Geomechanik und Tunnelbau最新文献

In Stockholm, Implenia builds of one of the world's deepest metro stations. This new metro station is an extension of the Blue Line to Södermalm. Beside the station single-track tunnels for the subway, lift shafts, and a collateral service tunnel are constructed. Due to the difficult geological conditions and the bad quality rock, the AT – Pipe Umbrella System with squeeze connections were used to reinforce excavations and bolster safety during construction (photo: DSI Underground).

Nowadays, both process data management and numerical analysis are necessary for decision-making in a tunnel project from its early design stage to the construction phase. Traditional generation of simulation models largely depends on tunnel design and reports, which are error prone due to the involvement of manual intervention. This article presents the application of a digital workflow to efficiently transfer automatically acquired data from tunnel projects to computational simulations. The application workflow is developed and executed through a web-based environment. Project data from the Victory Boogie Woogie tunnel is retrieved from the process controlling software PROCON via web services to generate numerical simulations for settlement predictions at different tunnel sections. The simulated results are validated using real measured settlements in the project to prove the quality of the simulation model. Different scenarios of applying operational steering parameters are then investigated, utilising the simulation model, which can be used to support the on-site engineers as an assistance system to drive the tunnel boring machines. The work has been carried out within the framework of the transfer project T2 of the Collaborative Research Center “Interaction Modeling in Mechanized Tunneling” (SFB 837), which aims to implement and test a digital twin for process control under practical conditions in the tunnelling industry.

The 420 MW Cetin Dam Project in Turkey was subject to severe setbacks, including substantial geotechnical problems. Since 2011, several concessionaires, contractors and designers were involved. In June 2016, a major failure occurred at a high cut slope of the right bank (RB) valley flank. In 2017, contractor Limak took over the project with a US$ 600 mio concession contract. To secure the contractual agreement for state-guaranteed energy remuneration, Cetin Dam and hydro hydroelectric power plant (HEPP) had to be operative in 2020. Missing the time target would have implied high economic losses for the concessionaire, and this set-in-stone deadline imposed extraordinary pressure for developing fast and reliable solutions. Worryingly, progressing failure became evident at the failed RB cut slope, while rehabilitation works were ongoing. In late December 2017, shortly after a review of geotechnical conditions and slope design for the troubled RB slope had started, also parts of the left bank (LB) cut slope failed below crest level and threatened to grow into a global slope failure. With only 26 months’ time left for starting energy production, the slope instabilities jeopardised the economic success of the entire project. Within a 3-month emergency mission for both RB and LB slopes, a dedicated team succeeded in understanding the geotechnical problems, planning and implementing immediate mitigation measures, and developing design solutions. Operation of Cetin Dam and HEPP commenced in 2020.

For recent hydroelectric pumped storage projects, the construction of embankment dam structures on alluvial deposits consisting of exceptionally soft soil and in areas with high seismicity was required. This contribution shares experiences and challenges from the static and seismic design of embankment dam structures and ground treatment options. Finite element-based static and seismic analyses using the Hardening Soil Small Strain model (HSS) showed that preconsolidation has clear benefits compared to stone columns for ground improvement purposes. Regardless of general advantages of surface sealing systems for frequent and rapid impoundment level changes, it was found that clay core design options perform very well under seismic loading conditions and even better than surface-sealed structures. Seismic ground and structure response analyses involving soft soil considering shear strain-dependent stiffness degradation revealed that deamplification is expected in contrast to the rule-of-thumb amplification approaches enshrined in many seismic design guidelines and codes. It was found that this effect increases with seismic magnitudes and that saturation of peak ground acceleration (PGA) takes place. This results in relatively moderate structure excitations even under significant dynamic excitation.

Lining stress controllers (LSC) have been developed as special supporting measure for tunnelling in zones with stress-induced failure involving large ground volumes and large deformations. The shotcrete lining is divided into several segments by longitudinal construction joints. The purpose of this segmentation is to absorb large deformations occurring during tunnel driving in weak ground. LSC elements are installed into these deformation joints. These elements have a defined workload during compression so the primary lining is not damaged (Source: DSI Underground).