Reasearch On Accelerated Pavement Test(MLS66) For Semi-rigid Base Asphalt Pavement

Semi-rigid base asphalt pavement is widely used in China,while its strutural response is different from the flexible asphalt pavement,thus different design specifications should be specified for them.In order to understand the actual structural response of pavement under wheel load,a full-csale testing road was built based on the typical pavement structure in Jiangsu province in China.The tesing road is embedded with a series of sensors,such as strain sensors,stress sensors,moisture and temperature sensors,to measure its spontaneous response under Mobile Load Simulator 66(MLS66).First,a research was conducted to summarize the typical pavemenet structure and materials in Jiangsu province.Then the site for full-scale testing road was selected and the construction and testing plans was determined.Performance of various gauge in home and abroad were compared in terms of sensivity,range,and survival rate,to decied which kind of gauge is to be used in this project.Finally,the final plans for sensors distribution and installation methods were determined,including the loading planning for testing road.A loboratory test was conducted to study the deformation coordination between strain gauges and asphalt mixture.A four-point-bending test was designed to determine the effectiveness of strain measurement,with a strin gauge embeded in the bottom of a beam with a dimension of 10×10×40cm.Performance of FBG sensor and sensor based on resistance were compared,and a finite element model was estabilished to analyze its effect on the stress and strain distribution in asphalt mixture.Results shows that the measured value in FBG sensor is more close to the calculated strain,based on the displacement uder beam bottom.And result from finite element model indicates that the existence of strain sensor does change the distribution of stress and strain in asphalt beam,espically in space around the strain gauge.Due to its high modulus,the calculated stress in strain gauge is much greater than that without gauge,while the calculated strain is a little smaller than that without gauge.The method for data processing is proposed,and the temperature distribution in pavement structure is analyzed,in which the temperature in middle asphalt layer reach 40? in April.Pavement structural response is analyzed as well,result indicates that the bottom of asphalt is under the combined effect of tensile and compression strain.Compression strain is witnessed in bottom layer before and after the arrival of wheel load,while a sharp increase in tensile strain is found in botton layer when wheel load is on the top of meassured point.And the peak tensile strain is about 10?? in longitude direction in the bottom of surface layer,while strain response in transverse direction is complex,which depends on the relative direction between strain sensor and wheel load.As for the strain response in base and subbase layer,it ranges between 3?? and 5??,and strain response in the bottom of subbase layer is greater than that in base layer.In addition,strain response of optical FBG sensor is greater than that of traditional strain sensor.A 3-D finite element model was established and calibrated by measured stress and strain response in testing road,then the calibrated model was applied to calculate the structural response of semi-rigid base pavement under actual wheel load in highway.Result shows that asphalt layer is subject to compression stress both in longitude and transverse direction,while strain response is a combination of tensile and compression strain.The effect of wheel load,running speed and temperature distribution is analyzed as well.Finally,the information system for accelerated pavement test was established to save and share all the testing data.