Engineering Services for Remedial Structures for the Safety of Koçköprü Dam – Turkey

Project Name: Engineering Services for Remedial Structures for the Safety of Koçköprü Dam

Country: TURKEY

Client: ÖZALTIN Construction Trade and Industry Company

Finance Source: Local sources

Tags: Turkey, Local, HEPP, Design

Narrative Description of Project:

Koçköprü Dam is a 73.5 m high zoned earthfill dam located in Van Province of Eastern Turkey. Its embankment with a crest length of 693 m and a volume of 2×106 m3 forms a reservoir of 86×106 m3. The gated spillway located on right bank has a maximum discharge capacity of 2270 m3 /sec expected from the drainage area of 700 km2 . The original diversion tunnel on the left bank below the dam fill was designed for 170 m3 /sec discharge capacity with a diameter of 5 m.

Geological formation of the dam foundation consists of quaternary basalt, pillow lava, claystone and tertiary basalt in accordance with their age sequence. Diversion tunnel passes through pillow formed basalt blocks within a fine, low density matrix material.

After completion of the construction and impounding the reservoir in the late of 1985 a serious collapse occured at the upstream reach of diversion tunnel. Although the old tunnel was plugged and a new by-pass tunnel was constructed, a second failure happened and reservoir was emptied again in April 1987. These failures were attributed to the washing away of fine matrix material in pillow lava layer and it was decided to apply long term remedial measures for overall safety of the project.

Description of Actual Services Provided by TEMELSU:

Final design and application drawings for the repair and foundation improvement of Koçköprü Dam has been conducted by Temelsu. For this purpose, old diversion tunnel has been plugged and cancelled completely and a new tunnel has been designed and constructed on the right bank. Furthermore, a 200 m long concrete lined repair tunnel has been drilled through pillow lava layer along the dam axis and a cut-off diaphragm wall down to the lower basalt layer has been built to prevent leakage through pillow-lava/claystone contact . Following the completion of these repair works Koçköprü Dam is in operation safely since 1992.