Seismic Design in Geotechnical Engineering

Seismic design is a critical component of geotechnical engineering, particularly in seismically active regions such as British Columbia. It focuses on how soil and rock respond to earthquake-induced ground motion and how these responses influence the stability and performance of foundations, slopes, and retaining structures.

DMC provides the following services:

• Seismic Hazard Interpretation: We work with the NRCan seismic hazard model to determine design response spectra at a site. We determine the hazard based on the Site Class or the Vs30 at the site or interpret a PSHA if the client can provide a site-specific report
• Ground Motion Development: Once the target spectra has been determined, we can scale the motion to the spectra over the period range of interest. DMC can either undertake linear scaling (using the PEER NGA West 2 and NGA Sub platforms) or we can spectrally match using software such as RSPMatch
• Local Site Effects: These can be assessed using simple site coefficients such as Fa or FPGA or we can assess these effects using site response analysis. DMC undertakes both equivalent linear (e.g. SHAKE) or can utilize non-linear analysis with a pore pressure generation model
• Liquefaction Assessment: We assess liquefaction triggering using the Cyclic Stress Ratio from the site response analysis or from the Seed and Idriss 1971 “simplified method”. The Cyclic Resistance Ratio (CRR) can be assessed using CPT, SPT, Vs or in some case cyclic DSS testing
• Soil–Structure Interaction: We undertake assessment of how dynamic earthquake loads transfer between the ground and structures, especially for deep foundations and buried infrastructure
• Seismic Slope Stability: DMC undertakes analysis of the potential for earthquake-triggered landslides or slope failures, particularly in steep terrain or engineered fill embankments
• Earthquake-Induced Earth Pressure Assessment: We design retaining walls and buried structures to safely resist transient lateral loads generated during seismic events.

Ultimately, seismic design goes beyond structural survival. It ensures that infrastructure remains safe, functional, and reliable, even under extreme earthquake conditions.