循环动载下软黏土路基变形响应的离心试验模拟

Centrifuge tests on behaviors of soft clay subgrade under cyclic loading

介绍了动力离心模型试验的关键性试验技术及循环动载下饱和软土累计变形响应规律。路面结构分别采用刚性路基板,路基基层采用压密的砂垫层模拟,地基采用上海地区的饱和软黏土,并考虑了地基土的超固结效应。详细探讨了离心试验过程中若干试验技术的实现过程,包括饱和黏土的重塑土制样技术、重力场的固结技术及不同超固结比的实现技术,并给出了如何在离心场实现地基变形的图像分析技术(PIV)。最后,给出典型的试验观察成果,揭示往复动载下饱和软黏土累计变形时空演变规律。试验表明,累计超孔压表现为先增大后减小的变化规律;通过PIV技术分析发现,在循环动作用下饱和软黏土路基竖向变形影响区域随着循环次数的增大而增大。

A couple of key test technologies for dynamic centrifuge modeling and the permanent deformation responses of saturated clay to cyclic loading are introduced. The rigid pavement is used in the model system. The subgrade base is simulated by using the compacted sand cushion. The modeling subsoil is Shanghai saturated soft clay in an over-consolidation state. The testing process and key test techniques are discussed, such as the reconstruction of saturated clay and the pre-loading consolidation with an given over-consolidation ratio in clay subsoil. The image analysis techniques(PIV) is also adopted for the calibration of deformation. Finally, a series of test results are given to reveal the cumulative deformation behaviors of saturated soft clay under cyclic loading. It is shown that the cumulative pore pressure increases rapidly and then decreases slowly. PIV indicates that the effective impact zone in the deformation of subsoil subgrade expands with the increasing number of load cycling.