Table 1. Examples of Soil Dynamic Property and Strength Tests

DOE-STD-1022-94

Table 1. Examples of Soil Dynamic Property and Strength Tests

D 3999-91

Standard Test Method for the Determination

of the Modulus and Damping Properties of

Soils Using the Cyclic Triaxial Apparatus

D 4015-92

Standard Test Methods for Modulus and

Damping of Soils by the Resonant-Column Method

D 5311-92

Standard Test Method for Load Controlled

Cyclic Triaxial Strength of Soil

For coarse geological materials such as coarse gravels and sand-gravel mixtures, special testing equipment

and testing facility should be used, (e.g., University of California Rockfill Testing Facility, Richmond,

California). Larger sample size is required for laboratory test on this type of materials, (e.g., samples with

12-inch diameter were used in the Rockfill Testing Facility). It is generally difficult to obtain in-situ

undisturbed samples of unconsolidated gravely soils for laboratory tests. If it is not feasible to collect test

samples and, thus, no laboratory test results available, the dynamic properties should be estimated from the

published data of similar gravely soils.

5.5.2 Site Response Analysis

As part of the quantification of earthquake ground motions at a facility site, an analysis of soil response

effects on ground motions may be needed. Note that a specific analysis is not required if the site is a hard

rock site or if the subsurface soil conditions have already been adequately accounted for in the selection and

use of strong motion data and attenuation relationships for subsurface conditions similar to those that exist

at the site. For facilities with SSCs in Performance Category 1 or 2, it is sufficient to comply with the

criteria for ground motions specified in the model building codes although sufficient site-specific information

is needed to select the proper site category.

Site response analyses (often referred to as site amplification analyses) are relatively more important when

the site surficial soil layer is a soft clay and/or when there is a high stiffness contrast (wave velocity contrast)

between a shallow soil layer and underlying bedrock because a few ground motion recordings have been

obtained for such conditions and have shown strong local soil effects on ground motion. Site response

analyses are always important for those sites having predominant frequencies within the range of interest for

the SSCs being evaluated. Thus, the stiffness of the soil and bedrock as well as the depth of soil deposit

should be carefully evaluated.

In a site response analysis, the ground motions (usually acceleration time histories) defined at bedrock or

outcrop are propagated through an analytical model of the site soils to determine the influence of the soils

on the ground motions. The required soil parameters for the site response analysis include the depth, soil

type, density, shear modulus and damping, and their variations with strain levels for each of the soil layers.

Internal friction angle, cohesive strength, and over-consolidation ratio for clay are also needed for non-linear

analyses. The results of the site response analysis shall show the input motion (rock response spectra),

output motion (surface response spectra), and spectra amplification function. Criteria for developing the

design response spectra are given in DOE-STD-1023-95.