Amid global climate change, freeze-thaw cycles in cold regions have intensified, reducing the stability of infrastructures and significantly increasing the demand for grouting reinforcement. However, the deterioration in the durability of existing grouting materials under the combined effects of freeze-thaw cycles and low temperatures has become a major technical bottleneck restricting their application in cold regions. This paper focuses on polyurethane (PU) grouting materials with foaming and lifting characteristics, systematically reviewing the research progress and technical challenges associated with their engineering applications in cold regions. First, in terms of material composition and preparation, the core components and modified additives are detailed to establish a theoretical foundation for performance regulation. Second, addressing the application requirements in cold regions, standardized testing methods and comprehensive evaluation systems are summarized based on key indicators such as heat release temperature, impermeability, diffusion properties, mechanical strength, and expansion properties. Combined with microstructural characteristics, the deformation behavior and failure mechanisms of PU grouting materials under freeze-thaw cycles and salt-freezing environments are revealed. At the engineering application level, the challenges faced by PU grouting materials in cold regions-such as inhibited low-temperature reactivity and insufficient long-term durability-are highlighted. Finally, considering current research gaps, including the unclear mechanisms of microscopic dynamic evolution and the lack of studies on the combined effects of complex environments, future research directions are proposed. This paper aims to provide theoretical support for the development and application of PU grouting materials in cold-region geotechnical engineering.

In performance-based design, it is crucial to understand deformation characteristics of geocell layers in soil under footing loads. To explore this, a series of laboratory loading tests were carried out to investigate the influence of varying parameters on the strain levels within the geocell layer in a sandy soil under axial strip footing loading. The results were analyzed in terms of maximum strain levels, strain variation along the geocell layer and the correlation between horizontal and vertical strains. In this study, the maximum observed strain levels for geocellreinforced strip footing systems reached 2.3 % for horizontal (tensile) strain and 1.4 % for vertical (compressive) strain. Furthermore, most strain levels were concentrated within a distance of 1.5 times the footing width from the axis of strip footing. In geocell-reinforced footing systems, the interaction between horizontal and vertical strains becomes a key factor, with the ratio of horizontal to vertical cell wall strains ranging approximately from 1 to 2.5. The outcomes of this study are expected to contribute to the practical applications of geocell-reinforced footing systems.

Recent studies have highlighted the potential benefits of allowing inelastic foundation response during strong seismic shaking. This approach, known as rocking isolation, reduces the moment at the base of the column by transferring the plastic joint beneath the foundation and into the soil bed. This mechanism acts as a fuse, preventing damage to the superstructure. However, structures with a low static safety factor against vertical loads (FSv) may experience unacceptable settlements during earthquakes. To address this, shallow soil improvement is proposed to ensure sufficient safety and mitigate risks. In this study, a small-scale physical model of a foundation and structure (SDOF model, n = 40) was placed on dense sandy soil, and seismic loading was simulated using lateral displacement applied by an actuator. A group of short-yielding piles with varying bearing capacities (QU/NU = 0.1-0.8) was installed beneath the rocking foundation. The results of the small-scale tests demonstrate that the use of short-yielding piles during seismic loading reduces the settlement of the shallow foundation by up to 50% and increases rotational damping by 59%. This is achieved through the frictional yielding of the pile wall and the yielding of the pile tip, which dissipate energy and enhance the overall seismic performance of the foundation. The findings suggest that incorporating yielding pile groups in the design of rocking foundations can significantly improve their seismic performance by reducing settlement and increasing energy dissipation, making it a viable strategy for enhancing the resilience of structures in earthquake-prone areas. The optimal bearing capacity ratio (QU/NU = 0.25-0.5) provides a straightforward guideline for designing cost-effective seismic retrofits.

Frequent road collapses caused by water leakages from pipelines pose a severe threat to urban safety and the wellbeing of city residents. Limited research has been conducted on the relationship between pipeline leakage and soil settlement, thus resulting in a lack of mathematical models that accurately describe the soil settlement process resulting from water erosion. In this study, we developed an equation for pipeline leakage, conducted physical model experiments on road collapses induced by drainage pipeline leakage, investigated the functional relationship between drainage pipeline leakage and soil settlement, and validated this relationship through physical experiments with pipelines of various sizes. The results indicated that drainage pipeline leakage triggered internal erosion and damaged the soil layers in four stages: soil particle detachment, seepage channel formation, void development, and road collapse. When the pipeline size was increased by a factor of 1.14, the total duration of road collapse induced by pipeline leakage increased by 20.78%, and the total leakage water volume increased by 33.5%. The Pearson correlation coefficient between the theoretical and actual settlement exceeded 0.9, thus demonstrating the reasonableness and effectiveness of the proposed settlement calculation method. The findings of this study serve as a basis for monitoring soil settlement and issuing early road collapse warnings.

The long-term settlement of subsea pipelines on a clayey seabed is crucial for the on-bottom stability of the pipelines, especially in deep waters. In this study, a poro-elasto-viscoplastic finite element analysis is performed for predicting long-term settlement of subsea pipelines by incorporating a rheological constitutive model. A method for identifying the creep-settlement (Sc) from the total-embedment (Sk) is proposed on the basis of the obtained linear relationship between the secondary consolidation coefficient (C alpha e) of the clayey soil and the total-embedment (Sk) of the pipe. The identifying method is validated with the existing theoretical solutions and experimental data. Parametric study is then performed to investigate the key influential parameters for long-term settlement of subsea pipeline. A non-dimensional parameter Gc is introduced to quantitatively characterize the soil rheology effect on pipeline settlement. The relationship between the proportion of creep-settlement in the total-embedment (Sc/Sk) and Gc is eventually established for identifying whether the proportion of creep-settlement in the total-embedment is remarkable.

Submarine landslides are a geological hazard that may cause significant damage, and are among the most serious problems in offshore geotechnics. Understanding the mechanism of submarine landslide/offshore structure interaction is essential for risk assessment, but it is challenging due to its complexities. In this study, ten centrifuge tests were conducted to determine how offshore wind turbines founded on four piles respond to consecutive submarine landslides. The tests highlighted two mechanisms of soil deformation and foundation settlement associated with the landslide cycle: (1) deformations of the clay were associated with induced excess pore water pressure, and increased with the number of landslides; and (2) by contrast, foundation settlements largely depended on the dynamic impact of the first cycle and remained unchanged for the remaining events. The settlements were 0.5 m for the 10 m pile foundation and about 0.1 m for the 20 m pile foundation, both in clay and in sand. It was also found that increasing pile length reduces the excess pore water pressure, soil deformation and foundation settlement.

As a potential source of damage, earthquake-induced liquefaction is a major concern for embankment safety and serviceability. Densification has been a popular method for improving the performance of liquefiable soils. Understanding embankment settlement mechanisms plays a fundamental role in determining densification remediation. In this work, nonlinear dynamic analysis of embankments on liquefiable soils is conducted by the finite-difference program FLAC3D (version 6.0) with the simple anisotropic sand constitutive model. Numerical models are validated via dynamic centrifuge test results reported in the literature. The effects of densification countermeasures on the mean and differential settlements are explored in this study. Furthermore, the effects of the densification spacing and width are investigated to optimize the geometry of the densified regions. The development of pore pressure and the movement of the surrounding loose soil are discussed. The results show that both the mean settlement and differential settlement should be simultaneously utilized to comprehensively assess the overall effectiveness of densification treatment. The mean settlement is influenced by the densification spacing and width, but the differential settlement is highly associated with the inner edge of the densified region. This study provides insight for improving the design of the location and lateral extent of densification regions to prevent excessive embankment settlement.

Seismic actions are usually considered for their inertial effects on the built environment. However, additional effects may be caused by the volumetric-distortional coupling of soil behaviour: the fast cyclic shaking on saturated soils caused by earthquakes generates temporary undrained or quasi-undrained conditions and subsequent pore pressure variations that, if positive, reduce the effective stresses, eventually leading loose granular soils to liquefaction. Whatever the amount of seismically induced pore pressure build up, buildings on shallow foundations suffer settlements and tilts that may be extremely large when soils approach liquefaction, as demonstrated by several recent case histories. The paper proposes an equivalent elastic approach in effective stresses to predict the co-seismic (undrained) component of the seismically induced settlement of shallow foundations, which usually is the most relevant one, by considering the decrease of soil stiffness during the seismic event. The total settlement can be then estimated by adding the post-seismic (drained) component, also evaluated in this paper via a quite simple approach. Even though the equivalent elastic model is stretched into a highly non-linear soil behaviour range, especially when the soil is approaching liquefaction, the model considers the relevant capacity and demand factors and proved effective in simulating some centrifuge tests published in the literature. In the paper, the simplifying assumptions of the approach are clearly indicated, and their relevance discussed. It is argued that notwithstanding some limitations the model is physically based and therefore it allows for understanding and checking the relative relevance of all the parameters related to soil, foundation, and seismic action. Thus, it is a tool of possible interest in the design of shallow foundations in liquefaction-prone seismic areas.

The occurrence of settlements induced by soil liquefaction will exert a substantial influence on buildings situated in earthquake-prone regions. Previous studies integrated the viscous-damping force into the governing equation to characterize building settlements and considered the apparent viscosity as an important parameter. The existing equation can be utilized to predict the settlement magnitude in the final stage as well as its evolution. However, due to the insufficient description of apparent viscosity, it is commonly regarded as a constant during the process of evaluating settlement. When adopting this mechanism, the evolution of building settlement often proves inadequate in fully capturing actual conditions. The aim of this study is to propose a prediction model for estimating liquefaction-induced settlement of shallow-founded buildings, which is formulated by an analytically differential equation. The proposed model incorporates the time-dependent viscosity of liquefied soil and introduces the concept of a soil column submerged in liquefied soil during seismic shaking. The evolution of settlement and the final settlement magnitude induced by soil liquefaction is evaluated through the analytical estimation, and these findings are subsequently compared with the results obtained from centrifuge experiments and numerical simulations. Furthermore, the proposed model is employed to investigate the correlation between building settlement and the geometric characteristics of shallow foundations. The proposed methodology shows considerable promise as an intermediate tool for assessing building settlement, offering practical simplicity in real scenarios.

Shield tunnelling through densely populated urban areas inevitably disturbs the surrounding soil, potentially posing significant safety risks to nearby buildings and structures. The constitutive models currently employed in numerical simulations for tunnel engineering are predominantly confined to the assumptions of isotropy and coaxiality, making it challenging to adequately capture the complexity of the mechanical response of the soil surrounding the tunnel. Based on the proposed non-coaxial and anisotropic elastoplastic Mohr-Coulomb yield criterion, this study carries out numerical simulation analyses of soil disturbance induced by urban shield tunnelling. Herein, the anisotropic parameters n and /1 jointly determine the shape of the anisotropic yield surface. The results demonstrate that rotation of the principal stress axes is observed in most areas of the soil surrounding the tunnel face, with the phenomenon being particularly pronounced at the crown and the invert of the tunnel. As the anisotropic parameter n decreases, the maximum surface settlement above the tunnel axis increases. The influence of anisotropy on higher-stress unloading coefficients is significant, resulting in the development of a wider plastic zone around the tunnel. As the coefficient of lateral earth pressure at rest K0 increases, the maximum surface settlement gradually reduces. Under the influence of anisotropic parameter /1 or non-coaxial parameter k, the maximum surface settlement exhibits an approximately linear relationship with K0. However, the anisotropic parameter n has a significant influence on the trend of the maximum surface settlement with respect to K0, which leads to a non-linear relationship. Neglecting the effects of soil anisotropy, noncoaxiality, and the coefficient of lateral earth pressure at rest may lead to design schemes that are potentially unsafe. The results of this research can provide engineers with design bases for construction parameters and soil disturbance control while shield tunnelling in sandy pebble soil.