冷拌冷铺乳化沥青混合料在不同应变组合下的疲劳性能研究

Study on Fatigue Performance of Cold Mix Emulsified Asphalt Mixture under Different Strain Combination

目的 研究在单级应变与双级应变组合的不同加载方式下冷拌冷铺乳化沥青混合料劲度模量及疲劳寿命的变化规律,为冷拌冷铺乳化沥青混合料的抗疲劳性能研究提供借鉴。方法 综合考虑车辆荷载的大小,选定A(200×10^(-6))、B(400×10^(-6))、C(600×10^(-6))三个应变水平,以单级应变为试验对照组,以A-B和C-A为双级应变组合,对冷拌冷铺乳化沥青混合料分别进行单级及双级应变下的四点弯曲疲劳试验,由此对比分析混合料疲劳寿命与劲度模量随应变量及应变组合不同而变化的规律。结果 在单级应变作用下,试件劲度模量先急剧下降,然后缓慢衰减,且应变越大劲度模量衰减越快;在应变水平由低到高的双级应变A-B组合作用下,由A应变转入B应变加载后,劲度模量瞬间增大了35%,之后先急剧降低再进入平缓阶段,且疲劳寿命在A、B单级应变加载之间;而在应变水平在由高到低的C-A加载组合中,由C应变转入A应变加载后,劲度模量瞬时衰减11%,之后先急剧降低再进入平缓阶段,且疲劳寿命要长于在应变中值水平B单级应变加载下的。结论 从低应变到高应变的加载过程中,恢复了试件的劲度模量,延缓了沥青混合料的破坏过程,进行A-B应变加载模式的试件疲劳寿命要多于由C-A应变的加载模式。

In this paper,the variation of stiffness modulus and fatigue life of cold-mixed emulsified asphalt mixture under different loading modes were compared and studied,which include single-stage strain and the two-stage strain combination.It can provide reference for the study of fatigue resistance of cold-mix emulsified asphalt mixture.Comprehensively,considering the weight of vehicle load,three strain levels of A(200×10^(-6)),B(400×10^(-6))and C(600×10^(-6))were selected from low to high.The single-stage strain was used as the experimental control group,and A-B and C-A were used as the two-stage strain combinations.The four-point bending fatigue tests of cold-mixed emulsified asphalt mixture under single-stage and two-stage strains were carried out,respectively.Thus,the variation laws of fatigue life and stiffness modulus of mixture with different strain and strain combinations were compared and analyzed.The results show that,under the action of single-stage strain,the stiffness modulus of the specimen decreased sharply at first and then attenuated slowly.Besides,the greater the strain was,the faster the stiffness modulus decreased.Under the combined action of the two-stage strain A-B with the strain level from low to high,the stiffness modulus increased by 35% immediately after the strain was transferred from A strain to B strain loading,and then decreased sharply.Afterwards,the stiffness modulus entered the gentle stage.Moreover,the fatigue life under the combined loading of two-stage strain A-B is between the single-stage strain loadings of A and B.When the strain level is changed from C strain to A strain in the C-A loading combination from high to low,the stiffness modulus decreases by 11% instantaneously,then decreased sharply,and finally entered the gentle stage.Moreover,the fatigue life of the two-stage strain combination C-A loading was longer than that of the single-stage strain loading at the strain median level B.During the loading process from low strain to high strain,the stiffness modulus of the specimen was restored,and the failure process of the asphalt mixture was delayed.The fatigue life of the specimen under A-B loading mode was longer than that under C-A loading mode.