Heave Pressure Research Articles

Initiation mechanism of landslides in cold regions: Role of freeze-thaw cycles

Freeze-thaw cycles are recognized as one of the key triggers for some major landslides in cold regions around the world. Though the effects of freeze-thaw cycles on the rock strength degradation have been studied extensively, little effort has been made to qualitatively evaluate how it contributes to the evolution from a stable rock slope to a large-scale mass movement. In this study, we use a discrete element-based numerical model to simulate the entire process of the initiation of landslide under the action of freeze-thaw cycles in a slope with randomly distributed initial cracks. The main goal of this work is to quantitatively describe the landslide evolution process regarding the slope displacement, crack propagation, stress chain and load-bearing structure. Our results show the essence of the displacement evolution of a landslide subjected to freeze-thaw cycles; namely frost heave pressure induces the generation of new cracks, leading to the failure and reconstruction of the load-bearing structure of the slope. Deep-seated landslides can occur when the slope is crossed by a fault; otherwise, the slope is prone to surface erosion or shallow landslides.

On the development of effective heave pressure in deep excavations

On the development of effective heave pressure in deep excavations

A frost heave pressure model for fractured rocks subjected to repeated freeze-thaw deterioration

Rock engineering in the Tibetan Plateau is usually suffered severe freeze-thaw (F-T) deterioration, triggering numerous geotechnical engineering disasters. As the essential triggering factor of F-T damage, the frost heave pressure (FHP) in rocks should be quantitatively described and predicted. In this study, a novel theoretical model is established and validated to estimate the critical entire evolution process of FHP in fractured rocks subjected to repeated F-T deterioration, in which the influence of fracture geometric configuration, rock mechanical properties and F-T conditions are comprehensively considered. Besides, given the obvious five-stage manner of FHP evolution, the combination effect of different dominant mechanisms in different stages is theoretically addressed. During freezing, after a silence stage induced by temperature above freezing point of water, volumetric expansion and frost-heave cracking separately controls the generation and reduction stages of FHP, and the solutions are obtained based on elastic mechanics and Griffith energy balance theory, respectively. During thawing, ice segregation dominates the second-arising stage of FHP that is quantitatively described via segregation potential and water migration velocity, and then the FHP enters the dissipation stage owing to complete melting of fracture ice. In addition, a decay coefficient is introduced to estimate the influence of F-T cycle number on FHP, and a piecewise FHP model is finally constructed for fractured rocks subjected to repeated F-T deterioration. To validate our new model, a total of 12 F-T cycle tests with real-time FHP monitoring are conducted on granite and sandstone specimens considering three typical influencing factors, i.e., fracture width, rock types and freezing temperatures. A rational consistency is identified between the theoretical and testing results in terms of the FHP evolution curves and the peak FHPs in rock fracture, demonstrating the generalizability and robustness of our proposed model.

Fracturing behavior and damage model of spatial-rotation fissured sandstone: An experimental study on freeze–thaw and fatigue loads coupling

Earthquake exposure can greatly weaken the mechanical properties and affect the failure process of fractured rocks in cold regions. Creep tests of the spatial-rotation (SR) fissured rock with sandstone as the bedrock under different fatigue combinations and angles were carried out. The effects of freeze–thaw and fatigue loads (FT-FLs) on the deformation behaviour of samples, for example, creep, fatigue deformation, frost heave pressure, and creep rate, were explored. The mechanical responses and failure modes of the specimens were analysed in detail. Based on the experimental results, a new coupled damage model was explored. The results show that in addition to the typical creep stage, the rheological curve also included the phase of disturbance deformation under fatigue loading. The attenuation rates of the rock samples had downward trends with increasing load level under the fatigue combinations and angles, and these decreasing trends had linear characteristics. Moreover, the fatigue rate values increased gradually as the fatigue amplitude, fissure angle and rotation angle increased. In addition, with the change in the fissure and rotation angles, the curves of the tensile crack number had inverted U-shaped trends. The 3D fracture patterns under fatigue were dominated by vertical and vertical-lateral penetration, in which secondary fissure expansion also occurred at different angles. A combined damage model based on the damage variable of freeze–thaw cycles, fatigue loading, and spatial rotation of fissures was established. Compared with test data and other models, the coupled model has good accuracy in describing the entire failure process of specimens under FT-FLs and provides a new framework for the stability of fractured rock masses.

Mechanical behavior assessment of retaining wall structure due to frost heave of frozen ground

Frost heave action is a major issue in permafrost regions, leading to various geotechnical engineering problems. In this study, we assess the mechanical behavior of a concrete retaining wall subjected to frost heave under different ground conditions. The assessment utilizes ABAQUS integrated with several user subroutines. The numerical simulation model employs a thermo-mechanical coupled analysis with a porosity rate function, which enables to simulate time-dependent variations in porosity and frost heave of the backfill soil. After verification of the predictive reliability of the simulation model, the frost heave action in the soil and mechanical response of the retaining wall were evaluated regarding the initial groundwater level and presence of a drainage material on the backside of the retaining wall. According to the simulation results, as the initial groundwater level decreased in the backfill soil, the area susceptible to frost heave decreased. However, the von Mises stresses applied to the retaining wall increased. Under the same ground conditions, when the drainage material was installed on the backside of the retaining wall, the frost heave pressure acting on the wall significantly decreased, and less deformation and distortion of the retaining wall occurred.

An Analytical Solution of Frost Heaving Pressure for Cold-region Tunnel Considering Freeze-thaw Cycles and in-situ Stress

The damage caused by the frost heaving pressure on the surrounding rocks and lining structure of cold-region tunnels is always common, which can seriously threaten the safety and stability for cold-region tunnels. Although many achievements of frost heave pressure model have been obtained, two factors have been often ignored, which are in-situ stress and freeze-thaw cycles. Therefore, the calculation mechanical model of coldregion tunnels is established and the expression of frost heaving pressure considering frost heaving effect and in-situ stress is derived based on the elastic theory. The relationship between the elastic modulus of surrounding rocks and the number of freeze-thaw cycles was fitted by experimental data and the calculation formula of frost heaving rate of rocks considering their porosity change caused by freeze-thaw cycles is derived. Based on that, the calculation method of frost heaving pressure considering in-situ stress and freeze-thaw cycles is proposed. The example analysis results show that frost heaving ratio and frost heaving pressure gradually increase with freeze-thaw cycles, which are eventually subjected to a steady value. Simultaneously, the frost heaving pressure acting on lining increases with in-situ stress for tunnels in cold regions and some effective insulation measures should be applied to prevent frost damage. KEYWORDS: Frost heaving pressure, Cold-region tunnels, Freeze-thaw cycles, Analytical solution, Zero-frost heave displacemen

A fully coupled thermo-mechanical peridynamic model for cracking analysis of frozen rocks

In cold regions, the crack propagation and coalescence behaviors of frozen rocks with ice-filled flaws are very complex. Research on the failure mechanisms of such rock masses is essential to ensure the structural safety of geological engineering in low-temperature environments. Therefore, a fully coupled thermo-mechanical model considering the frost heave effect was constructed using the ordinary state-based peridynamic (OSBPD) theory, and the cracking characteristics of frozen rocks were analyzed. The constitutive equations of the OSBPD model were modified by introducing the coupling term for the thermal-structural interaction and an equivalent pressure density term for frost heave. An improved global convergence criterion was also proposed to achieve a fast convergence to the numerical solution. The correctness and validity of the proposed coupling model were confirmed using several numerical examples. Additionally, the effect of frost heave pressure on the cracking behavior and mechanical properties of frozen rocks was thoroughly discussed. The results show that (a) the frost heave pressure drives the rock to crack along the direction of prefabricated flaws, and (b) the ultimate compressive strength of frozen rocks exhibits a decreasing trend with an increase in frost heave pressure.

Numerical simulation of frost heave of saturated soil considering thermo‐hydro‐mechanical coupling

AbstractFrost heave can lead to both the ground uplifting and frost heave pressure under different circumstances, and cause many engineering problems. To describe the characteristics of frost heave under various thermo‐hydro‐mechanical (THM) coupling conditions and calculate both the frost heave amount and the frost heave pressure, the coupled THM process, as well as the phase change of the pore water, should be considered for freezing soil. In this paper, thermodynamic equilibrium conditions in saturated freezing soil were derived to account for the mechanical effect on the cryogenic suction and unfrozen saturation of pore water during phase transition. Then the governing equations were developed considering the water flow, heat transfer, stress equilibrium, phase change, ice segregation, and their complex interactions. Based on that, a numerical model considering fully THM coupling is presented within the framework of finite element provided by COMSOL. Both frost heave amount tests and frost heave pressure tests were simulated to verify the proposed model. Then the model was applied to subgrades with different types of soil and different boundary conditions, to reveal the characteristics of frost heave amount and frost heave pressure under different conditions, and at the same time to demonstrate the model's applicative prospect.

Characterizing frost heave pressure distribution on rock crack surfaces during freeze–thaw

Frost heave pressure plays a pivotal role in driving the occurrence and expansion of rock cracks. Thus, understanding the distribution and evolution of frost heave pressure on rock crack surfaces is integral to elucidate the mechanism of rock mass damage caused by freeze-thaw. In this study, a unique frost heave pressure monitoring experiment was performed, employing a membrane pressure sensor to provide real-time monitoring of frost heave pressure distribution across an entire rock crack surface. Simultaneously, temperature changes within the crack during freeze-thaw were monitored. Various factors including freezing temperature, crack water content, and lithology, were analyzed for their influence on the frost heave pressure distribution on the crack surface. Findings indicate that the frost heave pressure evolution during freeze–thaw can be divided into five stages: incubation, eruption, fall, equilibrium, and dissipation. The frost heave pressure is not uniformly distributed across the rock crack surfaces, with 0 MPa pressure on the upper part of the crack. The distribution pattern of frost heave pressure on the crack surface features smaller edges surrounding a larger middle area. No obvious correlation is observed between the maximum frost heave pressure and the freezing temperature. However, as the freezing temperature decreases, the maximum pressure-bearing area on the rock crack surface gradually increases. Additionally, as the water content within the crack decreases, there is a noticeable decrease in the distribution of frost heave pressure on the rock crack surface. Regarding frost heave pressure monitoring tests under four different lithological conditions, crack expansion was observed in fine sandstone, granite, and limestone specimens, but not in coarse sandstone specimens. The findings from this research enrich our understanding of the incubation mechanism of rock mass freeze–thaw disasters in cold regions, and serve as a reference for calculations and numerical simulations of rock crack frost heave pressure in these areas.

Cyclic freezing-thawing induced rock strength degradation, crack evolution, heave and settlement accounted for by a DEM model

A general discrete element method-based model is proposed to investigate the cyclic freezing-thawing induced damage of fractured rocks. A set of cracks is defined as an assembly of interparticle pores that are interconnected due to self-definition (pre-existing) or contact breaking (external force induced). During the freezing-thawing simulation, only the rock grains surrounding the cracks are subjected to frost heave pressure, which are expected to cause contact breaking and crack propagation. In this sense, most of the pores that do not form cracks in the numerical model will not participate in the calculation, so the computational cost and time are substantially reduced. The cracks connected to the atmosphere, i.e. the model boundaries, are classified as inactive cracks and their frost heave pressures are removed accordingly. Therefore, model convergence is recognized when all cracks are converted to inactive. Parametric analysis is further performed to show the influence of some important input parameters, including the unfrozen water content, calibration factor of frost heave pressure, crack density and dip. Finally, the freezing-thawing damage of rocks is quantified by the reduction in uniaxial compressive strength after a prescribed number of freezing-thawing cycles. The results are validated with an analytical solution. It is shown that the rock strength degradation, crack evolution, heave and settlement can be well simulated by the proposed model. This methodology can be extended to large-scale problems such as glacier slope instability or landslides.

ВЗАИМОДЕЙСТВИЕ ПУЧИНИСТЫХ ГРУНТОВ С ПОДПОРНЫМИ СТЕНАМИ В МАССИВЕ

Assessment of the stress-strain state of the freezing heaving soil behind retaining walls is an important scientific and practical task. Freezing of the soil leads to the development of horizontal normal pressure of frost heaving and deformation of the walls. The article contains a method for estimating the amount of soil heaving deformation in orthogonal planes. A method for estimating the pressure of frost heaving of the soil using the theory of thermoelasticity, acting with vertical and horizontal conjugate freezing of the heaving soil, is proposed. An analytical formula is obtained for estimating the heaving pressure during horizontal freezing of the soil behind the wall, taking into account the nonlinearity according to the hyperbolic law. The components of the pressure on the walls are determined taking into account the effect of frost heaving and thawing of the soil using the theory of ultimate equilibrium. Comparative calculations of the heaving pressure according to the proposed method and the measured pressure are presented in field conditions in Sergiev Posad Moscow region.

Study on the evolution and dominant mechanism of frost heave pressure in the fracture of rock masses

Study on the evolution and dominant mechanism of frost heave pressure in the fracture of rock masses

Peridynamic investigation on crack propagation mechanism of rock mass during excavation of tunnel group in cold regions

An extended ordinary state-based peridynamic model was developed to investigate the crack propagation of surrounding rock due to tunnel excavation. The frost heave effect on the crack surface was described by an equivalent pressure density. Two numerical examples were conducted to verify the effectiveness and robustness of the proposed model. Moreover, the influence of frost heave pressure, buried depth and rock elastic modulus on damage characteristics of the surrounding rock was investigated. The results demonstrate that massive microcrack damage will be formed at the invert when the tunnel is excavated in a deeply buried rock mass or soft rock stratum. HIGHLIGHTS A peridynamic model of rock mass under excavation and frost heave was constructed. Damage characteristics of surrounding rock could be simulated efficiently. Frost heave load was exerted on the crack surface by an equivalent pressure density. The effects of frost heave load, buried depth and rock elastic modulus were studied.

Model test and numerical simulation of foundation pit constructions using the combined artificial ground freezing method

With the increasing demand for water resources protection, realizing undrained excavations in foundation pit engineering has become a crucial technical problem to be urgently solved. In this study, we proposed a new design concept—the combined artificial ground freezing method. This method uses the diaphragm wall as the vertical support and the frozen curtain generated by freezing pipes in a temporary shaft as horizontal support. A model test and numerical simulation were performed to analyze the evolution law of the temperature field and the interaction mechanism between the freezing process and the diaphragm wall. The above research results show that the combined artificial ground freezing method could effectively and inexpensively seal the foundation pit. During the freezing period, the frost heave pressure on the contact surface of the frozen curtain and diaphragm wall was 30– 60 kPa and 25– 35 kPa in numerical simulation, much lower than the diaphragm wall's critical design value. Therefore, frost heave would not damage the diaphragm wall. In the end, the design criterion of the freezing pipes deflection form was proposed. The study provided a reference for designing and constructing foundation pits using the combined artificial ground freezing method.

Frost Heaving and Induced Pressure of Unsaturated Interfacial Zone between Gravel Ballast and Subgrade

Most existing railroads are composed of gravel ballast. One of the major issues with gravel ballast is frost damage in cold regions. Gravelly soils are known to be not prone to frost action due to their low water retention capacity and high hydraulic conductivity. However, reports indicated continued frost damages resulting from the mixed zone between gravel ballast and subgrade. This study evaluated the frost heaving and induced pressure of gravel ballast–subgrade soil mixtures via 1D soil column testing in a cold chamber. Gravel ballast and subgrade soil were collected from the railroad in situ. Various mixing ratios and degrees of saturation were used as factors affecting the frost experiments. The mixtures were placed in the cold chamber, and vertical displacements and pressures were measured. Overall evaluations showed that gravelly soils are not a geomaterial prone to frost damage; however, the frost potential of gravel ballast increases as the degree of saturation and the mixing portion of the subgrade soil increase. Therefore, the interfacial zone between gravel ballast and subgrade soil, especially where possible mixing with low drainage exists, needs cautions of potential frost damage.

ANALYSIS OF POROSITY, PERMEABILITY, AND ANISOTROPY OF SANDSTONE IN FREEZE–THAW ENVIRONMENTS USING COMPUTED TOMOGRAPHY AND FRACTAL THEORY

An in-depth understanding of the deterioration characteristics of porous rock materials in freeze–thaw (F–T) environments is very important for rock mass engineering in cold regions. However, quantitative descriptions of key rock indicators such as porosity, permeability, and anisotropy are lacking. In this paper, computed tomography (CT) was used to study saturated intact sandstone, saturated fractured sandstone, and ice-filled fractured sandstone under various F–T cycles and stress states. Meso-structural parameters were obtained by reconstructing the three-dimensional fracture networks from CT images. Then, based on fractal geometry theory, the fractal dimension ([Formula: see text], tortuosity fractal dimension ([Formula: see text], and anisotropic two-dimensional fractal dimension ([Formula: see text] of the sandstone samples were analyzed quantitatively. The [Formula: see text] gradually increased during the F–T process, while [Formula: see text] gradually decreased. Compared with [Formula: see text], [Formula: see text] was found to describe changes in the absolute permeability of rocks under F–T cycling more accurately. Anisotropy in sandstone was enhanced by F–T cycling. After uniaxial compression, the [Formula: see text] value was the greatest in ice-filled fractured sandstone. In addition, the tree-like fracture structure produced by F–T cycling expanded the range of self-similarity, which enhanced the fractal characteristics of sandstone. However, due to the large frost heave pressure of ice-filled sandstone, fracture expansion accelerated in the later period of F–T cycling, which destroyed the self-similarity. These results assist in understanding the F–T characteristics of porous rock materials. The method described provides a new way to better evaluate and predict F–T-related engineering disasters.

A fully coupled thermo-hydro-mechanical model with ice-water phase change for liquid nitrogen injection simulation

Cryogenic liquid nitrogen (LN2) fracturing or treatment in nearly impermeable reservoirs has attracted widespread attention due to its strong thermal shock and frost heave effects. We derive a fully coupled thermo-hydro-mechanical (THM) model considering the ice-water phase change to simulate the process of LN2 injection into shale gas reservoirs. The novel model accommodates the following dominant phenomena: (1) LN2 driving unfrozen water flow in porous media; (2) pore water freezing into ice below the freezing temperature; (3) fully coupled thermo-poroelastic effect incorporating frost heave pressure; (4) effective fluid permeability associated with unfrozen water content and phase saturation; (5) temperature and pressure-dependent fluid thermodynamic properties. The proposed model is verified against a classical thermo-poroelastic model and a coupled THM model for freezing rocks. Simulation results show that LN2 injection into water-bearing shale reservoirs will result in ultra-high injection pressure. A high injection rate is beneficial for the fracture initiation, but it is detrimental from phase solidification. Reducing the injection rate is not conducive to the subsequent penetration of LN2 into the reservoir. The evolution of effective permeability, as well as phase saturation, can be reasonably captured during LN2 injection. The comparative advantages between fluid infiltration and temperature propagation are different at high and low injection rates, which leads to significant differences in phase saturation and effective permeability changes. The multiple mechanisms, including pore pressure, frost heave pressure, and thermal stress that induce rock damage, can be efficiently revealed. At relatively low temperatures, the deformation of the reservoir at high and low injection rates is dominated by high-pressure expansion and cryogenic contraction, respectively. The research results can provide some insights for cryogenic non-aqueous fracturing.

Transport coefficients and pressure conditions for growth of ice lens in frozen soil

In this paper, the transport of sub-cooled water across a partially frozen soil matrix (frozen fringe) caused by a temperature difference over the fringe, is described using non-equilibrium thermodynamics. A set of coupled transport equations of heat and mass is presented; implying that, in the frozen fringe, both driving forces of pressure and temperature gradients simultaneously contribute to transport of water and heat. The temperature-gradient-induced water flow is the main source of frost heave phenomenon that feeds the growing ice lens. It is shown that three measurable transport coefficients are adequate to model the process; permeability (also called hydraulic conductivity), thermal conductivity and a cross coupling coefficient that may be named thermodynamic frost heave coefficient. Thus, no ad hoc parameterizations are required. The definition and experimental determination of the transport coefficients are extensively discussed in the paper. The maximum pressure that is needed to stop the growth of an ice lens, called the maximum frost heave pressure, is predicted by the proposed model. Numerical results for corresponding temperature and pressure profiles are computed using available data sets from the literature. Frost heave rates are also computed and compared with the experimental results, and reasonable agreement is achieved.

Interaction of a Single Pile with Freezing Heaving Soil

The article is devoted to the study of the interaction of a single pile with freezing heaving soil. The calculation of the pile loading area by the normal pressure of frost heaving is proposed. The cases of pile behavior under the influence of frost heave on it depending on the value of the heave pressure, the freezing forces of the frozen soil and the pile, and the adhesion forces of the anchored part of the pile are considered. The calculation of the radius of the cylinder shifting under the action of soil heaving is given.

Field Research of the Heaving Pressure Occurring at Frost Penetration in the Soil under the Foundation Bed

This article describes the results of field experimental studies of the heaving pressure development during freezing of the soil under the foundation bed. Due to the intensive development of areas North and North-East of Russia, studies on the impact of heaving soils on foundations and underground structures are currently assuming a special significance. The research that we carried out allowed us to reveal features of the heaving pressure development of clay soils during freezing under the foundation bed depending on conditions of freezing. We found that pressure formation depends largely on the location of the frozen area and the compressibility of the melt zone of the freezing soil. In the article, we propose measures to reduce the impact of heaving pressure on the foundation bed.