Frost Heave Pressure Research Articles

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.

Deterioration of non-persistent rock joints: A focus on impact of freeze–thaw cycles

Existing research on rock freeze-thaw mainly focuses on a single freeze-thaw process, while little attention is paid to the cumulative effect of cyclic freeze-thaw on rock mass joints. However, the accumulated freeze-thaw effects are precisely the leading cause of rock mass deterioration and damage in severe cold regions. This study aims to investigate the use of a novel laboratory testing method, i.e., membrane pressure sensors in the joint, to demonstrate the impact of cyclic frost-thaw on jointed rocks. With the sensors, the change of frost-heaving pressure in the joint under cyclic process is continuously monitored. The measurements indicate that under freeze-thaw cycles, the initiation of frost-heaving pressure is critical, which is followed by an explosion, stability, and ablation stages. In these stages, the maximum frost-heaving pressure is observed to emerge at the early stage of the freeze-thaw cycle. Based on the experimental observations, frost-heaving pressure evolution law and damage mechanism of jointed rock masses are analyzed. For example, the peak frost-heaving pressure increases exponentially with the decrease of temperature and decreases exponentially with the increase of freeze-thaw cycles. Also, the pressure has a positive linear relationship with the geometric size of the joint. In essence, the deterioration of freeze-thaw cycles on jointed rock masses is mainly due to crack propagation caused by the frost-heaving pressure.

Experimental Study on the Shear Behavior of the Bonding Interface Between Sandstone and Cement Mortar Under Freeze–Thaw

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.

Experimental Studies of Soil Frost Heaving Pressure Development in Confined Space

This article describes the results of experimental studies of the frost heaving pressure development at the soil freezing in confined space. Studies devoted to the investigation of heaving soil influence on the structures acquire special significance at present due to the intensive development of the North and North-East regions of Russia. The conducted researches made it possible to reveal the features of the development of frost heaving pressure of clay and sandy soils under one-sided and uniform freezing in confined space, depending on the degree of their water saturation, temperature regime and possible deformations. It was revealed that in sandy soils the formation of the frost heaving pressure is caused by the freezing of free (gravitational) water and can be determined by the Bridgman-Tammann formula. In clay soils, the development of frost heaving pressure is associated with the freezing of loosely-bound (film) water and can be determined by the method proposed by the authors both in the absence and in the presence of heaving volumetric deformation.

A unified model for frost heave pressure in the rock with a penny-shaped fracture during freezing

In order to investigate the mechanisms of rock deterioration at low temperature, a unified model for frost heave pressure in the rock with a penny-shaped fracture during freezing was proposed, in which the main influencing factors can be classified into four groups: 1) the mechanical properties of ice and rock (Ei, υi, Es and υs); 2) the external loading conditions (q and λ); 3) shape characteristic of the fracture (η); and 4) effective volume expansion coefficient (βe). The model attempts to unify the volume expansion theory, water immigration theory and combination theory. Validation was carried out, and the comparisons indicated that the proposed model can accurately reflect the variation of the frost heave pressure. Parametric sensitivity analyses were performed to examine the effect of various parameters and to improve the understanding of the damage of fractured rock mass subjected to frost heave. The results showed that βe is the most important parameter that affects the magnitude of frost heave pressure, apart from it, the mechanical properties of ice (Ei and υi) are also crucial, and then is the parameters of Es, q and η. Relatively speaking, υs and λ have little influence. Besides, some discussions were given to the newly defined variableβe, which is a crucial parameter that can unite the three existing frost heave mechanics of rock.

Frost heaving and frost cracking of elliptical cavities (fractures) in low-permeability rock

A 9% expansion of freezing water in the elliptical cavities (fractures) of rock leads to frost heaving pressure and thermal stress, which are the main cause of the freeze-thaw damage of a fractured rock mass. Considering the influence of thermal stress and water flow in elliptical cavities (fractures), a mathematical model for predicting frost heaving pressure in the elliptical cavities (fractures) of rock is presented, assuming that the rock matrix is impermeable. The maximum tensile stress and frost cracking angle on the elliptical cavity are deduced and the critical condition for simplifying the elliptical cavity to planar fracture is suggested based on the method of complex variable function and elastic mechanics theory. Moreover, the effects of the main parameters on frost heaving pressure and frost-cracking conditions are determined to investigate the frost cracking of water-filled elliptical cavities (fractures). The flow flux of water, the aspect ratios of cavities (fractures) and the elastic moduli of rock have a great direct influence on the frost heaving pressure and cracking angle, whereas the dip angle of the cavity (fracture) and the thermal expansion coefficient of rock indirectly affect them by changing the thermal stress. It is suggested that the stress intensity factor is adopted to predict the frost propagation of planar elliptical cavities only if the aspect ratio exceeds fifteen.

Frost-heaving pressure in geotechnical engineering materials during freezing process

Energy and resources including coal, oil, and gas are in demand all over the world. Because these resources near the earth’s surface have been exploited for many years, the extraction depth has increased. As mining shafts in the coal extraction process become deeper, especially in western China, an artificial freezing method is used and is concentrated in the fractured rock mass. The frost-heaving pressure (FHP) is directly related to the degree of damage of the fractured rock mass. This paper is focused on FHP during the freezing process, with emphasis on the frost-heaving phenomenon in engineering materials. A review of the frost phenomenon in the geotechnical engineering literature indicates that: (1) During the soil freezing process, the ice content that is influenced by unfrozen water and the freezing rate are the determining factors of FHP; (2) During the freezing process of rock and other porous media, the resulting cracks should be considered because the FHP may damage the crack structure; (3) The FHP in a joint rock mass is analyzed by the joint deformation in field and experimental tests and can be simulated by the equivalent expansion method including water migration and joint deformation.

Evaluation of Frost Heave Pressure Characteristics in Transverse Direction to Heat Flow

The freezing method for underground construction has been attracting attention owing to its non-polluting characteristics. This method requires precise forecasting of freezing behavior and countermeasure technology against frost expansion. To improve this method, it is necessary to know the expansion characteristics in a transverse direction to heat flow as well as in the heat flow direction. In this study, we developed a new apparatus for frost heave experiments that can measure the pressure due to expansion in the transverse direction. As a conclusion, we successfully evaluated the characteristics of frost heave pressure in the transverse direction to heat flow through experiments.

In situ monitoring of frost heave pressure during cross passage construction using ground-freezing method

The artificial ground-freezing method has the dual effect of ground reinforcement and waterproof sealing, and the frozen curtain can be designed flexibly. It is widely used in the construction of cross passages for shield tunnels in soft ground with high groundwater levels. However, due to the lack of in situ monitoring data, it remains difficult to determine the frost heave pressure acting upon a tunnel. In this study, based on the use of an anti-freezing pad-type earth pressure gauge, in situ monitoring was carried out to measure the frost heave pressure acting upon tunnel segments during the construction of cross passages for the Shanghai Yangtze River Tunnel. The monitoring results show that the earth pressure acting upon the tunnel could decrease dramatically during freezing, and this kind of decrease can take place suddenly and unpredictably, which can be illustrated using the finite element method. The maximum measured frost heave pressure during freezing and cross passage excavation was approximately 0.2 MPa, which was much smaller than the predicted value. Combining the distribution of temperature in the ground and construction countermeasures, the observed phenomena are mainly related to three factors: water migration during the freezing process, the tunnel–ground interaction, and the countermeasure of pressure release holes. The tunnel showed a horizontal extension–deformation, which was consistent with the releasing frost heave pressure acting upon it.

Numerical Analysis and Spot-Survey Study of Horizontal Artificial Ground Freezing in Tunnel Connecting Passage Construction

In this paper, a comprehensive method combined spot-survey and numerical simulation tests has been used to make an approach to systematically study of the technology of level artificial ground freezing in tunnel connecting passage construction. By simulating the freezing process of artificially frozen soils of Dalian Road tunnel connecting passage with finite element analysis method, the varying laws of temperature fields, displacement fields and stress fields had been worked out. According to the results of actual field survey, the changing laws of frost heave pressure and tunnel deformation with freezing temperature, elapsed freezing time during the artificial ground freezing period are obtained. The laws from finite element analysis are consistent with that from field survey, which has proved that finite element analysis is correct. The conclusions of the research prove the advantages of horizontal artificial ground freezing in such similar construction and set up a successful model for related freezing projects in the future, which, will guide the coming practice and safeguard the success.

Frost-Heaving Pressure on Lining of Tunnel Constructed in Severe Cold Regions

A 3D water contained space model for calculation of frost-heaving load on lining is presented in this paper. After the calculation and analysis some key points on characteristics of frost-heaving pressure up on lining of rock tunnel constructed in severe cold regions are concluded.

Basic Study on the Frost Heave Pressure of Rocks

Frost heave in rocks is caused by the frost heave pressure (pore ice pressure) generated by the freezing of pore water, which then cracks the rock. The present work attempts to clarify the frost heave pressure of rocks by experiments at four temperature conditions. Ohya tuff and Kimachi sandstone, in which the occurrence of frost heave has previously been confirmed, were used as specimens.Measurements of these experiments were the internal temperature of the rocks during the freezing process and the location where the ice lens formed.These two parameters made it possible to determine the temperature of the location where the ice lens formed. A generalized Clausius-Clapeyron equation was used to calculate the pore ice pressure. The results indicated that the temperature at the location of ice lens formation depends on the types of rock, but not on the temperature gradient during freezing.It was also confirmed that frost heave in rocks with a higher tensile strength appears at locations with a lower temperature, while that in rocks with a lower tensile strength appears at location of temperatures close to 0°C.These findings suggest that the location and temperature of the ice lens formation are dependent on the strength of the rock.

Growth Rate of Frost Heave in Helium and Mass Transport in Solid 4He

Frost heave phenomena have been studied in 4He on porous vycor glass, in which 4He in the pores remained supercooled fluid below the bulk melting temperature, Tm. When we cool a bulk solid at T below Tm on the vycor, the bulk solid sucks the supercooled liquid in the pores and grows. We measured the maximum frost heave pressure over bulk melting pressure, Pm, as a function of ΔT=Tm−T. When temperature was suddenly lowered, the frost heave pressure increased in time to a next equilibrium pressure and we measured the time constant and derived the frost heave rate. The frost heave rate was measured as a function of temperature and decreased very rapidly as temperature was lowered. We propose models to explain the mass transport in solid either by vacancy or by amorphous solid between bulk solid 4He and vycor. From measured temperature dependence of the rate in comparison with our model, we conclude the frost heave rate is determined by mass flow in solid 4He due to thermally-activated vacancy diffusion.

Frost heave in He

Frost heave occurs in various phenomena in natural environment. It has been studied in helium on porous glasses under perfect ice-segregation condition. The maximum frost heave pressure was investigated for various conditions and was in good agreement with the thermodynamical prediction. The dynamical properties of frost heave are discussed and some of the preliminary results of the growth rate measurement are presented.

Frost-heave phenomena of 4He on porous glasses.

We observed the frost-heave phenomena of $^{4}\mathrm{He}$ on porous glasses. The static property of the frost heave was mainly studied, where the pressure jump across the boundary between bulk solid and liquid in the pores was measured in equilibrium as a function of the amount of supercooling of liquid in the pores from the bulk melting temperature. These measurements were performed at several constant pressures in the range 26\char21{}60 bars and at temperatures above 1.3 K. The results obtained above 28.5 bars were in good agreement with the modified Clausius-Clapeyron equation deduced by assuming that the chemical potential in the solid and liquid phase is the same. When the pressure was below 28 bars, the measured maximum frost-heave pressure became less than the prediction of the modified Clausius-Clapeyron equation. For a sample at 26.1 bars almost no indication of the frost-heave effect was observed.

Method of evaluating the frost-heave pressure of soil against the ice-soil enclosure of an underground structure : Orlov, V O; Kim, V K Soil Mech Found EngngV25, N3, May–June 1988, P129–135

Method of evaluating the frost-heave pressure of soil against the ice-soil enclosure of an underground structure : Orlov, V O; Kim, V K Soil Mech Found EngngV25, N3, May–June 1988, P129–135

A method of evaluating the frost-heave pressure of soil against the ice-soil enclosure of an underground structure

A method of evaluating the frost-heave pressure of soil against the ice-soil enclosure of an underground structure

The adsorption force theory of frost heaving

Presented in this paper are the theorization of a traditional concept of the mechanics of frost heaving, as well as a critical review of the recent developments in this field. The key to the theorization is the following: (1) the film water adsorbed on soil particles can build up an internal solid-like stress, and (2) the flow of film water is different from the conventionally accepted flow of pore water. It is expected that modern continuum mechanics will, in the future, improve the theory of film water which, in this paper, has been formulated by use of the classical method. The freezing film water, trying to retrieve the loss of its thickness to the frozen ice, generates a suction force that draws water to the freezing front where the frost-heaving pressure pushes up the overburden. The temperature of the freezing film water that has generated the solid-like stress, is lower than the temperature of the freezing pore water. This distribution of freezing temperatures in the region of film and pore waters explains the observation that the freezing front causing frost heaving is not a planar surface but a three-dimensional zone diffused in the direction of heat transfer. Frost-heaving pressure can be derived as part of the solution of the boundary-value problem of the frost-heaving differential equations.