What are the best methods to reduce the risk of slope instability for subsea structures?

1 Site investigation

Before designing and installing any subsea structure, you need to conduct a thorough site investigation to understand the seabed conditions, such as soil properties, bathymetry, and seismicity. You can use various tools and techniques, such as geophysical surveys, boreholes, cone penetration tests, and laboratory tests, to collect and analyze the data. Site investigation can help you identify the potential triggers and mechanisms of slope instability, such as earthquakes, gas hydrates, erosion, and pore pressure.

2 Slope stability analysis

Based on the site investigation data, you can perform a slope stability analysis to assess the factor of safety (FOS) of the subsea slope under different loading scenarios. You can use analytical or numerical methods, such as limit equilibrium, finite element, or finite difference, to model the slope behavior and evaluate the critical slip surfaces and failure modes. Slope stability analysis can help you determine the design parameters and criteria for the subsea structures, such as slope angle, embedment depth, and anchoring system.

3 Geohazard mitigation

If the slope stability analysis indicates a high risk of slope instability, you can implement geohazard mitigation measures to enhance the slope stability and protect the subsea structures. These measures include grading the slope geometry to reduce driving forces and increase resisting forces, installing drainage systems to reduce pore pressure and increase effective stress, adding structural elements such as piles, anchors, or geosynthetics to increase shear strength and cohesion of the soil, and covering the slope surface with materials such as riprap, concrete, or mattresses to prevent erosion and scour.

4 Monitoring and maintenance

After installing the subsea structures, you need to monitor and maintain them regularly to ensure their integrity and performance. You can use various sensors and instruments, such as inclinometers, piezometers, strain gauges, and acoustic devices, to measure and record the slope movements, pressures, stresses, and deformations. You can also use remote or manned vehicles, such as ROVs or AUVs, to inspect and repair the subsea structures. Monitoring and maintenance can help you detect and respond to any signs of slope instability or damage in a timely manner.

5 Risk management

Finally, you need to adopt a risk management approach to deal with the uncertainty and complexity of slope instability for subsea structures. You can use various tools and methods, such as hazard identification, risk assessment, risk mitigation, risk communication, and contingency planning, to identify, analyze, evaluate, and control the risks associated with slope instability. Risk management can help you improve the reliability and resilience of the subsea systems and reduce the potential impacts and costs of slope instability.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?