Asphalt Pavement High Temperature Deformation Suprimposed Effect Under Aircraft Multi-wheel Load

When an aircraft with multi-wheel landing gear passes by a point of pavement, the multi-wheel will produce stress interference and superposition phenomenon in pavement. However, airport asphalt mixture high temperature performance evaluation follows the highway engineering test method without considering effect of aircraft multi-wheel superposition to asphalt mixture high temperature deformation. This condition makes the airport asphalt pavement much more prone to rutting damage, and makes a significant security risk to the safe operation of the airport. In view of this, asphalt mixture high temperature performance superposition evaluation method is established based on fully analysis of airport pavement multi-wheel loading mechanical response superposition characteristic. Several influence factors of rutting superposition damage is analysed. Through this research, the anti-rutting evaluation method of airport asphalt pavement material can be much more scientific and reasonable.Airport asphalt pavement surface structure information wireless transmission and real-time monitoring system was established based on fiber Bragg gratting(FBG) sensing technology and WLAN technology. The aircraft loading positions, aircraft taxiing speed, asphalt pavement surface temperature, asphalt road surface stress and strain stress, and load superposistion characteristic were obtained by this system. According to the monitoring information, airport asphalt pavement visco elastic non-uniformly distributed load moving finite element model was established based on ABAQUS. The model was verified through on-site monitoring results. The stress and strain along the asphalt surface layer distribution curves of six representative locations were extracted. The results show that, shear stress and shear strain superposition decreases and the triaxial strain increases at the inner region in multiple-wheel loads encircling. Shear stress, shear strain, horizontal normal stress and normal strain superposition superposition increase at the outer region in multiple wheel loads encircling.Judgment can be drawn that multi-wheel loads surrounded by interior areas prone to uplift deformation, load surrounded by the outer region more susceptible to shear failure. Four- wheel loading was determined as the analysis object of multi-wheel superposition effect.The four points loading shear test fixture and test methods with pavement mechanic response characteristics caused by aircraft multi-wheel loading was developed. Four points loading shear test model was established based on ABAQUS. Stress and strain on key point analysis results show that four point loading shear test has the same mechanical distribution characteristics as asphalt layer under aircraft multi-wheel loading. By calculating the finite element model with different diameter to hight ratio, the reasonable specimen size was determined. The aggregate angle variation of asphalt mixture in the process of four penetration shear test and rutting test was compared by industrial CT technology. The two were found to have a similar aggregate angle variation trend. So, deformation characteristic of the test was verified.The influence of superimposed load on the penetration shear test indexes were tested by comparing the results of four point penetration shear test and uniaxial penetration shear test. At the same time, the four point loading shear fatigue test and uniaxial penetration shear fatigue comparison test were done to analysis the effect of superimposed load on asphalt mixture viscoelastic parameters. By using five element damage coupling model, the effect of four point loading shear fatigue test on asphalt mixture creep damage was analyzed. Penetration shear test index changes, viscoelastic parameters change and damage curves showed that the superimposed load increase the the occurred possibility of asphalt mixture deformation failure at high temperature. 8 kinds of asphalt mixtures penetration strength, anti shear strength, penetration load growth rate, shear fatigue life and damage factor were analysed by single factor analysis of variance and grey relational analysis. Results show that penetration load growth rate is the best indicator, which is sensitive to evaluate load superposition on high temperature deformation and associated with dynamic stability. Experimental process to obtain dynamic stability DS* considering several rounds of superimposed effect was proposed based on penetration load growth rate.The factors affecting deformation superposition effect based on load growth rate index were analyzed. The major influencing factors of superposition effect and significant influence were analyzed by orthogonal design method. The mechanism of main influence factors was analyzed by discrete element method. The results showed that the skeleton structure is the main factor of high temperature deformation superposition effect. Discrete element calculation results show that the skeleton structure asphalt mixture has much more shear stress superposition.Multi-wheel rutting test instrument was development based on the similarity theory, which is suitable to apply in the asphalt mixture ruting evaluation used in multi-wheel aircraft passed pavement. The test wheel cloth row, reasonable size of specimens and other key issues were analysed by ABAQUS modeling. The hierarchical times of specimen compaction was proposed based on FBG sensing technology.By using FBG sensor embedded inside the asphalt mixture specimen transmiting information, the superposition force was proved to be existence. The experiment results were verified through the multi-wheel rutting test instrument.