Seasonal Variation of Backcalculated Subgrade Moduli

1997 ◽  
Vol 1577 (1) ◽  
pp. 70-80 ◽  
Author(s):  
Bing Long ◽  
Mustaque Hossain ◽  
Andrew J. Gisi
Keyword(s):  
Seasonal Variation ◽  
Moisture Content ◽  
Temperature Effect ◽  
Resilient Modulus ◽  
Natural Soil ◽  
Temperature Regimes ◽  
Almost All ◽  
Moisture Conditions ◽  
Falling Weight ◽  
And Behavior

Seasonal variations in pavement material properties and behavior due to variations in temperature and moisture conditions are known to affect the structural performance of pavement. Temperature, subgrade moisture content, and falling weight deflectometer (FWD) deflection data were collected monthly on four asphalt pavement test sections for a year. Subgrade moduli were backcalculated using the elastic layer theory with two calculation schemes and pavement models. Backcalculation of subgrade moduli by subdividing the subgrade into a compacted subgrade layer and a natural soil subgrade layer resulted in compacted subgrade moduli that are more sensitive to the seasonal variation for all sites. It was found that for almost all sites, the patterns of subgrade response, in terms of subgrade moduli versus subgrade moisture content, simulated sine-shaped forms signifying a temperature effect. The temperature effect was confirmed by the strong correlation between backcalculated subgrade moduli and pavement surface temperature during FWD tests. The lowest backcalculated subgrade moduli were obtained for two sections during months when asphalt surface temperatures were excessively high (greater than 40°C). Both backcalculation schemes showed similar trends in variation of subgrade moduli over seasons. When the AASHTO relative damage concept was used to compute the effective roadbed soil resilient modulus for design, similar values were found for both schemes for most of the sites. The minimum frequency of FWD testing to capture the seasonal variation of subgrade was found to be three tests per year, or testing every fourth month, assuming that unusually high temperature regimes could be avoided.

Modeling Stress- and Moisture-Induced Variations in Pavement Layer Moduli

2003 ◽  
Vol 1860 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Cheryl Richter ◽  
Charles W. Schwartz
Keyword(s):  
Moisture Content ◽  
Constitutive Model ◽  
Resilient Modulus ◽  
Monitoring Program ◽  
Elastic Theory ◽  
Pavement Materials ◽  
Seasonal Basis ◽  
Stress States ◽  
Stress Dependent ◽  
Moisture Conditions

The in situ moduli of unbound pavement materials vary on a seasonal basis as a function of temperature and moisture conditions. The development of empirical models to predict backcalculated pavement layer moduli as a function of moisture content and stress state is addressed. The work is based on data collected via the Seasonal Monitoring Program of the Long-Term Pavement Performance Program. This research identified fundamental incompatibilities between the stress states computed from layer moduli backcalculated using linear layered-elastic theory and those used in laboratory resilient modulus testing. Important implications of this finding are that (a) application of laboratory-derived constitutive model coefficients in combination with stress states computed using linear layered-elastic theory may yield inaccurate stress-dependent modulus values and (b) meaningful advances in the state of the art for backcalculation of pavement layer moduli cannot be achieved without addressing the inaccuracies and limitations inherent in the use of linear layered-elastic theory to model nonlinear pavement response. Other important findings include the following: (c) variation in moisture content is not always the most important factor causing seasonal variations in pavement layer moduli and (d) a constitutive model form suitable for approximately incorporating the stress and moisture sensitivity of layer moduli backcalculated using linear layered-elastic procedures for practical design purposes is identified.

Experimental Verification of Resilient Deformation for Granular Subgrades

1998 ◽  
Vol 1639 (1) ◽  
pp. 12-22 ◽  
Author(s):  
W. Virgil Ping ◽  
Zenghai Yang
Keyword(s):  
Moisture Content ◽  
Laboratory Test ◽  
Resilient Modulus ◽  
Soil Samples ◽  
Load Test ◽  
Experimental Program ◽  
Rigid Plate ◽  
Plate Load Test ◽  
Reconstituted Soil ◽  
Moisture Conditions

Results of an experimental program utilizing the repetitive rigid plate load test in a test-pit facility and the laboratory resilient modulus test are presented for five typical subgrades in Florida. The subgrade materials were tested in the test pit under three different moisture conditions, that is, (1) optimum, (2) drained and dried, and (3) soaked. Laboratory resilient modulus tests were conducted on reconstituted soil samples simulating the various moisture conditions. The resilient modulus was significantly affected by the moisture content of granular subgrades. A comparison between the deformations measured from the test-pit test and the deformation calculated from the laboratory test was made. It was experimentally verified that the resilient modulus resulting from the laboratory triaxial test could be used to predict the resilient deformation of pavement subgrade layers.

Seasonal Variation of Moisture and Subsurface Layer Moduli

2000 ◽  
Vol 1709 (1) ◽  
pp. 98-107 ◽  
Author(s):  
Vincent Janoo ◽  
Kent Shepherd
Keyword(s):  
Seasonal Variation ◽  
Moisture Content ◽  
Subsurface Layer ◽  
Field Measurements ◽  
General Description ◽  
Subsurface Temperature ◽  
Future Design ◽  
Pavement Structures ◽  
Base Course ◽  
Almost All

In 1995 the Montana Department of Transportation initiated a study on the seasonal variation of pavement strength, with an emphasis on spring thawing. Ten sites representing a cross section of Montana subgrade soil and pavement structure were selected and instrumented with moisture and temperature sensors. Field measurements of surface deflections, moistures, and temperatures were initiated in autumn 1996 and continued through the spring of 1997. The moisture and deflection data were used to determine the thaw-weakening characteristics of the sites and to develop subgrade modulus values for use in the future design of pavement structures using AASHTO mechanistic design methodology. Results indicated that in several areas not only the subgrade but also the base course layers were prone to thaw weakening. The length of thaw weakening varied from 4 days to a 3-week period. In addition, it was found that in almost all cases the subsurface moisture content began to increase rapidly when the subsurface temperature rose to around–2°C during the spring. In some cases it was found that when the subsurface temperature finally warmed to 0°C, the moisture content had reached its prefreeze value. This research provides a general description of the test sites and measurements; it quantifies the effects of thaw weakening on typical roads in Montana based on deflection and surface and subsurface moisture and temperature.

CLT construction without weather protection requires extensive moisture control

2021 ◽  
pp. 174425912199638
Author(s):  
Lars Olsson
Keyword(s):  
Moisture Content ◽  
Field Measurements ◽  
Scientific Work ◽  
Field Studies ◽  
Microbiological Analysis ◽  
Mould Growth ◽  
Extensive Growth ◽  
Almost All ◽  
Dry Out ◽  
Moisture Conditions

This study examines how cross-laminated timber (CLT) constructions, including joints, connections and attachment points, are affected by precipitation during construction. The case studies are based on moisture content measurements and material sampling as well as microbiological analysis during the structure’s construction stage. The study does not include remediation control. The field measurements show microbiological growth in all buildings and almost all floor structures that were investigated. Of a total of 200 measuring points analysed, half had mould growth and around a third had moderate or extensive growth. The moisture content measurements for one of the locations with the largest percentage of elevated or high moisture content was at the top of the floor structure in the bottom gap between timbers in the CLT top layer. This is one example of several materials or construction components where there is limited possibility of dry out. Based on the outcome, it would appear difficult, or impossible, to avoid the appearance of microbial growth during construction with CLT without weather protection. Previous studies indicate that microbiological analysis of CLT is extremely rare in both laboratory and field studies, which implies that there are obvious shortcomings in the scientific work. The fact that mould growth is often invisible needs to be disseminated, especially in practical studies. However, there seems to be a good level of awareness in the literature that theoretical studies often conduct mould growth risk evaluations. There do not appear to be any moisture safety assembly methods or solutions for CLT construction that do not have weather protection or a declaration of the critical moisture conditions for CLT products.

Physical and bacterial processes affecting suspended particulate matter in a tidal river

1998 ◽  
Vol 38 (6) ◽  
pp. 327-335
Author(s):  
Yasunori Kozuki ◽  
Yoshihiko Hosoi ◽  
Hitoshi Murakami ◽  
Katuhiro Kawamoto
Keyword(s):  
Particle Size ◽  
Particulate Matter ◽  
Suspended Particulate Matter ◽  
River Mouth ◽  
Tidal River ◽  
Natural Soil ◽  
Size Change ◽  
Run Off ◽  
Suspended Particulate ◽  
And Behavior

In order to clarify the origin and behavior of suspended particulate matter (SPM) in a tidal river, variation of SPM in a tidal river was investigated with regard to its size and constituents. SPM was separated into three groups according to size. Change of contents of titanium and organic substances of each group of SPM was examined. SPM which was discharged by run-off was transported with decomposition and sedimentation in a tidal river. Concentration of SPM with a particle size greater than 0.45 μm increased due to resuspension in a tidal river. Origin of SPM with a size of less than 0.45 μm at upstream areas was from natural soil and most of such SPM which had been transported settled near a river mouth. It was determined from examination of the CN ratio and the ratio of the number of attached bacteria to free bacteria that SPM with a size greater than 1.0 μm at upstream areas was decomposing intensively. At the downstream areas, SPM with a size of less than 0.45 μm came from the sea. SPM with particle size greater than 1.0 μm consisted of plankton and substances which were decomposed sufficiently while flowing.

scholarly journals Spatial and temporal variation of methane emissions in drained eutrophic peat agro-ecosystems: drainage ditches as emission hotspots

2008 ◽  
Vol 5 (2) ◽  
pp. 1237-1261 ◽  
Author(s):  
A. P. Schrier-Uijl ◽  
E. M. Veenendaal ◽  
P. A. Leffelaar ◽  
J. C. van Huissteden ◽  
F. Berendse
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Water Table ◽  
Soil Moisture Content ◽  
Explanatory Variable ◽  
Spatial And Temporal Variation ◽  
Spatial And Temporal Variability ◽  
Ch4 Emissions ◽  
Intensively Managed ◽  
Moisture Conditions

Abstract. Our research investigates the spatial and temporal variability of methane (CH4) emissions in two drained eutrophic peat areas (one intensively managed and the other less intensively managed) and the correlation between CH4 emissions and soil temperature, air temperature, soil moisture content and water table. We stratified the landscape into landscape elements that represent different conditions in terms of topography and therefore differ in moisture conditions. There was great spatial variability in the fluxes in both areas; the ditches and ditch edges (together 27% of the landscape) were methane hotspots whereas the dry fields had the smallest fluxes. In the intensively managed site the fluxes were significantly higher by comparison with the less intensively managed site. In all the landscape element elements the best explanatory variable for CH4 emission was temperature. Neither soil moisture content nor water table correlated significantly with CH4 emissions, except in April, where soil moisture was the best explanatory variable.

scholarly journals ANALYSIS OF PHYSICS LEARNING MATTER INTEGRATED DISASTER IN WEST SUMATERA

2019 ◽  
Vol 6 (2) ◽  
pp. 114
Author(s):  
Muhammad Arif ◽  
Dina Syaflita
Keyword(s):  
Natural Disasters ◽  
Natural Disaster ◽  
Teaching Material ◽  
Learning Material ◽  
Physics Learning ◽  
Descriptive Research ◽  
Prone Area ◽  
Almost All ◽  
And Behavior

West Sumatera is a disaster prone area, especially disasters such as earthquakes, landslides, floods,tsunamis, and volcanoes. The high potential of natural disasters has consequences for the importance ofdisaster mitigation efforts. School is an effective tool in shaping of mindset and behavior of students. Oneeffort that can be done is integrate the topic of natural disaster into learning, especially physics learning.Integrating physical matter in learning requires material analysis aimed at making disaster topics integratedin accordance with learning topic. The type of this research is descriptive research. The results of theresearch indicate that an analysis of the relevance of learning material to the topic of integrated disastersneeds to be done so that the integration between teaching material and the topic of disasters is carried out inharmony. Almost all physics learning material can be integrated with the topic of disasters that often hit theWest Sumatra region. The classification of material on the topic of integrated disasters is classified into factand metacognitive material.

scholarly journals Experimental Study on Dynamic Resilient Modulus of Lime-Treated Expansive Soil

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Zheng Lu ◽  
Yang Zhao ◽  
Shaohua Xian ◽  
Hailin Yao
Keyword(s):  
Moisture Content ◽  
Environmental Changes ◽  
Resilient Modulus ◽  
Expansive Soils ◽  
Expansive Soil ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
The Stability ◽  
Compaction Degree

Dynamic resilient modulus is the design index of highway subgrade design code in China, which is significantly affected by the traffic loads and environmental changes. In this study, dynamic triaxial tests were conducted to investigate the influence of moisture content, compaction degree, cyclic deviator stress, and confining pressure on lime-treated expansive soil. The suitability of UT-Austin model to lime-treated expansive soils was verified. The results indicate that the dynamic resilient modulus of lime-treated expansive soils increases nonlinearly with the increase of compaction degree, while decreases nonlinearly with the increase of dynamic stress level. The dynamic resilient modulus decreases linearly with the increase of moisture content and increases linearly with the increase of confining pressure. Moreover, the moisture content has a more significant effect on the dynamic resilient modulus of lime-treated expansive soil. Therefore, it is necessary to ensure the stability of soil humidity state and its excellent mechanical properties under long-term cyclic loading for the course of subgrade filling and service. Finally, the calculated results of the UT-Austin model for dynamic resilient modulus show a good agreement with the test results.

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