How can you account for seismic loads in retaining wall design?

2 Seismic load calculation

Once you have the seismic design criteria, you can calculate the seismic load on the retaining wall. There are different methods to do this, depending on the type and complexity of the wall and the soil. One common method is the pseudo-static approach, which assumes that the seismic load is equivalent to a constant horizontal force acting on the wall and the soil behind it. The magnitude of this force is proportional to the weight of the wall and the soil, and the seismic coefficient, which is a factor that depends on the seismic hazard level and the soil properties. Another method is the dynamic approach, which considers the actual time-varying forces and motions of the wall and the soil during an earthquake. This method requires more advanced analysis and software, but it can capture more realistic effects and interactions.

3 Seismic stability analysis

After you calculate the seismic load on the retaining wall, you need to check the seismic stability of the wall. This means verifying that the wall can resist the seismic load without failing or exceeding the performance objectives. There are two main aspects of seismic stability: sliding and overturning. Sliding occurs when the horizontal force exceeds the frictional resistance between the wall and the base. Overturning occurs when the horizontal force creates a rotational moment that exceeds the restoring moment of the wall. To prevent sliding and overturning, you need to design the wall with adequate dimensions, reinforcement, anchorage, or counterweights.

4 Seismic deformation analysis

In addition to checking the seismic stability of the retaining wall, you also need to estimate the seismic deformation of the wall. This means predicting how much the wall will move or crack under the seismic load. Seismic deformation can affect the functionality and appearance of the wall and the adjacent structures. There are different methods to estimate seismic deformation, depending on the type and complexity of the wall and the soil. One common method is the displacement-based approach, which uses empirical formulas or charts to relate the seismic displacement to the seismic coefficient, the wall height, and the soil stiffness. Another method is the performance-based approach, which uses numerical models or tests to simulate the seismic behavior of the wall and the soil.

5 Seismic detailing and construction

The final step in accounting for seismic loads in retaining wall design is to ensure proper seismic detailing and construction, which includes applying principles and practices that enhance the strength, ductility, and durability of the wall. Adequate reinforcement should be used at corners, joints, and openings of the wall to prevent cracking and spalling. Additionally, sufficient concrete cover and corrosion protection should be provided for the reinforcement to prevent deterioration. Appropriate materials and mixtures should also be used for the concrete to ensure adequate compressive and tensile strength and strain capacity. Furthermore, specifications and standards should be followed for the fabrication, transportation, placement, curing, and testing of the concrete to ensure quality and consistency. Lastly, inspection and monitoring of the wall and soil should be done during and after construction to detect any defects or damages.

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?