重复荷载作用下沥青混合料的永久变形

Permanent deformation of asphalt mixture under repeated load

对Burgers模型中串联粘壶进行了改进,并将改进模型看成是由三单元VanDerPoel模型与改进粘壶串联组成.采用半正弦波间歇荷载模拟路面受到的车辆荷载,推导了重复荷载作用下沥青混合料永久变形的力学模型.进行了三轴重复荷载永久变形试验,验证了模型的准确性,研究了永久变形的变化规律.试验结果表明:该模型能够全面反映重复荷载作用下沥青混合料三阶段永久变形特性;温度越高、应力越大,混合料的永久变形越大,流变数越小.而残余粘弹性变形随着荷载作用次数趋向于定值,其占永久变形的比例逐渐减小;应力越大、温度越高、间歇时间越短,残余粘弹性应变定值越大.随着荷载间歇时间的增长,残余粘弹性应变占永久应变的比例先迅速衰减,而后逐渐变缓;温度越高、荷载越大,应该设计更长的荷载间歇时间以便粘弹性变形的恢复.

The series-wound dashpot of Burgers model was modified and then considered as a combination of modified dashpot and Van Der Poel model. Pulse load consisting of a haversine loading and a rest period was selected to simulate the dynamic vehicle load, and a new mechanical model was derived to describe the permanent deformation of asphalt mixture under repeated load. Subsequently, triaxial repeated load tests were conducted for model validation. It is indicated that the proposed model can describe the three phases＇ permanent deformation well. The higher the temperature and stress, the bigger the permanent deformation and the smaller the flow number. Residual viscoelastic deformation tends to a fixed value with the increase of load cycles, and its proportion to permanent deformation decreases gradually with the load cycles; the fixed value becomes bigger if stress and temperature are higher and the load rest period is shorter. Its proportion to permanent deformation decreases rapidly first and then slowly with the increase of rest period, and a longer rest period is needed for the residual viscoelastic deformation recoverv when stress and temoerature are higher.