Research progress on the dynamic characteristics of lightweight soil

Lightweight soil possesses characteristics such as low density, high strength, thermal insulation, vibration isolation, environmental friendliness, and cost-effectiveness. It holds extensive potential applications across diverse geotechnical engineering domains, encompassing roadbed backfill, soft foundation treatment, and tunnel load reduction. As a novel geotechnical material, significant attention has been directed towards the influence of vibration loads resulting from transportation, earthquakes, waves, and other factors on the mechanical properties of lightweight soil. This paper expounds on the influence of factors, including mix ratio (content of lightweight materials, dosage of curing agent, moisture content, etc.), stress state, vibration frequency, and dry-wet alternation, freeze-thaw cycles on the dynamic deformation characteristics and dynamic strength properties of lightweight soil. The study summarizes the calculation model for the dynamic shear modulus and damping ratio of lightweight soil. Findings indicate that the use of curing agents, such as cement and flyash, substantially improves the resistance of lightweight soil to dynamic loads. Additionally, the distinctive pore structure of lightweight soil markedly enhances its vibration isolation effect. As dynamic strain increases, the dynamic modulus of lightweight soil exhibits a nonlinear decrease, while the damping ratio nonlinearly increases. A reduction in the content of lightweight materials and an increase in the dosage of curing agents lead to a substantial increase in the dynamic modulus of lightweight soil, accompanied by a gradual decrease in the damping ratio. Therefore, the adjustment of the content of lightweight materials and curing agents can significantly enhance the seismic reduction effect and endow it with greater dynamic stability. The coupling effects of dry-wet cycles, freeze-thaw cycles, and dynamic loads may result in the degradation of the dynamic performance of lightweight soil. In practical engineering, the service life of lightweight soil can be extended through the implementation of a waterproof layer. Model tests and numerical simulations substantiated the commendable dynamic stability and durability of lightweight soil in actual engineering. Finally, following a comprehensive literature review, potential research directions are deliberated. Presently, the exploration of dynamic characteristics in lightweight soil is in its early stages, and the dynamic properties of novel solid waste lightweight soil remain inadequately studied. Further exploration is required for understanding the response mechanisms, mechanical properties, and constitutive models of lightweight soil under the coupling effects of complex environmental factors and dynamic loads. Additionally, research on the design and construction methods of lightweight soil in various engineering contexts is still necessary. This paper serves as a valuable reference for the investigation of lightweight soil dynamics and its extensive application in geotechnical engineering.