Research on the characteristics of pore water distribution of calcium carbonate waste soil based on NMR tests

Understanding pore water distribution in soil is essential for elucidating water movement and mechanical properties, as it significantly influences soil strength and stability. Accurate assessment of this distribution provides a scientific foundation for civil engineering design, ensuring structural safety and durability. This study examines pore water distribution using plate load tests and Nuclear Magnetic Resonance (NMR). Results indicate that matric suction expels free water first, leaving bound water until a critical suction point is reached. As matric suction increases, the peak value of the T₂ relaxation time curve decreases, shifting leftward, reflecting water drainage from larger to smaller pores. Then, water expulsion occurs in three stages, with Stage III primarily indicating bound water content, quantified at 19.23%, including 3.3% as strongly bound water. An equation is derived to calculate the surface relaxation rate of 0.0176 μm/ms. Thus, the distribution of T₂ relaxation time can be transformed into pore size distribution, summarizing the characteristics of pore water distribution during the drying process. Finally, comparative analysis confirms the effectiveness of NMR in measuring bound water. These findings enhance our understanding of soil water distribution and highlight the need for advanced models that incorporate pore connectivity and water retention dynamics.