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为了模拟海床及海洋建筑物遭受波浪荷载时所引起的循环应力,进行了一系列均等固结条件下的应力控制式轴向-扭转双向耦合循环剪切试验。试验时在竖向和扭转向同时施加动应力,使加载路径在正应力偏差(σz-σθ)/2与剪应力τzθ应力空间内为椭圆。分别控制竖向和扭转向循环荷载的大小,以此来探讨双向耦合剪切试验中竖向应力与剪应力幅值的变化对饱和松砂变形特性的影响。试验结果显示,所有的竖向应变均以拉伸向为主。对于椭圆应力路径所包围的椭圆面积相同的一组试验,当竖向荷载分量与扭转向荷载分量之比小于某一临界值时,竖向应变完全表现为单拉伸方向的变形,大于临界值时则呈现出拉伸向更为显著的双向循环累积特性破坏。剪应变虽都表现为双向循环累积,但是两个荷载分量的比值不同,应力应变关系的滞回圈曲线形状不同。而椭圆面积的大小对土样的变形特性几乎没有影响。
In order to simulate the cyclic stress caused by wave loads on the seabed and marine structures, a series of stress-controlled axial-torsional two-way coupled cyclic shear tests under equal consolidation conditions were carried out. In the test, dynamic stress is applied in both vertical and torsional directions so that the loading path is elliptical within the normal stress deviation (σz-σθ) / 2 and the shear stress τzθ stress space. The vertical and torsional cyclic loadings were controlled respectively to study the influence of the vertical and torsional cyclic amplitude on the deformation characteristics of saturated sands in two-way coupled shear tests. The test results show that all the vertical strain is dominated by the tensile direction. For a series of experiments with the same elliptic area surrounded by elliptical stress paths, when the ratio of vertical load component to torsional load component is less than a certain critical value, the vertical strain completely shows the deformation in the single tensile direction and is larger than the critical value When it is stretched to more significant two-way cycle cumulative damage characteristics. Although the shear strain is shown as two-way cyclic accumulation, the ratio of the two load components is different, and the shape of the hysteresis loop of the stress-strain relationship is different. The size of elliptical area has little effect on the deformation characteristics of soil samples.