Investigations into end constraints and specimen conditioning in direct simple shear testing of sands

1. Home
2. Publications
3. Online Library
4. Investigations into end constraints and specimen conditioning in direct simple shear testing of sands

The direct simple shear (DSS) test is a backbone laboratory test for cyclic and earthquake related designs for all foundation types for an offshore wind farm. Furthermore, the test type is used for site characterization and as input to finite element models adopted in the calibration of soil-structure interaction curves for design of e.g. a dynamically loaded monopile. Despite the comprehensiveness of ASTM D6528 and ASTM D8296 for monotonic and cyclic DSS testing, respectively, the standards leave room for choices and do not cover all aspects of the test. In addition, DSS tests are not standardized in ISO. This results in data which are influenced by operator experience, equipment design, and the various in-house testing traditions, potentially compromising quality, suitability of results as well as hindering a comparison of results between laboratories. Boundary constraints and testing procedures related to the choice of end platens and cyclic pre-shearing have a significant impact on the measured soil behaviour. Cyclic pre-shearing is generally used for conditioning the test specimens. This paper compares test results on dense sand specimens using different end platen designs and examines how cyclic pre-shearing influences monotonic and cyclic DSS test results. The purpose is to provide insights into testing aspects, which current standards do not address.

5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)

2 - Site characterization, in-situ and laboratory testing, measurement