Discharge Capacity of Piano Key Weirs

In recent years, spillway rehabilitation has increased in importance and become the subject of many projects worldwide. One solution for this problem is the implementation of a new type of labyrinth spillway, called Piano Key Weir (PK-Weir). This is an excellent alternative for increasing the overflow capacity of existing dams. Similarly to traditional labyrinth weirs, the hydraulic capacity of a PK-Weir is a function of its geometrical characteristics. Currently, there is a lack of systematic experiments, and the existing data does not allow the proposition of a universal design procedure. This paper reviews the previous studies on the efficiency of planned and built PK-Weirs. The results are evaluated by comparing an actual PK-Weir's discharge to that theoretically obtained for a sharp-crested spillway with crest length equal to the width of the PK-Weir for a given hydraulic head. On the basis of this evaluation, a preliminary design procedure is proposed. DOI: 10.1061/(ASCE)HY.1943-7900.0000490. (C) 2012 American Society of Civil Engineers.