Pore Structure and Fractal Characteristics of Frozen–Thawed Soft Soil

Abstract

Freezing action always results in great damage to the pore structure and fractal characteristics of freezing–thawing soft soil. Nuclear magnetic resonance (NMR) can help collect data to describe the microstructure of frozen–thawed soft soil. This paper conducted a series of nuclear magnetic resonance (NMR) tests to interpret the effect of freezing duration, freezing–thawing pressure and freezing temperature on soil’s micro-pore structure and fractal characteristics. The pore size distributions (PSDs) of the tested materials were obtained from the NMR T2 spectra, and fractal theory was introduced to describe the fractal properties of PSD. The results demonstrate that the soil assembly with a larger pore structure tends to be a skeleton pore structure with strong fractal characteristics; the shorter the freezing duration is, the less damage caused by the freezing action; a larger pressure during freezing and thawing results in a lower fractal dimension value for thawing soil’s structure, while a lower freezing temperature causes a larger fractal dimension of frozen-thawed soil.

Gas–Water Two-Phase Displacement Mechanism in Coal Fractal Structures Based on a Low-Field Nuclear Magnetic Resonance Experiment

“…However, this kind of method generally has the disadvantages of a small model and low experimental pressure and cannot fully study the gas-water two-phase seepage mechanism in the actual coal-rock mass. Meanwhile, nuclear magnetic resonance (NMR) detection technology can not only characterize the microscopic pore structure of coal-rock mass [21][22][23][24][25][26], but also reflect the flow characteristics of reservoir fluid, and has no such disadvantages [27][28][29][30]. Therefore, Xiao et al [31] carried out water-drive gas reservoir experiments based on NMR online detection technology, studied the displacement characteristics and displacement efficiency of water-drive gas reservoirs under different water injection pressure gradients, and analyzed the breakthrough pressure of water seal and water lock.…”

Study on the Construction Waste Composition and Strength Mechanism of Recycled Mixture

“…e microscopic morphological characteristics and chemical composition of metals, rocks, concrete, soil, asphalt, and other materials have been studied by SEM images and XRD diffraction tests [10][11][12][13][14][15], and the pores, fractures, microstructure, and composition of rocks have been studied indirectly by professional image-processing software and chemical analysis software. Researchers have studied the permeability of concrete, the fractal characteristics of fly ash, the influence of magnesium phosphate cement paste pore structure fractal characteristics and hydration simulation, as well as the different alkali sulfate on low-heat Portland cement, the heat Portland cement and ordinary Portland cement shrinkage, hydration, pore structure, fractal dimension, and the influence of the microstructure [16][17][18][19][20][21][22][23].…”