This study investigates the freezing process and mechanical impact behavior of saturated soil to provide new insights into soil thermodynamic and improve its comprehensive investigation under a cryogenic engineering environment. The unfrozen water content is a major focus of study during soil freezing. Many studies have proposed models for calculating the unfrozen water content in frozen and unfrozen pores. However, they lack uniformity and consistency on a physical basis and mathematical derivation. An unified theoretical model was derived based on the principle of thermodynamic equilibrium. The main theoretical results indicated that the dimensionless total volume of the unfrozen water membrane in the frozen pores first increased and then decreased with increasing temperature, revealing the temperature effect on the unfrozen water content in frozen pores. By combining the theoretical model with the distinct element method (DEM), water freezing into ice in saturated soil was numerically simulated using two modes of particle expansion. One of the two modes proposed by the authors was to change the coefficient of expansion during saturated soil freezing to further consider the non-linear variation in unfrozen water content. Subsequently, the effects of the two modes on crack generation during saturated soil freezing were compared and analyzed. Finally, based on the dissipation energy produced in particle contacts, a method for calculating the rises in impact temperature in different particles was proposed for revealing the local and discrete changes in frozen saturated soil under impact loading. The main numerical results indicated that the proportion of the number of particles for different temperature rise ranges followed a Weibull distribution, and the average temperature rise of the particles near the incident end was higher than that of the particles near the transmission end.

A coupled electrothermal damage theory model for pipelines is proposed to assess the failure behavior of buried pipelines under lightning strikes. This article considers local thermal nonequilibrium (LTNE) conditions in the soil-water porous medium and the nonlinear characteristics of lightning functions. The calculation results show that the proposed theoretical model has better applicability and accuracy compared with previous models. Parametric analysis shows that under lightning conditions of Im = 20 kA and T1/T2 = 1.2/50 mu s, the maximum local temperature of the soil around the pipeline can reach 2160 K, leading to pipeline breakdown. Metal pipelines are shown to be more effective in conducting charges, which alters the electric field distribution in the soil and impacts the formation of plasma channels. The half-peak value of the lightning waveform has a significant impact on pipeline breakdown, and its increase will increase the risk of pipeline breakdown gradually. When considering LTNE conditions, the change in the pipeline surface temperature becomes more pronounced. Under 8/30 and 8/40 mu s lightning waveforms, the pipeline surface temperature is approximately 150 and 550 K higher, respectively, compared with the thermal equilibrium conditions. The thermal conductivity and porosity of backfill soil can also affect the thermal damage of lightning-struck pipelines. With clay filling, the highest pipeline surface temperature can reach 2590 K, while with fine sand and coarse sand, it is 1980 and 1510 K, respectively. The pipeline lightning disaster model proposed in this article has engineering significance for the investigation of pipeline lightning failure and disaster prevention mechanisms.

The resilience and performance of quay walls during devastating events such as tsunamis and earthquake are critical for coastal infrastructure. Conventional design standards mostly address vertical or inclined quay walls, neglecting the potential benefits of more complex geometry, such as bilinear backface. This study presents a seismic design and stability analysis of quay walls with a bilinear backface under the combined action of tsunamis and earthquake. The study findings reveal a significant reduction in safety factors in terms of sliding and overturning when quay walls are simultaneously exposed to tsunami and earthquake forces. The study also proposes a bilinear wall geometry, considering key factors such as tsunami wave height, water depth, submergence height, excess pore pressure ratio, and wall inclination. This study aims to enhance the design and construction of quay walls with a bilinear backface, thereby improving the safety of coastal structures and communities against these rare but devastating events.

In practical engineering, soil strength displays characteristics of spatial heterogeneity and anisotropy. Neglecting these characteristics complicates reliably evaluations of slope stability. Therefore, this study conducts an in-depth analysis of slope stability considering the spatial heterogeneity and anisotropy of soil strength. First, improvements were made to the existing spatial heterogeneity model and the original Casagrande anisotropy model to enhance their universality and practicality. Next, the spatial heterogeneity and anisotropy of soil strength were coupled and incorporated into the Mohr-Coulomb (M-C) strength criterion using an improved tensile-shear mode. Subsequently, within the framework of the limit equilibrium (LE) theory, a calculation mode of slip surface stress was employed to replace the conventional assumption mode of inter-slice force. This was achieved by constructing slip surface stress functions and introducing the concept of the local factor of safety for the slip surface, along with stress constraint conditions at the ends of the slip surface. This approach integrates the combined mechanisms of tension-shear and compression-shear, as well as the progressive failure modes of slopes. Finally, based on the overall mechanical equilibrium conditions satisfied by the sliding body, a rigorous LE solution for slope stability was established, accounting for the characteristics of the spatial heterogeneity and anisotropy in soil strength. Through comparative analysis of specific examples, the feasibility and effectiveness of the proposed method were validated. Additionally, this research can also be applied to thoroughly elucidate the slope failure mechanism influenced by the spatial heterogeneity and anisotropy of soil strength.

Sudden and unforeseen seismic failures of coal mine overburden (OB) dump slopes interrupt mining operations, cause loss of lives and delay the production of coal. Consideration of the spatial heterogeneity of OB dump materials is imperative for an adequate evaluation of the seismic stability of OB dump slopes. In this study, pseudo-static seismic stability analyses are carried out for an OB dump slope by considering the material parameters obtained from an in-situ field investigation. Spatial heterogeneity is simulated through use of the random finite element method (RFEM) and the random limit equilibrium method (RLEM) and a comparative study is presented. Combinations of horizontal and vertical spatial correlation lengths were considered for simulating isotropic and anisotropic random fields within the OB dump slope. Seismic performances of the slope have been reported through the probability of failure and reliability index. It was observed that the RLEM approach overestimates failure probability (Pf) by considering seismic stability with spatial heterogeneity. The Pf was observed to increase with an increase in the coefficient of variation of friction angle of the dump materials. Further, it was inferred that the RLEM approach may not be adequately applicable for assessing the seismic stability of an OB dump slope for a horizontal seismic coefficient that is more than or equal to 0.1.

The metropolitan region of Belo Horizonte city is home to several high-risk areas with a significant number of mass movement occurrences. Additionally, there are cases of movements in areas that are not considered high-risk, where constructions exhibit a medium to high construction standard. This emphasizes that, in addition to disordered occupations, the terrains have a natural susceptibility to the process. Intervention in slopes through cuts and fills is an unquestionable necessity in geotechnical projects to reinforce unstable or damaged areas. This article explores the field of soil nailing and presents the necessary design practices for its utilization, including safety checks based on deterministic, probabilistic, and finite element analysis. The case study is based in Belo Horizonte, more specifically in the 'Buritis' neighborhood, Brazil. The reinforced slope has a height of 18.5 meters and covers a total area of 1425 square meters. Based on different methodologies, the solution was validated as the most technically feasible, executable, and financially viable.

This study introduces the Passive Earth Reinforcement for Lateral Equilibrium Optimisation (PERLEO) methodology, a novel approach to enhancing stability in deep excavations. Aimed at addressing limitations in existing geotechnical practices, especially in reducing deformations and bending moments in retaining structures, PERLEO utilises soil-cement blocks as passive reinforcement. Employing comprehensive numerical analysis through PLAXIS 2D software, the research advances traditional methods with sophisticated computational modelling. This study thoroughly evaluates the effect of soil-cement blocks' geometrical configurations on the lateral displacement and bending moments of retaining walls. Key findings indicate that optimal dimensions of these blocks significantly mitigate wall deflection and bending moments, thereby enhancing the stability and the overall integrity of deep excavation projects. Additionally, this research introduces design charts, providing tools for engineers to determine the estimates for maximum lateral displacement and maximum bending moment, based on the specific dimensions of soil-cement block configurations and the depths of excavation and embedment. This methodology not only contributes to improved safety and efficiency in deep excavation works but also offers a more economical approach by reducing potential financial and temporal hazards associated with structural failures in complex geotechnical projects.

Pleistocene loess records of the Khovaling Loess Plateau (KLP) in Tajikistan provide rich collections of lithic artifacts demonstrating past human presence in the region. To understand the timing of human activity and environmental conditions prevailing at that time U-Th dating and clumped/stable C/O isotope measurements have been applied to modern and Pleistocene soil carbonates (SCs) collected at several sites on the KLP and surroundings. U-Th ages were corrected by two methods: 1) assuming an initial [Th-230/Th-232] activity ratio of 0.85 +/- 0.25 based on gamma spectrometry of loess/paleosol samples, and 2) the isochron technique using leachates and fully dissolved subsamples. Diagenetic alteration and potential U/Th mobilization and related isotope fractionation due to alpha-recoil was also modelled and found to be minor in the studied soil carbonates. Compared to model ages as references, uncorrected 230 Th ages are only acceptable if measured [Th-230/Th-232] activity ratios of leachates are high (>30), while Th-230 ages derived using method 1 are mostly overcorrected. It appears that SCs can be reliably dated by the U-series disequilibrium method in this sedimentary setting, but isochron dating cannot be spared. Application of the isochron method is required to derive (230)Thmodel ages, which ensures that the non-zero initial (230) Th and possible U-Th gain/loss due to alpha-recoil can be simultaneously corrected and reliable U-Th ages obtained. U-Th ages of Pleistocene SCs clearly demonstrate postpedogenic ingrowth of multiple, non-contemporaneous populations of SCs within loess/paleosol units, and that SC formation happened in many cases under cold, presumably dry glacial climate conditions. Considering that U-Th ages of SCs provide minimum ages of the sediment in which they form, these ages can be useful in developing loess stratigraphic models and for correlation of paleosols with marine isotope stages. This implies that the age of a given paleosol and any lithic artifacts it may contain, indicating human activity, cannot be younger than the age of SCs formed in that paleosol. This is due to the nature of soil carbonates, which can be the product of both syn- and post-depositional processes. Clumped isotope thermometry of SCs collected from modern soils at three sites in Tajikistan provide evidence for SCs dominantly recording summer season soil temperatures, while the calculated soil water oxygen isotope signatures reflect annual signals and carbonate precipitation from source waters incorporating rainfall from prior to and during SC formation. In contrast, some Pleistocene SCs record soil temperatures and stable isotope compositions more appropriate to glacial conditions, confirming the findings of U-Th ages, and highlighting the primary role of aridity-driven soil moisture changes in SC precipitation in this setting. Considering the interpretative complexities of SC stable isotope compositions, involving issues such as SC formation depth within a soil/paleosol profile, seasonality of SC growth and violation of the law of superposition, SC stable isotope proxy records of past climates cannot be considered as a set of clearly sequential data through time. This implies that such SC-based stable isotope records must be accompanied by U-Th dating of carbonates to be meaningful.

This study aimed to emphasize the significance of spatial variability in soil strength parameters on the behavior of nailed walls, highlighting the necessity of probabilistic design approaches. The investigation involved a 7.2-m nailed wall reinforced with five nails, simulated using the local average subdivision random field theory combined with the limit equilibrium method and the FEM, known as the random limit equilibrium method (RLEM) and the random finite-element method (RFEM) approaches. Initially, the wall stability was evaluated by RLEM using 10,000 Latin hypercube sampling realizations. The wall was globally stable among all samples for a correlation length equal to its height (7.2 m). The wall behavior, associated displacements, moments, wall shear forces, nail axial forces, and ground settlements were examined using RFEM. The RFEM analysis reveals that different random fields influence the maximum displacement (H-max), maximum moment (M-max), and maximum shear force (Vmax) experienced by the wall. The cumulative distribution function plots were generated for the wall critical parameters, including H-max, M-max, and V-max. Leveraging the simple weighted averaging and ordered weighted averaging techniques, different combinations of H-max, M-max, and Vmax were assessed with varying weight assumptions. This allowed us to identify critical random field realizations and estimate the level of risk using a newly introduced parameter, the decision index. Finally, the effect of different correlation lengths (isotropic and anisotropic) for two different coefficients of variation of soil strength parameters on the distribution of H-max, M-max, and Vmax was studied. The findings highlight the importance of considering the spatial variability of soil properties to achieve a reliable design of nailed walls.

The presence of oil contamination causes changes in mechanical properties of clayey soil trenches with low liquid limits (CL) such as stress-strain behavior, rupture plain position, plastic zone, and strain energy for soil trenches compared with uncontaminated soils. These changes usually lead to a lower factor of safety against failure and expansion of the plastic zone. The effects of crude oil contamination on the soil shear strength were evaluated by direct shear and plate load tests for various clays and sandy soils. In this research, a numerical finite element modeling in ABAQUS software was used to estimate the effect of oil contamination in the range of 0 to 16% (0%-4%-8%-12%-16%) on the stability safety factor of vertical clayey trenches with heights of 3 m, 4 m, 5 m, and 6 m, and the results were compared with results of a limit state analysis. The findings of the limit equilibrium method show that adding 4% of oil contamination to a clayey trench will decrease 62% of its critical depth. Also, the numerical analysis results show that adding oil contamination in the range of 0 to 16% to the clayey soil will increase the maximum displacements of the trenches to five times their clean state.