Study On Damage Characteristics And Model Of Coupled Heat-water In Rock Under Freezing-thawing

Rock produces lots of structural planes during the long geological process, such as cracks, joints, etc. Structural planes have a great influence on strength,stiffness and stability of rock. Aiming at the engineering demands in cold regions, this paper focus on freezing-thawing rock. Based on the study on experinment, firstly, analyzing the model of predicting the deterioration degree; and researching on damage constitutive model of freezing-thawing rock. In the end, According to the migration of hydrothermal rock mass under freeze-thaw conditions, based on the continuum mechanics, thermodynamics, segregation potential theory, the coupled equations of seepage field and temperature field are established.The main research works are introduced in the dissertation as following:(1)According to hydraulic pressure theory, considering the Relationship of frost between stress and crack extension length in a single fracture, a formula of the relationship between value of rock macroscopic damage and freezing-thawing cycles is established based on elastoplastic mechanics and fracture mechanics. An analysis model of predicting the deterioration degree is developed. The validity of the model is examined by experiments. The effect on elastic modulus by value of freezing-thaw cycles and heaving stress and permeability coefficient is also discussed. The theoretical results are analyzed and compared to existed experiments.(2)Combined the equation of relationship between ice pressure and microcrack propagation length, the initial damage compliance tensor of the rock under the different freezing-thawing cycles can be calculated. Considering the pore size distribution curve of crack length, which is updated by value of freezing-thawing cycles. The strain of rock is made up of initial damage strain, additional damage strain and plastic damage strain and a micro-mechanical elastoplastic damage model for rock under different number of freezing-thawing cycles is developed based on frictional sliding of pre-existing micro-microcracks in this work. In the damage model, the plastic yield criterion of Drucker–Prager yield criterion is used simultaneously with the micro-mechanics damage model to simulate the inelastic deformation of rocks and Voyiadjis’ strain hardening function under compression is used to define plastic behaviors of such materials.(3)According to the migration of hydrothermal rock mass under freeze-thaw conditions, based on the continuum mechanics, thermodynamics, segregation potential theory, the coupled equations of seepage field and temperature field is established. This model not only considers the influence of heat transfer, phase change latent heat and seepage velocity influence on temperature distribution, but also analyse the effect of crack propagation under the condition of freeze-thaw and segregation potential. The equations is solved by finite difference method which verifies the agreement with the experiment results.