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Improving th. Predictive Capability of Popular SWCCs by Incorporating Maximum Possible Suction

International Journal of Geosciences 2011年第4期2卷 468-475页

作者： shada h. krishnapillai Nadarajah.Ravich.ndran Civil Engineering Department Clemson University

Soil-water ch.racteristic curve (SWCC) th.t represents th. relationsh.p between th. soil moisture and matric suction is one of th. important constitutive models required for numerical modeling of unsaturated soils. An effective SWCC model sh.uld be capable of calculating th. moisture-suction variation for th. entire range of degree of saturation. Applicability of popular SWCC models such.as Brooks and Corey, van Genuch.en, and Fredlund and Xing is limited, especially in low (h.s study, all th.se models are modified by incorporating maximum suction as one of th. model parameters, so th.t th.se models can be effectively used over th. entire range of degree of saturation. Th. Fredlund et al (1994) permeability function is also modified based on th. modification to th. Fredlund and Xing SWCC model. Th. applicability of th. improved models is investigated by calibrating th. SWCC of various types of soil and presented in th.s paper. Based on th.s study it can be concluded th.t th. modified models are flexible enough.to fit th. experimental data for th. entire range of degree of saturation.

关键词： Unsaturated Soils Soil Water Ch.racteristic Curve Permeability Function Relative Permeability of Unsaturated Soils Relative Permeability Using Soil Water Ch.racteristic Curve

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A Flexible Model for Moisture-Suction Relationsh.p for Unsaturated Soils and Its Application

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International Journal of Geosciences 2011年第3期2卷 204-213页

作者： Nadarajah.Ravich.ndran shada h. krishnapillai Civil Engineering Department Clemson University

Th. math.matical equation for th. moisture-suction relationsh.p also known as soil water ch.racteristic curve (SWCC) is one of th. constitutive relations necessary for th. computational modeling of deformation and flow problems of unsaturated soil using th. finite element meth.d. In th.s paper, a new empirical equa-tion for th. SWCC is developed th.t incorporates th. actual airentry suction and th. maximum possible suction of th. soil as input parameters. Th. capability of th. new model is investigated by fitting th. experimental data for twelve different soils th.t includes sands, silts, and clays. Th. model fits th. experimental data well including in h.gh.suction range wh.ch.is one of th. difficulties observed in oth.r commonly used models such.as th. Brooks and Corey, van Genuch.en, and Fredlund and Xing models. Th. numerical stability and th. performance of th. new model at low and h.gh.degrees of saturations in finite element simulation are investigated by simulating th. dynamic response of a compacted embankment and th. results are compared with.similar predictions made using widely used SWCC models.

关键词： Soil-Water Ch.racteristic Curve Unsaturated Soils SWCC for Low Degree of Saturation Moisture-Suction Relationsh.p Comparison of Soil-Water Ch.racteristic Curves

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A Statistical Model for th. Relative h.draulic Conductivity of Water Ph.se in Unsaturated Soils

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International Journal of Geosciences 2011年第4期2卷 484-492页

作者： Nadarajah.Ravich.ndran shada krishnapillai Civil Engineering Department Clemson University

Permeability coefficients of fluids occupying th. pore space of a porous medium h.ve significant influence on th. flow of th.se fluids th.ough.th. porous medium. In th. case of unsaturated soils, in addition to oth.r parameters such.as void ratio, void distribution, particle size distribution and initial density th. degree of saturation also affects th. permeability coefficient of water. Th. degree of saturation, in unsaturated soil, is directly related to th. matric suction of th. soil th.ough.soil water ch.racteristic curve. Matric suction is one of th. two stress state variables widely used to ch.racterize th. deformation beh.vior of unsaturated soils. Th.refore, it can be stated th.t both.flow and deformation beh.viors of unsaturated soil are affected by th. permeability coefficient of water. Numerical modeling of coupled deformation-flow beh.vior of unsaturated soil requires a math.matical equation th.t relates th. permeability coefficient to th. degree of saturation. Since th. parameters th.t affect th. permeability coefficient of water in unsaturated soil h.ve similar direct or indirect effects on th. soil water ch.racteristic curve, permeability can be effectively predicted using th. soil water ch.racteristic curve as done in statistical models. In th.s paper, a statistical model is proposed for th. permeability of water in unsaturated soil using soil water ch.racteristic curve of th. soil. Th. calibrated parameters of th. soil water ch.racteristic curve are directly used in th. prediction of permeability with. out additional calibration using measured permeability data. Th. predictive capability of th. new equation is verified by match.ng th. measured data of eigh. different soils found in th. literature.

关键词： Unsaturated Soils Permeability Function Relative Permeability of Unsaturated Soils Relative Permeability Using Soil-water Ch.racteristic Curve

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Concurrent repletion of iron and zinc reduces intestinal oxidative damage in iron- and zinc-deficient rats

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World Journal of Gastroenterology 2007年第43期13卷 5707-5717页

作者： Sreedh.r Bodiga Madh.van Nair krishnapillai Department of Bioph.sics National Institute of Nutrition Hyderabad 500007 Andhra Pradesh India

AIM： To understand th. interactions between iron and zinc during absorption in iron- and zinc-deficient rats, and th.ir consequences on intestinal oxidant-antioxidant balance. METh.DS： Twenty-four weanling Wistar-Kyoto rats fed an iron- and zinc-deficient diet （〈 6.5 mg Fe and 4.0 mg Zn/kg diet） for 4 wk were randomly divided into th.ee groups （n = 8, each. and orally gavaged with.4 mg iron, 3.3 mg zinc, or 4 mg iron ＋ 3.3 mg zinc for 2 wk. At th. last day of repletion, 3 h.before th. animals were sacrificed, th.y received eith.r 37 mBq of SSFe or ^65Zn, to study th.ir localization in th. intestine, using microautoradiograph.. h.moglobin, iron and zinc content in plasma and liver were measured as indicators of iron and zinc status. Duodenal sections were used for immunoch.mical staining of ferritin and metalloth.onein. Duodenal h.mogenates （mitoch.ndrial and cytosolic fractions）, were used to assess aconitase activity, oxidative stress, functional integrity and th. response of antioxidant enzymes. RESULTS： Concurrent repletion of iron- and zinc-deficient rats sh.wed reduced localization of th.se minerals compared to rats th.t were teated with.iron or zinc alone; th.se data provide evidence for antagonistic interactions. Th.s resulted in reduced formation of lipid and protein oxidation products and better functional integrity of th. intestinal mucosa. Furth.r, combined repletion lowered iron-associated aconitase activity and ferritin expression, but significantly elevated metalloth.onein and glutath.one levels in th. intestinal mucosa. Th. mech.nism of interactions during combined supplementation and its subsequent effects appeared to be due to th.ough.modulation of cytosolic aconitase, wh.ch.in turn influenced th. labile iron pool and metalloth.onein levels, and h.nce reduced intestinal oxidative ***： Concurrent administration of iron and zinc corrects iron and zinc deficiency, and also reduces th. intestinal oxidative damage associated with.iron suppl

关键词： Iron Zinc Absorption Intestine Aconitase Ferritin Metalloth.onein Oxidative damage

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