Previous studies have shown that structure has a significant influence on the mechanical deformation of unsaturated loess, but there is little published information focused on the influence mechanism of microstructure and mesostructure on the mechanical properties of loess. In this paper, the unsaturated undisturbed loess and its remolded loess under the same physical condition were taken as the research objects. The unsaturated triaxial shear tests with constant suction and net confining pressure were carried out, and the microstructure differences between the two are compared by using SEM and CT scanning to reveal the influence of structure on strength characteristics. The test results show that the cohesion and internal friction angle of undisturbed loess are greater than those of remolded loess. The angle of undisturbed soil particles is obvious, and the particles are bracket contact with good cementation. The remolded loess particles are close to round shape, and the particles are inlaid contact with destroyed cementation. The average radius of undisturbed soil is higher than that of remolded soil, indicating that there are bracket pores in undisturbed soil, but the bracket structure and macropores are deformed during shear deformation, and good structural and cementation ensure the strength of loess specimens.

A combined blast fence is introduced in this paper to improve the solid blast fences and louvered ones. Experiments

This study aims to investigate the mechanical characteristics of precast concrete runway cement pavement under the wheel load of aircraft, and to promote the construction of precast concrete pavement. In this study, based on the elastic layered Boussinesq calculation theory and ABAQUS finite element numerical model, the distribution law of stress, the displacement of the aircraft wheel load acting on different positions of the pavement slab, the influence of the added dowel bar on the pavement slab, and the load transfer between adjacent slabs are obtained. The results revealed that when the wheel load of the aircraft acts on the edge and joint of the slab, the vertical stress of the adjacent slab edge is largest, followed by the middle of the slab, and then the joint; the maximum vertical stress is 0.295 MPa. Furthermore, the aircraft wheel load on the slab edge, and the joint vertical displacement, is larger than that of the slab middle, and the adjacent slab edge transverse displacement attenuation coefficient is approximate. Moreover, the load transfer efficiency of the dowel bar was lower when the wheel load of the aircraft was closer to another unloaded slab. Finally, the validity and sensitivity of the simulation results are verified by laboratory test data. These results can provide a reference and suggestions for the design and production of the precast concrete pavement of airport runways.

No abstract

Operation scheduling of apron support vehicles is an important factor affecting aircraft support capability. However, at present, the traditional support methods have the problems of low utilization rate of support vehicles and low support efficiency in multi-aircraft support. In this paper, a vehicle scheduling model is constructed, and a multi-layer coding genetic algorithm is designed to solve the vehicle scheduling problem. In this paper, the apron support vehicle operation scheduling problem is regarded as a Resource-Constrained Project Scheduling Problem (RCPSP), and the support vehicles and their support procedures are adjusted via the sequential sorting method to achieve the optimization goals of shortening the support time and improving the vehicle utilization rate. Based on a specific example, the job scheduling before and after the optimization of the number of support vehicles is simulated using a multi-layer coding genetic algorithm. The results show that compared with the traditional support scheme, the vehicle scheduling time optimized via the multi-layer coding genetic algorithm is obviously shortened; after the number of vehicles is optimized, the support time is further shortened and the average utilization rate of vehicles is improved. Finally, the optimized apron support vehicle number configuration and the best scheduling scheme are given.