Explore the vast range of titles available.

Water-bearing joints within rock engineering in cold areas are often subjected to frost heaving force in cold season due to water–ice phase transition. To evaluate the damage and stability of rock mass in cold regions, a 3D model that considers moisture migration loss during freezing and thawing was established to study the characteristics of frost heaving force within joints. Then, the numerical simulation of cyclic freeze-thawing of water-bearing joints was carried out through equivalent expansion coefficient and particle flow calculation methods. The distribution of frost heaving force in and around the joints was obtained. According to the results of the numerical tests and theoretical calculations, the frost heaving force in joints is basically stable, the tensile stress concentration area appears at the joint tip, and the frost heaving force decreases gradually away from the jointed rock mass area. The frost heaving force decreases considerably with increasing cycle number and moisture migration loss but it increases with increasing mechanical strength and joint geometric size of rock and ice. The comparison between the numerical solution of the equivalent expansion coefficient method and the theoretical solution shows that the force size and distribution law of frost heaving for the two methods are consistent.

To address the severe issue of subgrade frost heave in season-frozen soil highway engineering in the Qinghai-Tibet Plateau (QTP) region, this studied investigated the frost-heaving characteristics (FHC) of subgrade soil with different initial water content (IWC) and fine particle content (FPC) under unidirectional freezing (UDF) and surrounding freezing (SDF) conditions through laboratory experiments. Furthermore, based on the thermo-hydro-mechanical (THM) coupling theory, variations in the temperature, moisture, and stress fields were analyzed numerically. The findings aim to provide a reference for the development of preventive and control measures against subgrade frost heave. The results show that the frost-heaving deformation (FHD) of subgrade soil can be divided into four stages: frost-shrinkage deformation stage, FHD rapid increase stage, FHD slow increase stage, and FHD stabilization stage; A sensitivity analysis suggests that controlling the IWC and FPC at approximately 8% and 9%, respectively, in the subgrade gradation design can effectively inhibit frost heave. Compared to the SDF condition, the UDF condition resulted in a more significant temperature gradient and a distinct freezing front. However, stress concentration points were observed under both freezing conditions

An attempt has been made in this paper to conduct an Electrokinetic (EK) enhanced large-scale model study to analyze the heaving phenomena observed in fields. The application of the EK technique on fields to study alkali-induced heaving has been simulated in the laboratory using a rectangular and circular model. The EK technique was mainly employed to facilitate alkali soil interaction. Analysis of the geometry of the model boundary on the various physiochemical as well as geotechnical properties of the soil was conducted. Before that, a simple heaving analysis was also performed in an oedometer without the EK technique. Compare to the maximum heaving of 5.55% observed in the oedometer the soil in EK-equipped circular and rectangular models showed the heaving of 5.42% and 4.21% respectively. The heaving pressure recorded for the oedometer was 67.5 t.m-2 while for the circular and rectangular models these values were 37.7 t.m-2 and 18.8 t.m-2 respectively. Further, the value of unconfined compressive strength of soil decreases from 141 kPa to 80 kPa after interaction with alkali and the decrease was more prominent in the circular EK model. However, there was an increase in the friction angle and a decrease in cohesion value after alkali interaction. The structural alteration due to alkali solution was examined by SEM and XRD analysis.

The accurate determination of unfrozen water content is significant to evaluating the freezing process of pore water and to revealing the freezing damage mechanism. In this study, an in-situ low filed nuclear magnetic resonance (LF-NMR) testing system equipped with a low temperature thermal cycle system were designed to conduct freezing–thawing cycle tests. The pore water freezing process of three sandstone samples (Coarse-grained sandstone, Medium-grained sandstone, Fine-grained sandstone) was studied by using the LF-NMR technology. The results indicate that the free water content of the three sandstone samples decreases sharply as the temperature decrease, the free water signal intensity and peak region decrease significantly from 0℃ to -5 ℃, whereas bound water that exists in small pores needs a much lower temperatures to freezing. The larger the equivalent average pore size, the faster the water–ice conversion rate. The more movable water the sample contains, the greater the frost heaving force generated inside the sample. At the temperature range of 0 ~ -10 ℃, the freezing-heaving strain increasing sharply, and gradually become gentle as the temperature declining. Coarse-grained sandstone with the highest porosity has the largest freezing-heaving strain, while the Fine-grained sandstone with the lowest porosity has the smallest freezing-heaving strain. The freezing damage of Coarse-grained sandstone is more serious than the other two sandstone. P-wave velocities and scanning electron microscope (SEM) test also indicate that Coarse-grained sandstone has more serious damage than Fine-grained sandstone subjected to freezing–thawing cycle.

The phenomena of freezing damage in the cold regional tunnels have happened frequently. Therefore, in order to precisely calculate frost heaving force (σ1), based on the displacement method, a new analytical solution was proposed. The analytical solution presented in this paper was verified by the results of the model test and field measurement of σ1, the imperfect contact effect between frozen and unfrozen zones of surrounding rock was considered and the influence of the interaction between any two factors on frost heaving force was studied by means of orthogonal experiment and analysis of variance. The results show that: (1) the inner radius of lining (ra), excavation radius (r1) and freezing radius (rf) are highly significant for σ1 and the interaction between the inner and outer radiuses of lining (i.e., changes of the size in inner and outer radius of lining) is also highly significant for frost heaving force (σ1); (2) the analytical solution presented in this paper can avoid the frost heaving force (σ1) with tensional property under the condition of the circular tunnel under hydrostatic pressure; and (3) sensitivity function shows that the larger Young’s modulus of lining (EI), inner radius of lining (ra), freezing radius (rf), linear frost heaving rate (β0) and Young’s modulus of frozen surrounding rock (EII) are, the more sensitive the factors EI, ra, rf, β0 and EII are to σ1. It is expected that the results of this paper can give some novel insights for the anti-freezing design of tunnels.HighlightsInner radius of lining is the more sensitive to frost heaving force.The interaction between the inner and outer radiuses of lining is highly significant.The ra, r1 and rf are highly significant for frost heaving force.The analytical solution can avoid frost heaving force (σ1) with tensional property.

Landslides occurring under low-temperature conditions in winter with spatio-temporal unexpectedness can result in significant losses of human life and property. At about 5:51 a.m. on January 22, 2024, a landslide disaster occurred in Liangshui Village, Zhenxiong County, Yunnan Province, China, resulting in 44 deaths. This study analyzes the characteristics and discusses the disaster’s mechanism using a combination of on-site investigation, drone aerial survey, remote sensing interpretation, InSAR analysis, and numerical calculation. The results show that (1) the landslide in Zhenxiong was relatively small in volume, approximately 118,800 m3, but with significant consequences of 44 fatalities; (2) the regional factors such as geology, geomorphology, meteorology, and hydrology are conducive to the development of landslide disasters. The landslide occurred near the top of the steep slope with a height difference of 250 m and was in the form of a “boot-shaped terrain.” The lithology of the area consists of siltstone and mudstone of the Triassic Feixianguan Formation, and the vertical joints of the rock body have cracked up to 1.4 joints per meter; (3) before the landslide occurrence, the slope was in a critical state with extensive development of cracks, and a large number of these cracks were parallel and perpendicular to the ridge. The ratio of historical weathering sections in the stone blocks in the accumulation area is more than 60%. InSAR results show that the landslide source area has been undergoing continuous creeping subsidence since 2020, with a maximum displacement rate of − 61.31 mm/yr; (4) three factors contributed to the slope’s freeze-up and destabilization: the catchment at the slope’s back-end, the sandstone-mudstone interlayer’s geology, and the sustained low temperature before the landslide. The low-temperature frost-heaving effect may finally trigger the landslide. Considering the frost-heaving force, the factor of safety of the block was 0.99, and a landslide debris flow with a high-speed rate of 40.09 m/s was formed after the block was destabilized. This type of geological disaster in winter is highly unexpected and requires great attention.

Shear experiments were conducted on the cement mortar–sandstone bonding interface and the materials themselves to investigate their loss of shear strength and the deterioration mechanism caused by freezing and thawing cycles. The experimental results show that the shear strength of the bonding interface is much lower than that of the original materials themselves under the same normal stress. The shear strength of this interface decreases linearly with increasing number of freeze–thaw cycles, but it linearly increases with increasing normal stress. The cohesion and internal friction angle also decrease as the number of freeze–thaw cycles increases. In addition, obvious freeze–thaw debonding of this interface is observed and it is first caused by the difference in frost-heaving deformation between the cement mortar and the red sandstone, followed by the frost-heaving pressure in the crack formed in the interface. Finally, the shear damage of this interface has been quantified by reconstitution of the interface morphology. As a result, almost all the shear breakage occurs on the red sandstone side, and a concave rough face arises. With the absence of normal stress, the shear abscission area in the red sandstone increases quickly with increasing number of freeze–thaw cycles. However, with increasing normal stress, this shear abscission area decreases, and the layered composite specimens were prone to shear failure straightly along the bonding interface, because the shear dilatancy deformation is constrained. This study provides the shear failure characteristics of cement mortar–rock interfaces under freeze–thaw cycles and contributes to a better understanding of the freeze–thaw debonding mechanism of protective cement mortar layers on rock surfaces.

With the vigorous construction of water conservancy projects in the cold regions of western China, the frost heaving cracking problem of rock mass fissures in cold regions under the water-ice phase change seriously threatens the safety of projects. This study aims to explore the fracture laws of rock masses containing random fissures under frost heaving, providing a basis for frost-resistant design and disaster prevention in cold region projects. The study uses the Smoothed Particle Hydrodynamics (SPH) method. A failure coefficient, a discrete format of the heat conduction equation, and an equivalent thermal expansion coefficient method are introduced to build the model. The Monte Carlo method is used to generate random fissures, and numerical simulations are carried out by setting different fissure lengths, numbers, and dip angles. The results show that different fissure lengths, numbers, and dip angles have different effects on the frost heaving failure patterns of rocks. An increase in length makes secondary cracks more likely to overlap, the cracks become coarser, more complex, and their expansion accelerates. An increase in the number of fissures makes the crack distribution denser, the overlapping and merging of cracks accelerate, and they are distributed in blocks. Changes in the dip angle affect the crack direction, finally, through-going cracks can be formed. By comparing with previous experiments, the rationality of the simulation method is verified. Although the SPH method has certain advantages, there are differences between the simplifications of random fissures and the actual situation. In the follow-up, a three-dimensional SPH method should be developed and combined with non-destructive testing techniques to more accurately simulate the frost heaving mechanical behavior of rocks and support the construction of rock engineering in cold regions.

In order to estimate the ship heave displacement information in real time and accurately, combined with the ship heave motion model, a dual inertial measurement units (IMU) ship heave displacement estimation method is proposed, the corresponding observer is established, and the heave information of the two Imus is fused. The simulation results show that the dual IMU ship heave estimation method has higher accuracy than the single IMU ship heave estimation method.

The stability and performance of loess infrastructure in cold regions are often challenged by seasonal freezing–thawing action. The action of the foundation loess is a complex thermo-hydro-mechanical coupling process, and it is crucial to understand this process for the loess infrastructure in cold regions. A series of controlled tests were conducted to observe the changes in temperature, moisture, and frost heave variations within loess samples under freezing–thawing, and the influences of cycle period, freezing–thawing amplitude, and cycle number on the thermo-hydro-mechanical behavior of loess were investigated. The results reveal that freeze–thaw cycles significantly affect the heat transfer, water migration, and deformation of the loess. The temperatures of sample at different heights periodically vary under freezing–thawing. Water is absorbed to the samples, which undergoes a rapid water intake stage, a water drained stage, and a slow water intake stage under freezing–thawing, resulting in moisture redistribution in loess. Loess undergoes frost heave, thaw settlement, and consolidation processes during freezing–thawing, and a slight wetting collapse may occur after several freezing–thawing cycles. Within the same cycle, frost heave is the largest while consolidation deformation is the smallest. Frost heave and consolidation deformation reach their maximum values at the second cycle, whereas thaw settlement reaches its maximum value during the second or third cycle. Each stage deformation increases with an extended cycle period and almost decreases as the freezing–thawing amplitude increases. Freeze–thaw cycles can induce wetting collapse of loess, resulting in negative residual deformation. Furthermore, the thermo-hydro-mechanical coupling process and the deformation mechanism of loess have been elucidated. These insights contribute to a more comprehensive understanding of the failure mechanisms in loess engineering in cold regions.