Subsurface Investigation: The geotechnical engineer conducts detailed site investigations to understand the soil, rock, and groundwater conditions at the proposed metro route. This includes drilling boreholes, collecting soil samples, and performing geophysical surveys.
Soil Characterization: They analyze the soil properties, such as shear strength, compressibility, permeability, and consolidation, to determine how these factors might affect tunneling and construction.
Geological Mapping: The engineer assesses the geological profile of the area, identifying fault lines, rock types, groundwater levels, and any potential hazards that may impact the underground construction.
2. Tunnel Design Support:
Ground Behavior Modeling: The geotechnical engineer provides input on the expected behavior of the ground during tunneling. They use advanced software and models to simulate how the soil or rock will react to excavation and construction activities.
Tunnel Lining Design: Based on the findings from site investigations, they assist in the design of tunnel linings and support systems to ensure the tunnel remains stable under varying ground conditions (e. g. , loose soils, hard rock).
Selection of Tunneling Method: The geotechnical engineer recommends the most suitable tunneling method based on subsurface conditions. Options include tunnel boring machines (TBM), cut-and-cover techniques, or drill-and-blast methods, depending on the soil or rock encountered.
3. Groundwater Management:
Groundwater Flow Analysis: In underground metro projects, groundwater can pose significant challenges. The geotechnical engineer assesses the presence of groundwater and the potential for water ingress during excavation and construction.
Dewatering Plans: The engineer develops dewatering strategies to manage groundwater levels, such as the installation of pumps and drainage systems to control water flow and avoid flooding the construction site.
Waterproofing Solutions: They also design waterproofing systems for tunnels and stations to prevent water infiltration that could damage structures or disrupt operations.
4. Risk Assessment and Mitigation:
Settlement Analysis: The geotechnical engineer evaluates the potential for ground settlement caused by tunnel excavation or underground construction. They assess whether nearby structures, roads, or buildings may be impacted by settlement or ground movement.
Ground Stability and Safety: They identify potential geotechnical risks, such as the risk of landslides, soil liquefaction, or tunnel collapse, and recommend mitigation measures to enhance ground stability during and after construction.
Earthquake Resistance: For areas prone to seismic activity, the geotechnical engineer assesses how the tunnel and station structures will react to earthquakes and recommends seismic-resistant design features.
5. Foundation and Support Systems:
Station Foundations: The geotechnical engineer designs foundations for underground metro stations, ensuring they can support the weight and forces from the station structure and the trains operating within it.
Ground Improvement: In some cases, they may recommend ground improvement techniques, such as soil stabilization or grouting, to enhance the strength of weak or loose soils before tunneling or station construction.
Shoring and Support Systems: During construction, the engineer designs temporary shoring or support systems to stabilize excavated areas, especially in deep trenches or when tunneling in challenging ground conditions.
6. Monitoring During Construction:
Ground Movement Monitoring: The geotechnical engineer monitors ground movements during tunneling and construction using instruments like inclinometers, settlement markers, and strain gauges. They track any deformation, settlement, or tilting of nearby structures to ensure safety.
Instrumentation and Data Collection: The engineer sets up instrumentation to collect data on ground conditions, tunnel behavior, and groundwater levels throughout the construction phase. This helps detect early signs of potential issues and adjust construction methods accordingly.
7. Collaboration with Other Engineering Disciplines:
Coordination with Structural and Civil Engineers: The geotechnical engineer works closely with structural engineers to integrate the geotechnical data into the overall design of the metro system, including tunnel linings, foundations, and support systems for stations.
Collaboration with Contractors: They collaborate with construction teams to ensure that the geotechnical recommendations are implemented correctly during excavation, tunneling, and station construction.
Regulatory Compliance: They ensure that all geotechnical activities comply with local and national regulations regarding underground construction, safety, and environmental standards.
8. Environmental Considerations:
Environmental Impact Assessment (EIA): The geotechnical engineer contributes to the EIA by evaluating the potential environmental impacts of underground construction, such as disruption to groundwater flow, contamination risks, or land subsidence.
Sustainability Practices: They incorporate sustainable practices, such as minimizing the use of chemicals for ground stabilization or designing the project to reduce long-term environmental impacts on the surrounding area.
9. Post-Construction Monitoring:
Long-Term Monitoring: After construction, the geotechnical engineer may be involved in the long-term monitoring of the underground metro system. This includes assessing the structural integrity of tunnels and stations, monitoring ground movement, and ensuring that groundwater management systems continue to function effectively.
Maintenance and Inspection: They may also help develop maintenance plans to regularly inspect tunnel linings, station foundations, and other geotechnical elements to ensure the continued safety and longevity of the metro system.