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Macro-and Micro-Properties of Two Natural Marine Clays in China

China Ocean Engineering 2009年第2期23卷 329-344页

作者：蒋明镜彭立才朱合华林奕禧黄良机 department of Geotechnical Engineering Tongji University Zhuhai Center for Supervision and Inspection on Quality of Infrastructure Engineering

In this paper,macro-and micro-properties of natural marine clay in two different and representative regions of China are investigated in *** addition to in-situ tests,soil samples are collected by use of Shelby tubes for laboratory examination in Shanghai and Zhuhai respectively,two coastal cities in *** the laboratory tests,macro-properties such as consolidation characteristics and undrained shear strength are ***,X-ray diffraction test,scanning electron microscope test,and mercury intrusion test are carried out for the investigation of their micro-properties including clay minerals and *** study shows that：（1）both clays are Holocene series formations,classified as either normal or underconsolidated *** initial gradient of the stress-strain curves shows their increase with increasing consolidation pressure;however,the Shanghai and the Zhuhai clays are both structural soils with the latter shown to be more structured than the *** a result,the Zhuhai clay shows strain softening behavior at low confining pressures,but strain hardening at high *** contrast,the Shanghai clay mainly manifests strain-hardening.（2）An activity ranges from 0.75 to 1.30 for the Shanghai marine clay and from 0.5 to 0.85 for the Zhuhai marine *** main clay mineral is illite in the Shanghai clay and kaolinite in the Zhuhai *** Zhuhai clay is mainly characterized by a flocculated structure,while the typical Shanghai clay shows a dispersed *** porous structure of the Shanghai clay is characterized mainly by large and medium-sized pores,while the Zhuhai clay porous structure is mainly featured by small and medium-sized *** differences in their macro-and micro-properties can be attributed to different sedimentation environments.

关键词： marine clay macro- and micro- properties comparison microstructure

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Arbuscular mycorrhizal fungal community assembly in the Brazilian tropical seasonal dry forest

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Ecological Processes 2017年第1期6卷 9-18页

作者： Tancredo Augusto Feitosa de Souza Helena Freitas Centre for Functional Ecology Department of Life SciencesUniversity of Coimbra3000-456 CoimbraPortugal

Introduction:Here,we compare the arbuscular mycorrhizal fungal(AMF)community composition in soils from the root zone of the exotic invasive species Prosopis juliflora(EXO soils)and soils from the root zone of the native species Mimosa tenuiflora(NAT soils)from five locations in the Brazilian tropical seasonal dry forest,Paraíba,Brazil,using morphological ***:AMF community composition in EXO and NAT soils were *** phosphorus,diversity index,spore abundance,and species richness were the main factors differing between the EXO and NAT *** general,the most dominant order present in the soils were Glomerales(44.8%)and Gigasporales(41.4%).The most abundant AMF genus in all studied soils was ***:Differences in AMF community composition were associated with(1)differences in the dominant plant species(*** ***)and(2)changes in soil chemical factors(soil,pH,total organic carbon,total nitrogen,and available P)in EXO *** results contribute to a deeper view of the AMF communities in exotic soils and open new perspectives for ecological processes involving AMF species and exotic plant species in the Brazilian tropical seasonal dry forest.

关键词： Glomeromycota AMF community AMF diversity Native plant species Exotic plant species Caatinga

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An approach to evaluate ground surface rupture caused by reverse fault movement

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Earthquake Engineering and Engineering Vibration 2006年第1期5卷 29-39页

作者：赵纪生陶夏新师黎静王海云 Institute of Engineering Mechanics China Earthquake Administration department of Civil Engineering Harbin Institute of Technology

An approach for estimating ground surface rupture caused by strong earthquakes is presented in this paper, where the finite element （FE） method of continuous and discontinuous coalescent displacement fields is adopted. The onset condition of strain localization is introduced to detect the formation of the slippage line. In the analysis, the Drucker-Prager constitutive model is used for soils and the rate- and state-dependent friction law is used on the slippage line to simulate the evolution of the sliding. A simple application to evaluate the ground surface rupture induced by a reverse fault movement is provided, and the numerical simulation shows good agreement with failure characteristics observed in the field after strong earthquakes.

关键词： surface rupture reverse fault localized band slippage line onset and evolution strain localization friction law

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Plane strain consolidation of soil layer with anisotropic permeability

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Applied Mathematics and Mechanics(English Edition) 2009年第11期30卷 1437-1444页

作者：艾智勇吴超 department of Geotechnical Engineering and Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji University

This paper presents an alternative analytical technique to study a plane strain consolidation of a poroelastic soil by taking into account the anisotropy of permeability. From the governing equations of a saturated poroelastic soil, the relationship of basic variables for a point of a soil layer is established between the ground surface （z=0） and the depth z in the Laplace-Fourier transform domain. Combined with the boundary conditions, an exact solution is derived for plane strain Biot＇s consolidation of a finite soil layer with anisotropic permeability in the transform domain. Numerical inversions of the Laplace transform and the Fourier transform are adopted to obtain the actual solution in the physical domain. Numerical results of plane strain Biot＇s consolidation for a single soil layer show that the anisotropic of permeability has a great influence on the consolidation behavior of the soils.

关键词： plane strain consolidation finite soil layer anisotropic permeability,Laplace-Fourier transform

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Trigger mechanism of loess-mudstone landslides inferred from ring shear tests and numerical simulation

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Journal of Mountain Science 2021年第9期18卷 2412-2426页

作者： WANG Xin-gang LIAN Bao-qin Liu Kai Luo Li State Key Laboratory of Continental Dynamics Department of GeologyNorthwest UniversityXi'an 710069China

Whereas loess-mudstone landslides are widely distributed and frequently occurred at the loess Plateau,this type of landslides is hard to detect due to its particularity,and easily generates serious *** clarify the shear characteristics and formation mechanism of loess-mudstone landslides,field investigations,ring shear tests and numerical simulation analyses were performed on the loess specimens collected from the Dingjiagou landslide in Yan’an city,*** test results showed that both the peak strength and residual strength of slip zone soils have a decreasing tendency with moisture content,while the increasing of normal stress caused an increase in the shear *** phenomena indicate that the rise in the moisture content induced by precipitation or the decreasing of normal stress due to excavation activities would result in the weakening of slip zone *** simulations of the evolution process of slope failure using the finite element method were conducted based on the Mohr–Coulomb *** was found that the heavy precipitation played a more important role in the slope instability compared with the *** addition,the field investigation showed that loess soils with well-developed cracks and underlying mudstone soils provide material base for the formation of loess-mudstone ***,the formation mechanism of this type of landslides was divided into three stages,namely,the local deformation stage,the penetration stage,the creeping-sliding *** study may provide a basis for understanding the sliding process of loess-mudstone landslides,as well as guidelines for the prevention and mitigation of loess-mudstone landslides.

关键词： Loess-mudstone landslides Slip zone soil Ring shear tests Numerical simulation Formation mechanism

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A plasticity model for sand-structure interfaces

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Journal of Central South University 2012年第4期19卷 1098-1108页

作者： A.Lashkari department of Civil&Environmental Engineering Shiraz University of TechnologyShiraz 71555-313Iran

The predictive capacity of numerical analyses in geotechnical engineering depends strongly on the efficiency of constitutive models used for modeling of interfaces *** are considered as thin layers of the soil adjacent to structures boundary whose major role is transferring loads from structures to soil *** interface model within the bounding surface plasticity framework and the critical state soil mechanics is *** this aim,general formulation of the interface model according to the bounding surface plasticity theory is described *** to granular soils,it has been shown that the mechanical behavior of sand-structure interfaces is highly affected by the interface state that is the combined influences of density and applied normal ***,several ingredients of the model are directly related to the interface *** a result of this feature,the model is enabled to distinguish interfaces in dense state from those in loose state and to provide realistic predictions over wide ranges of density and normal stress *** evaluation of the model,a reasonable correspondence between the model predictions and the experimental data of various research teams is found.

关键词： soil-structure interface sand dilatancy bounding surface plasticity

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In-depth analysis of soil management and farmers’perceptions of related risks in two olive grove areas in southern Spain

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International soil and water Conservation Research 2021年第3期9卷 461-473页

作者： José A.Gòmez Ana Sanchez Montero Gema Guzman Marfa-Auxiliadora Soriano a Institute for Sustainable Agriculture CSICCordobaSpain Agronomy department University of CordobaCordobaSpain

This manuscript presents a questionnaire-based study aimed to provide a detailed analysis on the different soil management carried out by olive farmers in two representative olive-growing areas in southern Spain(Cordoba and Estepa),their perceptions on cover crop use and the possible influence of the different types of farms and farmers’typologies on these *** results show a relatively large variability of soil management,with fourteen options,as a result of a combination of different alternatives for bare soil and cover crops with the use or not of pruning residues,but with a great similarity between both *** results indicate a high adoption of soil conservation measures in the two study areas,with 63%of farmers using cover crops and 80%a mulch of pruning residues,higher than that reported in previous studies in Southern Spain,and a trend of lower use of these techniques by less experienced and younger *** high penetration of soil conservation measures resulted in a significant reduction of soil erosion risk,as indicated by the relatively low values for the cover and management factor(C)of RUSLE,also calculated and presented in this study,but also the possibility of focusing further efforts on fanners with less *** results indicate the persistence of a minor,but relevant,percentage of farmers using bare soil management(37%)and no mulching(20%),with a moderate concern on the impact of soil erosion on soil degradation and provision of ecosystem *** suggests the need to concentrate efforts also on this cluster of farmers to enhance the success of what seems to be a remarkable expansion of the use of soil conservation measures in recent decades in Southern Spain,but also in similar areas in the Mediterranean basin.

关键词： Tillage Cover crops Olive yield Erosion risk Irrigation Questionnaire

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Effect of elevated [CO_2] and nutrient management on wet and dry season rice production in subtropical India

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The Crop Journal 2015年第6期3卷 468-480页

作者： Sushree Sagarika Satapathy Dillip Kumar Swain Surendranath Pasupalak Pratap Bhanu Singh Bhadoria Agricultural and Food Engineering department Indian Institute of Technology Kharagpur Orissa University of Agriculture and Technology

The present experiment was conducted to evaluate the effect of elevated [CO_2] with varying nutrient management on rice–rice production system. The experiment was conducted in the open field and inside open-top chambers(OTCs) of ambient [CO_2](≈ 390 μmol L-1) and elevated [CO_2] environment(25% above ambient) during wet and dry seasons in 2011–2013at Kharagpur, India. The nutrient management included recommended doses of N, P, and K as chemical fertilizer(CF), integration of chemical and organic sources, and application of increased(25% higher) doses of CF. The higher [CO_2] level in the OTC increased aboveground biomass but marginally decreased filled grains per panicle and grain yield of rice, compared to the ambient environment. However, crop root biomass was increased significantly under elevated [CO_2]. With respect to nutrient management, increasing the dose of CF increased grain yield significantly in both seasons. At the recommended dose of nutrients, integrated nutrient management was comparable to CF in the wet season, but significantly inferior in the dry season, in its effect on growth and yield of rice. The [CO_2] elevation in OTC led to a marginal increase in organic C and available P content of soil, but a decrease in available N content. It was concluded that increased doses of nutrients via integration of chemical and organic sources in the wet season and chemical sources alone in the dry season will minimize the adverse effect of future climate on rice production in subtropical India.

关键词： Climate change Nutrient management Elevated [CO2] Rice yield soil fertility

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Undrained stability of a spherical cavity in cohesive soils using finite element limit analysis

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第6期11卷 1274-1285页

作者： Suraparb Keawsawasvong Boonchai Ukritchon Centre of Excellence in Geotechnical and Geoenvironmental Engineering Department of Civil EngineeringFaculty of EngineeringChulalongkorn University

A parametric study of undrained stability of a spherical cavity in clays is investigated by finite elementlimit analysis with an axisymmetric condition. Influences of cover depth ratio of cavity and dimensionlessoverburden factor on predicted failure mechanisms and dimensionless load factor are *** is found that a previously recommended and up-to-date lower bound solution to the problem wassignificantly inaccurate for practice use. Thus, an accurate approximate solution to the problem is proposedfrom nonlinear regression analysis of the computed average bound solutions. New cavity stabilityfactors for the soil cohesion and soil unit weight are proposed. New findings are revealed for the threedimensionaleffect of the cavity shape on these factors between the axisymmetric and plane strainconditions, and their applications to the undrained stability evaluation of cavity problems in practice aredescribed.

关键词： Limit analysis Undrained stability Spherical cavity Sinkhole Axisymmetry

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Analysis of coupled thermo-hydro-mechanical behavior of unsaturated soils based on theory of mixtures I

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Applied Mathematics and Mechanics(English Edition) 2010年第12期31卷 1561-1576页

作者：秦冰陈正汉方振东孙树国方祥位王驹 department of Architectural and Civil Engineering Logistical Engineering University Beijing Research Institute of Uranium Geology

This paper analyzes a coupled thermo-hydro-mechanical behavior of unsaturated soils based on the theory of mixtures. Unsaturated soil is considered as a mixture composed of soil skeleton, liquid water, vapor, dry air, and dissolved air. In addition to the mass and momentum conservation equations of each component and the energy conservation equation of the mixture, the system is closed using other 37 constitutive （or restriction） equations. As the change in water chemical potential is identical to the change in vapor chemical potential, a thermodynamic restriction relationship for the phase transition between pore water and pore vapor is formulated, in which the impact of the change in gas pressure on the phase transition is taken into account. Six final govern- ing equations are given in incremental form in terms of six primary variables, i.e., three displacement components of soil skeleton, water pressure, gas pressure, and temperature. The processes involved in the coupled model include thermal expansions of soil skeleton and soil particle, Soret effect, phase transition between water and vapor, air dissolution in pore water, and deformation of soil skeleton.

关键词： unsaturated soil thermo-hydro-mechanical temperature theory of mixtures

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