Chinese gripper TBM sets pace in Lebanon 11 May 2017

On 5 May 2017, a CREG 3.5m diameter gripper TBM made its first breakthrough on Tunnel Drive 3 of the Greater Beirut Water Supply Project which is scheduled to be operable from 2019 and supply drinkable water to 1.6 million people in the region.

TBM breakthrough in Lebanon

A celebration was attended by representatives from the Council for Development and Reconstruction, contractor CMC di Ravenna, the local authorities, CREG and all project partners.

This World Bank financed project involves the construction of 24km of tunnels and transfer pipes. The contract was awarded to Italian CMC di Ravenna by the Council for Development and Reconstruction, Beirut (Lebanon) in 2014. The project is divided into two parts: tunnels in the hill area and underground pipelines in the urban area. The tunnels (called Drives 1, 2 and 3) will be excavated by two gripper type hard rock TBMs ordered in 2015 from CREG that will mine through rock strengths of between 50-170MPa.

The first TBM is to bore Tunnel Drive 3 (4.13km) and then transfer to bore Tunnel Drive 1 (8.10km) while the second is to bore Tunnel Drive 2 (10.37km). The TBMs are designed to manage the local geology which consists of moderately weathered limestone, dolomitic limestone and dolomitite. The cutter heads are equipped with 17-inch back loading Wirth disc cutters, which allow safe cutter head maintenance. The TBMs are also fitted with a probe drilling system and a grouting system for pre-excavation consolidation grouting. A short cutter head shield allows initial support close to the tunnel face and the TBMs main shield and back-up systems are also tailored to accommodate many complicated operations in the limited TBM space.

Path taken by the TBM

The first TBM was launched in August 2016 at Quardaniyeh Outlet Portal. Faults and high fractured rock were encountered during the tunneling of Drive 3, which slowed excavation and required the use of supports like mesh and ring beams to avoid the risk of falling rock. An inclination of 4.97% for Tunnel Drive 3 alignment allowed the TBM to pass under an existing valley. Despite difficulties, the average overall rate of the first TBM was 18m/day, with a maximum daily rate of 48.22 m/day. The monthly rate was 894.8 m/month with 98.63% machine availability. These impressive records were attributed to the quality of the machine and the joint efforts and close co-operation between the teams of CMC di Ravenna and CREG.

The second TBM was launched on 11 September 2016, and has covered over 4.5km in Tunnel Drive 2 with minimum radius curves of 300m in the initial stage, and sound conditions.

The performance of the TBMs was highly praised at the breakthrough ceremony by Paolo Mauri, Area Manager of Middle East of CMC di Ravenna. “We have reached a good record - more than 48m daily rate, which is better than we expected. It is definitely a good machine and the assistance from engineers at CREG has added value and given great results.”

Established in 1901, CMC di Ravenna is a leading Italian construction company that has been operating in International markets for more than 40 years.