检索结果-南通市图书馆

Creep of frozen soil by damage mechanics

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 1995年第8期38卷 996-1002页

作者：苗天德魏雪霞张长庆 Department of Mechanics Lanzhou UniversityLanzhou 730000China State Key Laboratory of frozen Soil Engineering Lanzhou Institute of Glaciology and GeocryologyChinese Academy of SciencesLanzhou 730000China

A microstructure damage theory for creep of frozen soil under the frame of damage mechan-ics is *** on the test study and microscope observation,several internal variables are chosen tocharacterize the microstructure changes and the evolution equations of these internal variables are *** theory can describe both the "hardening" and "softening" behavior in the creep process.A detailed analysis hasbeen made for the uniaxial compressure and compared with the test data.

关键词： frozen soil creep microstructure damage mechanics

Improving the estimation of hydrothermal state variables in the active layer of frozen ground by assimilating in situ observations and SSM/I data

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2009年第11期52卷 1732-1745页

作者： JIN Rui LI Xin Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of SciencesLanzhou 730000China

The active layer of frozen ground data assimilation system adopts the SHAW (Simulteneous Heat and Water) model as the model operator. It employs an ensemble kalman filter to fuse state variables predicted by the SHAW model with in situ observation and the SSM/I 19 GHz brightness temperature for the purpose of optimizing model hydrothermal state variables. When there is little water movement in the frozen soil during the winter season, the unfrozen water content depends primarily on soil temperature. Thus, soil temperature is the crucial state variable to be improved. In contrast, soil moisture is heavily influenced by precipitation during the summer season. The simulation accuracy of soil moisture has a strong and direct impact on the soil temperature. In this case, the crucial state variable to be improved is soil moisture. One-dimensional assimilation experiments that have been carried out at AMDO station show that land data assimilation method can improve the estimation of hydrothermal state variables in the soil by fusing model information and observation information. The reasonable model error covariance matrix plays a key role in transferring the optimized surface state information to the deep soil, and it provides improved estimations of whole soil state profiles. After assimilating the 4-cm soil temperature by in situ observation, the soil temperature RMSE (Root Mean Square Error) of each soil layer decreased by 0.96℃ on average relative to the SHAW simulation. After assimilating the 4-cm soil moisture in situ observation, the soil moisture RMSE of each soil layer decreased by 0.020 m3·m-3. When assimilating the SSM/I 19 GHz brightness temperature, the soil temperature RMSE of each soil layer during the winter decreased by 0.76℃, while the soil moisture RMSE of each soil layer during the summer decreased by 0.018 m3·m-3.

关键词： land data assimilation active layer of frozen ground soil moisture soil temperature passive remote sensing

Evaluating model of frozen soil environment change under engineering actions

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2002年第10期45卷 893-902页

作者：吴青柏朱元林刘永智

The change of frozen soil environment is evaluated by permafrost thermal stability, thermal thaw sensibility and surface landscape stability and the quantitatively evaluating model of frozen soil environment is proposed in this paper. The evaluating model of frozen soil environment is calculated by 28 ground temperature measurements along Qinghai-Xizang Highway. The relationships of thermal thaw sensibility and freezing and thawing processes and seasonally thawing depth, thermal stability and permafrost table temperature, mean annual ground temperature and seasonally thawing depth, and surface landscape stability and freezing and thawing hazards and their forming possibility are analyzed. The results show that thermal stability, thermal thaw sensibility and surface landscape stability can be used to evaluate and predict the change of frozen soil environment under human engineering action.

关键词： engineering actions, frozen soil environment, permafrost stability, thermal thaw sensibility.

A constitutive model of frozen soil with damage and numerical simulation for the coupled problem

在线全文

学校读者我要写书评

暂无评论

Science China(Physics,Mechanics & Astronomy) 2010年第4期53卷 699-711页

作者： ZHU ZhiWu, NING JianGuo& MA Wei 1 School of Mechanics and Engineering, Southwest Jiaotong University, Chengdu 610031, China 2 State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081, China 3 Key Laboratory of frozen Soil Engineering, CAREERI, CAS, Lanzhou 730000, China 1. School of Mechanics and Engineering Southwest Jiaotong University Chengdu 610031 China2. State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing 100081 China3. Key Laboratory of Frozen Soil Engineering CAREERI CAS Lanzhou 730000 China

Based on the microcosmic mechanics of composite materials, an elastic constitutive model for frozen soil with damage is presented. For frozen sandy soil with a range of ice contents and under a range of temperature conditions, quantitative results determined by this constitutive model agree with practically measured stress-strain curves. After numerically simulating the coupled water, temperature and stress fields of channel frozen and frozen roadbed using a self-developed finite-element routine, more accurate and practical calculation results for the temperature field coupled with stress, displacement and strain fields are obtained; the results match predictions and tests undertaken by earlier researchers. Our results support the reliability of our routine for calculating interdependent physical quantities of frozen soil and for describing the relationships between them. Our program can offer necessary constraints for engineering design and construction in permafrost regions.

关键词： frozen soil microcosmic mechanics roadbed coupling stress field

Monitoring the 2008 cold surge and frozen disasters snowstorm in South China based on regional ATOVS data assimilation

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 2010年第8期53卷 1216-1228页

作者： DALE M.Barker National Center for Atmospheric Research BoulderColoradoUSA

In January 2008, South China experienced extremely low temperatures, heavy snowstorms, and severe frosts (2008 Frost Disaster, for short), which led to (partial) failures of observations from ground stations and ground radars resulting in a lack of necessary emergency information. To compensate for the failure of ground observations and to provide timely disaster information, the National Satellite Meteorological Center of China (NSMC) established a snow storm monitoring system for the 2008 Frost Disaster, which was based on the WRF Three Dimension Variational Assimilation and Forecast system (with NOAH as the land surface sub-process model) cooperatively developed by NSMC and the National Center for Atmospheric Research (NCAR), US. This system made full use of ATOVS and NCEP data to provide estimates of snow water equivalent every 6 hours during the storm. In this study, the ATOVS assimilation based snowstorm monitoring scheme was explored in detail, while the modeled results with and without ATOVS assimilation were compared against related observations. Results showed that the coupling of ATOVS assimilation into the proposed monitoring system evidently delineates weather characteristics of the snowstorm process more accurately, and demonstrated the feasibility of the system for snowstorm monitoring and forecasting. Through theoretical analyses and case discussion, this study proposes a reliable and practicable scheme to provide timely and accurate information on snow spatial distribution and temporal development for disaster mitigation, and illustrates a new application of ATOVS data.

关键词： 2008 cold surge and frozen disaster in South China ATOVS data assimilation snow depth snowstorm monitoring

The protective performance of a molten salt frozen wall in the process of fluoride volatility of uranium

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2019年第6期30卷 138-146页

作者： Jin-Hao Zhou Ji-Lin Tan Bo Sun Qiang Dou Qing-Nuan Li University of Chinese Academy of Sciences Beijing 100049 China Shanghai Institute of Applied Physics Chinese Academy of Sciences Shanghai 201800 China

The fluoride volatility method (FVM) is a technique tailored to separate uranium from fuel salt of molten salt reactors. A key challenge in R&D of the FVM is corrosion due to the presence of molten salt and corrosive gases at high temperature. In this work, a frozen-wall technique was proposed to produce a physical barrier between construction materials and corrosive reactants. The protective performance of the frozen wall against molten salt was assessed using FLiNaK molten salt with introduced fluorine gas, which was regarded as a simulation of the FVM process. SS304, SS316L, Inconel 600 and graphite were chosen as the test samples. The extent of corrosion was characterized by an analysis of weight loss and scanning electron microscope studies. All four test samples suffered severe corrosion in the molten salt phase with the corrosion resistance as: Inconel 600>SS316L>graphite>SS304. The presence of the frozen wall could protect materials against corrosion by molten salt and corrosive gases, and compared with materials exposed to molten salt, the corrosion rates of materials protected by the frozen wall were decreased by at least one order of magnitude.

关键词： Molten salt reactors Fluoride volatility method Corrosion frozen wall Protective performance

Microstructure and strength features of warm and ice-rich frozen soil treated with high-performance cements

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2019年第6期16卷 1470-1482页

作者： SUN Gao-chen ZHANG Jian-ming DANG Ying-sheng DING Cong State Key Laboratory of frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 10049China China State Construction Engineering Corporation Aecom Consultant Co. Ltd.Lanzhou 730000China College of Water&Architectural Engineering Shihezi UniversityShihezi 832000China Shanghai Investigation Design&Research Institute Co.Ltd.Shanghai 200434China

Warm and ice-rich frozen soil(WIRFS) exhibits lower shear strength due to the weak binding forces between soil particles and ice crystals. To enhance the strength of WIRFS, frozen soil was treated separately with Portland, Phosphate, Sulphoaluminate, Portland-Phosphate and PortlandSulphoaluminate cements. After the samples were cured under -1.0°C for 7 days, the microscopic pore distribution characteristics and the macro-mechanical properties of WIRFS were investigated using mercury intrusion porosimetry(MIP), scanning electron microscopy(SEM) and unconfined compressive strength(UCS) tests. To quantitatively analyze the laws of pore-size transformation and the variation of Hausdorff volumetric fractal dimensions for pre-and post-treated WIRFS, the CURVEEXTRACT and Image-Pro Plus(IPP) image analysis system has been developed for analysing SEM images of the soil samples. Statistics of the pore-area dimension and pore-volume dimension were calculated. The results reveal that the cement-based treatment of WIRFS can improve the cementation fill of soil pores and the bond forces between soil particles. There is an evident correlation between the microstructure characteristics and the mechanical properties of the treated WIRFS. As the fractal dimensions of pore-area decrease, the unconfined compressive strength of cement-treated WIRFS increases significantly. In contrast, as the fractal dimensions of pore-volume increases, the unconfined compressive strength decreases remarkably.

关键词： Soil stabilizer frozen soil Microstructure characteristics Macro-mechanical properties Fractal theory Scanning electron microscopy

Constitutive theories on viscoelastoplasticity and damage of frozen soil

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 1999年第S1期42卷 38-43页

作者：何平程国栋朱元林 State Key Laboratory of frozen Soil Engineering Lanzhou Institute of Glaciology and Geocryology Chinese Academy of Sciences

The constitutive theory on the viscoelastoplasticity and damage of frozen soil is based on the continuous mechanics and thermodynamics. The basic principles of the theory, dissipation potential function and damage model are presented. The constitutive theory explains the mechanical properties of frozen soils under complicated stresses, especially under high confining pressures which make frozen soil harden and soften. The agreement between the calculated results by the constitutive theory and the experimental results of triaxial creep of frozen soil is seen to be very good.

关键词： viscoelastoplasticity damage unfrozen water frozen soil creep.

Fractal approximation of the stress-strain curve of frozen soil

在线全文

学校读者我要写书评

暂无评论

Science China Earth Sciences 1999年第S1期42卷 17-22页

作者：令锋吴紫汪朱元林何春雄朱林楠 State Key Laboratory of frozen Soil Engineering Lanzhou Institute of Glaciology and Geocryology Chinese Academy of Sciences

A method to approach the stress-strain curve of frozen soil is presented based on the fact that the stressstrain curve of frozen soil has fractal property. First, a linear hyperbolic iterated function system (LHIFS) in which the perpendicular contraction factors are regarded as parameters is established using fractal geometry theories. Secondly, a method to calculate the best point which makes the attractor of the LHIFS an optimal approximation of the stress-strain curve of frozen soil is presented. Then, a method for calculating the fractal dimension of the stress-strain curve of frozen soil is obtained. Finally, a simple example is provided. The method presented in this paper provides a new method for simulating the stress-strain curve and calculating its fractal dimension of geomaterials that have the fractal feature by using computer.

关键词： frozen soil stress-strain curve fractal attractor fractal dimension.