The road base and subbase are normally situated above the underground water table and thus in the unsaturated state. To study the cyclic behavior of unbound granular materials (UGMs) in the road base and subbase courses under controlled matric suction conditions, a series of cyclic tests on the unsaturated UGMs were conducted by the large-scale triaxial apparatus. The large-scale triaxial apparatus was upgraded using an unsaturated module to control the matric suction by the axis-translation technique. Emphases were placed on the effects of matric suction and cyclic stress amplitude on the accumulated axial strain and resilient modulus of UGMs. Test results showed that the increase in matric suction reduced the development of accumulated axial strain exponentially under different cyclic stress amplitudes. Based on the shakedown theory, both the plastic shakedown and plastic creep limits were determined, which tended to grow linearly with the increase in matric suction. A new empirical model was proposed to predict the accumulated axial strain of unsaturated UGMs. Moreover, the increase in both matric suction and cyclic stress amplitude led to the increase in resilient modulus, and linear relationships existed between the resilient modulus and matric suction.

路基和路基通常位于地下水位上方，因此处于非饱和状态。为了研究在受控基质吸力条件下未粘结颗粒材料（UGM）在路基和底基层中的循环行为，使用大型三轴仪对不饱和UGM进行了一系列循环测试。大型三轴设备使用不饱和模块进行升级，以通过轴平移技术控制基质吸力。重点放在基质吸力和循环应力振幅对UGM累积轴向应变和弹性模量的影响上。测试结果表明，在不同的循环应力振幅下，矩阵吸力的增加成倍地减小了累积轴向应变的发展。根据重组理论，确定了塑性减振极限和塑性蠕变极限，它们都随着基质吸力的增加而线性增长。提出了一种新的经验模型来预测不饱和UGM的累积轴向应变。此外，基质吸力和循环应力振幅的增加导致弹性模量的增加，并且弹性模量和基质吸力之间存在线性关系。