A series of unconfined compressive strength tests and flexural strength tests are carried out to evaluate the improved effect of polypropylene fiber on the defects of cement mortar soil. The following factors, including the fiber content, cement content, sand content and curing age, are studied to investigate the influences on the mechanical properties and microstructure of the samples. The results show that the unconfined compressive strength (UCS), residual strength and flexural strength of the fiber reinforced cement mortar soil (FRCMS) substantially increase with increasing fiber content. The peak strain and ratio of the flexural-compression strength (R_fcs) of the FRCMS first increase and then decrease with an increase in fiber content, and the optimal fiber content is 3.5%. The brittleness index of the FRCMS is found to be inversely proportional to fiber content. The results suggest that the addition of an appropriate amount of fibers can substantially improve the plasticity and lateral stress capacity of the FRCMS. The strength of the FRCMS improves with the increase in cement content, sand content and curing age within a certain range. The microstructure of the FRCMS are analyzed by scanning electron microscopy (SEM) tests.

The soil freezing characteristic curve (SFCC) plays a crucial role in investigating the soil freezing‐thawing process. Due to the challenges associated with measuring the SFCC, there is a shortage of high‐quality or rigorous test results with sufficient metadata to be effectively used for applications. Current researchers typically conduct freezing tests to measure the SFCC and assume a singular SFCC when studying the freezing‐thawing process of soils, although limited studies indicated that there is a hysteresis during the freezing and thawing process. In this paper, a series of freezing‐thawing tests were performed to assess the SFCC, utilizing a precise nuclear magnetic resonance apparatus. The test results reveal a hysteresis between the SFCC obtained from the freezing process and that from the thawing process. Through analyzing the test results, the hysteresis mechanism of the SFCC is attributed to supercooling. Supercooling inhibits initial pore ice formation during freezing, causing a drastic liquid water‐ice phase change once supercooling ends. Despite being considered closely related, the hysteresis of the SFCC differs from the soil water characteristic curve (SWCC), and the models used to simulate the hysteresis of SWCC cannot directly be used. To address the impact of supercooling on soil freezing‐thawing hysteresis, a novel theoretical model is proposed. Comparisons between the measured and predicted results affirm the validity of the proposed model.

Tortuosity is an important parameter for studying the permeability of soil. Existing studies of soil tortuosity are usually of empirical nature and attempt to relate tortuosity to soil porosity alone. By assuming a laminar flow through the pores of two‐dimensional square solid particles, we present a mathematical model for calculating soil tortuosity under different particle arrangements. The effect of the randomness of the particle arrangement on the tortuosity is evaluated, which generates the variation range of the tortuosity. The proposed model provides the upper and lower bounds of the tortuosity, while existing empirical models tend to fall within these bounds. The consistency between the proposed model and the numerical calculation provides a validity for the proposed model.

The landslide signs were discovered in a high filling embankment slope, which was located on an express highway construction site in Guizhou, China. According to the in-situ monitoring results, the landslide mechanism and the stabilization effect of the portal anti-slide pile were preliminarily analyzed. The sliding shear zone of the landslide was obtained by the in-situ monitoring. Tw o numerical models with imposed sliding shear zone were established to analyze the evolution of the landslide instability and the stabilizing effect of the portal anti-slide pile. The comparative analysis of in-situ monitoring data and numerical simulation result shows that the two numerical model are reliable. Furthermore, the numerical model of embankment slope that reinforced by portal anti-slide pile was implemented to analyze the structural behavior of pile under the different pile parameters, and the pile-soil interaction was considered in the numerical model. The influence of the pile parameters (pile spacing, pile row spacing, and linked beam size) on the stabilization effect, structural deformation, and economic benefit were studied. The numerical results provide a guide for determining the optimum parameters of the portal anti-slide pile.

Liquid water in frozen porous media provides the path for moisture and solute migration, which is one of the essential problems to study thaw‐weakening and frost‐heave in freezing region engineering. Determining and monitoring liquid water saturation and permeability in saturated frozen porous media are therefore critical issues in cold regions. To this end, geophysical methods are tools of choice given their non‐invasive nature. Electrical conductivity as a physical property is related to both the bulk characteristics of saturated porous medium submitted to frozen temperatures, like porosity as well as liquid water content, and surface properties, such as the solid surface‐liquid water and bulk ice‐liquid water interfaces. In this study, we upscale a microstructural procedure of liquid water‐saturated frozen soils to predict the electrical conductivity with different pore size distributions (PSDs). Then, we analyze the model sensitivity to the model parameters and compare the lognormal and fractal PSD models. Furthermore, the proposed model successfully predicts the experimental data of electrical conductivity for different samples from experiments that are part of this work and published data. The proposed model for characterizing electrical conductivity opens up new possibilities to describe the distribution and dynamics of liquid water with geoelectrical and electromagnetic techniques in frozen environments.