Risk-assessment of hydropower plant susceptible to seismic hazard by 3D spectrum analysis

Abstract

Recently, new fault zones are identified in central Borneo due to the ongoing geomorphological anomalies along the Rajang-Crocker Belt. The Kapit-Belaga region along the Rajang River system are located in between active trending strike-slip faults. By 2025, this region will have 3 operational large hydropower dams namely, Bakun, Murum and Baleh which are approximately 120 km apart in radius. Even though central Borneo is known to be a stable area, the assessment of seismic risk for existing dams is vital. The seismic failure of Konya Dam, India in 1967 proved that occurrences of catastrophic earthquake in low seismicity region is possible. Furthermore, earthquake frequency model shows that it is plausible for the Crocker fault system to produce seismic ruptures of magnitudes ≥7.0. The research of risk-assessment for hydropower in this work is motivated by the possibility of larger seismic hazard within the Crocker fault system. Hypothetical seismic loadings from Tosya and Aydin earthquakes’ records are adopted as inputs to replicate long-distance waves for the Response Spectrum Analysis (RSA) by ANSYS© ACADEMIC. Results show that tensile zone develops at the reservoir bed, extending to the dam foundation. When the seismic load is at 0.625 g Peak Ground Acceleration (PGA) – which is equivalent to magnitude 6.0 earthquake, the mechanical responses of the dam body excitation and hydrodynamic pressure from the impact of the reservoir due to seismic excitation triggers structure failure at the mid crest and bottom of the dam.