Safety control during the Alto Tâmega Construction

Abstract

During the excavations stage of Alto Tâmega dam construction, a landslide occurred on the right bank slope, immediately downstream of the dam’s insertion surface, involving a rock mass volume of about 23,000 m3. This paper presents a brief description of the events that led to the slope failure, the countermeasures that were implemented to ensure the safety of the dam (resurfacing of the insertion surface of four blocks of the dam; construction of a new concrete structure to partially restore the geometry and the loading conditions of the rock mass existing before the landslide; extension of the rock gallery under the affected zone, to survey the rock mass foundation in depth and promote waterproofing and drainage of the rock mass; updating of the monitoring plan, including the definition of additional instrumentation to install in the new concrete structure, as well as adjustments to monitor the foundation area on the right bank; and moving the location of the dam’s bottom discharge to the left bank) and some results of the monitoring during construction and the first filling of the reservoir that showed the adequate behaviour of the dam.