FASEB Journal

AbstractIn tunneling and underground projects, the drill‐and‐blast method is most commonly utilized for rock excavation. It is notable for cost‐effectiveness and versatility in achieving different tunnel profiles. Though the technique has advantages, it also has challenges such as overbreak, undercut, and occasional poor advances, which can increase project costs and delays. The outcome of blast results is also associated with the competency of driller in effectively drilling the planned holes. Hence, frequent and substantial modifications in the blast designs to attain good profile and pull can adversely affect the driller's performance, thereby reducing the desired outcome. This article presents a case study of the Sivok‐Rangpo tunnels passing through different classes of rock mass (class III–VI). Minimum changes in cut pattern and periphery holes design were incorporated and found efficient in increasing the tunnel advance rate to 90–92 % of the drill hole length. The processes also reduced the overbreak and underbreak considerably.

AbstractThe Melo dam hydroelectric power plant in Nokia, Finland, was built between 1968 and 1971. The dam structure consists of a turbine hall on the right bank of the Kokemäenjoki river and a 120 m long earth dam adjacent to it. The earth dam was constructed with layers of moraine, gravel and rock fill. Over the years, seepage issues emerged, including a sinkhole in 2005, leading to temporary repairs. However, in 2019, a comprehensive renovation plan was initiated to develop a permanent solution. In 2022, KFS Finland carried out construction work to restrain seepage and ensure dam stability. This involved building a drilled steel pile wall along the entire length of the dam, using RD500 steel pipes drilled into the bedrock, reaching a depth of 67 m from the surface. The completed structure is now the deepest drilled pile wall in Finland, ensuring the dam's structural integrity for decades to come.

AbstractThe transition to sustainable energy is crucial for addressing anthropogenic climate change, with green ammonia emerging as a key alternative to fossil fuels. Iverson eFuels AS is planning a green ammonia plant in Sauda, Norway, including a ca. 2800 m long pipeline tunnel to transport ammonia to a storage area at the fjord. This article elaborates on the early‐phase variant optimization of the tunnel design, conducted at a pre‐Front‐End Engineering Design (pre‐FEED) stage with limited ground data. Despite common concerns about time and effort, advanced 3D ground modeling and parametric modeling were employed due to the project‘s complex ground conditions and specific technical requirements. These digital tools enabled efficient and comprehensive design assessments, leading to a tunnel route that is optimized with respect to multiple different objectives. Furthermore, the advanced 3D modeling helped to heavily revise a more complicated previous longer pipeline tunnel that also included a valve pit. This case study highlights the benefits of using advanced modeling techniques early in the project lifecycle, demonstrating how they can enhance both the efficiency and quality of engineering solutions, even with limited initial data.

AbstractCurrently, comprehensive construction works are ongoing within the West Link Project in Gothenburg, whereby a railway tunnel is built below central Gothenburg, consisting of five construction lots including three underground stations. The purpose of the Centralen lot is to connect the commuter traffic to Nils Ericson terminal and to Gothenburg's Central Station by a new four‐track underground station with two platforms. Designed as an underground structure, the new station was built by NCC Infrastructure (NCC) as a cut‐and‐cover tunnel. As the ground consists only of very soft clay down to great depth, the design and construction of the underground station was particularly challenging. Additionally, the complexity of the site conditions is enhanced by limited space, adjacent buildings and existing infrastructure crossing the site. Swedish Transport Administration, Trafikverket (TrV) decided for an early contractor involvement (ECI) contract to overcome the challenges of the Centralen lot. In the first phase, a multidisciplinary project team defined the construction methods, logistical constraints, general design and set a target price. Wayss & Freytag Ingenieurbau AG (W&F) was appointed as a subcontractor for heavy special foundation works. The team developed a solution using diaphragm walls (D‐Walls) to create the excavation pit for the new station, which is up to 18 m deep and 50 m wide. S&C Consult GmbH (S&C) served as a consultant during the planning and construction phase and in the quality assurance of the D‐Walls. It should be emphasised that this was only the fifth D‐Wall project in Sweden. Thanks to the constructive and open cooperation of all parties, the work was successfully completed on schedule in July 2023.

AbstractThis report explores the challenges and innovative solutions associated with constructing deep foundations for high‐rise buildings in Scandinavia. The focus is on three projects: Lighthouse and Mindet 6 in Aarhus, Denmark and Karlatornet in Gothenburg, Sweden. Each project faces complex geotechnical conditions, requiring advanced engineering techniques. The report highlights the importance of early involvement in project planning, allowing for tailored solutions to geotechnical challenges. Per Aarsleff A/S employed value engineering techniques to optimize designs, ensuring both cost‐effectiveness and structural integrity. Test piles were crucial in validating foundation designs, offering real‐time data for precise calibration. The report emphasizes the important collaborative approach between engineers, clients, and other stakeholders, leading to innovative design solutions and successful project execution. The strategic use of advanced machinery, such as Aarsleff's Bauer BG55 drilling rig, underscores the technical prowess required for these projects. The report showcases how complex soil conditions and engineering hurdles were overcome through meticulous planning, technology, and continuous collaboration, setting a standard for high‐rise construction in challenging environments in Scandinavia.

AbstractThe article highlights the innovative engineering solutions for complex geological conditions within Stockholm's metro expansion project. Key technical methods included ground freezing in the Mårtensdal fault zone and the use of secant piles as deep retaining walls at Sofia station, set to become one of the world's deepest subway stations. For sub‐sea tunnelling at Ladugårdslandsviken, the observational method was utilized to mitigate risks of tunnel collapse and uncontrolled water ingress. Lessons learned provide invaluable insights to navigate complex geological and logistical challenges and advance civil engineering practices. The ground freezing method is highly effective for stabilizing ground but requires meticulous design, precise casing alignment, and thorough monitoring to maintain optimal temperature levels. Early risk assessments and detailed site investigations, sampling, and lab testing are crucial for reliable modelling and predicting challenges. Use of secant piles in challenging soil conditions can be successful but demands careful logistical planning and consideration of space constraints. On‐site adjustments, such as extending piles or modifying grouting techniques, may be necessary. Utilizing the observational method allows for real‐time monitoring and adaptive measures which can prevent delays and maintain safety. Using technology like FME software for 3D modelling with aggregated production data greatly improves productivity and risk mitigation strategies.

AbstractThe use of cavern thermal energy storage (CTES) systems offers a promising solution for the long‐term storage of thermal energy, especially excess heat from industrial processes, contributing to the reduction of CO2 emissions. In the case of Graz, the potential of this technology is examined with a focus on geological, hydrogeological, and rock mechanical criteria. Geological analyses identify solid rock formations, particularly carbonates and crystalline rocks in the western and north‐western areas of the city, as suitable storage sites. Challenges such as the distance to district heating networks and the risk of karst phenomena were considered, with the Karolinensteinbruch site being recommended as particularly suitable. Conceptual storage designs focus on modular and expandable geometries to adapt to the fluctuating urban energy demand. The results indicate that CTES is a feasible solution for Graz, although further investigations, such as detailed analyses of geotechnical and geological properties, are necessary to ensure its successful implementation.

AbstractMajor tunnelling projects, like the extension of corridors for railway lines or the construction of large underground research facilities, are flagships in the European civil engineering industry. In order to deal with matters of sustainability and material management, as much of the generated excavation material must be reused – preferably directly on the construction site to avoid CO2 emissions from long transport routes. While tools for quantifying the process‐relevant carbon footprint are already available in other industry sectors, there is still no generally recognized method in the civil engineering and tunnelling industry, as every construction site has its own unique requirements. To find the best utilization option with the lowest possible carbon footprint, a life cycle assessment (LCA) is conducted, where the whole process is divided into three steps: use of construction equipment, transport, and landfilling/recycling of the excavation material. Finally, a ‘reference scenario’ for each process is determined and compared with optimized scenarios to calculate the potential of saved emissions.