CSA N289.3:20 Design procedures for seismic qualification of nuclear power plants

CSA N289.3:20 Design procedures for seismic qualification of nuclear power plants. 5.2 Soil material properties 5.2.1 Characteristics of the soil condition shall be determined using a sufficient number of boreholes and other field geotechnical tests to develop the site soil profile. Note: A borehole determines the soil layering at a specific location at the nuclear power plant site. In addition, the borehole determines both the depth to bedrock measured from the free field and the level of ground water table at that location. 5.2.2 A combination of field and lab testing shall be used to determine the material properties for each soil layer. The list of soil material properties shall include, as a minimum, a) shear modulus as a function of strain; b) damping ratio as a function of strain; c) Poisson’s ratio; d) density; e) shear-wave (S-wave) velocity; and f) pressure wave (P-wave) velocity. 5.2.3 The S-wave and P-wave velocity for each soil layer are required to perform soil-structure-interaction analysis. The variation of these two parameters along the depth to bedrock from all boreholes at the site of the nuclear power plant shall be established. In general, based on investigating the boreholes, a site can be either a uniform soil site or a layered soil site. The material properties of each layer vary with the strain due to ground shaking and the degree of soil saturation. To account for uncertainties in the soil material properties, the determined properties shall be considered best estimates and may vary by ±50%. Smaller values of these limits may be used if they can be justified along with supporting documentation. Therefore, seismic analysis of ground-supported structures is implemented for three soil cases: two bounding cases (i.e., lower and upper bound cases), in addition to the best estimate case. The envelope of the dynamic analysis results shall be used for design. 5.3 Soil-structure interaction Note: For guidance on SSI, see Annex B. 5.3.1 General The term “soil-structure-interaction” refers to the interaction effects between the supporting soil medium and the structure. Due to such interaction effects, during the ground motion, the foundation motion would differ from that of the free-field motion.CSA N289.3 pdf download.