Partial Face Excavation Machines:
Excavation above the groundwater level.
Herrenknecht shields with partial face excavation can achieve remarkable advances in the most diverse geological conditions and for a wide range of different tunnel profiles. The same basic equipment can be fitted with both excavators and roadheaders. Both of the classic types of excavation (section and tube excavation) are possible.
Hofoldinger Stollen, Munich, Germany
The renewal of the old feeder lines from Mangfall Valley, which date back more than 120 years, is one of the most pressing tasks for Munich municipal works. Investments into securing the fresh water supply of Bavaria’s capital exceed 180 million Euro. The mixed geological conditions and the high compressive strength of the conglomerate (up to 60MPa) as well as boulders of up to 70cm in diameter lead to the decision to use a Herrenknecht machine with partial face excavation with roadheader. Subsequent lining of the steel tubes with cement mortar create additional hygiene and corrosion protection. The spaces between the outside edge of the lining and the mounting as well as the circular space around the steel tube are filled with special mortar.
Sewage tunnel, Offenburg, Germany
The demanding second out of three excavations in Offenburg requires extreme caution: the tunnel has to be driven just 3.5m underneath the Church of the Holy Trinity in Offenburg in the south of Germany. To avoid the two spires from tilting, the excavation is preceded by extensive geological investigations. The solution is a Herrenknecht partial face excavation machine to excavate the mixed water pipe using Pipe Jacking technology. To avoid ground settlement, a betonite suspension supports the so-called intersection (the excavation diameter is slightly larger than the pipe diameter) directly behind the shield. On 23rd June 2006, the machine reaches the second milestone after 405m and with a deviation of less than one centimeter, without having damaged the church. The work is completed at the end of 2006.
