高频变幅水压下裂隙砂岩蠕变行为与劣化机理研究OA

To evaluate the long-term stability of surrounding rock under high-frequency variable amplitude water pres-sure in abandoned mine roadways converted into lower reservoirs of pumped-storage hydropower stations,this study focuses on sandstone from the Haizhou open-pit mine.Step-loading creep tests were conducted using a self-developed visualization device for coupled hydraulic-stress action testing and the effects of different included angles between fractures,variation amplitude and frequency of water pressure on creep characteristics,long-term strength,and failure mechanism were systematically examined in conjunction with scanning electron microscope(SEM)analy-sis.The results show:(1)High-frequency variable water pressure significantly enhances the creep effect,with the creep curve exhibiting a"climbing"phenomenon during the steady-state stage.Greater variation amplitude or higher frequency of water pressure leads to more pronounced creep deformation.(2)Long-term strength decreases with increasing fracture angle,variation amplitude and frequency of water pressure,with the maximum reduction observed at a 90° fracture angle,1.2 MPa amplitude,and a frequency of 3 cycles/day.A quadratic polynomial relationship exists between variation frequency and long-term strength,while a linear relationship exists between variation ampli-tude and long-term strength.(3)Specimen failure primarily propagates along the fracture tips.Larger water pressure amplitude intensifies shear failure,while higher frequency shifts the failure mode toward a tensile-shear composite type and increases the degree of fragmentation.(4)SEM analysis reveals that the water-rock chemical and physical interactions,coupled with the"compression-decompression"effect induced by high-frequency water pressure,accel-erate mineral dissolution,particle migration,and irreversible crack damage,ultimately leading to strength deteriora-tion and instability.