Andhika Sahadewa
"Lessons from the Construction Failure of X Dam: The Importance of Field Monitoring Andhika Sahadewa1, 3, Haris E. Setyawan1, Mahdi I. Tanjung1, Astyka Pamumpuni1, Abi M. Hakim2, Jagad S. Langit3, Pebri Herry1, 4, and Aris Wibowo1, 4 1. Bandung Institute of Technology 2. Indonesian Institute of Technology 3. Indonesian Geotechnical Inztitute 4. Nur Straits Engineering Hundreds of dam failures have occurred leading to environmental damages, massive property destruction, loss of lives, and economic lost. Dam failure during construction period has not been extensively reported as many as failures in operational period. This paper presents a case study of a dam construction highlighting that disparaging field monitoring may lead to a catastrophic failure. Field monitoring in a dam construction can capture deviation, variability, and complexity in a dam site that may not be able to be modeled in the design stage. Information from field monitoring plays vital role as it frequently becomes a basis in continuing the planned construction method or altering the construction method. X Dam, located in Indonesia, is an inclined-core fill type dam. This dam was under construction to reach 55-m tall with a total capacity of 1.68 M m3. During dam embankment construction stage, it experienced 3 progressive slope failures within 2 weeks. This event was started by a 2-m shallow failure surface. The last event was the largest one comprising a 22-m deep seated failure. Investigating the failure source and redesigning the dam required considerable effort and resulted in time and financial losses. Numerous site investigations were performed, including Multi-channel Analysis of Surface Wave and Vane shear tests. Forensic analysis showed that the failure was associated with multi-root causes, including an excessively fast embankment construction, challenging fill compaction, halloysite fill material, high rain intensity, and very optimistic design parameters. These circumstances were corroborated by improper field monitoring performance. Immediate remediation steps, involving collapsed material removal and temporary drainage construction, were conducted to avoid detrimental condition. Several design alternatives were proposed to continue the construction. The X Dam construction showed that performing appropriate field monitoring can help us avoiding any imminent negative consequences as it also serves as an early warning system. "