Development And Application Of A New Constitutive Model Considering Creep-damage And Healing For Salt Rock

To investigate the creep-damage healing characteristic of salt rock,a constitutive model coupling creep,damage and healing of salt rock is developed with consideration of creep-damage healing induced by unloading,based on our creep-damage model.The parameters of the constitutive model are then fitted using the measured data of the creep tests including loading and unloading periods,followed by the sensitivity analysis of the parameters relating to damage healing and creep healing in the constitutive model.According to the results:?1?the creep and damage healing of salt rock has an obvious primary feature,and the creep and damage rates are lowered due to unloading;?2?the extended constitutive model can not only describe appropriately the whole process of creep,damage,and rupture,but also represent effectively the healing behavior of salt rock;?3?no great value variation of parameters related to steady creep-damage and healing was observed.The Dynamic Link Library?DLL?of the expanded constitutive model is programmed using C++through the function of secondary development in FLAC^3D so as to apply the model to practical engineering.Then,two numerical simulations of triaxial compression test are carried out,and model predictions satisfactorily fit the experimental data,verifying the correctness of the DLL.Finally,the developed constitutive model was applied to the creep-damage computation of a natural gas storage cavern in rock salt with bedded mudstone interlayers.We found that:?1?incleasing the internal pressure of cavities triggers the mechanism of creep and damage healing if our healing constitutive model?userc_dh?is adopted;a period of time after unloading,the effect of healing on surrounding rock vanishes gradually,and the rates of creep and damage in surrounding rock are lower than that before unloading;?2?increasing internal pressure of cavities will greatly reduces the creep and damage rates of surrounding rock,especially of middle and top parts of surrounding rock around cavities;?3?the creep property of mudstone is weaker than rock salt;therefore,the rate of mudstone's displacement is smaller than rock salt,thereby constraining creep of the adjacent rock salt and is beneficial to long-term stability of cavities;?4?compared with our previously-proposed creep-damage model,increasing the internal pressure of cavities has more positive effect on constraining floor upheaval than on roof sinking when using our healing model;?5?if not considering unloading,our healing model is simplified to our creep-damage model.