Barrage Ahmed El hansali Dam, Morocco

Soil Instruments has supplied geotechnical monitoring instrumentation to the Moroccan Government's dam building program since 1990. One of the most recently completed contracts was Barrage Ahmed El Hansali (formerly Barrage Dchar El Oued), on the river Oum Er Rbia at the northern foot of the Middle Atlas mountains near Khenifra. (50)

Barrage Ahmed El Hansali has a height of 101m with a crest length of 342m and was the first concrete-faced, rock-fill dam to be completed in Morocco, designed for water supply, irrigation and hydropower.

The instrumentation supplied by Soil Instruments falls into two categories; (1) foundation and fill monitoring, and, (2) concrete joint monitoring. To monitor behaviour of the fill material, upstream-downstream profiles of long-based horizontal soil extensometers, with fill extension measured vibrating wire displacement transducers, were supplied, along with hydraulic overflow settlement cells to provide fill settlement information.

At two sections in the adjoining earth fill saddle-dam, vibrating wire piezometers were provided to provide data on any uplift due to the passage of water along the contact. Further vibrating wire piezometers were supplied to monitor the grout curtain’s effectiveness for preventing water flow.

During the pouring of concrete face slabs, strain gauges were required to indicate stresses induced within the concrete. Vibrating wire displacement transducers were needed to monitor the movement at the vertical joints, uniaxial jointmeters were supplied to measure the opening or closure of the joints and perimetric jointmeters were provided to be mounted orthogonally in a heavy tri-axial support frame. (194)