How can you manage ground settlement risks during underground construction?

1 Factors affecting ground settlement

Ground settlement can be influenced by various factors, such as soil properties, excavation depth and size, construction method and equipment, groundwater level and flow, and the surrounding environment. Common causes of ground settlement include soil consolidation, which is the gradual reduction of soil volume due to external loading; soil loss, which is the removal of soil particles from the excavation site; soil relaxation, which is the decrease of soil stress due to removal of overburden or lateral support during excavation; and soil swelling, which is the increase of soil volume due to absorption of water or chemical reactions. These processes can result in lateral or vertical displacement of the soil mass, collapse or subsidence of voids or cavities in the ground, and uplift or heave of the ground surface or excavation walls.

2 Methods and tools to measure and monitor ground settlement

To manage ground settlement risks, construction managers need to measure and monitor the ground movements and deformations during and after underground construction. Surveying, geotechnical instrumentation, and remote sensing are all methods and tools that can be used for this purpose. Surveying involves measuring horizontal and vertical positions and elevations of points on the ground surface or inside the excavation; geotechnical instrumentation involves using devices to measure soil pressure, strain, temperature, moisture, or vibration; and remote sensing involves capturing images or signals of the ground surface or structures using electromagnetic waves. All of these approaches can provide accurate and reliable data on ground settlement and displacement over time and space.

3 Best practices to prevent or reduce ground settlement impacts

To prevent or reduce the impacts of ground settlement, construction managers need to adopt best practices that can enhance the stability and integrity of the ground and the structures. These practices include site investigation, which involves collecting and analyzing information about the site conditions; construction method selection, which involves choosing the most suitable construction method for the project; ground improvement, which involves applying techniques to modify the soil properties; and structural protection, which involves installing measures to protect existing structures from damage or disruption. Site investigation can help to identify potential sources of ground settlement, while construction method selection can minimize ground disturbance. Ground improvement can increase ground resistance and resilience to settlement and deformation, and structural protection can support and secure existing structures.

4 Here’s what else to consider

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