Total Heave Research Articles

Role of Temperature Gradient and Soil Thermal Properties on Frost Heave

In cold regions, the soil temperature gradient and depth of frost penetration can significantly affect roadway performance because of frost heave and thaw settlement of the subgrade soils. The severity of the damage depends on the soil index properties, temperature, and availability of water. While nominal expansion occurs with the phase change from pore water to ice, heaving is derived primarily from a continuous flow of water from the vadose zone to growing ice lenses. The temperature gradient within the soil influences water migration toward the freezing front, where ice nucleates, coalesces into lenses, and grows. This study evaluates the frost heave potential of frost-susceptible soils from Iowa (IA-PC) and North Carolina (NC-BO) under different temperature gradients. One-dimensional frost heave tests were conducted with a free water supply under three different temperature gradients of 0.26°C/cm, 0.52°C/cm, and 0.78°C/cm. Time-dependent measurements of frost penetration, water intake, and frost heave were carried out. Results of the study suggested that frost heave and water intake are functions of the temperature gradient within the soil. A lower temperature gradient of 0.26°C/cm leads to the maximum total heave of 18.28 mm (IA-PC) and 38.27 mm (NC-BO) for extended periods of freezing. The maximum frost penetration rate of 16.47 mm/hour was observed for a higher temperature gradient of 0.78°C/cm and soil with higher thermal diffusivity of 0.684 mm2/s. The results of this study can be used to validate numerical models and develop engineered solutions that prevent frost damage.

Centrifuge modelling of the effect of base slab stiffness on long-term heave and swell pressure

Long-term heave of basement slabs is a significant problem in cities with overconsolidated clay, such as London. There is a dearth of data to calibrate the methods commonly used by designers to predict heave displacement and swell pressure. This paper presents results from two centrifuge tests aimed at reproducing the phenomenon of long-term basement heave. Reduced scale models of rectangular basements with different slab thicknesses underlain by overconsolidated clay were tested, to investigate the effect of base slab stiffness on heave behaviour. The centrifuge tests provided measurements of the profiles of vertical displacement, bending moments in the slab and contact pressure at the slab–soil interface. This is the first geotechnical centrifuge study to provide simultaneous measurements of vertical displacement and swell pressures during long-term basement heave. Whereas the flexible basement underwent significant differential heave and almost complete relaxation of swell pressures, the stiff basement generated large swell pressures and consequently large bending stresses. These results confirm that the prediction of high heave pressures is a self-fulfilling prophecy: a basement slab with high stiffness will beget large swell pressures. The experimental measurements of swell pressure and heave were compared to predictions by a simplified non-linear method of heave calculation. The simplified non-linear method produced acceptable predictions of total heave.

PREDICTION OF THE DYNAMIC RESPONSE OF A SHIP IN HEAD WAVES USING OPENFOAM TOOLBOX

Ships and marine structures, such as oil tanker, offshore platforms, etc., usually face extreme seaway environment in real situation. If under the action of strong waves large amplitude motions will occur, with the result that they may not work as usual or even lose stability. Thus, it is of great importance to access their dynamic responses under such bad conditions at the initial design stage, so as to ensure normal usage and safety. Herein, the original RANS (Reynolds-Averaged Navier- Stokes) solver based on OpenFOAM Toolbox has been extended to predict dynamic responses of ships and marine structures in waves. A new “inlet-velocity boundary condition” was implemented to generate waves. A damping term for wave absorption was added to the right-hand side of RANS equations in order to avoid wave reflection from the boundary where waves leave the computational domain. The related numerical methods are described in this paper. The purpose of this paper is to present a validation of the approach used. The prediction of the dynamic response of a ship in head waves was the focus. Five cases with different wave lengths and heights were considered. The predicted results, i.e. time histories of total resistance, heave and pitch, were compared with available experimental data and analysed. In addition, due to current experience it is very necessary that effort is devoted to determining appropriate grid and time step, so as to ensure the quality of waves generated.

Engineering approach to determination of the Segregation Potential by the upward-step-freezing testing method

The segregation potential (SP) is widely accepted in engineering design and for frost heave predictions, because it can be readily obtained in step-freezing laboratory tests. The SP at the onset of formation of the last ice lens (near the thermal steady-state condition, tp) in step-freezing tests is a representative value that applies in the field due to the low freezing rate there. The determination of tp is an essential prerequisite for obtaining a representative SP. However, it is difficult to determine when the thermal steady-state is achieved under freezing direction from bottom upwards for minimizing experimental error. Last ice lens (ice crystal) is elongated continuously even though the frost front reaches the center of the soil specimen by the boundary temperature conditions. Here, a frost ratio (Fz) is defined on the basis of the temperature profile with normalized specimen height. The tp is defined as being when the Fz reaches 90%, based on visual observation of the last ice lens formation. However, the determination of the representative SP may still involve a complicated analysis. This is alleviated here by a simple empirical logarithmic time-fitting method, without measuring the temperature profile across the soil specimen. The starting point of the tangential line in the heave curve with a logarithmic timescale empirically coincides with tp. The representative SP for engineering applications can then be easily determined with a simple frost heave testing method involving only total heave and cold–warm end temperatures.

Analysis of the Effect of Expansive Soil Against Deformation in Development Projects Cikampek - Palimanan Sta 166 + 650 Toll Road

On the pavement of the Cikampek-Palimanan Toll Road, STA 166 + 650, there is predicted deformation due to the influence of the expansive soil underneath. Based on this background, it is necessary to conduct research with the aim of obtaining information on the character and physical properties of the sub grade, so as to determine the type of soil stabilization. From the results of soil identification using the single index method according to Chen, 1988 and Snethen, 1977, if the land at the project site is not replaced (replaced) with land that is not expansive, it will have high swelling potential. The potential for settlement of settlement based on Terzaghi and Peck, namely the amount of reduction of 7.3 cm and the time required for a stable condition or consolidation process occurs for 4.8 months. Force height (total heave) for the original soil conditions is relatively large up to 8.52 cm which causes the pavement of the Cikampek-Palimanan Toll Road to experience deformation.

Suction measurement in freezing soils using pore pressure transducers

Frost heave is major problem for infrastructures build in cold regions. Frost heave occurs due to suction (negative pore water pressure) generated due to the freezing process close to the frost line, i.e., at the frozen fringe. To understand and predict these negative pore water pressures is a key factor to accurately calculate the segregation heave, i.e. heave related to the formation of ice lenses. Segregation heave is the major part of the total heave and also the most challenging to predict. Many attempts have been presented in literature where the generated suction during freezing is related to temperatures, temperature gradients, grain size of the freezing soil etc. Very few laboratory tests have been presented in which the actual suction is measured during the ice lens formation process and compared with theoretical estimations. One reason is that these measurements are challenging. This paper presents results from laboratory measurements of generated suction during freezing. Laboratory tests were conducted on a silty soil sample and suction was measured at the frozen fringe using small pore pressure transducers (PPT’s). The samples were subjected to one-dimensional freezing from top to bottom in an open water system at a constant temperature gradient. Temperatures were measured at various points along the height of the soil sample while suction was measured at middle of the sample. Test results have shown that PPTs do not show pressure change in long-term static pressure test under sub-freezing temperature. For suction measurement at the frozen fringe, pore pressure readings should be measured at various points along the sample height.

Heave analysis of shallow foundations founded in swelling clayey soil at N’Gaous city in Algeria

Abstract The design of shallow foundations on swelling soils needs a thorough study to evaluate the effect of swelling potential soil on the final foundation heave. For this reason, a simple analytical approach based on the soil stress state under the foundation can be used to calculate the foundation heave. This paper reports a set of analytical and numerical analysis using the finite-difference code (FLAC 3D), performed on an isolated shallow foundation founded on a swelling soil mass at N’Gaous city in Batna Province, Algeria, subjected to distributed vertical loads. Further, the influence of some parameters on total heave was analyzed, such as the embedded foundation and soil stiffness. The analysis results from the proposed 3D modelling was compared and discussed with analytical results. The numerical results obtained show a good agreement with the analytical solutions based on oedometer tests proposed in the literature, and deliver a satisfactory prediction of the heave of the shallow foundations.

Assessment of centrifuge modelling of internal erosion induced by upward flow conditions

A series of centrifuge modelling tests was performed in this study to evaluate the internal erosion induced by upward flow that typically occurs during the initiation phase of backward erosion piping. The study focuses on the assessment of the centrifuge scaling behaviour of models under different levels of centrifuge gravity. Tests were performed by maintaining the same model dimensions, soil and fluid properties and at centrifuge gravity ranging from 10g to 30g. The results from centrifuge tests are also compared with results under Earth's gravity or 1g. Two critical hydraulic gradients associated with the first visible movement of sand particles and the total heave were obtained. The critical hydraulic gradients obtained for the first visible movement of grains agree with the theoretical scaling law. However, the theoretical scaling is not applicable to the total heave due to the expansion of the models. Regardless, the critical gradients for first visible movement and total heave were 0.56–0.99 and 1.16–2.44, respectively, and these results agree with numerical and experimental values available in the literature. The seepage-induced stresses at the granular level were estimated and it was found that 16% of the critical total seepage stress was contributed by the viscous shear stress, while the remaining 84% was contributed by differential pressure across the grain.

Wave Exciting Force Maximization of Truncated Cylinders in a Linear Array

This study focuses on the determination of optimum layout configurations for a linear array of identical mutually interacting truncated cylinders. Optimum configurations correspond to those that maximize either the total heave exciting force acting on all cylinders of the array or the heave exciting force applied on pairs of cylinders within the array. For achieving this goal, we developed and applied an efficient optimization numerical process (ONP), where a robust hydrodynamic numerical model, capable of solving the diffraction problem of the examined multi-body arrangement in the frequency domain, was appropriately coupled with a genetic algorithm solver in an integrated computational environment. Initially, the efficiency of the ONP is demonstrated by comparing results with those of other investigations that resulted from the deployment of classical optimization methods. Then, ONP is applied for a linear array of nine cylinders for determining the optimum layout configurations under the action of the head and perpendicular to the array waves, and for different maximum allowable array lengths. The resulting optimum configurations correspond to a random positioning of the cylinders within the array. Nevertheless, they are characterized by the formation of clusters of closely-positioned cylinders, which induce positive hydrodynamic interactions in terms of maximizing the exciting forces.

Prediction of the Dynamic Response of a Ship in Head Waves Using OpenFOAM Toolbox

Ships and marine structures, such as oil tanker, offshore platforms, etc., usually face extreme seaway environment in real situation. If under the action of strong waves large amplitude motions will occur, with the result that they may not work as usual or even lose stability. Thus, it is of great importance to access their dynamic responses under such bad conditions at the initial design stage, so as to ensure normal usage and safety. Herein, the original RANS (Reynolds-Averaged Navier-Stokes) solver based on OpenFOAM Toolbox has been extended to predict dynamic responses of ships and marine structures in waves. A new “inlet-velocity boundary condition” was implemented to generate waves. A damping term for wave absorption was added to the right-hand side of RANS equations in order to avoid wave reflection from the boundary where waves leave the computational domain. The related numerical methods are described in this paper. The purpose of this paper is to present a validation of the approach used. The prediction of the dynamic response of a ship in head waves was the focus. Five cases with different wave lengths and heights were considered. The predicted results, i.e. time histories of total resistance, heave and pitch, were compared with available experimental data and analysed. In addition, due to current experience it is very necessary that effort is devoted to determining appropriate grid and time step, so as to ensure the quality of waves generated.

Evaluation of the swelling pressure for expansive soils

The interaction between light structures and expansive soils as mainly active clays was studied since the 1950’s. The first stage in foundation design on this problematic soil is the evaluation of the swelling potential, based on which one identifies the clay’s activity and its correlation with the value of the swelling pressure (ps) for the decisional support of the geotechnical design (p effective > ps). In the literature there are many formulas that can be used to predict the swelling pressure based on the correlation between various geotechnical parameters. This paper provides the swelling pressure as correlation with the consistency index (CI) and the liquid limit (LL), by linear regression of the experimental results for the 56 active clays from seven countries. Using the analytical methods, one can predict the total heave of a floor slab founded on expansive clay. The validity of the proposed correlation has been tested in the prediction of the total heave in the centre of a floor slab for a light industrial building in North-Central Regina, Saskatchewan, Canada.

Water–heat migration and frost-heave behavior of a saturated silty clay with a water supply

ABSTRACTIn this study, a large-scale one-directional freezing experiment with water supply was performed to investigate the water–heat migration and frost-heave behavior of the saturated silty clay. The results indicate that the temperature gradient is larger in the frozen zone than that in the unfrozen zone because of the heat release of the supplied water and its water–ice phase change during the freezing process. Furthermore, the different parts of the total frost heave are evaluated, respectively, and it is also found that the frost heave can be reduced if the advance rate of the freezing front is effectively controlled even if external water is sufficient.

Quantitative analysis of piping erosion micro-mechanisms with coupled CFD and DEM method

Piping, as one of the critical patterns of internal erosion, has been reported as a major cause for failures of embankment dams and levees. The fundamental mechanism of piping was traditionally investigated through experimental trials and simplified theoretical methods in macroscale. Nevertheless, the initiation and progressive evolution of piping is a microscale phenomenon in its essence. The current understanding of the micro-mechanism of piping erosion is limited due to a lack of quantitative analysis and visualized evidence. And in fact, seepage flows can affect the soil fabrics and the development of contact forces between particles. But how these fabrics and contact forces evolve under a critical hydraulic gradient is still not fully understood. In this paper, the detailed process of piping erosion is investigated by using a coupled computational fluid dynamics and discrete element method (CFD–DEM) approach. The treatment of soil–flow interactions in CFD–DEM is explained by exchanging the momentum between the two phases. During the simulation, the piping erosion process is initiated by incrementally ascending differential water head across the soil samples. The three main stages of piping erosion (initial movement, continuation of erosion and total heave) can be identified from monitoring the particle velocity and positions. In addition, the evolution of contact force, hydraulic force, coordination number and void fraction is inspected to provide insight into the micro-mechanism of piping erosion. Two cases are simulated, one with a uniform particle size and a relatively uniform porosity distribution and the other with specific particle size and porosity distributions. An interesting finding from this study is that piping does not always initiate from the free surface and the evolution of piping depends heavily on the particle size and porosity distribution.

Laboratory Modeling of the Mechanisms of Piping Erosion Initiation

A laboratory modeling program has been conducted to assess the mechanics of initiating the piping erosion process in sandy soils. The models were performed on several soils, differing in gradation, grain size, grain shape, and specific gravity. Observations and monitoring of pore pressures within the samples during the modeling identified four stages in the development of piping initiation: initial movement, progressive heave, boil formation, and total heave. By linking the observed behavior with the measured pore-pressure regime in the sample, a model for the mechanics of piping development has been developed. Finite-element seepage analyses were performed to model the progression of piping development in the laboratory models and corroborate the developed model of mechanics. The findings of the study identified a new model for the initiation of piping development that can be applied to the assessment of piping in the field.

Constant Gradient Piping Test Apparatus for Evaluation of Critical Hydraulic Conditions for the Initiation of Piping

A laboratory apparatus has been developed for assessing the hydraulic conditions necessary for the initiation of piping erosion. The apparatus is designed to provide a constant hydraulic gradient throughout a sample while retaining the sample in a sample holder. Increasing differential head is applied across the sampler while observations of soil behavior and measurements of pore pressure throughout the sampler are made. Observations of soil behavior during the tests have identified four stages of the initiation of piping: 1) first visible movement, 2) heave progression, 3) boil formation, and 4) total heave. Tests were performed on sandy soils representing a variety of grain size, grain shape, gradation, and specific gravity. The effects these soil properties have on the critical hydraulic conditions needed to initiate piping erosion were evaluated based on observations and test results.

Constitutive modeling approach for estimating 1-D heave with respect to time for expansive soils

Many studies are reported in the literature for estimating the potential heave of expansive soils; however, limited efforts have been directed towards estimating the heave with respect to time. In this Technical Note, a simple approach is proposed for estimation of the one-dimensional (1-D) heave of expansive soils over time. The approach involves integrating semi-empirical and numerical techniques into a unified method to estimate heave in response to the net changes in soil suction within the active zone. The information of the variation of modulus of elasticity with respect to suction is introduced into the soil structure constitutive equation proposed by Fredlund and Morgenstern (1976) to estimate the soil heave over time. The commercial software VADOSE/W, a product of Geo-Studio, is used as a tool to estimate the net changes in the soil suction. The approach is tested using the published results by Vu and Fredlund (2006) for Regina expansive clay. The estimated results of the proposed approach agree well with the published data in terms of both the total heave variations and matric suction changes in the soil. The proposed method is promising and can be used in engineering practice for estimation of the 1-D heave with respect to time.

Frost heave predictions of buried chilled gas pipelines with the effect of permafrost

Abstract Frost heave is an anticipated issue for the arctic pipeline design. In this study, the pipe displacement due to frost heave is assumed as the amount of soil heave at the free-field area, where the influence of the restraint of pipeline in frozen ground is negligible. To predict the pipe displacement, a quasi two-dimensional explicit finite difference model was developed and Segregation Potential (SP) concept was applied to the model. The developed frost heave model was verified by a full-scale buried chilled gas pipeline experiment in Fairbanks, Alaska. The simulated thermal analysis results agreed with the observed results. Simulation of the pipe displacement was conducted for two ground conditions — with and without permafrost. In the case with permafrost, rising of the permafrost table was simulated. The result indicated that pipe displacement stops when the freezing front reaches the permafrost table. However, heave continues for the ground free of permafrost. Segregation heave played a more significant role to the total heave in the case of no permafrost than that with permafrost. The total heave without permafrost was 30% more than that with permafrost in a 25-year simulation.

Formation of ice lenses and frost heave

I examine the morphology of ice growth in porous media. Intermolecular forces cause premelted fluid to migrate and supply segregated ice growth (e.g., lenses) and frost heave. I account for the net effect of these microscopic interactions in a homogenized model formulated in terms of fundamental physical properties and characteristics of the porous medium that can be measured; no ad hoc parameterizations are required. Force equilibrium constraints yield the rate of fluid migration toward the ice lens boundary and predict the conditions under which new lenses are initiated. By combining this analysis with considerations of the heat flow problem in a step‐freezing (Stefan) configuration, I elucidate the boundaries between different regimes of freezing behavior. At higher overburden pressures and relatively warm surface temperatures, ice lenses cannot form, and freezing of the available liquid occurs within the pore space, with no accompanying deformation. When conditions allow a lens to form, water is drawn toward it. If the fluid supply is sufficiently rapid, the lens grows faster than the latent heat of fusion can be carried away, and its boundary temperature warms until it reaches a stable steady state configuration. At lower fluid supply rates, the lens boundary temperature cools until a new lens can form at a warmer temperature beneath. With subsequent freezing this lens grows until yet another lens forms and the process repeats. An approximate treatment leads to estimates of the evolving lens thickness and spacing, as well as the accumulated total heave.

Frost boils and soil ice content: field observations

AbstractOur aim is to measure and explain the seasonal changes in soil ice content in the frost boils of Galbraith Lake, Alaska. Instruments were installed in a frost boil to monitor the ground surface position and soil state over a period of 4 years. By comparing the subsidence and thaw rates, we calculate the soil ice content as a function of depth. Measured soil temperatures, liquid water contents and bulk apparent thermal conductivities are used to estimate latent heat production and release in the soil. The frost boil heaves during freezing and settles during thaw while the surrounding tundra heaves negligibly, but subsides measurably. Despite large changes in freezing rates from year to year, total heave and its distribution across the frost boil are similar between years. Winter air temperature and snow depth influence the freezing rate and ice distribution as a function of depth, but not the overall heave. This suggests that heave is controlled by water availability rather than the rate of heat removal from the soil. Areal ground subsidence rates between 2 and 5 cm/yr are due to the disappearance of ice at the base of the active layer, raising the possibility of ongoing thermokarst expansion around Galbraith Lake. Copyright © 2006 John Wiley & Sons, Ltd.

A Laboratory Study of the Hysteresis of a Thermal Conductivity Soil Suction Sensor

Abstract An experimental program was set up to study the capillary hysteresis of the ceramic block for a newly developed thermal conductivity soil suction sensor. The testing program included two series of tests: one series of tests measured the capillary hysteresis of the ceramic blocks and the other measured the hysteresis of the relationships between the suction sensor output and the applied suctions. Test results show that there can be approximately 40% error from the correct suction value if the conventional calibration curve is used without considering the effects of capillary hysteresis. Based on the experimental testing program, a mathematical approach, which is able to take into account the effects of capillary hysteresis, was proposed when interpreting the measured soil suction data.