Analysis On Freeze-thaw Cycling And Mechanical Experiment And Thermo-hydro-mechanics Coupling Of Rock

According to the growing needs of the project in cold regions, around frozen rocks, on the basis of freeze-thaw mechanics, studied damage mechanics properties of rocks under the condition of freeze-thaw cycles; Then on the background of large scale rocks engineering in cold regions, studied the corresponding coupled mathematical model, did the temperature and stress field numerical analysis of surrounding rocks under the freeze-thaw environment.Two typical rocks that are red sandstone and shale were obtained from engineering sites, and they were prepared as standard specimens, did freeze-thaw cycles test in the opening filled water condition of two rocks, set a natural freeze-thaw cycle temperature range is from -20℃to +20℃. Two deterioration models, i.e. scaling mode for red sandstone and fracturing mode for shale were found, analyzed freeze-thaw thawing damage degradation and freeze-thaw vandalism of two rocks; The uniaxial compression tests were conducted on the two types of rocks subjected to different water status (dry and complete saturated) and freeze-thaw cycles (0, 5, 10, 16, 40, 60, 100 cycles), the deformation and compression strength of rocks varied with different cycles of freeze-thaw are recorded, and resistance to freeze-thaw of the two types of rocks are analyzed. Results show: the compressive strength and elastic modulus of sandstones reduce with cycles increase, but freeze-thaw cycle in strength and elastic modulus of shales decline in the first 20 times, after 20 to 100 times, they stable gradually; After rocks suffered from thawing cycles, axial strain under the same pressure of the phase coaxial increases; Relations of red sandstone elastic modulus and uniaxial compressive strength and the number of freeze-thaw can be fitted by quadratic polynomials, but shales'can be fitted by exponential function.According to the single temperature field equations about tunnels, as an example of DaBan mountain tunnel project in Qinghai province, used large scale finite element software to simulate temperature distribution under freeze-thaw cycles which from warming to cool and again; Introduced the frost force in cold region about tunnels, studied the mathematical model about rocks coupling of temperature, moisture and stress field. Finally, with finite element software simulated frost force of the rocks in cold regions. Research shows that, in freeze-thaw environment, tunnel walls near the ground are more susceptible affected by temperature changes and open ventilated convection, temperature and stress change severely; It must be considered in designing and constructing of tunnels in cold regions; In order to reduce freeze-thaw disasters in the cold regions, should take good insulation measures to reduce heat exchanges between temperature and surrounding rocks hole inside and outside, and control the range of freeze-thaw circles effectively.