Sandvik Akkoy - TunnelTalk
Drill rigs employed at Turkey's Gökçebel dam Jan 2010
Sandvik news release
Five Sandvik drill rigs, including a newly delivered DX800, are producing almost 4.5 million m3 of rockfill for the Gökçebel dam on Turkey's Akköy II hydropower project. The scheme is located some 150km from Trabzon and close to Gümüshane in the Eastern Black Sea region of Turkey. It 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 890 GWh of power.

Site of the quarry

The Aladereçam regulator is being constructed at a 'thalweg' elevation of 1,797m directing water to the Gòkçebel dam reservoir through a 4.5km long link tunnel with an inner diameter of 3.2m.The dam is designed as a 140m high, concrete faced rock fill construction.
Served by the Gelaver stream in the Gumushane and Giresun Province borders, the Gòkçebel reservoir will hold an estimated 65.07 million m3. The dam is in turn linked to the Yasmaki dam reservoir at a 'thalweg' elevation of 1527m via a 6.65 km long tunnel.
Yasmakli dam is a 100m high concrete gravity dam on the Gavraz scheme in Giresun Province. The dam has a water holding capacity of 15.51 million cm3 to channel water into a 4 km long surge tank and tunnel. Featuring a 1,219m high penstock makes it the highest head on a hydro scheme in Turkey. The project's tunnels are being excavated by a Robbins TBM of special design. After the initial 6.65km x 4.8m diameter tunnel, the cutterhead will be changed to 4m diameter for the two additional tunnels of 4.5km and 4km long.

Foundation of the rockfill dam

Virtual quarry
In a 'virtual' quarry style application the five Sandvik drill rigs will be used to produce almost 4.5 million m3 of rock for the Gòkçebel dam plus further rock for access roads and eventually the concrete production equipment.
Kolín Construction is currently using two DX700 and the new DX800 to prepare access roads at an elevation of 1,856m.
They will also be used, together with two Sandvik rigs for drill+blast operations to provide infill material for the rock fill dam; producing 300-450 drill metres every 10h shift.
Featuring a base of 140m x 340m rising to 6m x 250m at 140m height, the dam will require almost 4.5 million m3 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 57.5. Blasting is carried out twice daily. 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' 89mm 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 89s are used. Kolín is also shortly to introduce Sandvik guide tubes for poor ground conditions to achieve straighter holes.
Machine Manager, Mehmet Tuncay sums up the benefits of the Sandvik rigs as "powerful performance, easy operation and excellent after sales backup by the local Sandvik operation."

Drill rigs in action

Abrasive rock
The abrasiveness of the rock is the prime consideration reducing drill bit life to 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 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." He went on to describe that subcontractors with competitive 'marque' rigs are also specifying Sandvik tools across the project.
Each Sandvik drill rig is producing 200 m3/h per rig to ensure the specified 2,000 m3/rig production in each 10 hour shift. Drilling to 15m depths, each hole takes an average 20 minutes depending on the rock conditions.
Kolín Construction
Kolín Construction has been using Sandvik rigs since 1999 and today has a fleet of seven rigs - one Ranger 600; 2 x DX680, 3 x DX700 and its latest DX800.

Clearing the dam abutement

The company was founded in 1977 and has since established itself as leading contractor in Turkey with a turnover in excess of $US 400 million.
It has completed almost 80 major projects across Turkey and is currently working on 28 other projects including motorways, roads, railroads, housing, industrial plant, irrigation and dam projects, airports and military installations.
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 2,200 rpm. The rig offers 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.
Dynamic Robbins TBM will adapt mid-bore - TunnelTalk, Feb 2009

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