A Wirth TBM broke through marking the completion of 8km of boring on the Ermenek hydropower scheme in Turkey (T&TI, October 2004, p8) after nearly two years of tunnelling on 2 April.
A civils group comprising local firm BM Mühendislik ve Insaat with Alpine Mayreder Bau GmbH and Verbundplan from Austria had been using the TBM to drive the 6.7m excavated diameter pressure tunnel connection to a surface powerhouse. The TBM had to negotiate limestone and claystone with a compressive strength of up to 150MPa and a number of fault zones.
Alpine Mayreder selected Wirth to provide a complete TBM package including the entire backup installation. The open gripper TBM was equipped with an expendable cutter head jacket in case of squeezing ground, as well as two rockbolting units and a ring beam erector. Probe drilling as required, was facilitated from the rear of the machine. The backup allows for robot shotcrete application over a 320? arc and the placing of concrete invert segments of 40? arc to close the circumference.
The machine was launched from a 520m long access tunnel at the end of July 2003. Crews quickly overcame any learning curve and advances of 62m per day, 316m per week and 1,004m per month were achieved at their peak.
Once commissioned, water will flow through the tunnel at 778m3/sec with the power plant rated to an installed capacity of 302.4MW
