Frozen Red Layer Mechanical Properties Test And Frozen Scheme Optimization Research

In this paper, using the indoor freeze red layer uniaxial strength tests, the uniaxial creep tests, the triaxial shear strength test, the finite element numerical analysis combining method, studied the red layer of artificially frozen soft rock thermophysical parameters, and the mechanical properties of the frozen red layer and the frozen wall design. The following main research:By the experimental study of the red layer thermal physical parameters we know that the frozen red layer formation rock thermal conductivity was between2.368-2.664Kcal/mh℃:the specific heat of the frozen red layer was between0.908-1.149J· g-1K-1; the red layer freezing temperature was between-2.7and-3.7℃,0.7-2.3℃higher than that of the topsoil segment clay.The uniaxial compressive strength of the frozen topsoil increased significantly with the decreasing temperature and almost linear law of growth; the frozen red layer rock by the freezing temperature effect was small, the strength of the rock samples in the negative temperature conditions improved in different degrees compared with that at room temperature, the linear relationship was not good. The instantaneous uniaxial strength and elastic modulus:-5℃to-10℃growth faster than any other temperature range; the mechanical properties of red beds in the room temperature were similar to the soft rock.The creep of frozen red beds under low stress conditions (0.2σs,0.3σs and0.5σs) belonging to the stability creep, occurred only the first and second stages of creep; the creep of frozen red beds occurred non-stability creep deformation when the stress level was high (0.7σs); the frozen red layer formation was typical of viscoelastic-plastic geomaterials.The frozen red layer of triaxial shear test results showed that:the failure criterion of red layer rock samples was obeyed to the improved Drucker-Prager criteria. The triaxial shear strength values of red layer increased with the increasing confining pressure, the internal friction angle was located between2.31to5.52degrees, the cohesion between10.14to11.16MPa.With the simplified theoretical of viscoelastic-plastic constitutive model and the improved Drucker-Prager criterion, this paper deduced the stress and displacement field of the red layer frozen wall.Through the red layer frozen wall temperature field finite element numerical simulation and optimization design, access to the freezing temperature field variation, the single turn frozen pipe arrangement program was the most reasonable, the frozen red layer need65days to cross circle, the frozen wall thickness meet the design requirements when excavated to the depth of the red layer.The results of this paper are the thermodynamic calculations basis of the artificially frozen soft rock frozen wall of the red layer formation; it provides scientific guidance to the freezing temperature field analysis and engineering prediction and of great significance to promoting China’s freezing sinking theory and technological progress.