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The pore characteristics of saline soil greatly influence its engineering properties, such as deformation, strength, and permeability. To explore the microscopic pore characteristics of the saline soil profile in Qian’an country, Northeastern China, a study based on the mercury injection test (MIP) and the scanning electron microscope (SEM) test combined with fractal theory was carried out. The results reveal that the pore size of undisturbed saline soil at the sampling point presents the characteristic of trimodal distribution and shows different microscopic characteristics with a depth of 60 cm as the boundary. The shallow soil (surface—40 cm) has poor compactness, high porosity, and macropores (4–40 μm) dominate, while the deep soil (60–100 cm) has higher compactness, smaller porosity, and more uniform pore size distribution. In addition, the pore morphology of the saline soil profile is closer to the sub-long strip or oblate, which indicates the pore has a poor roundness, and the pore edge lines are relatively smooth. The geostatic stress, freeze–thaw cycle, clay content, and soluble salt affect the pore microstructure together. Furthermore, the pore characteristics were evaluated based on the fractal dimension (D ) and surface fractal dimension (Dr ). D has the strongest correlation with the content of small pores (0.04–0.4 μm), and Dr has the strongest correlation with the shape coefficient. D and Dr can jointly reflect the microscopic pore structure characteristics with a good corresponding relationship. [ABSTRACT FROM AUTHOR]

Dispersive soil features rapid disintegration characteristic while interacting with liquid water, which is attributed to the chief culprit for the failure of many earthen infrastructures worldwide. How to quickly identify such a problematic soil in the field relies on the prior knowledge of its failure mode. Take the seasonally frozen semiarid southwest Songnen Plain as investigation background, in this study, five typical failure modes on bare dispersive soil slope are sorted out, including soluble salt crystallization, rill erosion, relaxation tension fissure-associated collapse, subsurface suffosion, and gully erosion, and their formation and evolution features are analyzed. We figured that the silt-dominant soil composition governs the dispersity to a great extent, and the existence of high percentage of sodium ion contributes to reduce the cementation strength of clay particles to silt and sand particles in the presence of water. In addition, analyses indicate that rainfall is the direct trigger factor for failure, and fissures induced by freeze–thaw and dry–wet cycles speed up the water infiltration, enlarge the soil–water interaction surface, and aggravate the bare slope soil destruction in the final. Practices suggest that the adoption of water isolation measures or enhancing cementation strength between soil particles via mixing additives are core failure prevention principles of bare dispersive soil slope. [ABSTRACT FROM AUTHOR]

Slip zone soil is one of the most inherent factors affecting the stability of landslides. In engineering practice, the in situ slip zone soil layer may experience different stress histories and thus have different stress states. In order to clarify the influence of stress conditions on the shear characteristics of slip zone soil, ring shear tests were performed on specimens with different over-consolidation ratios (OCRs). The consolidation, unloading and shearing processes of the samples were numerically simulated using a particle flow code model, and the underlying mechanisms of soil shear characteristics across varying stress states were analyzed in terms of particle displacement. Moreover, the concept of stable residual strength over-consolidation ratio (SRSOCR) was proposed. During the shearing process, for a constant normal stress, the residual strength of the sample was observed to depend on the relationship between the OCR and the SRSOCR. When OCR values were less than or equal to the SRSOCR, the residual strength of the samples were essentially equal. The pre-consolidation stress increased the peak strength, while post-peak drop led to a reduction in the strength. During the consolidation, unloading and shearing processes, the particle displacement varied with consolidation state, causing different shear behavior of samples. It is necessary to determine the strength parameters of the slip zone soil according to its position in the landslide body and its stress history in order to accurately evaluate the stability of the landslide. [ABSTRACT FROM AUTHOR]

To explore the influence of confining pressure on the dynamic characteristics of saturated loess and variation of the characteristics in micro-mechanisms therein, dynamic triaxial testing of loess from Xianyang was carried out. The dynamic elastic modulus of saturated loess after different numbers of cycles was available through the test and the relationship between the dynamic elastic modulus and confining pressure can be analysed. A scanning electron microscope (SEM) examination was conducted to assess the microstructural characteristics of the specimens. From both qualitative and quantitative aspects, the variations in microstructure were analysed. The microstructural parameters which had greater correlation with macroscopic strength were found based on grey relationship theory, then the relationship between them was found by curve-fitting. The results show that, the dynamic elastic modulus of saturated loess was increased as the confining pressure increases, but decreased with increasing vibration cycle and tended to be stable over time. The approximate microstructural parameters selected were correlated to the dynamic elastic modulus in addition to the average pore shape factor; because of the high correlation with the dynamic elastic modulus, the average diameter of the pores, the average shape factor and fractal dimension of the morphology of structural units were selected to fit the dynamic elastic modulus. [ABSTRACT FROM AUTHOR]

Discontinuities formed by different geological processes strongly affect the inhomogeneity of a rock mass. Demarcation of statistically homogeneous regions is useful to speculate the tectonic evolution history. Therefore, a new method is introduced to divide the homogeneous structural domains based on multiple discontinuity characteristics. The new method is divided into three steps. Firstly, the 34-patch network on the lower-hemisphere Schmidt projection and the correlation coefficient are adopted to quantify the similarity of discontinuity orientation. Secondly, the Wald-Wolfowitz runs test is utilized to identify the similarity for trace length and trace type. Thirdly, the structural domains are comprehensively identified based on the similarity of discontinuity orientation, trace length and trace type. The comprehensive method is subsequently adopted to divide the structural domains within the Songta right abutment rock mass. The results illustrate that the rock mass around PD222 and PD234 belongs to the same structural domain D1 and the rock mass around PD224 and PD236 belongs to the other structural domain D2. The D2 located at the high elevation suffers longer and stronger unloading effect of the river valley, which is more likely to form the long discontinuities. However, the D1 located at the low elevation develops mainly the short discontinuities. Hence, it is reasonable and consistent with geological development background that the abutment rock mass is divided into two structural regions along the vertical direction using the new method. [ABSTRACT FROM AUTHOR]

Debris flows could cause large amounts of damage in the alluvial fan where many houses and transport infrastructures exist. Thus, runout analysis of potential debris flows in these areas is necessary for protecting human lives, houses and infrastructure. Currently, the numerical simulation method is an effective way to intuitively display the runout of a potential debris flow. In this paper, a well-balanced finite volume scheme over complex topography was employed for studying the runout of a potential debris flow in the Dongwopu gully. Through model testing and validation, the numerical model had a good potential to adapt to the complex topography and could reasonably simulate the runout of debris flow events. Then, runout distance and inundation path, as well as flow depths and flow velocities, for the potential debris flow were obtained using the model. The simulation results appropriately reflected the runout characteristics. [ABSTRACT FROM AUTHOR]

Rock-quality designation (RQD) plays a significant role in rock mass analysis and is an important parameter in geotechnical and geological engineering. However, the RQD variation with scanline length has not yet been comprehensively considered in RQD. In this study, three-dimensional fracture network modeling was used to simulate actual rock mass, and numerous scanlines were set in the fracture network for investigation on RQD variation. Models and equations (i.e., models A-A, N-N, and A-A-S, as well as the Priest-Hudson and Sen-Kazi equations) were summarized for the study. A corrected equation was proposed to eliminate the errors from using the Priest-Hudson and Sen-Kazi equations. In addition, inhomogeneous and anisotropic features were investigated, and the optimal thresholds for RQD calculation were determined, which varied with the study orientation and rock mass feature. When the inhomogeneity was studied in the x direction, the optimal threshold was found to be 4 m. When anisotropy was studied, the optimal threshold was found to be 3 m. [ABSTRACT FROM AUTHOR]