A modified discontinuous deformation analysis method considering the bonding effect for the simulation of structural loess

Bonding effects among non-contacting particles are key phenomena that drive the mechanical behavior and fracture process of structural loess. The existing discontinuous deformation analysis (DDA) methods are incapable of taking into account these microstructural interactions. This work presents a modified DDA method considering the bonding effect to analyze the role of bonds in structural loess at the microscale. Spring elements are used to calculate the bonding forces acting on the particle surface covered by bond materials. The proposed modified DDA method is validated through three benchmark tests: the bending of a cantilever beam, the Brazilian disc test and the compression of rods bonded by epoxy. The results show that the numerical solution agrees well with analytical and experimental data. Microstructure models of a structural loess sample with different contents of bond material are also studied and compression tests are simulated using these models. The results indicate that the content of bond material significantly influences the evolution pattern of the pore structure, which determines the deformation behavior of loess. In addition, structural yield stress and pore stability of loess increase with increasing bond content. It is also shown that the modified DDA method can capture the main pore deformation behaviors in real loess during compression. Finally, the study reveals that the bonding effect is crucial for maintaining the stability of the microstructure of loess.