Abstract: Red sandstone exhibits pronounced variability in strength and diverse disintegration behaviors, with its pore structure serving as a key factor governing macroscopic mechanical properties. To clarify the intrinsic relationship between pore structure and strength, red sandstones of different strength grades collected along the E’xi Xiangyi Expressway were selected as research objects. Nuclear Magnetic Resonance (NMR) was used to systematically characterize their pore features, and saturated uniaxial compressive strength tests were conducted to analyze how pore characteristics influence mechanical strength. The results show that red sandstone with the lowest porosity and smallest pore size exhibits the highest strength. When porosity is approximately the same, larger pore size corresponds to lower strength, indicating that pore size is also an important factor affecting the mechanical behavior of red sandstone. The findings provide essential data on pore characteristics across red sandstones of varying strengths and offer a useful reference for the design and stability evaluation of redsandstone subgrade engineering along the Xiangyi Expressway.

Key words: Nuclear Magnetic Resonance (NMR), Red Sandstone, Uniaxial Compressive Strength, Porosity Characterization