Stability of concrete retaining structures and their interface with rock foundations

Three failure mechanisms of concrete retaining structures situated on rock foundations: sliding, overturning and limit turning, are discussed. Investigations have shown that sliding is possible only in specific cases when weakened subhorizontal surfaces with low shear parameters are present near the interface between the structure and foundation. If these conditions are not present, then failure due to sliding does not occur. The classical over turning mode, which involves turning of the structure relative to the downstream toe, is not possible, as it requires unrealistic conditions of infinitely strong rock or concrete. The limit turning mode, which seems to be the most likely of the three, involves partial turning of the structure and is accompanied by down stream crushing and upstream rupture of the foundation. Finally, a practical method to analyze a structure's resistance to limit turning is presented, and preparation of the interface between a concrete retaining structure and its rock foundations, taking into account the specific characteristics of limit turning failure is discussed. (C) 2009 Elsevier Ltd. All rights reserved.