The construction of the 51 km long Abwasserkanal Emscher (AKE) sewer tunnel is the largest individual project to improve the River Emscher in the Ruhr, Germany and is technically and financially one of the greatest challenges that the Emschergenossenschaft as client and their construction partners have ever had to overcome. Among the individual construction sections of the major project, construction section (BA) 40 is exceptional, not only because of its construction with segment lining.
For this approx. 10 km long section of the new sewer tunnel, which is being constructed as a twin parallel 2600 diameter tube system by the JV ARGE Emscher BA40, consisting of Porr Bau GmbH and Porr Deutschland GmbH, VMT GmbH supplied services including the navigation technology. The company already has 20 years of experience in the field: VMT navigation systems have been developed for various types of tunnelling machines and ensure that even kilometre long tunnels reach their target with great accuracy.
In addition, VMT also provided a system for a fire protection and rescue concept, which can cope with all coordination and safety requirements on the major construction site. A powerful communications and safety system ensures in every stage of construction that all affected people are in contact with each other and can be located and alarmed in working situations and in emergencies. The newly developed system solution SCoUT (Safety Coordination by Underground Tracking, formerly HADES) for the tracking and recording of people, vehicles and mobile equipment was used for the first time on this site.
Emscher Improvement costs 5.3 Billion Euros
It is a superlative project: the Emschergenossenschaft will invest a total of about 5.3 billion euros in the Emscher improvement over a period of about 30 years. About 2 billion euros have already been spent on this major project for works such as the extension of four treatment works, about 330 km of sewers and the natural restoration of about 120 km of streams and rivers.
The largest individual project in this improvement is the new construction of the 51 km long sewer tunnel from the wasrewater treatment plant at Dortmund-Deusen to the treatment plant “Emschermündung” in Dinslaken. About 35 000 sewer pipes in sizes from 1400 to 2800 Ø and more than 16 000 segment rings 2600 Ø will be installed for the new sewer, which runs at depths of 8 to 40 m with a fall of 1.5 ‰. In December 2013, work started on BA 40, which extends between the town boundary Bottrop/Oberhausen and the “Holtener Feld” in Oberhausen.
BA 40: Sewer Tunnel constructed of Segments
In contrast to the previous construction sections, this 10 km long section of two parallel tubes of the new sewer tunnel was not driven by classic pipe jacking but constructed of segments, in a process with each new 2600 Ø sewer ring consisting of six individual segments assembled directly in the tunnel boring machine. More than 108 000 rings were installed by the completion of the excavation works at BA 40 in June 2017. The successful breakthrough of the two tunnel boring machines was described by the Emschergenossenschaft as “one of the most important moments in the history of the Emscher improvement”.
Above all due to the long flow and dwell times of the wastewater and the resulting danger of corrosion, the segments consist of acid-resistant concrete; in addition, the segments were provided with a polymer concrete lining near the shafts as a sealing protection layer.
The EPB shield machines from Herrenknecht built the two parallel runs in a slightly displaced arrangement. In an EPB machine, the excavated earth paste serves as a plastic support medium, which enables the necessary balancing of pressures at the face, prevents uncontrolled penetration of the ground into the machine and creates the preconditions for rapid tunnelling with minimal settlement. A screw conveyor transports the excavated material from the floor of the excavation chamber to a conveyor belt, with the relationship of the pumping rate of the screw conveyor and the advance rate being used to ensure precise control of the support pressure of the earth paste. Earth pressure sensors in the excavation chamber are used to continuously monitor this state of equilibrium.
Ten shafts and four connecting shafts with diaphragm wall support were required for the driving of the two tunnels in BA 40. These excavations have diameters of up to 20 m and depths of up to 40 m.
Challenging Safety Concept
In addition to the small diameter and the very tight curve radii in places, the installations (mainly smoke barriers) and shaft openings are technical challenges on the project. In particular the very stringent requirements for the fire protection and rescue concept pose a difficult task for the project parties, and a solution was commissioned from the company VMT GmbH, one of the leading providers of surveying systems and services in tunnelling and in industrial surveying. “This was to include the installation of a personnel tracking system in order to make possible the specified rescue times provided by the local emergency services”, explains Dipl.-Ing. (FH) Nadine Fenrich, Senior Engineer with VMT GmbH. “What was needed was a modern, modular communications and safety system, which would be flexible enough to network the entire construction site and which could be adapted to comply with the latest fire protection and rescue concept as the project progressed.” With solutions for personal tracking in real time, remote control of smoke bulkheads and an intelligent, priority-oriented alarm system, the company delivered technology to fulfil a key function during the construction period. In case of incidents or rescue interventions, this ensures an extensive overview at the intervention centre and also complies with the requirements of emergency services such as fire service or mine rescue.
SCoUT Personal Tracking System
„The modules used combine the latest technology with proven techniques from rescue interventions. All components are designed to cope with all intervention conditions and maintain their full function, even when wearing breathing apparatus and carrying heavy equipment“, explains VMT managing director Dipl.-Ing. (FH) Manfred Messing, who also points out that the SCoUT personal tracking system was used successfully for the first time on the Emscher project. The system solution consists of software, the SCoUT Control Center, receiver and transmitter hardware and tracking transponders, which are adapted to suit each individual project. Using tracking transponders, which are carried by everyone, the system continuously and reliably localises and identifies all the people in the tunnel, even those in trains. In the control centre, all people are shown with their current positions to an accuracy of metres (1–3 m). „Under the already described conditions, this was a real challenge,” agree both Messing and Fenrich. In case of an emergency, the information displayed in the SCoUT Control Center enables the emergency services management to make rapid and well-founded decisions. Rescue measures can be started according to the current situation ands efficiently coordinated: for example, rescue teams can be directed straight to the location of an accident without delay or people can be guided from the danger zone to the nearest separated area.
Intelligent Control of Alarming & Smoke Bulkheads
In addition to personal tracking, further modules of the VMT product control smoke bulkheads and provide intelligent, priority-oriented alarming. The control of smoke bulkheads enables their operation to prevent propagation of smoke in case of a fire through the visualisation software, both in the tunnel and from the control centre. Since the bulkheads can be opened and closed again, taking into account the position of the train, the risk of smoke gas poisoning is minimised. With the intelligent alarm system, alarms raised by emergency calls or the automatic fire detection system can be automatically and reliably forwarded to the responsible people by voice or text messages. All the modules enable the quickest possible action in case of an emergency and lead to improved safety in the working environment.