Dynamic Response Of Airport Runway Under Aircraft Break Taxiing And Field Test

There are many geological units crossing the high fill airport in mountainous area.The additional dynamic stresses produced by different sections of excavation and filling area under aircraft loads are different.The difference of runway surface is significant,which leads to the increase of the interaction force between aircraft and runway and accelerates the fatigue damage of runway.At the same time,in the process of aircraft landing deceleration and sliding,the pavement panel is subjected to the horizontal braking force generated by the wheel,and the internal stress and strain increase.Under the long-term action of the aircraft,the risk of pavement shear failure and cracking increase,which affect the safety of the runway.Therefore,it is important to study the dynamic response of runway under aircraft moving load to ensure the airworthiness of runway.Aiming at the dynamic response of mountain airport under aircraft moving load,the runway dynamic response models are established by ABAQUS finite element software and semi-analytical finite element program separately,and the similarities and differences between the two models are compared and analyzed.Finally,the semi-analytical finite element program is used to further analyze the runway surface structure and the non-uniformity of the runway foundation under aircraft moving load.Then simulating the process of aircraft landing deceleration and taxiing,considering the vertical load and horizontal longitudinal braking acceleration,the influence of different pavement structures and braking acceleration on the additional dynamic response of runway is analyzed.Finally,the field monitoring system of Chengde Puning Airport runway is used to monitor the additional dynamic response of runway.The main conclusions are as follows:(1)The dynamic response in the foundation under the flexible pavement structure is generally larger than that of the rigid pavement structure.In the 0.4m depth,the vertical normal stress and the xy-direction shear stress caused by the B738 aircraft in the former is 2.75 and 3.31 times that of the later separately.The lateral distribution of the stress in the channel is "saddle shape" in the shallow layer.Under the flexible pavement structure,the vertical stress of the aircraft load has a influence depth of 6.2 m,which is 1.29 times that of the rigid pavement structure;The longitudinal and lateral single-sided influence widths at a depth of 0.4 m are 4.6 m and 8.0 m,respectively,which are only 0.59 times and 0.88 times that of the rigid pavement structure.The vertical normal stress and shear stress at the interface between the excavation and filling of alternate track foundations are abrupt.Compared with the uniform foundation,the response time of vertical normal stress and xy-direction shear stress is shorter;The vertical normal stress in the base is more sensitive to the change of the speed of the aircraft.Especially when the aircraft moving speed is close to the shear wave velocity of the fill soil,the vertical normal stress can reach 1.2 times of the low speed.The principal stress axis will rotate significantly with speed(2)Under the braking force of B738 aircraft wheels alone,the transverse position of stress extreme in runway generally occurs between 2.5 and 3.25 m away from the longitudinal symmetry axis of runway.At the bottom of the base,the additional stresses generated by two adjacent wheels overlap each other,forming a continuous stress response zone.Compared with the single wheel braking force,the fatigue failure period of the runway surface structure reduce from 47 years to about seven years.When the braking force is considered comprehensively,the maximum value of longitudinal compressive stress on the top of the surface layer increases by 9.54%.The extreme value of XY shear stress in front of the wheel and its influence range increase.The longitudinal position of the extreme value moves forward by 0.2 m.Longitudinal normal stress decreases with the decrease of aircraft speed.When the velocity decreases from 70m/s to 50m/s,the extreme value of tensile stress decreases by 67%.When the velocity is lower than 50m/s,the extreme value of longitudinal normal stress does not change much.The shear stress is less affected by the velocity.When the velocity decreases from 70 m/s to 20 m/s,the decrease of the extreme value is less than 10%.(3)The FBG accelerometer working area used in field monitoring is 15-250Hz,which is suitable for Chengde airport runway with vibration response frequency of 100-200 Hz.The remote control technology adopted in the experiment can effectively save manpower,material and financial resources,and the measured data are reliable,which can be used as a monitoring means for a long time.FBG static sensor can effectively measure the field temperature,water content and settlement.Higher water content in the surface layer of foundation can easily reduce the strength of soil and aggravate the settlement of runway.The cumulative settlement of the top surface of FBG static sensor is millimeter level,and the settlement of excavation and filling alternation is obviously smaller than that of filling area.For the instantaneous soil pressure and stress-strain response,the strain alternation phenomenon in the subgrade measured by FBG sensor is consistent with the numerical simulation results.When the elastic modulus of the foundation is 40 MPa,the peak value of micro-strain matches the earth pressure.Influenced by the joint of the track panel,the three-dimensional acceleration of the runway appears multi-peak phenomenon,and the vertical acceleration value is the largest in the acceleration of each direction.Because the impedance of the foundation is small and the acceleration attenuation is slow,the impact time of the vibration on the foundation is longer and the harm is greater.