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| Equivalent unified hardening model of sand considering the stress direction dependence |
| DONG Tong1，2，KONG Liang3，WANG Xing3，FANG Yuyu1，LIU Chao3 |
| (1. Institute of Defense Engineering，Academy of Military Sciences，People's Liberation Army，Beijing 100850，China；
2. State Key Laboratory of Disaster Prevention and Mitigation of Explosion and Impact，Army Engineering University of PLA，Nanjing，Jiangsu 210007，China；3. School of Sciences，Qingdao Technological University，Qingdao，Shandong 266033，China) |
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Abstract The stress direction dependence of soil refers to the property that the mechanical properties of soil change with the change of the stress direction. The inner reason for the special property is that the soil formed by particle accumulation is anisotropic on the micro scale. To quantitatively describe the difference of pore characteristics of anisotropic granular materials along different directions，the pore area ratio is proposed，that is，the ratio of the pore area to the particle area on a certain section of granular material. Then，the quantitative correlation between the pore area ratio and the fabric tensor is established. On this basis，the anisotropic state parameter is defined as the difference between the pore area ratio in the current direction and the average value of the pore area ratio(or the value of the pore ratio)，so as to quantitatively describe the relationship between the state in different directions and the average state of the material. The equivalent stress method is used to “transform” the unified hardening model(UH model)，and the equivalent unified hardening model(EUH model) is established. Only two new parameters are added in the new model which can be directly obtained by the triaxial compression tests. The stress direction dependence of the stress path，pore pressure，stress-strain relationship can be accurate predicted. Moreover，the accurate prediction of the stress direction dependence of each strain component in the main space and physical space is also realized. The result further verifies the scientificity of the equivalent stress method，and lays a solid foundation for the engineering application of the equivalent stress method.
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2022, Vol. 41 
