This study introduces a novel discrete element method (DEM) model for compacted loess, incorporating a bond rate parameter within a linear contact bond model to simulate constitutive damage behavior. This enhancement significantly improves the characterization of structural damage from repeated wet-dry cycles, offering a quantitative method for predicting damage progression. Unlike existing DEM models, our model directly uses a bond rate parameter to quantitatively describe inter-particle bond deterioration, reflecting reduced bonding strength due to pore structure development and the weakening effect of water. Rigorous calibration and validation were performed using comparative experiments. A key innovation is the systematic analysis of microscopic parameters (contact stiffness, friction coefficient, contact strength, and bond rate) and their impact on macroscopic mechanical behavior. Our findings show that decreasing the bond rate significantly reduces the macroscopic mechanical properties, providing valuable insights into the micro-macro relationship. We comprehensively evaluated prediction sensitivity to these parameters. This methodology offers a new perspective on using DEM for predicting crucial civil engineering material properties, providing a valuable reference for incorporating bond rate parameters into future modeling, particularly for long-term geotechnical material behavior under environmental degradation. The model's accurate representation of wet-dry cycle effects on loess strength improves earth structure design and safety.

This study focuses on the Yanmazhuang West Station and Jinan West Railway Station of Jinan Rail Transit Line 1, China, examining the dynamic characteristics of eight-layered silty clay and subway station responses in Jinan. Through shaking table model tests, including free-field, two-story two-span, and three-story three-span stations, it finds relationships between the silty clay's dynamic shear modulus ratio and strain, damping ratio and strain, and confining pressure and dynamic shear modulus. It also reveals soil and station structural seismic responses to different intensities and waves.

Apples have been constantly damaged in collecting, transporting, and processing, leading research focus on apples' mechanical-structural damage behavior. To research apples' mechanical-structural damage behavior during collision, a dropping collision damage testing device was self-established, with PLC control, data acquisition-processing, in situ high-speed observation. The effect of impact material, drop height, impact orientation on apple deformation and bruise area was investigated with self-established device, considering three typical kinds of apples. The results indicated that apple dropping collision can be divided into two stages: dropping down contact deformation stage and recovering contact deformation stage. Three kinds of apples demonstrate the largest deformation and bruise area when the impact material is steel and acrylic plate. The deformation is similar when apples collide with soil and foam, apples have no bruise area when the impact material is foam. The correlation between apple deformation, bruising area, and drop height was established, reflecting the relationship between drop height and apples' mechanical-structural damage behavior. Yellow Marshal apple deformation is the largest compared to other two kinds of apples under the same collision condition. Red Fuji apple bruise area is the largest compared to other two kinds of apples. The largest bruise area of Yellow Marshal apple and Guoguang apple are in apple transverse, and Red Fuji apple is in apple top. The study can provide basic theoretical and practical guidance for apples postharvest work.