Grain Size Analysis and Maximum and Minimum Dry Density Testing of Ottawa F-65 Sand for LEAP-UCD-2017

Abstract

Ottawa F-65 sand (supplied by US Silica, Ottawa, Illinois) was selected as the standard sand for LEAP-UCD-2017. Between December 2017 and February 2018, each LEAP research team sent 500 g samples of sand to UC Davis for grain size analysis and minimum and maximum dry density testing. The purpose of this testing was to confirm the consistency of the sand used at various test sites and to provide updated minimum and maximum density index values. The variation of measured properties among the different samples is similar to the variation measured during repeat testing of the same sample. Modified LEAP procedures to measure index densities are used to confirm consistency of the sands, and the results from these procedures are compared to results from ASTM procedures. The LEAP procedures give repeatable results with median index densities of ρ min ¼ 1457 kg/m 3 , ρ max ¼ 1754 kg/m 3. Relative densities calculated with facility-specific index densities varied by less than 4%, so we conclude that average index densities from all the sites may be used for analysis of the results. The LEAP procedures are easier to perform than the ASTM procedures and do not require specialized equipment; therefore, continued use of the LEAP procedure for frequent quality control purposes is recommended. However, the values from ASTM procedures are expected to be more consistent with values adopted in liquefaction literature in the past; therefore, we recommend using the median ASTM values for analysis of LEAP data. Index densities from ASTM procedures (ρ min ¼ 1490.5 kg/m 3 , ρ max ¼ 1757.0 kg/m 3) produce relative densities that are 4-10% smaller than the index densities from the LEAP procedures. 2.1 Background and Introduction The standard sand selected for the LEAP-UCD-2017 exercise is Ottawa F-65, a clean, poorly graded, whole grain silica sand, with less than 0.5% fines by mass, supplied by US Silica, Ottawa, Illinois. The LEAP-GWU-2015 exercise also used Ottawa F-65 as the standard sand; therefore, material characterization and element

LEAP-UCD-2017 Comparison of Centrifuge Test Results

“…The same sand, Ottawa F65 from US Silica, was used in all of the experiments. Carey et al (2019c) describe results of grain size and max/min density tests of the sand used at different facilities to determine the index properties and to check the consistency of the sand used at various facilities.…”

LEAP-UCD-2017 Centrifuge Tests at NCU

“…The maximum and minimum dry unit weights under modified ASTM (American Society for Testing and Materials) method are 16.80 and 14.1 kN/m 3 measured by NCU, respectively, but they are 17.24 and 14.62 kN/m 3 measured by UCD (Carey et al 2019). The target unit weight of slope model in LEAP is 16.20 kN/m 3 which corresponding with 80% of relative density according to NCU max-min dry unit weight result and 64% following UCD's results.…”

Numerical Sensitivity Study Compared to Trend of Experiments for LEAP-UCD-2017

“…11.2, was based on a six-parameter regression surface: At the time the request for the sensitivity study was sent to the simulation teams, the maximum and minimum dry densities were estimated to be 1765 and 1476 kg/m 3 . Based upon the study by Carey et al (2019b), the maximum and minimum dry densities were updated to 1757 and 1490.5, respectively. Using the updated index dry densities, the relative densities corresponding to 1651, 1608, and 1683 kg/m 3 would be 64%, 48%, and 75% -slightly smaller than the relative densities listed in the above table…”