| The mechanical properties and degradation mechanism of rock under freezing-thawing conditions have become one of front direction concerned with rock mechanics field. In cold region mine, coupling effect of rock, water, temperature, ice, stress and other factors are leading to rock freezing-thawing degradation happen and disaster appear, and it has significant impact to mine engineering stability in cold regions. With more and more mining activities in cold regions in China, how to predict and solve the freezing-thawing disaster have been became one of most important research issues. So, studying the rock freezing-thawing degradation mechanical and evolution mechanism could provide theoretical basis for research the freezing-thawing disaster. It has great significance for safety mining in cold regions.Considering the needs of mine engineering in cold regions and relies on the method of testing and theory analysis, this paper finish the research works of mine rock freezing-thawing degradation mechanism and evolution mechanism by NMR technology as in following:(1) Study the rock freezing-thawing degradation theory and evolution mechanism, the effect factors of rock freezing-thawing degradation and its disaster characteristics in cold regions engineering were analyzed too. Combined with the disaster chain theory, freezing-thawing disaster chain-effect and broken chain&disaster mitigation methods of mine in cold regions were discussed.(2) Granite rock which taken from cold regions mine were used as samples and the rock freezing-thawing cycles testing and uniaxial compression strength testing were conducted. The variation law of samples quality, uniaxial compression strength, freezing-thawing factor and rock weathering degree factor of rock after freezing-thawing cycles were obtained. The freezing-thawing degradation models of granite were summarized out and the relationship curve between uniaxial compression strength and freezing-thawing cycles, modulus of elasticity and freezing-thawing cycles were obtained. The freezing-thawing degradation evolution equation of granite was build. (3) The NMR technology was used to measure the pore structure and containing moisture saturation of granite. The characteristic of NMR T2distribution, porosity, T2spectrum and magnetic resonance imaging were obtained, and it has revealed the rock porosity structure characteristic.(4) The granite with freezing-thawing cycles were measured by NMR technology and the characteristic of NMR T2distribution, porosity, T2spectrum and magnetic resonance imaging were obtained. It has revealed the rock degradation characteristic under freezing-thawing condition, and provides a new method for research the freezing-thawing rock mechanics.(5) The NMR analysis on one rock sample with different freezing-thawing cycles was conducted by using the nuclear magnetic resonance technology. The NMR T2distribution characteristics of granite were obtained. And the variation law of rock quality, porosity degree, T2spectrum was obtained too. The exponential relation between rock porosity and freezing-thawing cycles and the rock freezing-thawing degradation equation which used rock porosity as target value were obtained. Degradation process of rock microstructure characteristic under different freezing-thawing cycles condition were summarized.(6) The MRI analysis on one rock sample with different freezing-thawing cycles was conducted by using the magnetic resonance imaging technology. The porosity distribution characteristics and its variation features of granite under different freezing-thawing cycles condition were obtained. It has revealed the degradation evolution law of rock microstructure characteristic under different freezing-thawing condition.(7) Rock NMR analysis and uniaxial compression strength testing have been conducted, and the mechanics characteristics of granite rock under the different NMR character conditions have been studied. The relationship between rock NMR characteristics and mechanics behavior have been built too.
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