循环-间歇加载下粉土永久变形特性试验

Experimental on Permanent Deformation Characteristics of Silty Soil Under Cyclic Intermittent Loading

真实地揭示路基填料在交通荷载作用下的永久变形特性可为路基设计和评估提供依据。利用动三轴仪,对粉土开展了连续循环加载和间歇加载(连续加载阶段与间歇阶段交替循环)动三轴试验。分析了间歇阶段对粉土的轴向应变和累积塑性应变等发展规律的影响,并重点研究了间歇加载方式下粉土的累积塑性应变行为特征。试验结果表明,间歇阶段的存在对提高试样抵抗永久变形的能力有积极作用,动三轴试验中应考虑荷载间歇阶段的影响。依据安定理论,间歇加载方式下,粉土的动力行为可划分为三类:塑性安定、塑性蠕变和增量破坏,并提出了间歇加载方式下粉土试样临界应力的表达式和累积塑性应变预测模型。研究结果对深刻认识路基的永久变形特性具有参考价值。

Revealing the real permanent deformation characteristics of subgrade fillings under traffic loads can provide a basis for subgrade design and evaluation.The dynamic triaxial tests of silty soil under continuous cyclic loading and intermittent loading(cycle of continuous loading stage and intermittent loading stage)are performed by using dynamic triaxial apparatus.The effects of intermittent stage on the development of axial strain and accumulated plastic strain are analyzed,and the dynamic behaviors of accumulated plastic strain under intermittent loading are also studied.The results show that the existence of intermittent stage plays an active role in improving the ability of specimen to resist permanent deformation,the effect of load intermission should be considered in dynamic triaxial test.Based on shakedown theory,the dynamic behavior of silt under intermittent loading can be divided into three categories:plastic shakedown,plastic creep,and incremental failure.The expression of critical stress and prediction model of accumulated plastic strain of silty specimen under intermittent loading are proposed.The research results have reference value for deeply understanding the permanent deformation characteristics of subgrade.