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Linear shoring used in major Munich project

Unbeatable performance spectrum

In order to reduce the load on the existing sewer system in Pasing and Laim, a new 2.2-kilometer long, 3-meter diameter sewer was installed in Landsberger Strasse. It was built using the pipe jacking method by Wayss & Freytag Ingenieurbau AG, tunnel construction division, under a contract from the Munich municipal drainage department. After completion of the jacking work, 19 access shafts and three transfer structures were built to connect the existing sewer and the new one. To secure the excavations, the contractor opted for e+s linear shoring – a slide rail system with support frame – which thanks to its technological performance parameters was able to meet all the requirements on site.

Practical alternative

Compared with driving or vibrating sheet piles, the installation of linear shoring causes much less vibration in the surrounding area. Inner and outer shoring panels are held in vertically installed double slide rails in such a way that they can slide past each other and be brought to the required depth. Two rigid boogie cars, height-adjustable to match the increasing depth of the excavation, keep the beams and shoring panels the same distance apart at all times; the trench width stays the same at all stages of the project.

Stepping up to the challenge

In the longitudinal direction of the new sewer, it was possible to install the elements of the shoring system at the far end of the pipe using 9.13-meter-long beams extending down to the bottom of the excavation. At the other end, the 7.13-meter long beams and the shoring panel ended directly on the jacking pipe – as did the shoring on the head ends, which likewise could only be installed as far as the top of the jacking pipes. In order to secure the remaining working space – the approx. 2.70 meter high area next to the pipe string extending down to the trench bottom – the construction partners decided to install sheet piles behind the shoring down to the pipe and next to the shoring down to the pit bottom. In order to secure this structure, two end shoring adapters were integrated into the linear shoring system in addition to the two boogie cars. Like the boogie cars, the end shoring adapters are guided in the profile of the linear shoring beams, can be adjusted in height at any time and are flush with the head edge of the shoring system. A temporary support between the pipe and the lateral shoring wall secured the sheet piles during this phase of the project and was removed again after concreting a 25-centimeter-thick subbase.

thyssenkrupp Infrastructure
After pipe jacking had been completed, the access shafts and transfer structures were built at a depth of around nine meters. To secure the combination of shoring system and piles behind it to meet structural requirements, two end shoring adapters were integrated into the linear shoring system in addition to the two boogie cars.
A particular advantage in inner-city areas: With linear shoring, the ground outside the trench remains largely unaffected, and buildings and traffic flow are not impaired. With stepped linear shoring, these advantages can also be utilized for work at greater depths.
A particular advantage in inner-city areas: With linear shoring, the ground outside the trench remains largely unaffected, and buildings and traffic flow are not impaired. With stepped linear shoring, these advantages can also be utilized for work at greater depths.
Wayss & Freytag Ingenieurbau AG
The shoring elements are placed in the trench and gradually pressed into the ground by the excavator while the soil is removed.
Wayss & Freytag Ingenieurbau AG
In linear shoring, the opposite rails are not connected to each other by articulated struts but are kept the desired distance apart by a rigid, width-adjustable boogie car.
thyssenkrupp Infrastructure
Four by four meters in size and around nine meters deep: Rigid boogie cars, height-adjustable to match the increasing depth of the excavation, keep the beams and shoring panels the same distance apart at all times; the trench width stays the same at all stages of the project.
thyssenkrupp Infrastructure
Inner and outer shoring panels are held in vertically installed rails in such a way that they can slide past each other.