废旧回收沥青路面材料的直剪蠕变试验

Direct shear creep tests on recycled asphalt pavement material

通过对废旧回收的沥青路面(RAP)材料开展直剪蠕变试验,研究不同剪应力水平和竖向应力对其蠕变特性的影响规律.结果表明:RAP材料的临界剪应力水平约为0.73,试样高于临界值时发生直剪蠕变破坏,破坏开始的时间随剪应力水平增加而减小;反之,试样不发生蠕变破坏;剪应变率随时间在双对数坐标下为系列递减的平行线,采用土体的三参数蠕变模型可以有效地模拟此特性;竖向应力对蠕变参数的影响较小,对达到蠕变破坏的时间影响较大;相同剪应力水平下,剪应变随时间增加逐渐增大,竖向应力低的试样在低剪应变时先发生蠕变破坏,破坏时的剪应变随竖向应力的增加而增加,且剪应变率最先降到最小值,并发生蠕变破坏.

The effects of shear stress level and vertical stress on creep characteristics of recycled asphalt pavement (RAP) material were investigated by a series of direct shear creep tests. The results show that the yield shear stress level of RAP is about 0.73. The specimens at shear stress level greater than the value are observed creep rupture during the tests,and the time of creep rupture initiation is decreased with the increasing of stress level. On the contrary,the specimens are stable when the stress level is lower than the value. The variation of shear strain rate with time in log-log scale shows a series of decreasing parallel lines and can be well predicted by the three-parameter empirical creep model for soils. The vertical stress has slight influence on three model parameters but has great effect on the time of creep rupture. Under the same shear stress level,the shear strain is increased with time. The specimen with low vertical stress firstly undergoes creep rupture at low shear strain,and the shear strain at the time of failure is increased with the increasing of vertical stress. The shear strain rate under lower vertical stress is decreased faster to the minimum value than those of higher vertical stress.