The state of clean sand was mainly dependent on its void ratio (density) and confining stress that greatly influenced the mechanical behavior (compression, dilatancy and liquefaction) of clean sand. Confirming whether the confining stress was a state variable of sand required precise element tests at different confining stress, especially the tests under very low confining stress whose test data were very limited. In this study, static-dynamic characteristics of clean sand was comprehensively investigated by a unified test program under low and normal confining stress ranging from 5 to 98 kPa, under monotonic/cyclic and drained/undrained conditions, together with the literature available data under confining stress of 1.0 to 3.0 MPa. For monotonic loading tests, the contraction/dilation phase transition was observed for loose sand at low confining stress, and dilatancy angles were stress-dependent. In addition, the liquefaction resistance was observed to increase with reducing of confining stress, and the axial strain varied from compressive to dilative when confining stress increased. Special attention was also paid to the enhancement effect of membrane, and it was observed that its influence on the test results was limited. In addition, the experimental results were proved reliable by reproducibility.

洁净砂的状态主要取决于其空隙率（密度）和围压，极大地影响了洁净砂的机械性能（压缩，膨胀和液化）。要确定围压是否为砂的状态变量，需要在不同围压下进行精确的元素测试，尤其是在非常低的围压下的测试数据，该测试数据非常有限。在这项研究中，通过统一的测试程序，在单调/循环和排水/不排水条件下，在5至98 kPa的低和正常围压下，对洁净砂的静动力特性进行了全面研究，并提供了可用的文献资料。应力为1.0至3.0 MPa。对于单调加载测试，在低围压下观察到松散砂土的收缩/膨胀相变，并且膨胀角与应力有关。此外，观察到抗液化性随限制应力的减小而增加，并且当限制应力增加时，轴向应变从压缩变化到膨胀。还特别注意了膜的增强作用，并且观察到其对测试结果的影响是有限的。另外，通过再现性证明了实验结果是可靠的。还特别注意了膜的增强作用，并且观察到其对测试结果的影响是有限的。另外，通过再现性证明了实验结果是可靠的。还特别注意了膜的增强作用，并且观察到其对测试结果的影响是有限的。另外，通过再现性证明实验结果是可靠的。