This study integrates macroscopic dynamic triaxial tests with microscopic discrete element simulations to comprehensively examine the dynamic deformation characteristics of marine soft soils under cyclic loading. Unlike previous research that typically focuses solely on experimental or numerical methods, this approach combines both techniques to enable a holistic analysis of soil behavior. The dynamic triaxial tests assessed macroscopic responses, including strain evolution and energy dissipation, under varying dynamic stress ratios, confining pressures, and water contents. Concurrently, discrete element simulations uncovered the microscopic mechanisms driving these behaviors, such as particle rearrangement, porosity variations, and shear zone development. The results show that (1) The strain range of marine soft soils increases significantly with higher dynamic stress ratios, confining pressures, and water contents; (2) Cumulative dynamic strain and particle displacement intensify at water contents of 50% and 55%. However, at a water content of 60%, the samples exhibit significant damage characterized by the formation of shear bands throughout the entire specimen; (3) As water content increases, energy dissipation in marine soft soils accelerates under lower confining pressures but increases more gradually under higher confining pressures. This behavior is attributed to enhanced particle packing and reduced pore space at elevated confining pressures. This integrated methodology not only enhances analytical capabilities but also provides valuable engineering insights into the dynamic response of marine soft soils. The findings offer essential guidance for the design and stabilization of marine soft soil infrastructure in coastal urban areas.

Excessive tailings accumulation leads to secondary disasters and environmental pollution. Although the tailings used in this experiment have been filtered by beneficiation, the tailings soil itself has low strength and is not suitable for direct use as engineering materials. In order to make better secondary use of molybdenum tailings and improve the mechanical properties of tailings soil, the basalt fibre reinforcement method was used to improve the strength of tailings soil. We assessed the reinforcement embedding effect of fibre reinforcement in molybdenum tailings from macro and micro perspectives. Triaxial shear tests and numerical simulations of rigid fibre-modified tailings were performed and compared with indoor tests. We obtained the stress-strain curve, inter-particle displacement field, and soil particle friction cloud map. Tailings had fine- and medium-grained embedded particles with strong roughness and minimal agglomeration. Fibres exhibited good support and shear resistance. Microscopic analysis confirmed excellent tailings particle embedding. Under different confining pressures, the optimal combination of triaxial shear strength was as follows: water-cement ratio was 0.17, fibre content was 0.8% and fibre length was 9 mm. The results of laboratory triaxial test show that the peak strength of basalt modified tailings is increased by 21.70% compared with that of unmodified molybdenum tailings. By exploring the mechanical properties of fibre modified molybdenum tailings, it is found that basalt fibre can improve the strength of molybdenum tailings sand, and provide a reference for the application of fibre modified sand in civil engineering.