Experimental Study On The Effects Of Freeze-Thaw Cycles On Similar Materials With Different Porosity

The rock mass composition of the natural environment in the cold region is complex and its structure is variable.For the underground rock mass in the deep and shallow,the equilibrium relationship,geometric relationship and constitutive relationship all have relative diversity and certain commonalities.The complex and variable rock mass environment in the cold area has increased many difficulties to the national engineering construction.In particular,facing with the difficulties of the installation and maintenance of engineering equipment and the personal safety of the staff,people need to have a deep understanding of the engineering environment.Therefore,the study of cold rock mass is a very important reference for the construction of cold region.However,since the natural rock mass environment is both complex and variable,and some direct experimental methods have a certain degree of lag,it is unrealistic to carry out direct on-site tests on some rock mass in nature during engineering construction.Therefore,we carry out indoor simulation test by configuring similar material into similar model,and speculate on the actual situation of rock mass environment through the study of the model.Eventually the test has been widely recognized and applied.Based on the project of National Natural Science Foundation of China,"Multi-field Coupling Deep Soft Rock Solid Flow Conversion Theory and Energy Consumption Law "(51374134),a large number of similar models were simulated indoor to explore the impact of freeze-thaw cycles on similar materials with different shale porosity by Observing the change law of physical and mechanical parameters.The main contents of this paper are divided into the following aspects:On the basis of consulting a large number of relevant professional articles at home and abroad,based on the similarity theory of geomechanical model test,water,gypsum powder,cement and river sand are selected as the basic materials for model making.The selected materials are tested repeatedly.According to the physical properties of rock mass,a similar model of rock mass is selected by the ratio of river sand: cement: gypsum powder: water = 2: 1: 0.36: 0.4.The porosity of the similar model was changed by changing the particle size of the river sand,five similar shale materials with different porosities were produced and the porosity of similar shale materials was measured by saturation method.The five kinds of similar shale materials were subjected to freezethaw cycles.The uniaxial compression tests and triaxial compression tests were performed on similar shale materials without freeze-thaw cycles and with freeze-thaw cycles.The experimental research shows that after freeze-thaw cycles,the uniaxial compressive strength,triaxial compressive strength,modulus of elasticity,cohesion and internal friction angle of similar shale materials are reduced,the porosity and Poisson's ratio are increased to some extent compared with those before freeze-thaw cycles.With the increase of porosity,the influence of freeze-thaw cycles on shale similar materials increases first and then decreases.When the porosity is 9.4%~13.6%,the similar shale materials are most affected by freeze-thaw cycles.When the porosity is 5.8%~9.4%,the influence of the freeze-thaw cycles on shale similar materials increases with the increase of porosity.When the porosity is 13.9%~19.1%,the influence of freeze-thaw cycles on shale similar materials decreases with the increase of porosity.