Record for Microtunnelling with Amiblu GRP jacking pipes

Publicerad: 25 augusti, 2021

It was announced recently that the longest pipe jacked drive ever undertaken using GRP pipes has been successfully completed on a microtunnelling project as part of the 3rd lot of the Collettore della Crescenza - Isola Farnese for a sewer pipe installation. 

Microtunnelling on the ‘Collettore della Crescenza 3° lotto - Isola Farnese’, is the third phase of an environmental remediation project of the Fosso della Crescenza, one of the watercourses present in an area north of Rome that is of historical and natural value. The area has been protected since the end of the 90s with the establishment of the Regional Natural Park of Veio. 

The first two phases of the project were completed for the Municipality of Rome between 2009 and 2013, with approximately 1.3 km of DN2000 and 2 km of DN1600 CC GRP jacking pipes being installed using the microtunnelling technique, in addition to 1.2 km of diameters from DN1400 to DN2000, which were installed using traditional open trench techniques. 

Phase 3 was the most technically demanding and ACEA Elabori engineers specified Amiblu’s CC GRP DN2000 jacking pipes with the Phase being divided into six sections totalling in excess of 5.3 km. 

Contractors Impresa Mario Cipriani S.r.l. and ICOP S.p.A., faced technical challenges to deliver this project including depths of over 60 m and with four of the jacking drives being longer than 1 km (including one which was a curved drive), groundwater levels up to 30 m from the pipes’ invert and extremely cohesive clay ground conditions. 

Stainless steel PN 6 couplings were used for the pipe joints, which are able to withstand 6 bar and 3 bar of internal and external pressure, respectively. 

ACEA engineers requested special external pressure tightness tests for the couplings, which were carried out at the Amiblu Tech Centre in Norway, where the joints were successfully tested at
6 bar for 24 hours. 

Additional sealing systems (‘ACTIVE SEAL’) were designed for the intermediate jacking stations (IJS) to counteract the external pressure due to the ground water. 

Special checks with finite element calculations were carried out for the sizing of the IJS as well as the pipe clamp used to hold installed pipe in place to avoid movement whilst installing follow-on pipes to avoid the pipeline being pushed back by the force of the groundwater. 

For this project Amiblu supplied pipes with an external diameter of 2,047 mm, in 6 m lengths and stiffness classes SN50,000 and SN80,000 N/m2 (with wall thickness of just 75 mm and 85 mm, respectively). The maximum allowed jacking force was around 10,000 kN, which maintained a factor of safety of 3.5. 

The extremely smooth and non-porous external surface of the centrifugal cast GRP pipes made it possible to tackle unexpected, extremely cohesive clayey soils, reducing the jacking forces to the minimum possible. 

The project is currently underway and the first pipe jacked section of 1,235 m has been successfully completed, which is believed to be the longest drive ever made in the world with GRP pipes. 

The project is expected to be completed by 2022 at a cost of €32.5 million. 

Trenchless Works issue 179 July