Critical state line and state parameter have been proved to be an effective method to evaluate and predict the drained and undrained behaviors of sand. However, the existences of fines significantly affect the critical state and state parameter. To overcome this problem, the concept of critical sate line CSL, and state parameter ψ have been investigated with various fines contents in angular sand by processing some previous studies. Results indicated that there is a unique line CSL obtained with a specific fines content for various confining pressures and different initial global void ratios. An increasing in fines content increases the slope of CSL. The critical state line firstly moved down to a limited fines content of 50%, and then, it became to move up. For state parameter, the state parameter generally increased with an increase in fines content. In addition, the normalized shear stress significantly decreases with an increasing the state parameter

Unmanned Aerial Vehicle (UAV) photogrammetry is an effective method for acquiring terrain information. However, in hillside areas, the terrain is complex, and the altitude varies greatly. The mission flight is planned by using equal altitude; in the actual shooting, the geometry and resolution of the pixel within the same image or between adjacent images will be inconsistent due to the different shooting distances. The number and accuracy of point clouds are affected. We propose a contour mission flight plan method, which involves designing flight plans based on the existing digital elevation model (DEM) and the desired flight altitude. This method for aerial photography is more effective in maintaining a consistent ground shooting distance during image capture. Experiments were conducted using a simulated DEM and the undulating terrain of the Kaohsiung Liugui area in Taiwan to verify the effect of contour mission flight planning in the hillside area. The results show that, due to the significant variation of terrain in the hillside area, the use of a contour mission flight plan for aerial photography can be more consistent with the originally planned altitude but requires more planning and operating time. The minor height difference, higher overlap, and improved accuracy of the results show that contour mission planning can provide a suitable solution for UAVs in hillside areas.