Mode Crack Research Articles

Study on mechanism of lining cracking and distribution rule of void cracks behind lining based on XFEM

Various diseases such as lining defects, structural cracking, and water leakage are common in tunnel operation. Therefore, this paper considers the research object of the highway tunnel with typical lining defects, namely voids behind the lining. The stress distribution and crack distribution of the void behind the lining were analyzed by numerical simulation based on XFEM, and the cracking mode of the lining was studied by model test. According to the results:(1) The voids behind the tunnel lining change the stress distribution characteristics of the lining, and the lining structure within is stretched, significantly reducing the overall safety of the lining structure. (2) With the expansion of the void range (i.e. the void toroidal range and radial length), the lining area corresponding to the void is easy to crack, and the expansion of the void range leads to the increase of the crack area, which is also verified by the model test results. (3) A safety factor analyzes the bearing capacity of the lining structure. The safety factor of the lining area corresponding to the void is reduced, which is consistent with the results obtained by the XFEM method for the calculation of lining cracking, which proves that the XFEM method can be applied to the safety calculation of tunnel lining structure.

Effects of multiple edge cracks, shear force, elastic foundation, and boundary conditions on bucking of small-scale pillars

The buckling instability of micro- and nanopillars can be an issue when designing intelligent miniaturized devices and characterizing composite materials reinforced with small-scale beam-like particles. Analytical modeling of the buckling of miniaturized pillars is especially important due to the difficulties in conducting experiments. Here, a well-posed stress-driven nonlocal model is developed, which allows the calculation of the critical loads and buckling configurations of the miniaturized pillars on an elastic foundation and with arbitrary numbers of edge cracks. The discontinuities in bending slopes and deflection at the damaged cross-sections due to the edge cracks are captured through the incorporation of both rotational and translational springs. A comprehensive analysis is conducted to investigate the instability of pillars containing a range of one to four cracks. This analysis reveals interesting effects regarding the influence of crack location, nonlocality, and elastic foundation on the initial and subsequent critical loads and associated buckling configurations. The main findings are: (i) the shielding and amplification effects related to a system of cracks become more significant as the dimensions of pillars reduce, (ii) the influence of the shear force at the damaged cross-section related to the translational spring must not be neglected when dealing with higher modes of buckling and long cracks, (iii) an elastic foundation decreases the effects of the cracks and size dependency on the buckling loads, and (iv) the effects of the edge cracks on the critical loads and buckling configurations of the miniaturized pillars are highly dependent on the boundary conditions.

A Study of Acoustic Emission Based RA-AF Characteristics of Polypropylene Fiber-Reinforced Recycled Aggregate Concrete Under Uniaxial Compression

In order to research the acoustic emission characteristics of polypropylene fiber-reinforced recycled aggregate concrete under uniaxial load, 20 groups of test specimens with a coarse aggregate substitution rate of 25 % and 50 % are designed and fabricated to conduct the acoustic emission test under uniaxial compression, and the evolution laws of the acoustic emission b-value, the cracking modes and the acoustic emission RA-AF moving averages with time are studied. The laws of influence of the coarse aggregate substitution rate and coarse-fine polypropylene fiber on the acoustic emission b-value of RAC are discussed. The K-means clustering method is adopted for two-dimensional clustering analysis of the shear cracking and tensile cracking, and then the SVM is used to obtain the boundary between the two types of clusters. The time distribution laws of shear cracking and tensile cracking of the polypropylene fiber-reinforced recycled aggregate concrete are analyzed. The changes in the moving averages of RA and AF of RAC test specimens with time are studied, and the research indicates that as the RA value decreases, the shear cracking gradually reduces and the tensile cracking gradually increases and dominates.

Study on the dynamic characteristics of pile wharves subjected to underwater explosion

A test was conducted to investigate the dynamic response characteristics and damage modes of pile wharves subjected to underwater explosions. To simulate the explosion process, a fluid-solid coupling finite element model of the pile wharf was constructed. The structural damage process, response characteristics, and failure modes of the pile wharf were analyzed based on the experimental and numerical simulation results. The results showed that the main damaged components of the pile wharf were the piles, with damage modes of cracks, spalling, and brittle shear. The probability of moderate or more significant damage to the inclined piles was 25% higher than that of the vertical piles. The inclined piles with low deformation ability were more prone to local concrete brittle failure, significantly increasing the possibility of instability and failure of the pile wharf structure. The acceleration response spectrum indicated that although the structure of the pile wharf was severely damaged, the personnel on its surface slab still had a high probability of survival. The study indicates that replacing inclined piles with alternative optimized structures benefits the blast resistance of pile wharves.

Low cycle fatigue behavior and crack initiation mechanism of Ni-based single crystal curved thin-walled blade simulator specimen with film cooling holes

A novel curved thin-walled blade simulator (CTWBS) specimens was used to investigate low cycle fatigue (LCF) behavior and crack initiation mechanism nearby film cooling holes (FCHs) in Ni-based single crystal superalloy. LCF tests were conducted under two loading stress levels at 700 °C and 1000 °C. Experimental results demonstrated that LCF lifetime reduced as the fatigue load increased at both temperatures. Crack modes were characterized on macroscopic fracture paths, and the analysis of fatigue crack early propagation revealed its microscopic mechanism. The fracture morphology and microstructure evolution also showed temperature dependence, and oxidation played a role at high temperature. The finite element calculation was based on the crystal plasticity theory considering the back stress and slip damage. The resolved shear stress (RSS) distribution law under two temperatures led to the identification of the octahedral slip system activation type respectively. In addition, the resulting fatigue damage increased in direct proportion to the slip systems activated numbers locally surrounding the FCH. The damage distribution around the FCH was in good agreement with the experimental observation. Finally, the temperature dependence of LCF crack initiation mechanism was discussed from three perspectives: crack nucleation around the FCHs, microstructure evolution and dislocation motion near crack.

The effect of precipitates on low-cycle fatigue behavior of WE54 magnesium alloys under stress-controlled mode

The precipitates have a significant influence on fatigue behavior in magnesium (Mg) alloy. In this work, the effects of precipitates on deformation mode, cracking mode and mechanical behavior during low-cycle fatigue under stress-controlled mode in WE54 Mg alloy at room temperature (RT) was analyzed quantitively and statistically via quasi-in-situ electron backscattered diffraction (EBSD), slip trace analysis, coupled with transmission electron microscopy (TEM). The results reveal that precipitates promoted the activation of pyramidal < c + a > dislocation slip and suppressed the activation of tension twinning in the T6 alloy. In the T4 alloy, persistent slip band (PSB) induced cracking together with intergranular cracking dominated fatigue damage, while intergranular cracking was the primary cracking mode in the T6 alloy. The obvious cyclic hardening behavior of the T4 alloy was attributed to dynamic precipitation, whereas suppressed dynamic precipitation, restrained multiplication of dislocations, together with the appearance of PFZ generated the marginal cyclic hardening behavior in the T6 alloy. Both the T4 and T6 alloys exhibited ratcheting behavior, and precipitates suppressed ratcheting deformation in the T6 alloy. Moreover, the underlying mechanism for the higher fatigue resistance in the T6 alloy was also discussed.

Microstructural insights into fatigue short crack propagation resistance and rate fluctuation in a Ni-based superalloy manufactured by laser powder bed fusion

The microstructural sensitivity of fatigue short crack path and its propagation rate in a Ni-based superalloy GH4169 manufactured by laser powder bed fusion (LPBF) was investigated at room temperature. In-situ digital image correlation (DIC) observation and post-mortem microstructural analysis around the crack path were performed. The results show that the intragranular cracks developed in the shear cracking mode are closely aligned along the activated slip bands in the γ-matrix grains with the crystallographic characteristics of parallel to the γ-{111} slip planes. Multiple slip was also activated, causing the crack retardation or deflection. Low-angle grain boundaries and subgrain boundaries were shown to cause deflections of intragranular cracking, while high-angle grain boundaries significantly arrested the short crack propagation. Moreover, the resistance of grain boundaries to short cracking was assessed using combined metrics including the crystallographic and microstructural parameters of twist angle, the Schmid factor and the geometrical compatibility factor. These site-specific microstructural analyses around the crack path provide insights into the microstructural origins of resistance to the short crack propagation as well as an interpretation of the observed significant fluctuations in the crack propagation rate.

The research on weld pool morphology and passive film characteristic of high-nitrogen stainless laser-arc hybrid weld joint

In this paper, the dynamic weld pool morphology and metallographic structure on each zone of high-nitrogen stainless hybrid weld was investigated. By electrochemical test, the corrosion mechanism and evolution characteristic of passive film on weld surface was analyzed. It was found that by the laser keyhole stirring effect, the weld laser zone exhibited better ferrite dendrites distribution and corrosion resistance. By polarization method, it is observed that the weld passive film exhibited different morphology characteristic in each evolution stage. The passive film had strong regional tendency to ferrite dendrites structure in early stage. And the addition of molybdenum optimized the semiconductor properties of outer weld passive layer. For the failure stage, the passive film was greatly affected by Cr depleted zone and combined with the mode of cracking and dissolution.

Fatigue resistance of rib-to-bimetallic steel deck welded joints in orthotropic steel bridge decks

The stainless-cladding techniques have been applied in the top plate of the orthotropic steel decks in the high-speed railway steel bridges to improve the corrosion and wear resistance. The rib-to-deck (RD) welded joint with the stainless-clad bimetallic steel deck plate becomes a new critical fatigue detail. This study firstly examines the fatigue performance of this full-scale new RD joint through six high-cycle constant-amplitude fatigue tests and two beach-mark tests under eccentric over-rib loading. The structural hot-spot stress at the weld toe on the deck plate is obtained by strain gauges and the linear extrapolation method for each RD specimen before the cyclic loading. Experimental results indicate that five RD specimens suffer from the toe-deck failure modes, while the rests encounter root-deck cracking. The fatigue strength of these new RD joints satisfies the FAT100 hot-spot stress S-N curve based on the IIW design recommendation. Numerical simulation is further conducted to investigate the effect of different cracking modes and welding technologies on the fatigue crack propagation behavior of this new RD joint. Root-deck cracking mode shows weakly higher fatigue resistance than the toe-deck failure case. Using the double-side welds between the U-rib and deck plate, and the thickened-edge U-rib technology can slightly enhance the fatigue life in terms of toe-deck cracking mode in contrast with the traditional single-side groove welds. Experimental and numerical validation quantify the excellent fatigue performance of this new RD joint in comparison with the other types of RD welded joints.

Static axial tension or compression stress effects on shear cracks initiating under cyclic torsion loads in multiaxial fatigue tests

This work proposes models that can better fit and explain apparently contradictory mean stress effects observed when superimposing axial tension or compression loads on cyclic torsion fatigue tests. It introduces new shear-based multiaxial fatigue damage models, modifying the classic Fatemi-Socie equation to consider the peak deviatoric stress normal to the initiating shear crack as the actual driving force for the peak or mean effects of the normal stresses. This deviatoric hypothesis can quantify the odd detrimental effects of static axial compression observed on axial shear cracks tested under cyclic torsion. Additionally, applying the peak deviatoric correction term only to the elastic component of the shear strain range allows an even better description of the increasing mean normal stress effects in high-cycle fatigue, eliminating the need for a variable normal stress sensitivity coefficient in the multiaxial fatigue damage parameter. To evaluate the proposed shear-based models, their life and crack initiation direction predictions are compared for cyclic torsion experiments both with and without superimposed static axial stresses for steels and aluminum alloys, including both literature and original data. The experiments show that axial compression can be detrimental to fatigue crack initiation lives, depending on the cracking mode and on the presence of bifurcations, which effects could be explained from the proposed deviatoric damage parameters.

Study of crack extension and branching behavior of layered materials under impact loading

This study utilized a digital laser dynamic caustics experimental system to conduct three-point bending impact experiments on layered epoxy specimens with different values of angle α between the bedding and the prefabricated crack, as well as the epoxy specimen without bedding. A high speed camera was employed to record the dynamic caustic spot at the crack tip during specimen extension and branching, analyze the dynamic stress intensity factor for crack tip for Mode I and II, crack extension speed, and exploration of the influence of angle α on crack extension and branching behavior. Numerical simulations were performed using the cohesive element method. The findings indicate an increase in crack initiation toughness as the angle α increases. After the initiation of the main crack, the failure mode was Mode I-dominated damage. When it extended near the bedding, the failure mode of the main crack changed to Mode II-dominated damage due to the influence of the bedding, resulting in the formation of branching cracks and microcracks. The main crack again exhibited Mode I-dominated damage after branching. Notably, the branching cracks primarily exhibited Mode II-dominated damage. The occurrence of branching cracks and microcracks intensifies with higher α. The variation of α significantly influences the speed of crack extension.

Multiaxial fatigue of water pipe grey cast iron

Grey Cast Iron (GCI) water pipes are subjected to multiaxial, cyclic stresses caused by combinations of loads such as internal water pressure and road vehicle weight. However, the multiaxial fatigue performance of this material has not previously been characterised. To address this gap more than 45 fatigue tests, including some under non-proportional tension-torsion loading, were completed using a GCI material very similar to water pipe GCI. Of the four multiaxial fatigue criteria tested, the Smith-Watson-Topper (SWT) criterion provided the best predictions by a narrow margin, supporting the idea that a tensile cracking mode dominates the fatigue life of GCI.

Experimental and environmental investigations of the impacts of wood sawdust on the performance of reinforced concrete composite beams

The majority of sawdust is produced by various lumber industries located all over the world. It has been established that using recycled materials to replace some of the fine aggregates is a viable solution. Most researchers focused on the durability aspect of wood sawdust concrete, while less information is available on its structural performance. Therefore, this article aimed to investigate the performance of reinforced concrete beams fabricated from concrete with a partially replaced fine aggregate (FA) by wood sawdust (WS) in the range of 5–45 % (by weight). Six beams underwent 4-point bending tests till collapse. The beams' slump, density, compressive strength, cracking and failure mode, energy absorption, and economic and environmental aspects were studied. The findings showed that the failure region of sawdust concrete was more significant than the reference samples. Despite the compressive strength of the concrete containing different ratios of sawdust being reduced by about 7–30 %, the target compressive strength still has a limit of low to normal concrete grade. The results show that the increase in sawdust percentages decreased the acquired absorbed energy of the subjected load to reach failure. A cost reduction of 9 % and a cost index of 61 % is achieved using wooden sawdust-based concrete. By substituting sawdust for fine aggregate, the sustainability of sawdust concrete in terms of cost and environmental advantages may be improved. In addition, it is well-known that harnessing the transformative potential of industrial waste in concrete production not only minimizes landfill usage, but also promotes resource efficiency, reduces carbon emissions, and advances the circular economy, propelling designers, engineering and builders towards a greener and more sustainable future in the construction industry. According to the test findings, wood sawdust may be utilized to produce normal and low-strength structural concrete.

Prediction of the durability of a plate with a through crack taking into account biaxial constraints of deformations along the front of a normal rupture crack

A methodology for evaluating the durability of plate elements of structures taking into account biaxial constraints of deformations along the front of a normal rupture crack (Mode I crack) is presented. The absence of the available literature data in which the prediction of the crack growth is carried out using Txx- and Tzz-stresses which are non-singular terms in the Williams expansion for stresses at the crack tip is noted. The calculation of the fatigue crack growth rate is based on the Paris equation in which the range of the effective SIF is used instead of the range of the usual stress intensity factor (SIF). In this case, the expression for the effective SIF includes Txx- and Tzz-stresses in addition to the usual SIF. This approach provides taking into account, for example, the thickness of the plate for predicting the durability, which is impossible when only the SIF and Txx-stresses are used. The formula for the effective SIF is derived proceeding from the assumption that tangential stresses in the pre-fracture zone are equal to the local strength of the material. In this case, the size of the pre-fracture zone and the local strength of the material are determined taking into account Txx- and Tzz-stresses. The numerical simulation is based on the proprietary finite-element program which allows calculating Txx- and Tzz-stresses at the front of a through crack in a plate subjected to cyclic uniaxial and biaxial tension. It is shown that nonsingular Txx-stresses primarily describe the effect of biaxial loading on the survivability, whereas Tzz-stresses describe the effect of the plate thickness on the survivability. It is shown that with increasing thic kness of the plate the value of the effective SIF increases due to the increased constraint along the crack front, thus increasing the crack growth rate and decreasing the survivability. With an increase in the stress ratio R, under the condition of a constant stress range, the maximum effective SIF reaches the critical value equal to the fracture toughness much faster thus reducing the durability. It is shown that for uniaxial cyclic tension, the durability predicted by the proposed methodology is higher than that in the classical approach, when the conventional SIF is used in the Paris equation. For biaxial cyclic tension of a plate, an increase in stresses directed parallel to the crack banks leads to an increase of crack front constraints and therefore to a decrease in the durability compared to the classical approach. In other words, the classical theory does not always provide a conservative estimate of the durability, which indicates the expediency of using the developed method for calculating the durability taking into account biaxial constraints of deformations along the crack front.

Study on failure characteristics of basalt fiber reactive powder concrete under uniaxial loading

The uniaxial compression experiments of basalt fiber reactive powder concrete (BFRPC) were carried out by acoustic emission (AE) and DIC techniques, focusing on the AE characteristics in the process of BFRPC failure. The cracking modes of internal and surface cracks of BFRPC are judged by clustering analysis of average frequency (AF) and rise angle (RA) based on Gaussian mixture model (GMM) and displacement on both sides of cracks measured by DIC. Research investigates that the peak frequencies of BFRPC are mainly distributed in 5 ∼ 35 kHz, 60 ∼ 100 kHz, 185 ∼ 215 kHz and 230 ∼ 280 kHz. With the increase of stress level, the absolute energy in the peak frequency range increases gradually. The volume content of 0.5% and 1.0% basalt fiber increased the absolute energy in each peak frequency range. Basalt fiber can improve the compressive strength and the strength and density of AE energy of RPC to some extent. The shear failure of BFRPC mainly occurs in the later stage of loading. Basalt fiber can change the failure mode of BFRPC from tensile failure to tensile shear failure. Meanwhile, basalt fiber can effectively increase the stress level during cracking and reduce the damage degree of BFRPC. Judging the AE characteristics and crack types of concrete failure is of great consequence to predict the precursory failure of BFRPC.

Experimental Investigation of the Relationship of Failure Mode and Energy Dissipation in Grouted Rockbolt Systems under Pullout Load

In underground engineering, the deformation of surrounding rock caused by “three heights and one disturbance” leads to the failure of grouted rockbolt systems, which causes huge economic losses to the mining industry. The research shows that the failure process of grouted rockbolt systems is the result of energy accumulation and release, but the relationship between failure mode and energy dissipation is rarely studied. Based on this, the load transfer behavior, energy dissipation, failure mode and failure mechanism of the grouted rockbolt systems are investigated from the perspective of energy in this study using the indoor pullout test. Test results show that the load decreases rapidly, and the absorbed energy decreases due to the whole-body splitting crack. The absorbed energy of the specimen in the splitting crack mode is lower than that in the pullout failure mode. When the pullout load reaches its peak, the pullout load of the specimen with split failure mode decreases sharply. Meanwhile, the load of the specimen with pullout failure mode is relatively slow, and the energy absorption rate decreases gradually due to the occurrence of cracks. However, the reduction in the energy absorption rate under pullout failure is lower than that under split failure. The radial pressure in the grouted rockbolt systems increases due to the wedge action. When the radial pressure exceeds the tensile strength of concrete, the specimen will experience split failure, otherwise pullout failure will occur.

Sodium Penetration in Nasicon Solid Electrolytes Under High Current

High conductivity solid electrolytes, such as NaSICON, are poised to play an increasingly important role in safe, reliable battery-based energy storage, enabling a new class of sodium-based batteries. Coupled demands of high current densities (≥0.1 A cm-2) and low temperature (<200 °C) operation, combined with increased discharge times for long duration storage (>12 h), challenge the limitations of solid electrolytes. Here, we explore the penetration of sodium into NaSICON at 0.1 A cm-2 in a symmetric molten sodium cell. Previous studies of β’’-alumina proposed that Poiseuille pressure-driven cracking (Mode I) and low levels of electronic conductivity leading to ion-electron recombination (Mode II) can cause metal accumulation within solid electrolytes, but a comprehensive study at high current density is necessary. To understand and differentiate these modes in NaSICON, this work employs unidirectional galvanostatic testing of Na|NaSICON|Na symmetric cells at 0.1 A cm-2 over 23 1-hour intervals at 110 °C. While galvanostatic testing shows a relatively constant, yet increasingly noisy voltage profile, electrochemical impedance spectroscopy (EIS) between intervals reveals a significant decrease in cell impedance which can be correlated with sodium metal penetration, as observed in scanning electron microscopy (SEM). Significant sodium accumulation from the stripping-side electrode suggests that Mode II failure may be far more prevalent than previously considered. Further, these findings suggest that total charge transported per unit area (mAh cm-2), an important parameter for long duration storage, may be a more critical parameter than current density (mA cm-2) when examining solid electrolyte failure. Together, these results provide a better understanding of the limitations of NaSICON solid electrolytes under high current density and can guide the design of coatings to improve electrode-electrolyte interfaces.

Molten Sodium Penetration Through Solid-State Nasicon Electrolytes Under High Current

High conductivity solid electrolytes, such as NaSICON, are poised to play an increasingly important role in safe, reliable battery-based energy storage, enabling a new class of sodium-based batteries. Increasing demands of both high current densities (≥0.1 A cm-2) and low temperature (<200 °C) operation, coupled with increased discharge times for long duration storage (>12 h), challenge the limitations of solid electrolytes. Here, we explore the penetration of sodium into NaSICON at 0.1 A cm-2 in a symmetric molten sodium cell. Previous studies of β’’-alumina proposed that Poiseuille pressure-driven cracking (Mode I) and low levels of electronic conductivity leading to ion-electron recombination (Mode II) can cause metal accumulation within solid electrolytes, but a comprehensive study at high current density is necessary. To understand and differentiate these modes in NaSICON, this work employs unidirectional galvanostatic testing of Na|NaSICON|Na symmetric cells at 0.1 A cm-2 over 23 1-hour intervals at 110 °C. While galvanostatic testing shows a relatively constant, yet increasingly noisy voltage profile, electrochemical impedance spectroscopy (EIS) between intervals reveals a significant decrease in cell impedance which can be correlated with sodium metal penetration, as observed in scanning electron microscopy (SEM). Significant sodium accumulation from the stripping-side electrode suggests that Mode II failure may be far more prevalent than previously considered. Further, these findings suggest that total charge transported per unit area (mAh cm-2), an important parameter for long duration storage, may be a more critical parameter than current density (mA cm-2) when examining solid electrolyte failure. Together, these results provide a better understanding of the limitations of NaSICON solid electrolytes under high current density and can guide the design of coatings to improve electrode-electrolyte interfaces.

Impact of Thickness on Direct Ammonia Decomposition in Solid Oxide Fuel Cells, Numerical and Experimental Research

The growing share of renewable energy sources (RES) in the energy mix and the desire to reduce greenhouse gas and pollutant emissions are driving widespread technological progress. One of the main areas is the development of hydrogen technologies, as manifested, for example, in the emerging hydrogen strategies of countries around the world. However, the widespread use of H2 is limited by the high energy input required for storage. This makes ammonia a promising carbon-free hydrogen carrier. Its application is being considered, e.g. in power systems for deep-sea transportation. Ammonia can be used like a fuel in energy systems, but often requires proper processing or decomposition into hydrogen and nitrogen in the presence of a catalyst. These activities increase financial or technological inputs which can complicate energy systems and reduce their efficiency or energy density. Power plants based on solid-oxide fuel cells (SOFCs) have the ability to process NH3 as fuel whether in external or internal cracking mode. However due to the nickel-based anode and operating temperatures above 600°C, SOFCs can directly use NH3 as a fuel - direct-ammonia SOFCs (DA-SOFCs). Lowering the operating temperature of the cells and reducing their thickness brings with it a wider opportunity for SOFC-based systems e.g. decrease energy density, and reduction of used materials. An additional advantage of direct ammonia conversion in SOFC cells is the endothermic nature of the reaction, allowing for a reduction in the amount of cooling air supplied to the system. In this study, the performance of cells with different anode thickness was compared under similar operating conditions for direct ammonia-fueled solid oxide fuel cells (SOFCs). The experimental results were reproduced in the open source computational fluid dynamics (CFD) software, Open Fuel Cell, in which the source term responsible for internal cracking was introduced. Then calculations were made to determine the distribution of ammonia and temperature in the functional part. It was determined that in the case of counter-current flow of fuel and oxidizer, thinner cells show a smaller temperature gradient. Lowering the operating temperature and cell thickness does not lead to incomplete conversion of ammonia in the cell. Post-mortem analysis of the cells used in the experiment showed no negative effect of ammonia on the functional layers of the cells.

Recent Progress in the Cracking Mechanism and Control Measures of Tunnel Lining Cracking under the Freeze–Thaw Cycle

With the rapid increase in the scale and number of tunnels in cold regions, the frost damage problems, such as cracking of the lining structure under the action of freeze–thaw cycles are becoming increasingly prominent. This review article collects and sorts out the frost damage phenomena that occur in the lining structure of tunnels in cold regions under the action of freezing and thawing cycles, classifies the frost damage phenomena into structural frost damage and non-structural frost damage, and proposes that the research on the mechanism of lining frost damage and its prevention measures should focus on lining cracking. According to the damage degree of the freeze–thaw cycle to the lining structure and its influence on tunnel operation, the cracking mode and cracking stage of lining are introduced. The analysis focuses on the mechanism of cracking in lining structures subjected to freeze–thaw cycles, considering the external force caused by frost heaving, the alteration of mechanical properties in lining concrete, and the internal changes in the microstructure of the concrete. Additionally, the factors that contribute to the occurrence of lining cracking are summarized. Based on this, corresponding control measures have been organized to provide reference for the development of cracking of the lining structure under the action of freeze–thaw cycle.