Material Composition Of Zhong-ba Expressway Asphalt Pavement Based On True Triaxial Test

Any point of pavement internal structure was in pretty sophisticated triaxial state of stress.Traditional measuring methods of strength which was based on maximum normal stress theory or theory of maximum tensile strain holds that oversize uniaxial stress or uni-lateral strain was the main factor leading to the structure failure,which obviously disagreed with the practical failure states of pavement structure.Thus,it was really necessary to study the mechanical properties in complex stress condition,and correspondingly put forward the strength parameters.True triaxial test which had successfully applied to the research on the strength theory of geotechnical was indicated as the most effective method to study the strength properties.True triaxial strength characteristics under three-direction independent load of two sorts of cement stabilized macadam base materias were studied by using the true triaxial apparatus developed by CSUST.(1)、The test results showed that intermediate principal stress effect whose interval range value was determined by the least principle stress was obviously existed in semi-rigid base material which failure strength was significantly improved as for the existence of intermediate principal stress in the state of three-dimensional compression.(2)、Failure mode and failure mechanism under triaxial stress state were analyzed.The influence of indexes which was related to intermediate principal stress on the material strength were studied as well as the rationality used as the material failure control parameters was discussed.Based on what has studied above,the ultimate line of failure plane under same hydrostatic pressure was drawed compared with other strength theory ultimate lines,whose results showed that it was far different from the Mohr-Coulomb criterion which had been commonly used in field of engineering material,while relatively close to π plane failure curve of twin shear strength and twin shear strength smooth ridge model,and the potential strength space differed and varied with the composing material sorts and cement dosages.Material design method was put forward by comparing the strength with different composing material sorts and cement dosages based on the strength parameters the intermediate principal stress ratio which was established above.Strength test of asphalt mixture under low temperatures was conducted by using the true triaxial apparatus.(1)、The testing data indicated that a significant intermediate principal stress effect was also exhibited in asphalt mixture with test temperature-10℃.(2)、The material strength parameter was also chosen as the intermediate principal stress ratio by comparing the low temperature true triaxial strength of different indexes concerned to intermediate principal stress.(3)、Meanwhile,different aging methods were introduced and thermal aging was selected as the ultimated aging method.Study on low temperature strength characteristics considered ageing conditions was conducted,subsequently,the reason the test conditions on strength difference were analyzed.On the basis of the study above,different AC-13 gradation types corresponding to diffenet climate conditions were put forward.