Thaw Settlement Research Articles

A Model-Based Experiment on the Prevention of Frost Heave in Canals using Soil-bags

To study the effects of soil-bags on the prevention of frost heave in canals in cold regions, experiments were conducted on models of soil-bags -treated and conventional canals subjected to freeze-thaw cycles. The amounts of frost heave and thaw settlement, water content and changes in temperature over time in the soil-bags-treated canals and conventional canals were studied. The experimental results showed that a significant frost heave-preventing effect was found in the soil-bags-treated canals subjected to freeze-thaw cycles, and the mechanism of the soilbags prevention of frost heave in canals was revealed. The frost heave-preventing effect of soil-bags was achieved by inhibiting the rising of capillary water and film water, in addition to introducing a reinforcement effect. The study provides a theoretical basis for the prevention of frost heaving in canals in cold regions.

Thaw consolidation behaviours of embankments in permafrost regions with periodical temperature boundaries

A modified simulation method based on large strain thaw consolidation theory was proposed for the thaw consolidation behaviours of permafrost embankment. It was verified using monitored data that the new method has a good performance in simulating seasonal changes of thaw settlement. For permafrost embankment with different thermal and mechanical properties, the consolidation process in the post-thawed layer of top ground surface will accomplish during initial operating period. After that, thaw consolidation degree will decrease continuously. The decreasing rate of thaw consolidation degree (Dr) is proportional to thaw consolidation ratio (R) of deep permafrost layer. Regression analysis indicates that Dr is a power function of R.

포화 사질토 뒷채움재의 비배수 동결에 의한 매설 강관의 거동 - 실대형 모형실험 연구 -

동절기에 지반에 매설된 상수도관은 지반의 동결 융해로 인해 과대한 지반 응력을 받게 되고, 이러한 현상이 겨울철 상수도관의 파괴 또는 변형에 많은 영향을 끼친다. 본 논문에서는 실 대형 모형실험을 통해 외부 온도 변화에 따른 매설관 주변 지반 내 온도거동과 매설관의 변위 및 응력거동을 확인하였으며, 지반이 동결됨에 따라 매설관 주변에 응력이 집중되고 동상이 발생하는 것을 확인하였다. 또한, 실험에 사용된 시료가 비동상성 시료인 사질토임에도 불구하고 함수비 조건과 배수조건에 따라 동상현상이 나타나는 것을 발견하였으며, 본 논문을 통해 매설관의 배딩(bedding)과 뒷채움재를 비동상 시료로 치환하더라도, 주변 지반의 배수상태, 지하수위, 함수비 등에 따라 동상에 대한 별도의 대책을 세워야 함을 제시하고자 하였다. Frost heaving and thawing settlement cause unexpected stress around buried pipelines, which results in deformation and permanent demage. A large scale laboratory test has been performed to observe deformation, stress, and temperature of a buried pipe during atmospheric temperature changes. From the experimental results, the stress concentrated around the buried pipe is inevitable and deformation is caused by the frost heaving. Even though backfill materials are sandy soils which are normally assumed to be non frost susceptible, it is revealed that frost demage can happen due to drainage condition, the level of ground water table, and water content.

Permafrost environment monitoring on the Qinghai-Tibet Plateau using time series ASAR images

The permafrost in Qinghai-Tibet Plateau (QTP) has long been the focus of many researchers. In this study, we first use the method that integrates synthetic aperture radar (SAR) intensity and phase information to monitor permafrost environment in the Beiluhe Region, using time series advanced SAR images. The backscattering coefficients (σ0) and deformation were extracted for the main features, and the influences of meteorological conditions to them were also quantified. The results show that both the change in σ0 and surface deformation are closely related to the active layer, and the deformation is also affected by the permafrost table. First, over meadow and sparse vegetation regions, σ0 rose about 6.9 and 4 dB from the freezing to thawing period, respectively, which can be mainly attributed to the thaw of the active layer and increased precipitation. Second, seasonal deformation, derived from the freeze-thaw cycle of the active layer, was characteristic of frost heave and thaw settlement and exhibited a negative correlation with air temperature. Its magnitude was larger than 1 cm in a seasonal cycle. Last, significant secular settlement was observed, with rates ranging from –16 to 2 mm/a, and it was primarily due to the thaw of the permafrost table caused by climate warming.

Seasonal thaw settlement at drained thermokarst lake basins, Arctic Alaska

Abstract. Drained thermokarst lake basins (DTLBs) are ubiquitous landforms on Arctic tundra lowland. Their dynamic states are seldom investigated, despite their importance for landscape stability, hydrology, nutrient fluxes, and carbon cycling. Here we report results based on high-resolution Interferometric Synthetic Aperture Radar (InSAR) measurements using space-borne data for a study area located on the North Slope of Alaska near Prudhoe Bay, where we focus on the seasonal thaw settlement within DTLBs, averaged between 2006 and 2010. The majority (14) of the 18 DTLBs in the study area exhibited seasonal thaw settlement of 3–4 cm. However, four of the DTLBs examined exceeded 4 cm of thaw settlement, with one basin experiencing up to 12 cm. Combining the InSAR observations with the in situ active layer thickness measured using ground penetrating radar and mechanical probing, we calculated thaw strain, an index of thaw settlement strength along a transect across the basin that underwent large thaw settlement. We found thaw strains of 10–35% at the basin center, suggesting the seasonal melting of ground ice as a possible mechanism for the large settlement. These findings emphasize the dynamic nature of permafrost landforms, demonstrate the capability of the InSAR technique to remotely monitor surface deformation of individual DTLBs, and illustrate the combination of ground-based and remote sensing observations to estimate thaw strain. Our study highlights the need for better description of the spatial heterogeneity of landscape-scale processes for regional assessment of surface dynamics on Arctic coastal lowlands.

Thaw Settlement Hazard of Permafrost Related to Climate Warming in Alaska

Permafrost temperatures have increased in Alaska since the 1960s, and many impacts of climate warming are associated with permafrost thaw. Thaw of permafrost caused by increases in permafrost temperature may result in thaw settlement and significant damage to infrastructure. The goal of this research is to identify regions of Alaska at risk from thaw subsidence related to climate warming and to determine the relative risk of those regions. We developed a Permafrost Settlement Hazard Index (PSHI) by analyzing anticipated climate warming and the ecological characteristics that regulate thaw subsidence. This analysis provides statistical verification that the discontinuous permafrost region is at more risk of thaw settlement than other regions of Alaska. In addition, it estimates future thaw subsidence risk in Alaska in 2050 using future temperature increases projected by published climate models. Results indicate increased thaw subsidence risk in northern Alaska in 2050, with the greatest increase expected in parts of northwest Alaska. However, in the interior and southwest Alaska, projected disappearance of permafrost from the surface will reduce the risk of thaw subsidence.

Moisture–temperature changes and freeze–thaw hazards on a canal in seasonally frozen regions

Freeze–thaw action is a complex moisture–heat-mechanics interaction process, which has caused prevailing and severe damages to canals in seasonally frozen regions. Up to now, the detailed frost damage mechanism has not been well disclosed. To explore the freeze–thaw damage mechanism of the canal in cold regions, a numerical moisture–heat-mechanics model is established and corresponding computer program is written. Then, a representative canal in the northeast of China is taken as an example to simulate the freeze–thaw damage process. Meanwhile, the robustness of the numerical model and program is tested by some in situ data. Lastly, the numerical results show that there are dramatic water migration and redistribution in the seasonal freeze–thaw variation layer, causing repetitive frost heave and thaw settlement, and tension–compression stresses. Therefore, the strengths of soil are reduced after several freeze–thaw cycles. Further, the heavy denudation damage and downslope movement of the canal slope would be quite likely triggered in seasonally frozen regions. These zones should be monitored closely to ensure safe operation. As a preliminary study, the numerical model and results in this paper may be a reference for design, maintenance, and research on other canals in seasonally frozen regions.

Coastal products of marine transgression in cold-temperate and high-latitude coastal-plain settings: Gulf of St Lawrence and Beaufort Sea

Abstract Cold climate exerts a clear influence on the processes of marine transgression in mid- and high-latitude coastal-plain settings, but its signature in the depositional record is much clearer at high latitude. Both cases selected for this study are influenced by the legacy of past glaciation and the pervasive effects of ongoing Holocene marine transgression. Both are affected by sea ice. The high-latitude site lies within the zone of continuous permafrost and the abundance of excess ground ice along the Beaufort coast is the dominant factor distinguishing it from the mid-latitude Gulf of St Lawrence (GSL) setting and standard models of transgressive coasts elsewhere. In the southern GSL, the transgressive unconformity (TU) is at the seabed (or buried by a very thin veneer) across the inner shelf; shoreface sand moves landward, keeping pace with the transgressive front through deposition in barriers, dunes and estuaries. The pace of transgression in the Beaufort Sea is influenced by a number of distinctive periglacial erosion processes, including thermal abrasion and thaw subsidence. Marine transgression across this landscape creates intricate breached-lake estuaries and low sandy barrier beaches with limited dunes, leaving distinctive facies suites and geometry, while seaward sediment transport buries the TU on the inner shelf.

Cold Region Applications for In-Place Inclinometers Based on Microelectromechanical Systems Technology

Inclinometer probes are an industry standard for measuring ground movement; however, this technology has drawbacks, including costly trips for manual measurements, operator error, and limited measurements caused by casing deformation. Relatively new in-place inclinometers based on microelectromechanical systems (M-IPIs) consist of microelectromechanical systems accelerometer segments separated variously by flexible joints or field connection systems and encased in a watertight housing. M-IPIs provide nearly continuous ground movement measurements, accommodate greater ground movement because of their flexibility, and may contain temperature sensors, useful for applications in frozen ground. Two M-IPIs from different manufacturers were evaluated at four research sites in Alaska (a) to monitor creep in frozen ground (vertical installation), (b) to identify and monitor a slide shear zone (vertical installation), (c) to monitor thaw settlement under a newly constructed embankment (horizontal installation), and (d) to identify movement mechanisms within a slide and to evaluate the M-IPIs functionality through large amounts of shear (vertical installation). Each M-IPI was evaluated for ease of installation and subsequent retrieval, durability, and functionality in frozen ground. Measurements from both devices compared well with those from the inclinometer probe; this feature indicated that these devices were suitable for use in cold regions. However, field experience indicates that the installation procedure for each instrument is better undertaken at temperatures above freezing because of the manual dexterity required. For horizontal installations over permafrost, it is recommended that casing ends be secured to posts anchored below the permafrost table and any cold-affected plastic components be replaced between installations to avoid unwanted breakage during reinstallation.

Calculation theories and analysis methods of thermodynamic stability of embankment engineering in cold regions

The calculation theories and analysis methods of thermodynamic stability of embankment engineering in cold regions are systematically summarized. The engineering theories and methods taken to control frost heave and thaw settlement in seasonal frozen soil regions may not be applicable in permafrost regions. The active cooling technology of roadbed should be utilized to limit the effects caused by both climate changes and human engineering activities. The paper mainly discussed the calculation theories and analysis methods of four kinds of embankment structures, i.e., the crushed-rock embankment, duct-ventilated embankment, thermosyphon embankment, and composite embankment. It is expected that a scientific basis could be provided for the theory, design, and application of embankment constructions in cold regions.

Isotropic thaw subsidence in undisturbed permafrost landscapes

AbstractObservations in undisturbed terrain within some regions of the Arctic reveal limited correlation between increasing air temperature and the thickness of the seasonally thawed layer above ice‐rich permafrost. Here we describe landscape‐scale, thaw‐induced subsidence lacking the topographic contrasts associated with thermokarst terrain. A high‐resolution, 11 year record of temperature and vertical movement at the ground surface from contrasting physiographic regions of northern Alaska, obtained with differential global positioning systems technology, indicates that thaw of an ice‐rich layer at the top of permafrost has produced decimeter‐scale subsidence extending over the entire landscapes. Without specialized observation techniques the subsidence is not apparent to observers at the surface. This “isotropic thaw subsidence” explains the apparent stability of active layer thickness records from some landscapes of northern Alaska, despite warming near‐surface air temperatures. Integrated over extensive regions, it may be responsible for thawing large volumes of carbon‐rich substrate and could have negative impacts on infrastructure.

RADARSAT-2 D-InSAR for ground displacement in permafrost terrain, validation from Iqaluit Airport, Baffin Island, Canada

The use of Differential Interferometric Synthetic Aperture Radar (D-InSAR) is rapidly gaining acceptance as a source of ground displacement information for permafrost regions. The accuracy of the information however, is still not well established. This paper uses a stack of RADARSAT-2 D-InSAR data to map seasonal ground displacement at the Iqaluit Airport, Baffin Island, Canada. The accuracy and information content of the D-InSAR products are evaluated with a variety of ground truth data. The D-InSAR derived seasonal ground displacement patterns align well with surficial geology units and reflect the thaw settlement characteristics of the sediments; they also identify localised displacement patterns in the vicinity of features such as ice wedges and frost cracks. Comparisons with ground settlement measurements from in-situ thaw tubes indicate sub-centimetre agreement in dry areas. In low lying wet areas however, subject to saturation and flooding, the D-InSAR stack significantly underestimates the true settlement, detecting only 3.7cm of the 8.5cm thaw tube measurement. The combination of high phase gradients and poor coherence over intermittently flooded surfaces makes it challenging to preserve reliable phase measurements in these areas. Information from electromagnetic surveys shows that some surface displacement is related to sub-surface conditions (<6m depth), possibly conditions related to the presence and movement of water in the active layer and to a lesser extent, unfrozen water content within the permafrost.

Study on Thawing Settlement and its Influenced Factors of Embankment in Seasonal Frost Area

Frost heaving and thawing settlement were the common diseases in seasonal frost area. In order to study the influenced factors of the subgrade thawing settlement, a series investigation were done on the subgrade of the Beijing-Baotou-Lanzhou railway line at the Chasuqi and Wulate qianqi sections from January to June. It was found that thawing settlement existed in embankment had great influence on the safety of subgrad running. This was less influenced by the even settlement, but was dangerous under the uneven state because of the track irregularity and its divorce from the ballast. The main factors affected the embankment thawing settlement included soil composition, water content and kind, environment temperature and the loading on soil. The larger thawing settlement would observed in the soil with large amount of silt particle, at the regions of low underground water level, with the kind of salt sensitive to frozen, at the atmosphere of the higher negative temperature sustaining a long time.

Permafrost Hazard of MoHe-DaQing Crude Oil Pipeline

The crude oil pipeline from MoHe to DaQing (hereafter called Mo-Da pipeline) is part of China-Russia oil pipeline. Mo-Da pipeline is the first pipeline that through high latitude cold regions of China. The pipeline is in so complicated geography environment that many kinds of permafrost hazard are easily to happen including frost heave, thaw settlement, slope instabilities, and collapse and so on. The pipeline and the permafrost act and react upon one another. On one hand, soil frost heave and thaw settlement can produce extra stresses on pipe walls, which may result in centralized stresses and plastic deformations under certain conditions, even causes pipeline faults. On the other hand, buried pipeline will disturb ambient environment and then degrade the permafrost soil and finally impact safety of the pipeline. This paper mainly introduces the permafrost hazards of Mo-Da pipeline and demonstrates some methods for monitoring the influence of permafrost.

The Daxinganling Island Taliks Sheet Permafrost Feature

In order to study the features of permafrost in Daxinganling, based on t he methods of field investigation and borehole drilling, as w ell as theoretic analysis and the effects of frozen soil geological conditions, topography features, frozen soil type and permafrost classification the freeze-thaw depth(m),main physical indicators of the Frost soil, natural water content, plastic limit Liquid limit index were analysis .the thaw settlement and frost heave were studied in this paper.

Reorganization of vegetation, hydrology and soil carbon after permafrost degradation across heterogeneous boreal landscapes

The diversity of ecosystems across boreal landscapes, successional changes after disturbance and complicated permafrost histories, present enormous challenges for assessing how vegetation, water and soil carbon may respond to climate change in boreal regions. To address this complexity, we used a chronosequence approach to assess changes in vegetation composition, water storage and soil organic carbon (SOC) stocks along successional gradients within four landscapes: (1) rocky uplands on ice-poor hillside colluvium, (2) silty uplands on extremely ice-rich loess, (3) gravelly–sandy lowlands on ice-poor eolian sand and (4) peaty–silty lowlands on thick ice-rich peat deposits over reworked lowland loess. In rocky uplands, after fire permafrost thawed rapidly due to low ice contents, soils became well drained and SOC stocks decreased slightly. In silty uplands, after fire permafrost persisted, soils remained saturated and SOC decreased slightly. In gravelly–sandy lowlands where permafrost persisted in drier forest soils, loss of deeper permafrost around lakes has allowed recent widespread drainage of lakes that has exposed limnic material with high SOC to aerobic decomposition. In peaty–silty lowlands, 2–4 m of thaw settlement led to fragmented drainage patterns in isolated thermokarst bogs and flooding of soils, and surface soils accumulated new bog peat. We were not able to detect SOC changes in deeper soils, however, due to high variability. Complicated soil stratigraphy revealed that permafrost has repeatedly aggraded and degraded in all landscapes during the Holocene, although in silty uplands only the upper permafrost was affected. Overall, permafrost thaw has led to the reorganization of vegetation, water storage and flow paths, and patterns of SOC accumulation. However, changes have occurred over different timescales among landscapes: over decades in rocky uplands and gravelly–sandy lowlands in response to fire and lake drainage, over decades to centuries in peaty–silty lowlands with a legacy of complicated Holocene changes, and over centuries in silty uplands where ice-rich soil and ecological recovery protect permafrost.

Structure and properties of ice-rich permafrost near Anchorage, Alaska

Abstract Geotechnical investigations in the vicinity of Anchorage, Alaska revealed a body of ice-rich permafrost up to 12 m thick and approximately 150 m long. Mean annual air temperature in Anchorage is + 2.2 °C which is unfavorable to the existence of permafrost. However, isolated masses of relic permafrost exist at temperatures close to 0 °C protected from rapid thawing by a thick layer of peat and soils with high ice content. Frozen soils found at the study site include silty clay of glacio-lacustrine origin with numerous layers of segregated ice up to 70 cm in thickness. The average volume of visible ice is 42.5%; and total gravimetric water content is 68%. With an average permafrost thickness of 9.5 m and an average thaw strain of 40%, the thaw settlement of the surface is expected to be at least 3.8 m after degradation of permafrost, an unacceptable deformation for any engineered structure on these soils.

Periglacial landscape dynamics in the western Canadian Arctic: Results from a thermokarst lake record on a push moraine (Herschel Island, Yukon Territory)

Ice-rich permafrost landscapes are sensitive to climate and environmental change due to the melt-out of ground ice during thermokarst development. Thermokarst processes in the northern Yukon Territory are currently not well-documented. Lake sediments from Herschel Island (69°36′N; 139°04′W) in the western Canadian Arctic provide a record of thermokarst lake development since the early Holocene. A 727cm long lake sediment core was analyzed for radiographic images, magnetic susceptibility, granulometry, and biogeochemical parameters (organic carbon, nitrogen, and stable carbon isotopes). Based on eight calibrated AMS radiocarbon dates, the sediment record covers the last ~11,500years and was divided into four lithostratigraphic units (A to D) reflecting different thermokarst stages. Thermokarst initiation at the study area began ~11.5cal ka BP. From ~11.5 to 10.0cal ka BP, lake sediments of unit A started to accumulate in an initial lake basin created by melt-out of massive ground ice and thaw subsidence. Between 10.0 and 7.0cal ka BP (unit B) the lake basin expanded in size and depth, attributed to talik formation during the Holocene thermal maximum. Higher-than-modern summer air temperatures led to increased lake productivity and widespread terrain disturbances in the lake's catchment. Thermokarst lake development between 7.0 and 1.8cal ka BP (unit C) was characterized by a dynamic equilibrium, where lake basin and talik steadily expanded into ambient ice-rich terrain through shoreline erosion. Once lakes become deeper than the maximum winter lake ice thickness, thermokarst lake sediments show a great preservation potential. However, site-specific geomorphic factors such as episodic bank-shore erosion or sudden drainage through thermo-erosional valleys or coastal erosion breaching lake basins can disrupt continuous deposition. A hiatus in the record from 1.8 to 0.9cal ka BP in Lake Herschel likely resulted from lake drainage or allochthonous slumping due to collapsing shore lines before continuous sedimentation of unit D recommenced during the last 900years.

Use of geosynthetics for performance enhancement of earth structures in cold regions

Earth structures, such as roadways, embankments and slopes, and earth retaining walls, have been commonly used in cold regions for transportation and other applications. In addition to typical design considerations for earth structures at normal temperature, a design must also consider the unique problems associated with low temperature, such as frost heave, lateral expansion, thaw settlement and weakening, and degradation of material properties. Geosynthetics have been used in cold regions to stabilize earth structures during construction and mitigate potential problems during their service at low temperature. This paper provides a state of practice review of the use of geosynthetics for performance enhancement of earth structures in cold regions. This paper starts with basic information on available geosynthetic products and their functions, evaluates properties and behavior of geosynthetics and soil-geosynthetic systems at low temperature, and discusses past studies and their key results on the use of geosynthetics to enhance the performance of roadways, embankments, and earth retaining walls in cold regions. This review reveals that geosynthetics at low temperature have higher tensile strength and stiffness, lower creep rate, and lower elongation at failure. The effect of temperature becomes significant when nonwoven geotextiles are subjected to moistening and soil intrusion at subfreezing temperature. Freeze-thaw cycles may degrade hydraulic and mechanical properties of geosynthetic-soil systems. The inclusion of geosynthetics in soil provides drainage and/or barrier to water flow, retains mechanical properties, and reduces frost heave during and after freeze-thaw cycles. Effectiveness of geosynthetics has been confirmed in the field in bridging over voids, stabilizing roadways over temperature-susceptible soils during thaw, and proving drainage and barrier to temperature-susceptible soils before freeze. To avoid frost heave and lateral expansion of backfill in earth retaining walls, granular fill without fines should be used. When backfill with fines is used for earth retaining walls, additional lateral earth pressure induced by soil freeze and thaw settlement should be considered in the design.

Mudboil and ice‐wedge dynamics investigated by electrical resistivity tomography, ground temperatures and surface movements in svalbard

Arctic tundra surfaces are dominated by a variety of patterned ground forms. Whereas a large number of studies have described morphology, structure and processes of patterned ground, few have monitored detailed patterned ground dynamics and subsurface environments continuously. We applied electrical resistivity tomography (ERT) to understand near‐surface conditions of two types of patterned ground, ice‐wedge polygons and mudboils in Svalbard, where periglacial processes associated with permafrost are intensively monitored. Automated monitoring shows surface movement characterized by annual cycles of frost heave and thaw settlement, the amounts and rates of which are influenced by the intensity of ice segregation. A time series of ERT shows (1) a distinct resistivity boundary delimiting the active‐layer depth, (2) seasonal variation in resistivity controlled by thermo‐hydrological dynamics and (3) spatial variation in resistivity reflecting desiccation in summer and intensive ice segregation in winter. These results demonstrate ERT as a useful complementary technique for monitoring active‐layer depths and near‐surface hydrological conditions at periglacial patterned ground sites, where automated soil thermal and moisture measurements are limited.