ANALYSIS OF THE INFLUENCE OF MODERATELY DISSOLVED SALTS ON THE STRENGTH OF STRUCTURAL LOESS UNDER THE PATH OF REDUCING CONFINING PRESSURE

To study the effect of salt content on the strength of structural loess under specific stress paths,this paper conducted soil pressure reduction triaxial(RTC)tests and microscopic electron microscopy tests(SEM)on undisturbed loess with different salt contents(0,0.1%,0.2% and 0.5%). By analyzing the changes in micro pore structure and the stress-strain curve of triaxial tests,the strength variation law of structural loess was studied. The results indicate that the content of medium soluble salt will have a certain impact on the internal structural redistribution of structural loess soil. When the confining pressure is low,the time required for the confining pressure to decrease to 0 is relatively short,and the stress-strain curve only shows an upward trend. However,under the confining pressure conditions of 100 kPa and 200 kPa,the sample exhibits strain softening characteristics. When reaching a medium to high confining pressure of 400 kPa,the sample exhibits strain hardening,and the softening effect gradually weakens with the increase of salt content. Based on the binary medium theory,the strength criterion for structural loess has been revised,and a structural loess strength criterion suitable for the effect of dissolved salt content under the reduced confining pressure path has been proposed.