Study On Dynamic Response Of Pavement And Subgrade Under The Moving Load Of Aircraft

The mountain airport is built on the mountains, it's has poor terrain and geological conditions, and unique structure. Runway often cross a number of geological units, fill a large amount of filler, special filler, and there are many coupling effect, poor service environment, very high runway flatness requirements.The high-filled airports in the mountains have special structural forms. Uneven dynamic stresses in the pavement-track foundation will lead to uneven settlement of the pavement. The accumulation of sediment will seriously affect the airworthiness of the aircraft.In this paper, according to the characteristics of high-filling airport in mountainous area, this paper introduces the semi-analytical finite element method for dynamic response of runway under the moving load by Ling Daosheng, The dynamic response of the single-wheel load to the runway pavement-track structure is obtained by the calculation program, and the road-foundation dynamic response of the aircraft's main landing gear under the load is obtained by the superposition principle.Aiming at the special structure of the high-filling airport in the mountainous area,this paper studies the main landing gear configuration, the moving speed of the aircraft, the rigid and flexible pavement structure and the foundation form (the filling and digging alternately, the digging and filling alternately, the different slope Filling and digging alternately foundation and the uniform foundation) changes come into influencing on the dynamic response of the pavement structure and the road foundation provides the theoretical basis for the construction of the mountain airport,and the conclusion is as follows:(1) Under the action of the single-wheel load of the aircraft, the longitudinal and transverse normal stresses in the pavement structure are pressurized on the upper surface of the road panel, the bottom is pulled and the grass-roots over pull. The dynamic stress response in the foundation is mainly composed of vertical normal stress. The moving velocity has little effect on the vertical dynamic stress of the shallow soil, which has a great influence on the deep soil and the impact of the single load Depth of about 2.2m.(2) In the upper side and the bottom of the pavement slab, and the bottom of the basement will appear the stress wave obvious superposition effect under A3 80-800 and B747-400 aircraft moving load. Under the A380-800 aircraft moving load, the stress period of the pavement structure is distributed in three peaks, while the B747-400 is bimodal and the stress is 1 to 4 times larger than that of the single load.As the speed increases, the stress increases, and at the speed of 80m/s the longitudinal normal stress and transverse normal stress are about 1.2 to 1.3 times when the speed is 20m/s, up to 7.0MPa. The effect of the digging and filling alternately and the filling and digging alternately on the longitudinal normal stress in the pavement structure is similar, and the maximum stress at the interface. There is a interval of reverse tension& compression stress variation close to the excavation facies. This interval is 5m from the interface in the filling foundation and 2m in the digging foundation.(3) For the different types of aircraft,the maximum stress in the foundation corresponds to the location, A380-800 aircraft vertical maximum stress appears in the C axis, B747-400 aircraft vertical maximum stress appears in the B axis. In the soil foundation, the impact of the depth of A380-800 aircraft is about 1.1 times of the B747-400 aircraft. The moving velocity has obvious effect on the vertical dynamic stress peak, the faster the movement speed is, the higher the vertical dynamic stress peak, the additional dynamic stress in the deep soil under A380-800 aircraft moving load in 80m/s is 2 times of 20m/s, the impact of the depth in 80m/s is 1.45 times of 20m/s, which is 1.67 times under static load. The effect of the moving speed of the aircraft on the vertical dynamic stress and the long-term cumulative settlement of the road surface can not be neglected. The static analysis method will underestimate the additional dynamic stress level and the depth of the load, resulting in the actual cumulative settlement greater than the predicted value.(4) The dynamic response and the impact depth of the flexible pavement track are more likely to cause the runway settlement and differential settlement than the rigid pavement structure, which affects the airworthiness of the runway.(5) The vertical normal stress reached maximum in the filling and digging alternately interface, which is 6.2 times of in the filling foundation. The vertical normal stress in digging foundation is 2.0 times of the filling foundation. When the cross slope is increased, the dynamic stress peak is increased and the dynamic stress superposition effect is obvious. Dynamic stress path is egg shaped with "horn".