Thin Seals Research Articles

Resilient and rutting response of unbound granular material and subgrade soil influenced by initial state and stress conditions

Unbound pavements with thin seals, where traffic loads are primarily supported by unbound granular layers and subgrade soil, are favoured for their low initial cost. Rutting, the primary distress mechanism, leads to rough, uncomfortable surfaces, diminishing serviceability and safety. It depends on the material's initial dry density, degree of saturation, and applied stress levels. Resilient modulus, indicating layer stiffness, is crucial for determining load transmission to underlying layers, making accurate estimation essential for pavement design. This study conducted constant radial stiffness triaxial (CRST) tests on an unbound granular material and a subgrade soil at various dry densities, saturation degrees, and stress conditions. The CRST test applies dynamic confining pressure under constant radial stiffness boundary. New models for rutting and resilient modulus were developed, relating these parameters to initial dry densities, saturation degrees, and stress states. The study also presents rutting and resilient modulus isograms on the compaction plane, aiding field compaction control and robust pavement design.

Evaluation of climatic effects on moisture variation and performance of unbound pavements with sprayed seals

Over 90% of Australia's surfaced roads are unbound pavements with sprayed seals. However, achieving complete impermeability with these seals is challenging, leading to some moisture exchange between pavement layers and the environment. As moisture fluctuations influenced by climatic factors significantly affect the structural performance of particularly unbound granular layers, there is a pressing need to enhance Australian pavement design by incorporating climatic effects to meet better pavement performance. Hence, the current study numerically evaluates the degree of moisture saturation (Sr)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${S}_{r})$$\\end{document} variations of pavement layers under different Australian climates. This paper reveals how ambient climate impacts the moisture variations of pavement layers based on the results of 126 numerical simulations performed. Results indicated that the annual rainfall is not an appropriate parameter to decide the service moisture condition of the UGM layer, but the ratio between annual rainfall and annual pan evaporation (PPE\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\frac{P}{{\ ext{PE}}}$$\\end{document}) combined with the saturated permeability of the seal (Ks)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${K}_{{\ ext{s}}})$$\\end{document} is found to be a better indicator. More importantly, this study develops a novel empirical model to predict the service moisture condition of the UGM layers aiming to advance the current Australian pavement design guide. Furthermore, a correlation between pavement moisture and a widely used climatic index, Thornthwaite Moisture Index (TMI\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{TMI}}$$\\end{document}) is presented in this study. Furthermore, this paper proposes a novel approach to integrating climatic factors into the current Australian pavement design of unbound pavements with thin seals. This study enhances understanding of the complex relationship between climate and pavement moisture by taking a multi-dimensional approach.

Numerical evaluation of temporal moisture variations in unbound pavements with thin seals

The moisture condition of pavements is a crucial factor determining both their long-term and short-term performance in terms of the strength and stiffness of pavement materials. Unbound pavements with thin seals, the most common type of pavement in Australia and New Zealand, are vulnerable to moisture-related performance loss. Thin seals can be either bituminous or sprayed, the latter type being most common in Australia. This type of pavement can easily exchange moisture between the surrounding environment and the pavement structure, since the seal is relatively permeable. Therefore, changes in climatic factors such as precipitation, atmospheric temperature, evaporation, relative humidity and water table cause temporal moisture variations in pavement layers. These temporal moisture variations also affect performance losses. Hence, a reasonably accurate model is required to predict possible temporal moisture variation during service life in order to advance current Australian pavement design. This paper reports the development of a model to predict moisture conditions in terms of the degree of saturation (Sr), a critical parameter which determines rutting in the pavement layers of unbound pavements with sprayed seals. The model simulates the coupled moisture, vapour and heat flow through pavement layers in the middle section of the pavement, where the edge effects are not significant, employing 1-D numerical modelling. After validation of the model against some field data, the model was employed to analyse both the long-term and short-term hydraulic behaviour of pavements. Environmental factors substantially affect moisture conditions in the base and sub-base layers. Sensitivity analyses were performed to investigate the effects of the hydraulic properties of unbound granular materials (UGMs), the initial condition and the water table depth on long-term Sr and suction variation in unbound pavements with thin seals. It was found that the equilibrium moisture condition does not depend on the initial conditions, and the influence of the water table on subgrade equilibrium is significant only when the water table is within 6 m from the surface.

In-Plane and Out-of-Plane Elastodynamics of Thin Rings and Seals

Thin curved rings used mostly as seals, including in internal combustion engines undergo complex elastodynamic behavior when subjected to a combination of normal radial loading and tangential shear with friction. In turn, their complex modal behavior often results in loss of sealing, increased friction, and power loss. This paper presents a new finite difference approach to determine the response of thin incomplete circular rings. Two interchangeable approaches are presented; one embedding mass and stiffness components in a unified frequency-dependent matrix, and the other making use of equivalent mass and stiffness matrices for the ring structure. The versatility of the developed finite difference formulation can also allow for efficient modification to account for multiple dynamically changing ring support locations around its structure. Very good agreement is observed between the numerical predictions and experimental measurements, particularly with new precision noncontact measurements using laser Doppler vibrometry. The influence of geometric parameters on the frequency response of a high performance motorsport engine's piston compression ring demonstrates the degree of importance of various geometrical parameters on ring dynamic response.

Feasibility of Using 4th Power Law in Design of Plastic Deformation Resistant Low Volume Roads

A low volume road (LVR) structural design has two phases: first one is selection of appropriate construction materials and second is the determination of layer thicknesses under the certain traffic and environmental conditions with considering the subgrade bearing capacity. Pavements are prompted to serve the traffic without reaching the terminal serviceability index over its design life. Rut accumulation (plastic deformation) is the most common pavement deterioration type of flexible pavements. Therefore the main goal of the design is prevent rutting. Many low volume road design manual assume that plastic deformation occurs only in subgrade. Construction of overlying layers by selective high performance materials according to the related material and construction specifications is the reason of this assumption. In fact, the assumption is not much reasonable especially for with no, or thinly overlaid low volume road pavements, where the major structural strength is comprised of unbound granular pavement materials and where the principal distress mechanism is rutting in the aggregate layers.Subgrade bearing capacity and the traffic are the main input parameters in the design stage of low volume roads. Subgrade bearing capacity is expressed with California Bearing Ratio (CBR) or Resilient Modulus (Mr). The “traffic” term is determined by Equivalent Standard Axle Load (ESAL) repetitions which is often admitted as 80kN single axle load. Although it is not too difficult to determine an axle load for an individual vehicle, it becomes quite complicated to determine the number and types of axle loads that a particular pavement will be subjected over its design life. For calculation of Load Damage Factors of different vehicle types, which have various axle load and configurations, a generalized fourth-power law has been used for more than a half century. The objective of this study is to indicate the limitations and difficulties faced on reliably applying a power law relationship in design of LVRs with no, or only thin seals. If a power law relationship to be used due to its simplicity, several parameters must be considered in selection of the power value. Such as stress dependent behavior of unbound granular materials and the selected distress type.

51.4: Development of Flexible Electrowetting Displays for Stacked Color

AbstractElectrowetting displays show promise for realizing vividly colorful electronic paper using stacked color layers to obtain high reflectivity. We develop and demonstrate technologies needed to realize stacked displays including (1) strategies for controlling colorant location, (2) incorporating spacers, black surround, and thin seals, and (3) building working modules on flexible substrates.

Rut Accumulation and Power Law Models for Low-Volume Pavements under Mixed Traffic

The fourth-power law has been used for more than 40 years to assist the modeling of the damage that accumulates in pavements due to different traffic load levels and differing numbers of load applications. This paper studies the applicability and the limits of applicability of this law to typical low-volume road pavements with no or only thin seals that obtain their structural performance primarily from the aggregate base (or equivalent) layer and for which pavements’ deterioration is overwhelmingly due to rutting. After behavior of unbound granular pavement materials has been reviewed, data from four sources is used to show that it is sometimes impossible to model real pavement response by any power relationship. Furthermore, power values, even when usable, are highly variable and can vary widely with construction material and with distress criteria. It is shown that, even when a power law is a reasonable way of interpreting data, a value for the law of 4 is not. Some suggestions are given for alternative approaches and adaptations.

Yampi Shelf, Browse Basin, North-West Shelf, Australia: a test-bed for constraining hydrocarbon migration and seepage rates using combinations of 2D and 3D seismic data and multiple, independent remote sensing technologies

The Yampi Shelf on Australia's North-West Shelf is highly prospective, with two discrete hydrocarbon sources producing dry gas and oil. To reduce exploration uncertainty relating to gas flushing and poor top seal capacity, a study was undertaken to characterise hydrocarbon migration in the area. It used a combination of seismic amplitude and structural data integrated with shipboard water column geochemical sniffer (WaSi) data, satellite Synthetic Aperture Radar or SAR data and aircraft-acquired Airborne Laser Fluorosensor (ALF) data. Data were acquired synchronously and in staged programs, to allow both direct comparison and time-series analysis of results. Massive natural dry gas and oil seepage was detected, though the relative abilities of WaSi, SAR and ALF to detect and characterise this seepage were markedly different. The spatial distribution, concentration, and relative composition of the detected seepage were controlled principally by the regional seal's thickness and capacity, rather than by the inherent composition and flux of the migrating hydrocarbons. WaSi preferentially identified gas seepage, often in basin-ward locations, because the high relative permeability of gas favoured its early leakage, even through thick seals. SAR preferentially identified oil seepage, which was episodic and largely restricted to the basin-margin at the regional zero-edge-of-seal, reflecting the low relative permeability of oil, even through thin seals (it leaked ‘late’). ALF principally detected low-level oil seepage from charged traps, and was hence most useful for trap ranking. The ability of these remote sensing tools, as well as that of seismic data itself, to detect hydrocarbons appears critically dependant upon interplays between the relative sensitivity of the assorted tools to detect various hydrocarbon phases and the capacity of the top seal itself. The study has demonstrated that the interactions between geology and hydrocarbon charge are predictable, and that understanding these interactions is crucial for the reliable interpretation of remote sensing data.

Fault-seal analysis using a stochastic multifault approach

We have developed a stochastic multifault method for analysis of the impact of stratigraphic uncertainty on cross-fault leakage at sand-sand juxtapositions. This method assumes that all sand-sand juxtapositions leak across the fault. Stratigraphic uncertainty is modeled by stochastic variation of stratigraphic stacking. Structural uncertainty is addressed through variation of the input. Our objectives were to quantitatively predict the impact of uncertainties in stratigraphic and structural input and to simulate the complex system of structural spills and juxtaposition leak points that control hydrocarbon contact levels in traps with stacked reservoir systems and many faults.Three examples demonstrate how this stochastic multifault method has helped us evaluate uncertainty and understand complex leak fill-and-spill controls. The Ling Gu prospect demonstrates that widespread cross-fault leakage on two crestal faults with throw changes that exceed seal thickness causes only a single hydrocarbon column to accumulate in multiple-stacked reservoirs. This column is controlled by a juxtaposition leak point on a third, deeper fault. We have learned from examples like Ling Gu that the relative size of throw change and seal thickness is a fundamental control on the probability of cross-fault juxtapositions. An example at prospect A demonstrates the sensitivity of hydrocarbon entrapment to small faults in a sand-prone interval with thin seals. The prospect A analysis shows that if seals are thin, faults or channel incisions below seismic resolution can leak hydrocarbons out of stacked reservoirs that are interpreted as unfaulted on seismic data. This introduced significant predrill uncertainty and risk. Guntong field demonstrates that a thin sand in a juxtaposed seal interval can introduce large uncertainty in the prediction of hydrocarbon columns.These examples and many other analyses using the method demonstrate how small changes in stratigraphic and structural input to a fault-seal analysis can introduce significant uncertainty in the predicted range of hydrocarbon volumes. Such uncertainties need to be directly and systematically accounted for in a fault-seal analysis.

Total blubber burden of organochlorine pollutants in phocid seals; methods and suggested standardization

The purpose of the present paper was to investigate methods for calculating the total blubber burden of organochlorine pollutants (OCs) in phocid seals. Harp seals ( Phoca groenlandica) were used as the model species. A sample of fat pre-breeding adult females ( N=9) and a sample of thin moulting adult females ( N=7) were collected. From each animal blubber samples from five different body sites (complete blubber columns and samples from different blubber layers), in addition to a sample from a homogenate derived from the entire blubber mass, were analyzed for selected OCs. Significant differences in the concentrations of major OC contaminants were found between inner and outer blubber layer. Within each seal group, no significant difference in OC concentrations was found between homogenates from whole blubber columns from the five different sites of the animals or when comparing these with the OC concentrations found in the blubber sample deriving from a homogenate of the entire blubber mass. When comparing the two seal groups, the mean OC concentrations were significantly higher in the thin seals. However, blubber burden of OCs measured directly and calculated indirectly were not significantly different, and did not vary between the two groups of seals. Since these seals are of the same age and sex group and from the same population, this is not an unexpected result. The present results suggest that comparison of blubber concentrations of OCs in phocid seals should be avoided, especially when comparing differences between geographical areas or for time–trend analyses. For this type of study, we suggest that the blubber burden of OCs is applied as standard in the future. Furthermore, since blubber depth at a specific sampling site is required when using the estimator for calculation of the percent blubber content in phocid seals (the LMD-index), we suggest that this sampling site (central dorsally) is introduced as a standard when sampling blubber for OC analyses in phocid seals.

Blood is a poor substrate for monitoring pollution burdens in phocid seals

The present study investigated how concentrations of different organochlorines (OCs) vary with nutritional condition in adult harp seal ( Phoca groenlandica) females in a captive fasting experiment and in the wild. During the first part of this study seals in good condition ( N=5) were fasted for a period of 28 days and blood and blubber samples were collected at days 1, 14 and 28. Blubber OC concentrations remained unchanged throughout the experimental period, and were consistently significantly higher than concentrations in the blood. In contrast to blubber OC levels, blood OC levels showed a significant time-dependant increase. During the fasting experiment the seals lost an average of 24 kg of body mass, which is less than half the natural annual variation in this species in the wild. The second part of this study compared OC concentrations in blood and blubber from seals collected at prime condition before the breeding season ( N=10) with animals collected during molt when condition is poor ( N=7). The average mass difference between the two groups was more than 40 kg. Blood levels of most OCs were significantly higher in the thin seals compared with the levels found in the fat seals. These differences in blood OC concentrations were much greater than what was found during the fasting experiment. For example ∑PCB levels in the blood during the fasting experiment increased by ∼83%, while the corresponding increase in blood levels of ∑PCB between the two other samples was 720% (from 201 to 1447 ng/g lipid). Blubber levels of OCs from the animals in the wild were significantly higher in the thin seals compared with the fat animals. In addition, the blubber levels of OCs were significantly higher than blood levels of OCs only for the fat seals. This study demonstrates the extreme variability present in the concentrations of OCs in blood of seals in response to change in condition. Since the natural variation in condition is extreme during phocid seals’ annual cycles, we recommend that blood should not be used in studies of OCs where the aim of the study is to monitor OC levels for comparative purposes or time-trend analysis.

Field immobilisation of southern elephant seals with intravenous tiletamine and zolazepam

Southern elephant seals (Miroungo leonina) were immobilised with a mixture of tiletamine and zolazepam administered intravenously at a mean (sd) dose rate of 0.46 (0.08) mg/kg. This dose provided a...