Turkey’s Akköy II hydro power project is located approximately 150km from Trabzon, close to Gümüshane in the Eastern Black Sea region of Turkey. The project encompasses the Aladereçam regulator, the Gökçebel and Yasmaki dams and an electric power plant close to the Akköy 1 scheme also under construction, to produce a total of 890GWh.
The Aladereçam regulator is being constructed at a ‘thalweg’ elevation of 1797m directing water to the Gòkçebel dam lake through a 4.5km long link tunnel with an inner diameter of 3.2m. The dam has been designed as a rockfill construction with a concrete coated front and a final height of 140m.
Served by the Gelaver stream in the Gumushane and Giresun Province borders, Gòkçebel lake will hold an estimated 65.07Mm3. The dam is in turn linked to the Yasmaki dam lake area at a ‘thalweg’ elevation of 1527m via a 6.65km long tunnel.
Yasmakli dam is a 100m high concrete gravity dam on the Gavraz scheme in Giresun Province. The dam has a storage capacity of 15.51Mm3 to channel water into a 4km long surge tank and tunnel. The dam includes a 1219m high penstock, making it the highest head on an hydro scheme in Turkey.
Virtual quarry
In a ‘virtual’ quarry style application, five Sandvik drill rigs will be used to produce rock for the Gòkçebel dam plus further rock for access roads and eventually the concrete production equipment.
Project contractor Kolín Construction is currently using two DX700 and the new DX800 to prepare access roads at an elevation of 1856m. They will also be used, together with two Sandvik rigs in drill and blast operations to provide infill material for the rockfill dam; producing 300-450 drill metres every 10 hour shift.
Featuring a base of 140m x 340m rising to 6m x 250m at 140m height, the dam will require almost 4.5Mm3 of rock.
Rock conditions feature a mix of very hard and abrasive volcanic basalt, granites, granite diorite and quartz with a hardness factor of between 5 – 7.5. Blasting is carried out twice daily at shift change and lunch.
All five hydraulic rigs are fitted with Sandvik T51 3.6m long mf rods. Depending on the rock conditions three different Sandvik bits are used. Retrac ‘normal face’ 89 mm diameter bits are predominantly used, particularly in the harder rock. Retrac ‘drop center’ and ‘flat face’ bits are also used when the rock conditions dictate. If the contractor is drilling less than 10m in soft ground, standard drop center 89’s are used.
Kolín is also shortly to introduce Sandvik guide tubes for poor ground conditions to also achieve straighter holes.
Abrasive rock
It is the abrasiveness of the rock which is the prime consideration where the drill bit life can be as low as 100 drill metres.
The rig operators confirmed however that the bits are frequently lasting each 10 hour shift with around 400 drill metres.
“This performance is very high and quite exceptional considering the abrasiveness and inconsistencies of the rock,” said Machine Manager Mehmet Tuncay, adding, “Another challenge is being able to meet the speed of the drill and blast cycles. The MF rods are also providing high performances and exceptional life.”
Each Sandvik drill rig is producing 200m3/h per rig to ensure the specified 2000m3/rig is produced each 10 hour shift. Drilling to 15m depths, each hole takes an average 20 minutes depending on the rock conditions.
The DX800
The Sandvik DX800 is a hydraulic self propelled, self contained and crawler-based surface rig with an ergonomic high visibility cabin and rod handling system. It is powered by a Cat C7 diesel engine rated at 168 kW (225 hp) at 2200 rpm.
The rig has been developed to offer excellent stability even in uneven terrain and is designed for use in drilling 64-127mm diameter holes.
Additional features include up to 12 hours continuous drilling, high suction capacity dust collectors, advanced boom design and ROPS– and FOPS-certified safety cabin.
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