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Hello everyone, I have asked this question at many forums but didn't get any satisfactory and conclusive reply. A 5 story (59' including mumty) reinforced concrete structure needs to be constructed in a seismic zone 3. The structure is rectangular in shape with it's dimensions being 60' by 180'. To increase the dynamic stiffness of the structure, two expansion joints have been provided at equal distances so the structure finally ends up getting into 3 equal parts i.e 60' by 60'. The seismic stresses are approximately 10% of the dead load stresses. According to the geotechnical report, the construction site mostly contains gravels with less than 10% of the fine material. However, there is a small patch of rocky soil as well. The bearing capacity of soil is 2T/SFT at 3ft depth. Based on these details, I have few queries; 1. The size of foundation in this case is not a problem since the soil has a very good bearing capacity. Keeping in view the minimum cost of excavation, sliding and overturning what should be the minimum depth of foundation below natural surface level? 2. There is 20' retaining wall located 10' away from the structure which retains the same soil. Will it transfer any lateral thrust to the foundation of the structure? 3. The rocky soil covers a very small area, is there any need to provide anchoring to the foundation??? I suspect uplift in that region.