| How to control the initiation and development of the reflective cracking in Asphalt Concrete Overlay (ACO) is a great challenging in the Road Engineering. Since the reflective cracking of ACO on the Old Portland Cement Concrete Pavement (OPCCP) always happen easily and it is a serious problem, many researchers and engineers around the world have been involving in active research of the ACO structure and its reflective cracking, to discover the mechanistic mechanism of reflective cracking initiation, as well as to find the methods preventing its initiation and propagation. However, there are no unique opinions formed about this topic among current research achievements because this problem is very complex and the traffic and climate conditions are different in different regions. Currently, the research of our country on ACO structure type, design method and construction technique is still in an early stage of exploring and experimental trial. From the points of previous research, this dissertation, however, have been thoroughly and systematically extending the research on the initiating and propagating mechanism of reflective cracking and how to choose overlay structures. Also, based on the laboratory experiments and field testing, the design method for ACO on OPCCP is further discussed.This dissertation has mainly covered the study work on six aspects as follows:(l) According to the basic theories of pavement crack mechanics and Finite Element Modeling (FEM), the causes of initiating and propagating mechanism of reflective cracking is analyzed, and the influence of parameters like overlay thickness, modulus, preliminary cracking length, temperature variation, and axes loading on crack intensity factors is studied; (2) The anti-cracking mechanism of several new overlay types is analyzed, and the 3-D FEM is used to analyze the ACO stress in response to different ACO modulus and thickness, and foundation modulus under traffic loading and thermal loading. The loading stress, thermal stress, and coupled stress in ACO structures are emphatically analyzed, considering the ACO with geosynthetics, stress absorption layer, large-stone asphalt mixes cracking relief layer, and graded crushed rock cracking relief layer; (3) The relationships between concrete slab's cracking size and loading stress, thermal stress, coupled stress, and pressured stress on base top, separately, are analyzed. On the basis of theoretical analysis and field road testing, the concrete slab's cracking size of 100cm is considered reasonable; (4) A dynamic 3D FEM is applied to analyze the dynamic response of ACO structure on OPCCP under the moving loading, and the influence of vehicle speed, ACO modulus, foundation modulus, and damp coefficient on the stress, deflection, and deflection difference is studied, which is further compared with the results from static loading; (5) The large-scale experiment apparatus and MTS are applied to conduct fatigue-damage-contrastive experiments on different kinds of ACO structures with the ideal laboratory conditions, through which the initiating and propagating process of load-induced and thermal-induced reflective cracking is simulated, and hence theanti-cracking effects of these kinds of overlays are evaluated; and (6) The design parameters, design criteria and design methods for ACO structures on OPCCP and ACO structures on cracking and seating slab are discussed.The computation method for equal resilient modulus on top of cracked slab is studied.
|
PDF Full Text Request