Cli­ent: Stutt­gar­ter Stra­ßen­bah­nen AG
Pro­ject aut­hor: PSP Con­sul­ting Engi­neers GmbH, Munich
Con­s­truc­tion work: Roofing U12 3.TA Hall­schlag — Aubrü­cke
Part­ners: Leon­hard Weiss GmbH & Co. KG | Bauer Spe­zi­al­tief­bau GmbH | AUGUST REINERS Bau­un­ter­neh­mung GmbH
Tech. Manage­ment: Leon­hard Weiss GmbH & Co KG
Com­mer­cial manage­ment: AUGUST REINERS Bau­un­ter­neh­mung GmbH
Object: Light rail line Stutt­gart U12 3rd sec­tion Hall­schlag — Aubrü­cke
Period: 2013 to 2017

The 3rd sec­tion of the U12 light rail line com­pri­ses the rea­lignment of the sec­tion from Hall­schlag to the Aubrü­cke bridge. It beg­ins directly after the Hall­schlag stop (tran­si­tion from the 2nd sec­tion to the 3rd sec­tion) and initi­ally runs along Löwen­tor­straße, pas­ses under the freight bypass and ends at the sou­thern abut­ment of the Aubrü­cke bridge where it joins the exis­ting net­work. The sub­soil has a rapidly chan­ging and very varied struc­ture: The first few meters con­sist of arti­fi­cial fill ever­y­where, fol­lo­wed by locally hete­ro­ge­neous silt/sand mix­tures. In the area of the old “Klei­nes Feldle” land­fill, there was also a clay pit whose fill (at least 15 m thick) con­sis­ted lar­gely of excava­ted buil­ding pit mate­rial, quarry spoil, buil­ding rub­ble and waste. Adja­cent to the clay pit to the north-east was a quarry where tra­ver­tine was quar­ried in the past. The back­fill of the quarry also con­sists mainly of over­bur­den material. 

The 200 m long tun­nel sec­tion was built using the mining method. The dou­ble-track stan­dard cross-sec­tion has a clear width of 9.20 m and a clear height of 7.43 m. The inner shell of water­proof con­crete is also 40 cm thick. The mined tun­nel was excava­ted from an open excava­tion pit in the area of the nor­t­hern tun­nel sec­tion, ascen­ding in a sou­t­herly direc­tion. The stop was pro­tec­ted by a bored pile wall. In the course of the drive, the rail­road embank­ment of the DB line 4720 Unter­türk­heim — Korn­west­heim was crossed under­neath with an over­bur­den of 8.00 — 10.00 meters. Fur­ther­more, the entire mined tun­nel was built using a clo­sed con­s­truc­tion method with a vaul­ted cross-section. 

Dri­ving and sup­port were also car­ried out using the shot­crete con­s­truc­tion method; the drive was car­ried out in par­tial cross-sec­tions as an elm tun­nel drive. The main sup­port ele­ments were rein­forced shot­crete and steel sup­port arches; in addi­tion, due to the rela­tively unfa­vorable ground con­di­ti­ons, spi­les and pipe umbrel­las were used as advance sup­port. In addi­tion, the face was secu­red using shot­crete and face anchors. In the area of the stop wall, a pipe umbrella was inser­ted from the excava­tion pit, and a Car­in­thian cover was instal­led in the area of the cut-through wall. 

TECHNICAL DATA
Struc­tu­ral func­tion: Under­ground tun­nel
Tun­nel length: 200 m
Excava­tion volume: 15,400 m³
Con­s­truc­tion method: Shot­crete con­s­truc­tion method (excava­tor drive)
Tun­nel sup­port: pipe umbrel­las, anchors, sup­port arches, shot­crete
Spe­cial fea­tures: Elm tun­nel drive in seve­ral par­tial windows