Creep characteristics of fractured Beishan granite under the condition of multi-field coupling
After a disposal repository for high-level radioactive waste operates,the near-field surrounding rocks will be long in a ther-mal-hydrological-mechanical coupling environment.Therefore,their mechanical and permeability characteristics are crucial to the per-formance evaluation of the disposal repository.The surrounding rocks of the Beishan preselected area for the disposal of high-level radio-active waste in China are typical sparsely fractured granites,whose creep characteristics are directly related to the long-term safety of the disposal repository.Using water jet and wire cutting techniques,along with fracture surface blocking and combined sealing at rock sample ends,this study addressed the challenges of the sample preparation and sealing of fractured granite in thermal-hydrological-me-chanical coupling triaxial tests.Based on this,multi-loading triaxial creep tests were conducted.The test results indicate that under the condition of multi-field coupling,the triaxial creep strength of the fractured granite was approximately 80%of its triaxial strength.Creep deformation increased with the axial load level,with lateral creeps more pronounced than axial creeps.For the compacted and crack propagation sections of the rock samples,both the axial strain rate and permeability decreased initially and then increased.In the case of consistent osmotic pressure difference,a higher osmotic water pressure within fractures would lead to decreased peak strength of the rock samples and result in greater lateral creep deformation.The results provide scientific support for the site selection,surrounding rock evaluation,engineering design and construction of the repository.
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维普
