It is generally believed that loess is not prone to liquefaction. However, on December 18, 2023, a magnitude 6.2 earthquake occurred in Gansu Province, China (35.70 degrees N, 102.79 degrees E), triggering a large-scale loess liquefactioninduced flow slide spanning 2.5 km, approximately 10 km from the epicenter. To understand the disastercausing mechanism, this study obtained the physical and mechanical properties of loess in the source area through field surveys and laboratory tests, and characterized the liquefaction behavior of saturated loess layers. The findings indicate that the strong ground motion, saturated loess, and gentle slope collectively contribute to the prevailing dynamic, geological, and topographic conditions. The saturated loess layer primarily comprises silt particles with particle sizes less than 0.075 mm accounting for approximately 92.2 % of its composition. The saturated loess layer at a depth of 11m was liquefied under the action of seismic waves with a peak ground acceleration of 0.40 g, however, due to the unique pore structure of loess, it is observed that pore pressure development rate lags behind strain rise rate during liquefaction process. The majority of strain accumulation occurred during a distinct post-peak stabilization phase following peak seismic activity while pore pressure continues to escalate even after vibration ceases. The results provide scientific insights into understanding the cause contributing to loess liquefaction induced-flow slide disasters due to earthquake.

To investigate the microscopic pore evolution characteristics of Zhanjiang Formation structural clay during the disturbance process, unconfined compressive strength tests, scanning electron microscopy (SEM), and X-ray diffraction (XRD) were conducted on disturbed samples subjected to various disturbance conditions after vibrational disturbance. Based on the evolution characteristics of the microstructure, the microscopic pore characteristics of the disturbance damage of Zhanjiang Formation structural clay were examined. The results indicate the following. (1) The porosity in three-dimensional visualization images of the microstructure reconstructed by ArcGIS 10.1 increases with the disturbance degree, showing a linear growth trend. (2) The correlation analysis between macroscopic mechanics and microscopic pores shows that the unconfined compressive strength of Zhanjiang Formation structural clay is mainly affected by its porosity, with a significant linear negative correlation. Based on this, a reasonable regression model between the microscopic porosity and the unconfined compressive strength has been established. The model can rapidly estimate the unconfined compressive strength from porosity data, facilitating the assessment engineering properties of the soil. (3) The microscopic pore structure of Zhanjiang Formation structural clay exhibits prominent Menger fractal characteristics. The three-dimensional pore fractal dimension has a certain positive correlation with the disturbance degree, and can be utilized to characterize the pore structure and complexity, serving as a significant parameter for the quantitative evaluation of the pore structure characteristics of Zhanjiang Formation structural clay. Consequently, the complexity of the pore structure of the engineering soil can be evaluated by the pore fractal dimension. (4) The impact of disturbance on soil is primarily manifested in the structural changes in secondary clay minerals, transitioning from a relatively intact to a fully adjusted state. During this process, interparticle pores continuously increase, pore structure complexity increases, and interparticle cementation weakens, resulting in the continuous degradation of unconfined compressive strength. This study contributes to a deeper understanding of the disturbance damage characteristics of Zhanjiang Formation structured clays from a microscopic pore perspective, providing a theoretical basis for the engineering construction and operational maintenance in regions with Zhanjiang Formation structural clay.

Red clay as a special soil has a high liquid-plastic limit, water swelling and water loss shrinkage. To solve the problems red clay was modified by calcium carbonate produced in Hezhou, Guangxi. The Liquid-plastic limit, water loss shrinkage, nuclear magnetic resonance (NMR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and consolidated drained (CD) triaxial shear test were carried out on the modified soils. The results show that when the calcium carbonate content is 20%, the plastic limit is 24.38 and the liquid limit is 38.67, which are reduced by 35.04% and 22.16%, respectively. The Montmorillonite content in the modified soil is reduced by 27.7%. The shrinkage coefficient decreased from 0.325 to 0.102. The NMR test shows that the content is 5% and 10% would lead to a decrease in the macropores and an increase in the micropores pores. The phenomenon is the opposite (15% and 20%). All contents led to the porosity increase. The calcium carbonate content of 5% was selected for triaxial shear tests to obtain the stress-strain curves. The Duncan-Zhang was used to predict the modified soil. The model has a large error in the prediction of the peak of the principal stress difference, but the overall trend is relatively consistent. Therefore, the correction coefficient related to the confining pressure was introduced. The corrected model fits the triaxial shear test well. The research provides a method for the liquid-plastic limits and shrinkage properties of modified red clay, explores the influence of calcium carbonate content on microscopic pores, and the correction of the model provides a theoretical basis for practical application.

Due to the inhomogeneity and anisotropy of mine rock bodies, ionic rare earth ore bodies exhibit varying pore structures at different depths. This research focuses on an ionic rare earth mine in Fujian Province, where in situ ore samples rather than remodeled soil samples were studied. Samples from the fully weathered layer at depths of 1 m, 12 m, and 21 m, both before and after leaching, were collected for onsite analysis. Microscopic pore characteristics were evaluated using scanning electron microscopy, and digital image processing was utilized to study the evolution of the pore scale, distribution, and shape in rare earth ore samples at various depths pre- and post-leaching. The results indicate an increase in the ore body's porosity with the depth of the ore samples both before and after leaching. The variation in pore scale is predominantly dictated by the ratio of macropore and large pores. Pre-leaching, the middle ore sample showcased the highest uniformity, with the upper part being the most irregular. Post-leaching, the highest uniformity was observed in the lower ore samples, with the upper part remaining irregular. Pre-leaching, as depth increased, the pore distribution in ore samples became more dispersed, with decreasing orderliness. Post-leaching, the orderliness was most improved in upper ore samples, while middle ore samples became the least orderly. Additionally, before leaching, pore-shape roughness increased with depth; after leaching, the pore shape became more rounded as depth increased, simplifying the pore-shape structure of the ore samples both before and after leaching.