ABSTRACT
The Dam-reservoir of Lom Pangar is located in the East region of Cameroon. Its main function is to increase the regularization of the Sanaga River and the energy generation of the existing and future power plants. The feasibility design studies, completed in 2010, recommended the implementation of a physical hydraulic model to check the need for a pre-excavated plunge pool downstream of the dam spillway. These studies, carried out between 2011 and 2014, confirmed that a pre-excavated plunge pool was required to control the scouring of the dam downstream toe. The project consisted in the excavation of 65,000 m3 of rock adopting drilling and blasting methods, while the 57 m high mixed Roller Compacted Concrete (RCC)-embankment dam was almost completed and the 6 billion m3 reservoir was partially filled. These sensitive works required special precautions in order not to damage the existing neighboring concrete structures and their foundation. For this purpose, a safe vibration level was defined and, through the analysis of the vibrations measured from the first blasts, site-specific propagation laws were established and refined during the excavation works allowing the subsequent safe maximum explosive charges per delay to be defined and used to complete the works.
