Asphalt Mixture Main Force Chains Charactersitics And Skeleton Composition Force Mechanism

The skeleton composed of mineral materials is the main structure of asphalt mixture to bear and transfer external loading.The macroscpic volume index is used as the criterion for evaluating the state of SMA(Stone Matrix Asphalt)mixture skeleton structure.However,the skeleton formation mechanism of asphalt mixture cannot be effectively revealed only by macroscopic volume index.For asphalt mixture,the state of skeleton structure directly affects asphalt mixture performance,especially the mechanical bearing capacity.Therefore,it is necessary to study the asphalt mixture skeleton structure mechanical mechanism.In this paper,the concept of asphalt mixture main force chains and its corresponding force chains forming criteria are put forward based on the force chains theory in granular material mechanics and skeleton stress transfer characteristics.Asphalt mixture main force chains characteristics are quantitatively characterized and its evolution law is analyzed.On this basis,the correlation model between main force chains characteristics and aggregate gradation was established,and the mechanical mechanism of skeleton composition was analyzed from the perspective of transferring external loading.The main steps are as follows:Firstly,the two-dimensional asphalt mixture digital specimens were generated via MATLAB based on the random reconstruction technology.Dynamic modulus master curves of asphalt mortar at different temperatures and frequencies were established by dynamic modulus test.Based on the finite element software Comsol,asphalt mixture digital specimen mechanical tests were carried,and the skeleton stress transfer law was analyzed,which is laid a foundation for the asphalt mixture force chains research.Secondly,asphalt mixture virtual specimen assembly method was proposed to satisfy force chains study,and a variety of asphalt mixture discrete element models were generated based on discrete element PFC software.The force chains identification program was written according to the existing force chains criteria to analyze the feasibility and shortcomings of force chains theory in granular material mechanics for evaluating asphalt mixture force chains.In order to solve these shortcomings,a force chains model which is closely related to skeleton performance was proposed,which is defined as the main force chains structure.The new force chains criteria and the corresponding identification method were also proposed to evaluate the applicability of the new force chains criteria.Then,main force chains quantitative evaluation indices system was established from the main force chains geometric characteristics and carrying capacity.Based on the above virtual model,the virtual bearing plate test is carried out.Asphalt mixture mian force chains structure was identified via new force chains criteria and idenfitation algorithm.The influence of skeleton type,nomial maximum aggregate size,passing ratio of 2.36 mm and pavement structure thickness on main force chains characteristics were analyzed.The asphalt mixture main force chains were identified in different loading stages during the loading process of external load.The effects of skeleton type,nomial maximum aggregate size,passing ratio of 2.36 mm and pavement structure thickness on asphalt mixture main force chains evolution law were also analyzed.The complex network theory was introduced to establish the asphalt mixture main force chains network structure,and the main force chains network structure was quantitatively characterized by the complex network theory parameters.Finally,the relationship model between main force chains performance and aggregate gradation was established based on the above analysis results.The main force chains gradation was proposed based on the aggregate composition in main force chains.The participation of each grade aggregate in skeleton composition was analyzed to reveal the skeleton composition mechanical mechanism.The main force chains characteristics was verified by experiments.