长寿命路面的技术体系及关键科学问题与技术前沿

改革开放以来,我国公路交通事业取得了令人瞩目的巨大成就.截至2019年底,我国公路通车总里程为500多万千米,居世界第二位,高速公路总里程达14万多千米,居世界第一位,有力地支撑了中国的经济发展.但是,我国公路基础设施的人均占有量仅为美国的1/4左右,预计在2035年以前,我国还将新建普通公路1×10~6 km、高速公路5×10~4km以上.可见,我国高速公路建设任务依然繁重.

Efficient algorithm for 3D bimodulus structures

The bimodulus material is a classical model to describe the elastic behavior of materials with tension-compression asymmetry.Due to the inherently nonlinear properties of bimodular materials,traditional iteration methods suffer from low convergence efficiency and poor adaptability for large-scale structures in engineering.In this paper,a novel 3D algorithm is established by complementing the three shear moduli of the constitutive equation in principal stress coordinates.In contrast to the existing 3D shear modulus constructed based on experience,in this paper the shear modulus is derived theoretically through a limit process.Then,a theoretically self-consistent complemented algorithm is established and implemented in ABAQUS via UMAT;its good stability and convergence efficiency are verified by using benchmark examples.Numerical analysis shows that the calculation error for bimodulus structures using the traditional linear elastic theory is large,which is not in line with reality.

Study on triaxial test method and failure criterion of asphalt mixture

Asphalt mixture is the most widely used pavement material all over the world. In China, more than 90% of service expressways are asphalt pavement. However, current asphalt pavement design method still has irrationality. Even though maximum tensile stress theory is used as failure criterion, pavement structure under the effects of wheel load is in three-dimensional complex stress state. Obviously, one-dimensional strength theory cannot reflect the failure characteristics and the resistance of pavement structure. So it is necessary to study the failure criterion of asphalt mixture under three-dimensional com- plex stress state. Due to limitations of test equipment, there are almost no studies in related area. Under this background, this paper develops a new triaxial test method, ac- cording to the investigation of strength characteristics of asphalt mixture under complex stress state through plane isobaric/axial tensile test, plane isobaric/axial compression test, plane tensile and compression/axial tensile test, to reveal the general rules of asphalt mixture＇s strength failure. The failure mode is divided into three types： tensile failure, shear failure and rheological failure. The tensile meridian and compression meridian in the stress space and strength envelope in the π plane where hydrostatic pressure is greater than zero are obtained, and the failure criterion of asphalt mixture under complex stress state is established, providing theoretical method and scientific basis for structure design as well as strength check of asphalt pavement under three-dimensional stress state.

Anisotropic and valley-resolved beamsplitter based on a tilted Dirac system

We investigate theoretically valley-resolved lateral shift of electrons traversing an n–p–n junction bulit on a typical tilted Dirac system(8-Pmmn borophene). A gauge-invariant formula on Goos–H?nchen(GH) shift of transmitted beams is derived, which holds for any anisotropic isoenergy surface. The tilt term brings valley dependence of relative position between the isoenergy surface in n region and that in the p region. Consequently, valley double refraction can occur at the n–p interface. The exiting positions of two valley-polarized beams depend on the incident angle and energy of incident beam and barrier parameters. Their spatial distance D can be enhanced to be ten to a hundred times larger than the barrier width. Due to tilting-induced high anisotropy of the isoenergy surface, D depends strongly on the barrier orientation. It is always zero when the junction is along the tilt direction of Dirac cones. Thus GH effect of transmitted beams in tilted Dirac systems can be utilized to design anisotropic and valleyresolved beam-splitter.

Introduction to special issue on life-cycle assessment of infrastructure

Life-cycle assessment(LCA)is a methodological framework for assessing the environmental performance of products or services at all life-cycle stages,including raw materials extraction,materials processing,manufacture,use,maintenance and end-of-life.In recent years,LCA has been increasingly employed to evaluate the sustainability of subgrades,pavements and side slopes in highway engineering.This would necessarily lead to the advance of design and construction technologies of highways and the improvement of the durability of road infrastructure.