The Fully Coupled Modeling Of The Deformation-Hydraulic-Thermal-Chemical Behavior For The Fractured Rock Mass In Cold Regions

As the scramble for ownership of the Arctic resource on,the studies of the frozen geotechnical engineering has ushered in new opportunities.The vast frozen regions,accounting for nearly 50%of the earth's land,endows with abundant resources.However,there are a large number of frost damage problem of the fractured rock mass during the process of the resource extraction and engineering construction in cold regions.In consideration of the actual rock mass engineering in cold region,by taking the fractured rock mass as the research subject,the studies of coupling mechanism and theory of the deformation-hydraulic-thermal-chemical behavior for the fractured rock mass in cold regions are carried out on the basis of its anisotropic characteristics,and the classical thermodynamics and mechanics theory of fractured rock mass.The main research results are as follows:(1)The anisotropic moisture migration model of the fractured rock mass in cold regions was established.According to the essential difference between the frozen fractured rock mass and frozen soil,by considering the action of temperature(water/ice phase change),stress,chemical damage and penetration characteristics of fissure water and using the theory of adsorption-film and Clapeyron equation,the special migration mechanism of the fissure water caused by temperature was proposed and the driving potential model of moisture migration of the representative volume element(RVE)of fractured rock mass in cold regions was established based on the equivalent hydraulic aperture evolution model and single fracture seepage model.Based on the geometrical parameters of rock fissure,the permeability of fractured rock mass was treated in terms of the equivalent continuum,and the moisture migration model of the frozen rock mass with several dominant sets of fractures was established.(2)The anisotropic heat transfer model of the fractured rock mass in cold regions was established.Firstly,the shear and normal thermal resistance model of the single fracture were derived.Based on these two models and the principle of energy conservation,the anisotropic heat transfer model of the rock mass with single set of fractures were established under different water content and connectivity conditions.And the anisotropic heat transfer model of the rock mass with several dominant sets of fractures was established based on the coordinate transformation and superposition principle.In addition,the effects of the fracture aperture,length,connecting rate and the content and velocity of the unfrozen water on the heat transfer characteristics of the fractured rock mass in cold regions were also studied.Finally,the established heat transfer model was verified by two calculation cases.(3)The chemical damage model of the RVE of fractured rock mass were established by considering the effects of the velocity and temperature.Based on the rock chemical damage model under normal temperature that proposed by the advisor Prof.Li in 2003,the research ideas and methods of the chemical damage mechanism of fractured rock mass in cold regions and the effects of the chemical damage on the fracture aperture were further proposed.By considering the effects of ice/water phase transition,fluid velocity and temperature on chemical reaction,the chemical damage model of the RVE of fractured rock mass was established.In turn,the effects of chemical damage on the deformation,moisture migration and heat transfer of fractured rock mass were studied based on the chemical damage mechanism of the pressure dissolution and surface dissolution.(4)The fully coupled model of the deformation-hydraulic-thermal-chemical behavior for the fractured rock mass in cold regions was established.Based on the classical thermodynamics theory and models above established of the fractured rock mass,the stress balance equation,the continuity equation,the energy conservation equation and the solute transport equation were established.On the basis of equations above established,the fully coupled model of the deformation-hydraulic-thermal-chemical behavior for the fractured rock mass in cold regions and the governing differential equations were proposed,and then established the coupled theory framework of the fractured rock mass in cold regions.(5)The finite element model of the governing differential equations was proposed and the corresponding analytical procedures were developed.The governing differential equations of the fractured rock mass was discretized respectively in space domain by the Galerkin weighted residual method and in time domain by the two-points progressive format,and then the numerical analysis model was established.The fully coupled analysis procedure 4G2017 of the fractured rock mass in cold regions was developed by the means of the programming idea of geotechnical simulation software FINAL and the coupled analysis program 3G2012 of the saturated frozen soil.Finally,the coupled model and procedures above established were applied to two typical rock mass engineering in cold region to partial validation.The simulated maximum thawed depth coincide with measured well and the stress deformation were accord with the actual project experience and the-spot survey.