**Abstract**

Although geotechnical engineering design must meet seismic design specifications, many geotechnical failures, including foundations, retaining walls, and slopes, have nevertheless occurred during tectonic earthquakes. The evaluation of the ultimate bearing capacity of the foundation, the active and passive earth pressure of the retaining wall, and the safety factor of the slope all need to use the shear failure band and soil plasticity models at the same time. In view of this, it is first proven that shear failure bands can only appear in the strain softening model. Secondly, it is shown through case studies that traditional evaluation methods for determining the foundation ultimate bearing capacity, the active earth pressure of the retaining wall, and the safety factor of slope stability all adopt both the shear failure band and the perfectly plastic soil model. Since the perfectly plastic soil model is incompatible with shear failure bands, this results in a large number of foundations, retaining walls, and slopes failing during tectonic earthquakes. Based on the research results, it is suggested that a soil strain softening model compatible with shear failure bands be adopted in the analysis of geotechnical engineering projects so as to ensure safety during tectonic earthquakes.

**Keywords:** tectonic earthquake, geotechnical failure, shear band, foundation, retaining wall, slope
