Effect Of Various Temperatures On Creep Characteristics Of RAP As Fills

In environmental geotechnical engineering,the beneficial use of solid wastes as the key research direction has always been concerned by scholars,in which the waste asphalt pavement material as one kind of solid wastes with a huge annual production.The Recycled Asphalt Pavement(RAP)can be formed after milling and screening,however,it has a low reuse level and low utilization rate in China.To this end,based on the support of the National Natural Science Foundation of China(51978315),this paper mainly focused on the effect of temperature on the creep characteristics of RAP materials reused as fills in the retaining wall engineering.Through carrying out the strain-controlled direct shear test and stress-controlled direct shear creep test of RAP specimens at different temperatures,this paper explores the influence of temperature change on the quantitative rule of creep behaviors,reveals the creep mechanism of RAP specimens under the influence of temperature,and analyzes the influence of vertical stress and shear stress ratio on it.On this basis,the creep constitutive model of RAP as fills considering the influence of temperature is established,which provides theoretical support and design basis for the engineering application of RAP as retaining wall fills.The main work and conclusions are summarized below,(1)Using the improved temperature and strain-controlled direct shear apparatus,the direct shear tests were conducted on RAP specimens at various shear temperatures(0?,20?,50?)and various vertical stresses(50kPa,75 kPa,100 kPa).The test results showed that the shear strength of RAP specimen decreases with the increase of shear temperature,and increases with the increase of vertical stress.Further analysis of its shear strength index showed that with the increase of shear temperature,the internal friction angle of RAP specimen changed little,while its cohesion decreased significantly.(2)Using the self-developed temperature and stress-controlled direct shear creep apparatus,the direct shear creep tests were carried out at various creep temperatures(0?,20?,50?).The effects of various vertical stresses(50kPa,75 kPa,100 kPa)and various shear stress ratios(0.4,0.6,0.7,0.8,0.9)on the creep characteristics of RAP as fills were considered.The results showed that the creep temperature has a significant effect on the creep characteristics of RAP.With the increase of creep temperature,the initial creep strain,the termination creep strain and the creep rate of RAP specimen increase under the same conditions.Under high temperature and high stress,the creep strain is large or even fracture.Under the low shear stress ratio,the creep temperature has little effect on the creep characteristics of RAP specimen.Under the high shear stress ratio,RAP specimen is easy to creep to failure,especially when the shear stress ratio is 0.9.When the shear stress ratio is less than or equal to 0.6,the creep characteristic of RAP specimens is less affected by vertical stress,and the creep strain is smaller.When the shear stress ratio is greater than or equal to 0.7,with the increase of vertical stress,the creep characteristic of RAP specimen changes significantly,the initial creep strain and the end creep strain increase,and the time to creep rupture advances at the same time.For the engineering application of RAP fills,it is recommended to use it when the shear stress ratio is less than 0.7.(3)Based on the quantization law and creep mechanism obtained from the tests,the Singh-Mitchell model was cited to establish the creep constitutive model of RAP fills under the effects of various temperatures.By comparing the calculated results of the model with the experimental data,it is verified that the model can better reflect the creep potential of RAP fills at various temperatures.