1803.5.12 Seismic Design Categories D Through F

For structures assigned to Seismic Design Category D, E or F, the geotechnical investigation required by Section 1803.5.11 shall include all of the following as applicable:

1. The determination of dynamic seismic lateral earth pressures on foundation walls and retaining walls supporting more than 6 feet (1.83 m) of backfill height due to design earthquake ground motions.

2. The potential for liquefaction and soil strength loss evaluated for site peak ground acceleration, earthquake magnitude and source characteristics consistent with the maximum considered earthquake ground motions. Peak ground acceleration shall be determined based on one of the following:

   1. 2.1. A site-specific study in accordance with Chapter 21 of ASCE 7.
   2. 2.2. In accordance with Section 11.8.3 of ASCE 7.

3. An assessment of potential consequences of liquefaction and soil strength loss including, but not limited to, the following:

   1. 3.1. Estimation of total and differential settlement.
   2. 3.2. Lateral soil movement.
   3. 3.3. Lateral soil loads on foundations.
   4. 3.4. Reduction in foundation soil-bearing capacity and lateral soil reaction.
   5. 3.5. Soil downdrag and reduction in axial and lateral soil reaction for pile foundations.
   6. 3.6. Increases in soil lateral pressures on retaining walls.
   7. 3.7. Flotation of buried structures.

4. Discussion of mitigation measures such as, but not limited to, the following:

   1. 4.1. Selection of appropriate foundation type and depths.
   2. 4.2. Selection of appropriate structural systems to accommodate anticipated displacements and forces.
   3. 4.3. Ground stabilization.
   4. 4.4. Any combination of these measures and how they shall be considered in the design of the structure.