Type II Unbound Cohesive Subgrade Soil Synthetic Reference Sample Program

摘要

SHRP Protocol 46, Resilient Modulus of Unbound Granular Base/Subbase Materialsand Subgrade Soils was the specified procedure for laboratories performing resilient modulus tests on research samples of unbound cohesive subgrade soil obtained from LTPP field sites. All laboratories conducting tests for the LTPP program were required to be accredited by the AASHTO Accreditation Program (AAP). AAP includes site inspections of equipment and procedures, and participation in applicable proficiency sample testing. A few critical LTPP tests, such as the triaxial resilient modulus test, were not addressed fully by the AAP, and LTPP decided to conduct supplemental testing. P46 requires a test system which includes a triaxial pressure cell component, a closed loop electro-hydraulic repeated load component, and certain load and specimen response control, measurement, and recording components. In view of the complexity of P46, two elements of the supplemental testing were specially important: (1) verification that the system is calibrated and yielding reasonable results, and (2) a practical means of performing quality checks on a daily or more frequent basis. A set of three synthetic reference samples was acquired, instructions for testing were prepared, and the set was circulated to 14 participating laboratories for testing. Worksheets, supporting data, analyses, final comments, and conclusions are presented. A complete set of proficiency sample statements in AASHTO/ASTM format are provided. (Copyright (c) 1994 National Academy of Sciences.)