Acta Geotechnica最新文献

Saline soil poses challenges in engineering constructions such as roads, tunnels, and dams and is widely distributed globally, especially in the northwest of China. This study aims to investigate the stabilization effect and mechanism achieved by using an ionic soil stabilizer in combination with lime and fly ash to stabilize saline soil. Standard curing and rapid curing were conducted on stabilized specimens. After curing, unconfined compression tests, scanning electron microscopy, and mercury intrusion porosimetry were employed to investigate the mechanical and microstructural properties of stabilized soil. The results indicate that after treatment with these stabilizers, the strength of stabilized soil can be effectively improved. After long-term curing, the unconfined compressive strength of stabilized specimens reached up to 7455 kPa, corresponding to increases of approximately 51–54 times compared to the strength of specimens before curing. A series of reactions between these stabilizers and soil result in a denser microstructure and better integrity. The relationship between standard curing time and rapid curing time was established based on unconfined compressive strength and microstructural parameters. The mechanism of stabilization processes was revealed, and the proposed rapid curing substitution for standard curing provides relevant reference and guidance for future research.

Underground salt cavern oil storage (SCOS) had long been recognized as a reliable method for underground large-scale oil storage, but traditional approaches, typically relying on single-well with oil(gas) blanket for single-cavern, proved unsuitable for high-impurity salt mines due to the accumulation of insoluble sediment particles. To address this, we developed a novel salt cavern construction method that utilized insoluble sediment voids at the cavern bottom for oil storage, which was called sediment void oil storage (SVOS). Evaluations demonstrated that this method improved construction efficiency and reduced costs while maintaining cavern stability and tightness. Stability analysis showed a maximum volume shrinkage ratio increase of 7.77% over 30 years, and tightness assessments confirmed that interlayer permeability below 10⁻¹⁷ m² effectively contained the stored oil. Sediment particles played a pivotal role in enhancing storage capacity, structural stability, and containment integrity. The construction cost of SVOS is lower than that of traditional SCOS. This innovative method offered significant potential for oil storage application in high-impurity salt mines and provided valuable insights for advancing large-scale underground storage solutions.

Investigation on swelling properties of compacted bentonite with consideration of heating and salinity effects is of great significance for design and safe operation of deep geological repositories for disposal of high-level radioactive waste (HLW). In this study, one-dimensional deformation tests were performed on compacted GMZ bentonite specimens with infiltration of NaCl and CaCl₂ solutions at different temperatures. Thermal and saline effects on the swelling deformation properties were investigated. Meanwhile, MIP tests were performed to quantitatively find out evolutions of the pore size during solution infiltration at temperatures. Results indicate that in the primary stage, the swelling process was accelerated by increasing temperature and solution concentrations. In the final swelling stage, the combined effect of temperature and salinity greatly reduced the swelling strain. MIP results revealed that the total void ratio (e_t) and macropore void ratio (e_macro) decreased with increasing temperature and concentration, while the mesopore void ratio (e_meso) and inaccessible pore void ratio (e_i) slightly changed. This indicated that the decrease in swelling capacity could be related to the disappearance of macropores due to the increase in temperature and salinity. High temperature decreased the basal spacing of montmorillonite and reduced interlayer hydration; moreover, the salt concentration slowed down the diffuse double-layer swelling, resulting in a decrease in macropores and the reduction of swelling capacity of compacted bentonite. Finally, an equation was developed and verified for describing void ratio evolutions with consideration of temperature and concentration effects.

The rapid advancement of in situ monitoring technology has heightened the demand for accurate real-time prediction of landslide’s time of failure (TOF) using displacement data. Yet, the complexity and variability of in situ landslide displacement data pose significant challenges, necessitating further enhancements in the generalizability and accuracy of existing prediction methods. To address this, a new data-driven approach for dynamic landslide life expectancy prediction based on the kinematic features of landslides was proposed in this study. The commonality of overall trend features and abrupt change features of kinematic data in deformation patterns that stay stable and approaching failure were investigated, based on which, the overall trend fitting test (OTFT) for preliminary failure identification was defined. Furthermore, a multistep conceptual framework integrating preliminary stability assessment, onset of acceleration (OOA) identification, and TOF prediction was proposed for dynamic real-time TOF forecasting of landslides. Case study and generalizability assessment demonstrate that the OTFT can consistently identify data with significantly increasing trends before failure, which makes it suitable for preliminary imminent landslide failure detection. The combination of change point detection methods with the deformation standard anomaly index (DSAI) enables accurate and automatic identification of landslide’s OOA, with the sliding F test demonstrating the highest accuracy. Moreover, the predicted TOF time window under the proposed conceptual framework is narrow, and the last predicted TOF that close to the actual TOF.

Synthetic water repellent soil is often used to reduce water infiltration across different soil layers to mitigate frost heave hazards in cold regions. However, the freezing performance of water repellent soil itself remains unclear. Samples with different degrees of water repellency were prepared using octadecylamine. The contact angles, unfrozen water content, pore size distribution, and freezing deformation of the samples were measured. There is a positive correlation between the degree of water repellency and unfrozen water content, the growth rate of macropores, the duration of the rapid frost heave stage and the amount of stable frost heave. Increased water repellency caused an increase in the critical nucleation work for the water–ice phase transition and shifted the dominant heat transfer mode from solid–liquid conduction to air–liquid conduction. This led to an increased unfrozen water content and an extended duration of rapid frost heave. The increased water repellency also changed the ice crystal growth pattern on soil particle surfaces from attachment to detachment, leading to an increased proportion of large pores and frost heave deformation. These outcomes raise concerns about the durability of the protective effect of synthetic water repellent soil used in cold area geotechnical engineering practices.

Surcharge loading often induces excessive lateral displacement of soft soil and adjacent piles, necessitating the development of effective deformation control strategies. This study aims to investigate the influence of surcharge loading on adjacent piles and evaluate the efficacy of the capsule expansion technology (CET) as a lateral deformation control measure through field trials. Meanwhile, numerical simulations were also conducted to further elucidate the interaction mechanisms of the soil–piles–capsules, as well as the deformation control mechanisms associated with capsule expansion. The results indicate that the horizontal deformation of the piles displayed an inverted triangular distribution, closely resembling the deformation pattern of the surrounding soil under surcharge loading. During tube-a-manchette grouting, the injection of cement-based slurry into the soil resulted in undirected splitting and expansion, which failed to produce significant stress concentrations on the pile shaft, thus limiting its effectiveness in mitigating pile deformation. Conversely, CET treatment effectively reduced the maximum horizontal displacement to 10.5 mm, achieving a control efficiency of 56.1%. The capsule expansion could effectively squeeze and push the surrounding soil, inducing additional stress on the adjacent pile which is significantly greater than that caused by surcharge loading, ultimately achieving controlled pile deformation. Furthermore, surcharge-induced lateral stresses were found to increase pile deflection and bending moments. Following CET treatment, the maximum bending moment at a depth of -8 m was reduced by 43.9%. These findings confirm that CET is a promising technique for mitigating pile deformation induced by surcharge loading.

Loess landslides caused by the freeze-thaw cycle (FTC) have become increasingly frequent. In this study, a typical loess landslide in the seasonal freeze-thaw area was taken as the research object. Triaxial creep tests and scanning electron microscope tests were conducted on the undisturbed loess after FTC. The effects of FTC on the creep characteristics, long-term strength, and microstructure of loess were revealed, and the mechanism of FTC-induced loess landslides was discussed as well. The results show that (1) after FTC, the creep deformation of the sample noticeably increases, and the influence of FTC on the shallow loess is greater. (2) The long-term strength of loess after FTC obviously decreases. As the FTC times rise, the long-term strength initially declines, then increases, and then decreases again. The deterioration effect of FTC on shallow loess is more pronounced. With the increase in moisture content, the long-term strength of loess decreases, and the FTC action gradually weakens the strength difference caused by the change in moisture content. (3) The microstructural analysis of loess samples revealed that FTC results in the change of loess microstructure, the weakening of particle cementation, and the instability of particle contact. (4) FTC leads to the accumulation and evacuation cycle of groundwater in the slope. The formation process of freeze-thaw loess landslides is divided into initial stability stage, freeze-thaw deterioration stage, fracture development, and sliding surface formation stage and slope instability stage. The research results provide a new understanding for the study of loess creep characteristics and the formation mechanism of loess landslides.

In the presence of water, geomaterials, such as rocks and soils, may undergo a process of mineral dissolution, depending on the composition of solid minerals. Mineral dissolution increases the porosity, decreases the stiffness, and alters the hydraulic permeability of the material. In the present research, we develop a model for the study of mechanical behavior of fluid-saturated geomaterials undergoing mineral dissolution. An internal variable is introduced in the constitutive equations to account for the effects of mineral dissolution on the mechanical response of the material. The internal variable evolves with time, and its evolution equation is derived from the rate equation for dissolution. The mechanical properties of the material are dependent on this internal variable, and the Mori–Tanaka scheme is used to estimate the bulk and shear moduli of the material subject to mineral dissolution. Further, we present a mixed finite element formulation for solving a set of coupled governing equations. Finally, as an illustrative example, we examine a benchmark problem in soil mechanics to show the interactions between mineral dissolution, pore pressure diffusion, and solid deformation.

The sustainable utilization of excavated soil as a geomaterial requires a comprehensive understanding of its multi-dimensional properties, but correlating heterogeneous data (e.g., visual, mechanical, and electrical characteristics) remains a challenge. To address this, an excavated soil information collecting system was developed to acquire multi-source data including RGB images, cone index (CI) curves, and TDR waveforms—from China’s largest soil transfer platform, establishing a database of 23,122 sets. A generative-model-aided correlation analysis framework was proposed, leveraging a denoising diffusion probabilistic model to explore inherent relationships between soil properties. Performance metrics, such as SSIM, LPIPS, and RMSE, were employed to analyze the model's training results. Key findings reveal that: (1) soil images encode water content information, which correlates with CI curves and TDR waveforms; (2) CI and TDR data cannot capture color-based mineral composition details from images; and (3) TDR waveforms uniquely detect pollution indicators (e.g., electrical conductivity), undetectable via other methods. This AI-driven approach provides a novel methodology for analyzing multi-dimensional property correlations in geotechnics, enhancing sustainable soil reuse.

Bentonite pellets are utilized to fill gaps between the buffer layer, comprised of compacted bentonite blocks, and the surrounding rock in a deep geological repository (DGR) for disposing nuclear waste. Thermal contact resistance (TCR) arises at the interface due to the imperfect contact between the compacted bentonite blocks and the bentonite pellets. TCR is one of the parameters influencing the thermal performance of DGRs, therefore, understanding the TCR between bentonite blocks and pellets is essential for accurately assessing the thermal performance of DGRs. To this end, a testing system based on the steady-state method has been developed and implemented to measure the TCR. Utilizing this system, the TCR at the interface between bentonite block and pellets was evaluated under various conditions: temperature, dry density, water content and particle size distribution. The results indicate that the TCR of the interface between bentonite block and bentonite pellets is on the order of 10^–2 °C·m²/W. TCR increases with the difference between the thermodynamic properties of bentonite block and pellets increasing. Particle size distribution significantly affects the TCR, with mixtures containing only coarse particles exhibiting the highest TCR. Incorporating fine particles into these coarse pellet mixtures effectively reduces the TCR. As the mass fraction of fine particles increases, TCR initially decreases and then increases. TCR decreases as temperature rises, with a more pronounced decrease observed between 50 °C and 70 °C, while the decrease is less significant from 70 °C to 130 °C. Furthermore, multi-parameter sensitivity analysis revealed that the dry density of bentonite block has the most significant influence on the TCR, whereas heating temperature has the least influence.