In light of the problems of large operation resistance and small soil fragmentation during the harvesting operations of existing cassava harvesters, a long- and short-toothed digging shovel was designed. A virtual simulation soil trough model of cassava ridge soil particles was established using the discrete element method, and the Hertz-Mindlin with JKR contact model was employed to simulate the operation quality of the long- and shorttoothed digging shovel and the original digging shovel. In the movement and force analysis of the digging shovel, the angle of entry, the advance speed of the machine, and the height of the digging adjustment were the test factors. The response surface test was conducted on the digging rate and the damaged cassava rate. The results of the experimental field trial showed that the average digging rate of harvested cassava increased by 2.56%, and the average rate of damaged harvested cassava decreased by 1.54%, compared with the original digging shovel. The digging operation process was stable and met the requirements of cassava harvesting field operations. The results of this study may inform future studies on the design and improvement of a cassava harvester.

Active moisture control of wicking geotextiles is an effective way to prevent roadbed frost heave diseases. The performance of water conducting fibers determines the drainage function of the wicking geotextile. This study proposes a design method of the cross-sectional structure that synergistically consider drainage and mechanical properties in fibers. The circular or elliptical fiber profile and semicircular groove shape are first determined based on the maximization of the fiber cross-sectional specific surface area. Then, numerical simulation orthogonal experiments are conducted using COMSOL Multiphysics software to investigate the water conductivity and uniaxial tension of irregular fibers. The CRITIC weighted indicator of water conductivity to fiber volume ratio, tensile stress peak and fracture elongation is used as the analysis objects. The influence weights of fiber contour morphology, fiber size, groove number and groove area ratio on the weighted indicators are analyzed, and their optimal values are determined. The optimal M-shaped fiber is obtained, and the effectiveness of optimization design is verified through scanning electron microscopy and uniaxial tensile test. The M-shaped fiber is woven into the wicking geotextile, and geotextiles water conversion corporation test and drainage test of silty clay soil column is carried out. The test find that mass moisture content of the soil sample decreased by 4.73% within 8 days, which is 2.24% more than that of the staple fibers needling geotextile. This proves the effectiveness of M-shaped fibers and wicking geotextiles woven into them.