Research On Performance Requirements Of Embedded Asphalt Pavement Sensors

At present,the intelligent road is a collection of various information,technologies and functions.Self-perception,self-repair,and self-capture are important connotations of intelligent pavement.In order to realize the self-sensing function of intelligent asphalt pavement,it is necessary to embed sensors in the pavement to obtain and transmit various performance evolution information of the pavement structure and material in the whole life cycle.However,the high temperature and vibration environment of the asphalt pavement during the construction process,as well as the significant differences in the material properties of the sensing device and the road structure,will cause the survival of the sensing device during use and the accuracy and reliability of the collected data are difficult to guarantee.Therefore,it is necessary to put forward some performance requirements for the sensors in order to select the sensors that meets the technical requirements of the intelligent road.The meso-level finite element method is adopted to simulate the different use stages of the sensors,and some requirements are proposed for the sensors based on the simulation results.Firstly,a method is established for generating two-dimensional asphalt mixture mesostructure based on random algorithm,and then the sensors are modeled based on the sensing principle and basic structure of the sensors.The low survival rate of the strain sensors during the construction stage indicates that its performance evaluation method is not perfect.Therefore,the construction performance analysis model of the sensors is established based on the generation algorithm of the two-dimensional micro-asphalt mixture.According to the simulation results,four indexes for evaluating the construction tolerance of the sensors are proposed:high temperature resistance index,compression resistance index,maximum axial deformation resistance index and pullout resistance index,and the allowable value range is given.After the sensors are put into service,they mainly face the problem of measurement validity.For strain sensors,a two-dimensional meso-four-point bending beam model is established.Stress concentration will occur near the sensor in the trabecular model,and the strain in the tension zone will be reduced.Moreover,the measurement effectiveness of strain sensors is not ideal.For pressure sensors,a 20cm×20cm pressure model is established.The simulation found that there are obvious stress paths in the mixture under pressure.The pressure sensor with the sensitive surface diameter of 2cm failed to pass the measurement validity.For temperature sensing devices,a 10cm×10cm specimen temperature analysis model and a pavement structure temperature analysis model are established.The heat transfer mechanism of asphalt mixture and the influence of temperature sensors on the pavement temperature field are analyzed by simulation.If the temperature sensing device is too long,it will have an excessive influence on the temperature of the mixture above the sensors.Based on the above analysis,the indicators for evaluating the measurement effectiveness of strain sensors are proposed as package modulus E,strain length L₁,and flange length L₂;the indicators for evaluating pressure sensors measurement effectiveness are the diameter d of the sensitive surface;the index for evaluating the measurement effectiveness of the temperature sensors is the length L.In order to evaluate the construction tolerance of the strain sensors,according to the four indicators,the high temperature resistance test,the compression test,the maximum axial deformation resistance,and the pullout resistance test are designed respectively,and combined with the main performance detection methods given in the specification,a evaluation method is formed for construction performance of sensors.In the AC-25 mixture,the strain sensor of（0.45GPa 90mm 20mm）has the best measurement accuracy.The minimum diameter of the sensitive surface of the pressure sensors is 6cm.The measurement effectiveness is better when the length of the temperature sensors is between 2.5cm-5cm.Based on the construction tolerance and measurement effectiveness evaluation method of the sensors,the sensors that meet the technical requirements of the intelligent pavement can be screened out.