Fractal Characteristics Of Pores In Rock And Soil Based On NMR

In view of the promotion of nuclear magnetic resonance technology,more and more scientific research fields are involved.Because of its high precision and strong integrity,nuclear magnetic resonance is very popular in microstructure.In recent years,there are more and more researches on the pore structure of materials,especially in NMR,mercury injection test and nitrogen adsorption test,which are frequently used in the study of many micro pores.However,there are few researches on the correspondence between them and the consistency of the test results.There are quantitative explorations on the pore structure analysis and application models,especially on the hydration process of cement The exploration of pore structure is not common,and the dynamic change of pore fractal in the process of cement hydration is not involved.In this paper,the NMR data of various materials are selected and compared with the results of mercury injection test,and the relaxation rate is deduced according to the principle of NMR test.Two kinds of pore distribution models were used to analyze and evaluate the results of NMR.At the same time,the change of pore structure in the process of cement hydration is also analyzed,which has reference significance for practical engineering application.The main conclusions are as follows:1.Micro test is consistent in porosity.No matter mercury injection test or nuclear magnetic resonance test,the pore volume accumulation results of the two methods are basically the same,so the two methods can achieve effective results in the determination of micro pores.In contrast,nuclear magnetic resonance test is more detailed in measuring the distribution of pore size;mercury injection test is more advantageous in the distribution of specific pore size.2.The relaxation rate of different materials can be deduced through the principle of NMR and mercury injection test,combined with the consistency of NMR and mercury injection test in the pore structure of solid materials.From this,we can get the corresponding relationship between the two technical means,that is,relaxation rate,an attribute of the material.3.According to the related formula of relaxation rate,the T2 distribution curve of NMR can be converted to the distribution curve of pore radius,which has a good corresponding relationship.Relaxation rate is the key parameter of conversion.As a material property,different materials have different relaxation rates,and it is stable in a certain range.The relaxation rate is determined by the internal pore and Due to the interaction of water,the relaxation rate of rock is lower than that of soil due to the close combination of water and pore in the structure.4.Using fractal model and uniformity coefficient to analyze NMR results of various materials,the pore distribution of NMR test has good fractal characteristics,and the uniformity of pore distribution also has the trend of concentration or dispersion with the change of conditions.At the same time,it also proves the effectiveness of the two models,and the results are consistent with the characteristics and trends of pore distribution.Different materials and the same material have different model results.The mercury injection test also has such results.Through the calculation of fractal model and homogenization coefficient in the process of cement hydration,the two results are consistent in pore distribution.Combined with the function of pore change and hydration reaction in the process of hydration,the development of pores is different under different curing time,and the corresponding fractal dimension and homogenization coefficient of pores are also changing.At the same time,the change of fractal dimension and homogenization coefficient also reveals the change of pores in the process of cement hydration,and dynamically reflects the process of free water to combined water in pores...