Chuan Gu

One-Way Cyclic Triaxial Behavior of Saturated Clay: Comparison between Constant and Variable Confining Pressure

AbstractThe one-way cyclic triaxial test has been recognized as a useful tool for solving many engineering problems, such as the prediction of deformation in subsoils under traffic loading. Most studies of the one-way cyclic behavior of soils are performed in triaxial tests with constant confining pressure (CCP), which can apply cyclic compressive deviatoric stress only. However, the real stress field in subsoils under traffic loading includes varying normal stresses in three directions. Therefore, it is more desirable to simulate the in situ loading conditions induced by passing vehicles through a combination of the varying deviatoric stress and varying confining pressure. Recognizing this, two series of one-way cyclic triaxial tests on remolded saturated clay were conducted in this study; one in undrained conditions and the other in partially drained conditions. In each series, both tests with the CCP and variable confining pressure (VCP) were carried out. Comparisons between the results of the VCP and ...

Drained Instability in Loose Granular Material

AbstractThe constant shear drained (CSD) test is considered an appropriate test to simulate the instability behavior of soils in slopes under water infiltration conditions or lateral stress relief. However, contradiction of the drained instability in loose granular material exists in the reported test results, which is considered because of the condition of constant deviatoric stress (q) not strictly satisfied in the literature. Because the variation of q during the CSD test has significant effects on the test results, more data from tests under a true constant q condition are needed to clarify this subject. In this paper, CSD and conventional undrained triaxial tests in both compressive and extensive loading were performed to investigate the instability behavior of loose sand. All the CSD tests were conducted by advanced variable confining pressure triaxial apparatus, in which a true constant q was maintained during the test; thus, more reliable results were obtained. It is observed experimentally that w...

Influence of Matric Suction on the Long-Term Behavior of Fouled Road Base Materials Under Traffic Loading

The road base and subbase materials are normally in unsaturated condition, and fouled by fines due to subgrade pumping. These unsaturated fouled materials usually present different properties due to combined effects of matric suction and fine content. To study the long-term behaviors of these materials, a series of large-scale cyclic triaxial tests were conducted. Crushed tuff aggregates, incorporated with corresponding kaolin contents, were selected to be the testing materials. Cyclic loadings with two amplitudes were applied on the mixture specimens under four initial matric suctions and two fine contents. The matric suction was controlled by axis-translation method. The accumulated axial strain and resilient modulus were focally analyzed. The testing results show that for materials with higher fine content, the hysteresis phenomenon during the drying and wetting path of the soil-water characteristic curve will be more obvious. Under cyclic loadings, the resilient modulus increases with the increase of matric suction, and the increase rate decreases with the increase of matric suction. The accumulated axial strain decreases with the increase of the matric suction, and the decrease rate decreases with the increase of matric suction. Larger cyclic loading amplitude and higher fine content will amplify the influence of matric suction.