长期动载下级配碎石的塑性变形与临界应力

Critical Stress and Plastic Deformation of Graded Aggregate Material Under Long-term Dynamic Repeat Load

采用中型动三轴仪,在不同围压、不同动应力条件下,研究了级配碎石基层在长期车辆荷载作用下塑性变形的发展规律和分布状态.结果表明,在围压一定时,随着动应力的增加,级配碎石的塑性变形曲线可分为稳定型、衰减型和破坏型,3类塑性变形的分布确定了2个临界状态;临界动应力随围压线性增加,临界动应力比随围压呈对数递减,且两临界应力比在高围压下有趋同态势;级配碎石的塑性变形与动应力水平为指数关系,稳定临界和破坏临界的动应力水平分别为0.79和1.00;典型路面结构应力分析表明,标准荷载下级配碎石过渡层的应力水平为0.72~0.92,小于破坏临界应力水平,级配碎石在长期荷载作用下的塑性变形处于较稳定状态.

A research was made of the graded aggregate base bitumen pavement to investigate the rule of plastic deformation and its distribution in different confining stresses and dynamic stresses by using the middle dynamic triaxial instrument and sample compacted by vibration.Test proves that when confining pressure is fixed,the graded aggregate material＇s plastic deformation curve is stabilization type,disintegration type and destroy type with the increasing of dynamic load,two critical state can be confirmed by plastic deformation distribution.Critical dynamic stress increases in linearity and dynamic stress ratio descends in logarithm with confining stress,two critical dynamic stress ratio tends to the same when confining pressure is high.The relationship between plastic deformation and critical dynamic stress is exponential,stabilization critical stress level and destroy critical stress is 0.79 and 1.0,respectively.The analysis of representative pavement structure indicates that graded aggregate transition base＇s critical stress level is from 0.72 to 0.92 in standard axial load,which is lower than the destroy critical stress level.The graded aggregate base plastic deformation is stabilization under long-term vehicle load.