Research On Comprehensive Support Modulus Of Composite Pavement Based On Frequency Response Of Aircraft-runway Coupled Vibration

Most airports of our country are made of rigid pavement. With the rapid development of civil aviation, it rises so rapidly in aircraft load and aircraft off and landing times that airport pavement damage is widespread and varying degrees of damage phenomena of pavement often occurs, particular in the major hub airport. In order to meet the normal operation of the airport, when rigid pavements is damaged in varying degrees, overlay layer of asphalt concrete pavement is often used for structural reinforcement and repair. Airport composite pavement emerges.Calculating methods of the bearing capacity of rigid pavement and flexible pavement has been used widely, but calculating methods of bearing capacity of composite pavement have not been unified. The main way to calculate the bearing capacity of composite in different countries and regions is that : The thickness of composite pavement is converted to to a rigid or flexible pavement thickness, and then the method of the rigid or flexible pavement is used to calculate the capacity of composite pavement. However the methods are different in converting way of different countries and regions, and some of the parameters are influenced by different users that would directly affect the calculation accuracy of the results.This dissertation presents a method to calculate the bearing capacity of composite pavement in order to get the bearing capacity status of the composite pavement quickly and accurately. The main idea is: The relationship between vibration frequency response and pavement structure is solved by establishing a large number of finite element models of airport pavement to measured pavement vibration frequency so that we can ger the parameters of pavement structure by comparing the value we solved by calculating and the one we got by testing.The vibration frequency of composite pavement structure obtained by field tests is used to calculate the parameters of the structure of composite pavement. Then the aircraft load is applied to the finite element models established basing on the parameters obtained to solve the original concrete slab bottom bending tensile stress. Based on the equivalents of the bottom plate bending tensile stress, the writer solves conversing thickness for complex pavement and uses the corresponding support comprehensive modulus of the composite pavement to calculate the modulus of foundation response modulus K',Combined with K' and the thickness determined in terms of the principle of equivalent of cement concrete slab bottom stress for rigid pavement bearing capacity calculation formula, the PCN value is solved.The work finished in this dissertation basing on the main idea above is bellow:1. A number of different parameters of structure of composite pavement are established to calculate the relationship between the parameters and the vibration frequency in the surface and the point underground 6m which Providing a reliable database support to get the true parameters of composite structure.2. A comprehensive conversion among support modulus of composite pavement, the grass-root modulus, the thickness and soil modulus are established.Then foundation response modulus K' with the relationship conversed by support modulus of composite pavement is calculated to provide a reliable parameter to calculate the bearing capacity of composite pavement.3. An idea is proposed to calculate the converting thickness based on the equivalents of original concrete slab bottom tensile pull stress of composite pavement structure as combined with the domestic airport case, calculated converting thickness and PCN of composite pavement under different conditions.4. Combined with composite pavement detection example of an example airport in the southwest, the feasibility of the method of composite pavement bearing capacity which based on equivalent of bending tensile stress is verified.