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The ability to model and predict the formation of desiccation cracks is potentially beneficial in many applications such as clay liner design, earth dam construction, and crop science, etc. However, most studies have focused on statistical analysis of crack patterns and qualitative study of contributing factors to crack development rather than prediction. Because it is exceedingly difficult to capture the nonlinear processes during desiccation in analytical modelling, most such models handle crack formation without considering variation of material properties with time, and are unattractive to use in realistic modelling. The data obtained from laboratory experiments on clay soil desiccating in moulds were used as a basis to develop a more refined model of desiccation cracking. In this study, the properties, such as matric suction, stiffness and tensile strength of soil, and base adhesion, could be expressed approximately as functions of moisture content. The initial conditions and the development of suction due to desiccation and the varying material properties were inputted to UDEC, a distinct element code, using its internal programming language FISH. The model was able to capture some essential physical aspects of crack evolution in soil contained in moulds with varying lengths, heights, and materials of construction. Extension of this methodology is potentially beneficial not only for modelling desiccation cracking in clay, but also in other systems with evolving material properties such as concrete structures and road pavements. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Ross S. Lunetta Yang Shao Jayantha Ediriwickrema John G. Lyon 《International Journal of Applied Earth Observation and Geoinformation》2010
The Moderate Resolution Imaging Spectrometer (MODIS) Normalized Difference Vegetation Index (NDVI) 16-day composite data product (MOD12Q) was used to develop annual cropland and crop-specific map products (corn, soybeans, and wheat) for the Laurentian Great Lakes Basin (GLB). The crop area distributions and changes in crop rotations were characterized by comparing annual crop map products for 2005, 2006, and 2007. The total acreages for corn and soybeans were relatively balanced for calendar years 2005 (31,462 km2 and 31,283 km2, respectively) and 2006 (30,766 km2 and 30,972 km2, respectively). Conversely, corn acreage increased approximately 21% from 2006 to 2007, while soybean and wheat acreage decreased approximately 9% and 21%, respectively. Two-year crop rotational change analyses were conducted for the 2005–2006 and 2006–2007 time periods. The large increase in corn acreages for 2007 introduced crop rotation changes across the GLB. Compared to 2005–2006, crop rotation patterns for 2006–2007 resulted in increased corn–corn, soybean–corn, and wheat–corn rotations. The increased corn acreages could have potential negative impacts on nutrient loadings, pesticide exposures, and sediment-mediated habitat degradation. Increased in US corn acreages in 2007 were related to new biofuel mandates, while Canadian increases were attributed to higher world-wide corn prices. Additional study is needed to determine the potential impacts of increases in corn-based ethanol agricultural production on watershed ecosystems and receiving waters. 相似文献
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Historical trends in Florida temperature and precipitation 总被引：1，自引：0，他引：1
Michelle M. Irizarry‐Ortiz Jayantha Obeysekera Joseph Park Paul Trimble Jenifer Barnes Winifred Park‐Said Erik Gadzinski 《水文研究》2013,27(16):2225-2246
Because of its low topographic relief, unique hydrology, and the large interannual variability of precipitation, Florida is especially vulnerable to climate change. In this paper, we investigate a comprehensive collection of climate metrics to study historical trends in both averages and extremes of precipitation and temperature in the state. The data investigated consist of long‐term records (1892–2008) of precipitation and raw (unadjusted) temperature at 32 stations distributed throughout the state. To evaluate trends in climate metrics, we use an iterative pre‐whitening method, which aims to separate positive autocorrelation from trend present in time series. Results show a general decrease in wet season precipitation, most evident for the month of May and possibly tied to a delayed onset of the wet season. In contrast, there seems to be an increase in the number of wet days during the dry season, especially during November through January. We found that the number of dog days (above 26.7 °C) during the year and during the wet season has increased at many locations. For the post‐1950 period, a widespread decrease in the daily temperature range (DTR) is observed mainly because of increased daily minimum temperature (Tmin). Although we did not attempt to formally attribute these trends to natural versus anthropogenic causes, we find that the urban heat island effect is at least partially responsible for the increase in Tmin and its corresponding decrease in DTR at urbanized stations compared with nearby rural stations. In the future, a formal trend attribution study should be conducted for the region. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
5.
Ha H. Bui Jayantha K. Kodikara Abdelmalek Bouazza Asadul Haque Pathegama G. Ranjith 《国际地质力学数值与分析法杂志》2014,38(13):1321-1340
Segmental retaining wall (SRW) systems are commonly used in geotechnical practice to stabilize cut and fill slopes. Because of their flexibility, these systems can tolerate minor movements and settlements without incurring damage or crack. Despite these advantages, very few numerical studies of large deformations and post‐failure behavior of SRW systems are found in the current literature. Traditional numerical methods, such as the finite element method, suffer from mesh entanglement, thus are unable to simulate large deformations and flexible behavior of retaining wall blocks in SRW systems. To overcome the above limitations, a novel computational framework based on the smoothed particle hydrodynamics (SPH) method was developed to simulate large deformations and post‐failure behavior of soils and retaining wall blocks in SRW systems. The proposed numerical framework is a hybrid continuum/discontinuum approach that can model soil as an elasto‐plastic material and retaining wall blocks as independent rigid bodies associated with both translational and rotational degrees of freedom. A new contact model is proposed within the SPH framework to simulate the interaction between the soil and the blocks and between the blocks. As an application of the proposed numerical method, a two‐dimensional simulation of an SRW collapse was simulated and compared to experimental results conducted under the same conditions. The results showed that the proposed computational approach provided satisfactory agreement with the experiment. This suggests that the new framework is a promising numerical approach to model SRW systems. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Simulation of daily rainfall scenarios with interannual and multidecadal climate cycles for South Florida 总被引：4，自引：3，他引：1
Hyun-Han Kwon Upmanu Lall Jayantha Obeysekera 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(7):879-896
Concerns about the potential effects of anthropogenic climate change have led to a closer examination of how climate varies
in the long run, and how such variations may impact rainfall variations at daily to seasonal time scales. For South Florida
in particular, the influences of the low-frequency climate phenomena, such as the El Nino Southern Oscillation (ENSO) and
the Atlantic Multi-decadal Oscillation (AMO), have been identified with aggregate annual or seasonal rainfall variations.
Since the combined effect of these variations is manifest as persistent multi-year variations in rainfall, the question of
modeling these variations at the time and space scales relevant for use with the daily time step-driven hydrologic models
in use by the South Florida Water Management District (SFWMD) has arisen. To address this problem, a general methodology for
the hierarchical modeling of low- and high-frequency phenomenon at multiple rain gauge locations is developed and illustrated.
The essential strategy is to use long-term proxies for regional climate to first develop stochastic scenarios for regional
climate that include the low-frequency variations driving the regional rainfall process, and then to use these indicators
to condition the concurrent simulation of daily rainfall at all rain gauges under consideration. A newly developed methodology,
called Wavelet Autoregressive Modeling (WARM), is used in the first step after suitable climate proxies for regional rainfall
are identified. These proxies typically have data available for a century to four centuries so that long-term quasi-periodic
climate modes of interest can be identified more reliably. Correlation analyses with seasonal rainfall in the region are used
to identify the specific proxies considered as candidates for subsequent conditioning of daily rainfall attributes using a
Non-homogeneous hidden Markov model (NHMM). The combined strategy is illustrated for the May–June–July (MJJ) season. The details
of the modeling methods and results for the MJJ season are presented in this study. 相似文献
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Tophel Amir Walker Jeffrey P. Dutta Troyee Tanu Kodikara Jayantha 《Acta Geotechnica》2022,17(8):3479-3497
Acta Geotechnica - This paper introduces a theory-guided machine learning (TGML) framework, which combines a theoretical model (TM) and a machine learning (ML) algorithm to predict compaction... 相似文献
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A Wetland Simulation Module for the MODFLOW Ground Water Model 总被引：8，自引：0，他引：8
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Jayantha Obeysekera Michelle Irizarry Joseph Park Jenifer Barnes Tibebe Dessalegne 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(4):495-516
Recent climate change projections suggest that negative impacts on flood control and water supply functions and on existing
and future ecosystem restoration projects in south Florida are possible. An analysis of historical rainfall and temperature
data of the Florida peninsula indicates that there were no discernible trends in both the long-term record and during the
more recent period (1950–2007). A comparison of General Circulation Model (GCM) results for the 20th century with the historical
data shows that many of the GCMs do not capture the statistical characteristics of regional rainfall and temperature regimes
in south Florida. Investigation of historical sea level data at Key West finds evidence for an increase in the occurrence
and variance of maximum sea level events for the period 1961–2008 in relation to 1913–1960, along with a shift of energy from
shorter to longer timescales. In order to understand the vulnerability of the water management system in south Florida in
response to changing precipitation and evapotranspiration forcing, a sensitivity analysis using a regional-scale hydrologic
and water management model is conducted. Model results suggest that projected climate change has potential to reduce the effectiveness
of water supply and flood control operations for all water sectors. These findings emphasize that questions on the potential
impacts of climate change need to be investigated with particular attention paid to the uncertainties of such projections. 相似文献
10.
Joseph Park Jayantha Obeysekera Michelle Irizarry Jenifer Barnes Paul Trimble Winifred Park-Said 《Climatic change》2011,107(1-2):109-128
Water resource management in South Florida faces nearly intractable problems, in part due to weather and climate variability. Rising sea level and coastal storm surge are two phenomena with significant impacts on natural systems, fresh water supplies and flood drainage capability. However, decision support information regarding management of water resources in response to storm surge is not well developed. In an effort to address this need we analyze long term tidal records from Key West, Pensacola and Mayport Florida to extract surge distributions, to which we apply a nonlinear eustatic sea level rise model to project storm surge return levels and periods. Examination of climate connections reveals a statistically significant dependence between surge distributions and the Atlantic Multidecadal Oscillation (AMO). Based on a recent probabilistic model for AMO phase changes, we develop AMO-dependent surge distributions. These AMO-dependent surge projections are used to examine the flood control response of a coastal water management structure as an example of how climate dependent water resource forcings can be used in the formulation of decision support tools. 相似文献