Research on Strength Prediction Model of Sand-like Material Based on Nuclear Magnetic Resonance and Fractal Theory

Abstract

Micro-pore structure has a decisive effect on the physical and mechanical properties of porous materials. To further improve the composition of rock-like materials, the internal relationship between microscopic characteristics (porosity, pore size distribution) and macroscopic mechanical properties of materials needs to be studied. This study selects portland cement, quartz sand, silica fume, and water-reducing agent as raw materials to simulate sandstone. Based on the Nuclear magnetic resonance (NMR) theory and fractal theory, the study explores the internal relationship between pore structure and mechanical properties of sandstone-like materials, building a compressive strength prediction model by adopting the proportion of macropores and the dimension of macropore pore size as dependent variables. Test results show that internal pores of the material are mainly macropores, and micropores account for the least. The aperture fractal dimension, the correlation coefficient of mesopores and macropores are quite different from those of micropores. Fractal characteristics of mesopores and macropores are obvious. The macropore pore volume ratio has a good linear correlation with fractal dimension and strength, and it has a higher correlation coefficient with pore volume ratio, pore fractal dimension and other variable factors. The compressive strength increases with the growth of pore size fractal dimension, but decreases with the growth of macropore pore volume ratio. The strength prediction model has a high correlation coefficient, credibility and prediction accuracy, and the predicted strength is basically close to the measured strength.

Research on Strength Prediction Model and Microscopic Analysis of Mechanical Characteristics of Cemented Tailings Backfill under Fractal Theory

“…However, the correlation coefficient between the fractal dimension of more harmful pores and the compressive strength is lower than that of the first two types of pores, which is only 0.6283. The analysis results of the relationship between the fractal dimensions of pores with different radii and the compressive strength are consistent with the conclusion in [21].…”

“…Based on the above analysis, the strength prediction model to be established is a quadratic function of the two independent variables of the proportion of harmless pores and the fractal dimension of harmful pores. By repeatedly adjusting the expression of the model and referring to the relevant literature [21], the preset strength prediction model is expressed as:…”

“…Hu [20] studied the pore structure of stone powder CTB, quantified the fractal dimension of pores, calculated the grading index of mixed aggregate and studied the relationships of strength with grading index and pore structure. Deng [21] studied and analyzed the microscopic characteristics such as porosity and pore size distribution of sandstone-like materials and established a compressive strength prediction model with the proportion of macropores and the fractal dimension of macropores as independent variables. Zhang [22] studied the pore structure of electrically broken coal samples by using NMR and fractal theory and quantitatively studied the relationship between porosity growth and breakdown capacity.…”

Experimental Investigation of Porous and Mechanical Characteristics of Single-Crack Rock-like Material under Freeze-Thaw Weathering

“…The NMR system applied in this study contained an NMR test device and a saturation device [46]. The NMR test device in this study was a MiniMR-60 type low-field nuclear magnetic resonance analysis system.…”

Correlation Analysis between Microscopic Pore Parameters and Macroscopic Mechanical Properties of Rock-like Materials from the Perspective of Water-Cement Ratio and Sand-Cement Ratio

“…In recent years, many scholars have carried out a series of studies on the internal relationship between micro-pore structure and mechanical properties. Many researchers [ 16 , 17 , 18 ] have used different detection methods to explore the micro-pore structure. Zhang [ 19 ], Deng [ 20 ], Li [ 21 , 22 , 23 , 24 ] discussed the evolution of the micro-pore structure of sandstone and granite samples under freeze-thaw cycles through NMR, establishing the relationship between porosity and mechanical properties.…”