主应力方向对砂土剪胀性的影响分析

剪胀性是土特有的一种材料属性，而准确地描述砂土的剪胀性则是建立砂土本构模型的重要基础。大量常规三轴试验发现，在以相同加载条件下剪切时密砂和松砂会表现出完全不同的剪胀性和应力-应变关系特性，说明砂土的剪胀性不仅与其所处的应力状态有关，也与其物理状态相关。状态参量理论很好地解释了砂土所处应力状态和物理状态对剪胀性的共同作用。空心扭剪三轴试验仪可以实现不同主应力方向的单调剪切试验。试验结果表明，当砂土以不同主应力方向单调剪切时，即使处于相同初始应力条件和物理状态，砂土也会表现出不同的剪胀性，说明了主应力方向也是决定砂土剪胀性的重要条件。本文通过分析试验中主应力方向对砂土剪胀性的影响，提出了一个含有主应力方向的状态参量，并建立了相应的剪胀方程。通过与试验数据的对比，验证了该方法的正确性和准确性。

Analysis of effect of principal stress direction on dilatancy of sand

Dilatancy is a special material property of soil; and it is important for sand to describe its dilatancy accurately in the constitutive modeling. Through a large number of triaxial tests, it has been found that dense sand and loose sand show different dilatancies and stress-strain relation characteristics under the same loading condition, which indicate that the dilatancy of sand is not only related with the stress condition , but also with its physical state. The state parameter theory explains the combined effects of stress condition and physical state on the dilatancy of sand successfully. Hollow cylindrical torsional shear apparatus can be used to perform monotonic shear tests in different principal stress directions. Through such experimental tests, the difference in the dilatancy of sand in different principal stress directions is examined even under the same initial stress condition and physical state, which shows that the principal stress direction is also important to the dilatancy of sand. A state parameter including the principal stress direction is proposed by analyzing the effects of principal stress direction on the dilatancy of sand in the tests; and a dilatancy equation considering the principal stress direction is established. Compared with the experimental results, the method is proved to be correct and accurate.