems in channelized flow conditions.