Liquefaction resistance from cyclic simple and triaxial shearing: a comparative study

While cyclic triaxial (CTX) tests are widely used in liquefaction studies due to their simplicity, direct simple shear (DSS) tests and their ilk (e.g., the combined triaxial simple shear, TxSS) are more representative of stress conditions produced during an earthquake. Therefore, the CTX results should be properly correlated to simulate field conditions. In the current study, a series of CTX testing results performed on reconstituted samples of Baie-Saint-Paul, Ottawa C-109, and Quebec CF6B sands are compared to the corresponding TxSS and DSS results under both stress- and strain-controlled conditions. The cyclic TxSS stress-controlled tests are numerically simulated by adopting a coupled energy-based pore water pressure model using the computer code, FLAC. The TxSS numerical results are successfully compared with those obtained experimentally from (1) alternative stress-controlled TxSS, (2) available liquefaction potential curves (CSR-N-liq) in the literature, and (3) stress-controlled DSS testing results. As anticipated, the outcomes of the cyclic stress-controlled CTX testing results in the form of liquefaction potential curves are usually higher than that of the TxSS testing results. In contrast, due to the difference in the applied (strain-controlled tests) and the induced (stress-controlled tests) strains, the liquefaction resistance curves of TxSS are higher than those of CTX under cyclic strain-controlled test.

Automated summary

The study compared the results of cyclic triaxial (CTX) and direct simple shear (DSS) tests under stress and strain-controlled conditions. It found that the liquefaction potential curves of cyclic stress-controlled CTX testing results are usually higher than those of direct simple shear (TxSS) testing results.