Study On Rock Energy Characteristics And Creep Characteristics Of Reservoir Bank Slope Under Water-Rock Action

The safety of reservoir bank slope under water-rock interaction is becoming increasingly prominent.The mechanical response of reservoir slope rock mass under water-rock interaction is different from that of general rock mass.The phenomena of rock damage,deformation and creep failure under the dramatic fluctuation of reservoir water level have attracted the attention of scholars,but the cause of formation is still lacking in-depth study.Therefore,aiming at the problems of mechanical deterioration and aging deformation of slope rocks under the large fluctuation of reservoir water level,taking red sandstone of reservoir bank slope in the Three Gorges Reservoir Area as the research object,considering the three situations of "different water content,different water content state and different water-rock cycle" that reservoir rocks often encounter in the operation of hydropower stations,indoor experiments and theoretical analysis are combined to deal with the three problems.The creep deformation and energy characteristics of red sandstone under different water-rock conditions were systematically studied by laboratory tests.The main research results are as follows:(1)According to the acoustic wave test and uniaxial compression test of different water content,the uniaxial and triaxial compression test analysis of different water content states and different water-rock cycles,it is found that the strength of red sandstone is obviously weakened under three conditions: different water content,different water content states and different water-rock cycles.The compactly arranged particles gradually become loose,the cementite gradually dissolves,and the internal pore gradually enlarges.Relatively speaking,the deterioration degree of red sandstone with different water-rock cycles is greater than that with different water content and different water state.(2)From the results of triaxial creep tests under different water-rock cycles and pore water pressures,it is found that the creep of red sandstone increases gradually with the increase of water-rock cycles and stress horizontal loads.The deformation ability of red sandstone is obviously stronger than that of red sandstone without pore water pressure.Variable water pressure makes the steady creep rate of red sandstone increase obviously.Comparing the applicability of stress-strain isochronal curve cluster method and steady-state creep rate method to determine the long-term strength of red sandstone,it is found that the steady-state creep rate method is more suitable to calculate the long-term strength of red sandstone,which has no obvious steady-state creep phenomenon.(3)Based on the creep test curve of red sandstone,which has the characteristics of elastic deformation and viscous flow,an ideal viscoplastic body mechanics model is embedded on the basis of nishihara's model,and a non-linear constitutive model describing the viscoelastic-plastic properties of red sandstone is established.A non-linear viscoelastic-plastic creep model of red sandstone is established by introducing damage variable of red sandstone under water-rock cycling and fitting test curve to obtain model parameters.(4)According to the energy dissipation analysis of uniaxial compression test,uniaxial compression test and triaxial compression test with different water content,different water-bearing state and different water-rock cycle,it is found that the elastic strain energy of red sandstone increases with the increase of confining pressure,and the confining pressure enhances the energy storage capacity of red sandstone.Compared with the other two cases,the dissipation of strain energy of red sandstone is more affected by water-rock cycle.Based on the energy characteristics of red sandstone,an energy damage constitutive model is established to describe the internal structural changes and the internal energy evolution process of rock system under triaxial compression.