Micro-tunnelling at 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 of historical and naturalistic value, protected since the end of the 90s with the establishment of the Regional Natural Park of Veio.
The first two phases were completed for the Municipality of Rome between 2009 and 2013, with approximately 1.3 kilometres of DN2000 and 2 kilometres of DN1600 CC GRP jacking pipes installed with the micro-tunnelling technique, in addition to 1.2 kilometres of diameters from DN1400 to DN2000, installed with the traditional open trench technique.
Phase 3 was the most technically demanding, ACEA Elabori engineers specified Amiblu’s CC GRP DN2000 jacking pipes 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: with depths of over 60 meters and four of the jacking drives were longer than 1 kilometre (one of which being a curved drive), groundwater level up to 30 meters from the pipes’ invert and extremely cohesive clays.
Stainless steel couplings PN 6 are used for the joints, to withstand 6 bar and 3 bar of internal and external pressure, respectively.
ACEA engineers requested special external pressure tightness tests for the couplings, 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 thrust force of the groundwater.
For this project Amiblu supplied pipes with an external diameter De2,047mm, in 6 metre lengths and stiffness classes SN50,000 and SN80,000 N/m2 (with wall thickness of just 75mm and 85mm, respectively), maximum allowed jacking force circa 10,000 kN, 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 jacking section of 1,235 meters has been successfully completed, the longest drive ever made in the world with GRP pipes.
Country/City- Italy / Rome
Year of construction – 2020-2022
Contracting Authority – ACEA ATO 2
Contractors – Mario Cipriani – I.CO.P. S.p.A.
Designer – ACEA Elabori
Amount of the contract – € 32.5 million
Total length – 5.320 m
Installation technique – Microtunnelling
Pipes – CC GRP Amiblu Hobas jacking pipes, DN 2000 (DE 2.047), PN 1, stiffness SN 50.000-80.000, length 6 m
Joints – Stainless steel couplings PN 6, 3 bar external pressure tightness
Application – Sewer
Highlights of the projects – The longest jacking drive ever made with GRP pipes (1,235 m), laying depth of over 60 meters, ground water level up to 30 meters, presence of highly cohesive clays.