Dynamic Damage Constitutive Model Of Frozen Soil Under Passive Confining Pressure

Frozen soil is a multiphase material with a complex composition,whose strength characteristics are of great importance in frozen soil mechanics.In cold areas,the construction of infrastructure,such as buildings,roads and railways,as well as the laying of pipelines and construction of houses,will inevitably encounter issues associated with frozen soil.During frozen ground engineering,in addition to the static loads caused by all kinds of structures,the frozen soil is often subjected to a variety of impact loads,such as train driving,mine excavation,and blasting.In this study,an aluminum sleeve was utilized as a passive confining pressure device,and a modified SHPB device was adopted to test the dynamic behaviors of frozen soil at different temperatures and high strain rates.Thus,the stress-strain curves and failure model of frozen soil were investigated and compared with the uniaxial state.By comparing these results for two stress states,the experiment shows that besides the temperature and strain rate effects,frozen soil exhibits obvious stress strengthening characteristics,and the failure mode is viscoplastic failure instead of the brittle failure observed under the uniaxial state.The deformation of frozen soil under impact loading is usually accompanied by the evolution of internal defects and micro-damage.By taking the strain and strain rates into account,a rate-dependent damage equation was developed to describe the damage characteristics of frozen soil.Subsequently,a damage-modified rate-dependent constitutive model is proposed to describe the dynamic mechanical properties of frozen soil.Theoretical calculated results are in good agreement with the experimental data,demonstrating that the proposed constitutive model describes the mechanical behavior of frozen soil at various strain rates very well.Regarding frozen soil as a particle reinforced composite material,the soil and ice particles were taken to be the solid matrix and reinforced phase,respectively.Then,the debonding damage of the ice particles was taken into account,and the thermal activation theory was used to explain the damage evolution of the soil matrix.Based on the Mori–Tanaka method,a dynamic constitutive model for frozen soil under a multiaxial state was developed.The theoretical and experimental results agree well,verifying the rationality and applicability of the model.The proposed model does well to describe the dynamic characteristics and axial stress-strain relationship of frozen soil under multiaxial loading.