Design Feature of the Nam Ngiep 1 Hydropower Project

摘要

A main dam and a re-regulation dam are constructed for power generation of the Nam Ngiep1 hydropower project ("Project"),located in the Lao People's Democratic Republic.The Project consists of a main power station and a re-regulation power station.The main dam with 148 m in height and the main power station creates the reservoir by which the main power station generates the power of272 MW.The re-regulation dam with 20.6 m in height and the re-regulation power station is planned to re-regulate and stabilize the maximum plant discharge of 230 m3/s released from the main power station for the safety to the downstream area of the re-regulation dam.The design features of the Project including hydrology,seismic analysis,dam stability analysis,and spillway design are introduced in this paper.The Probable Flood discharge is calculated by using a frequency distribution curve of "Log Peason Ⅲ ".1,000 years return period of flood discharge is adopted as the design flood which is calculated to be 5 210 m3/s.Additionally,Probable Maximum Flood is calculated to 9 050 m3/s.The dam stability on earthquake is considered under Operating Basis Earthquake (OBE) and Maximum Credible Earthquake (MCE).The design seismic intensity of OBE is decided based on Global Seismic hazard Assessment Map (GSHAP).At the point of NNP1 the intensity estimated to be ranged between(0.041 ～ 0.082)g from the map.Accordingly the design seismic intensity as OBE of NNP1 is set at0.10g conservatively.For the calculation of MCE,hypocenter modeling based on the historical earthquake data are carried out.Peak ground acceleration (PGA) is calculated based on attenuation relation modeling and hypocenter modeling and MCE is calculated to be 0.2 g.RCC is adopted for the main dam.Both rigid static analysis and dynamic elastic analysis are carried out to confirm the stability of the dam.In case of MCE,open crack and sliding failure are quite limited and the stability of the dam is confirmed.RCC trial mixing tests are underway and the design are to be revised based on the results of the RCC trial mixing tests.The spillway types of the main dam and the re-regulation dam are ski jump type and labyrinth type.The details of each structure are determined based on the hydraulic model tests.Applicability of both types has been confirmed.