Page - 1032 - in Book of Full Papers - Symposium Hydro Engineering

COMMISSION INTERNATIONALE DES GRANDS BARRAGES ------- VINGT-SIXIÈME CONGRÈS DES GRANDS BARRAGES Autriche, juillet 2018 ------- SCOUR ESTIMATION FOR NAM THEUN 1 SPILLWAY PLUNGE POOL F. TAKHTEMINA Senior Engineer, PÖYRY ENERGY Dr. M.P. BIERI Senior Engineer, PÖYRY ENERGY Dr. B. ZÜEND Senior Engineer, PÖYRY ENERGY S. Martin Senior Engineer, PÖYRY ENERGY THAILAND AND SWITZERLAND 1. INTRODUCTION Nam Theun 1 (NT1) dam is a 180 m high RCC curved gravity dam situated in Lao PDR. The dam is equipped with four gated spillway bays and a bottom outlet, both terminating at flip buckets as energy dissipaters. To prevent any dam foundation undermining, tailwater level increase and blockage of the draft tube gates as a result of erodible material being deposited at the powerhouse located circa 300 m downstream of the dam, a pre-excavated plunge pool was designed within the river just downstream the spillway and bottom outlet. This paper describes the step-by-step methodology applied for design and functionality checks of the proposed pre-excavated plunge pool downstream the dam. 1032