A hybrid computational approach to formulate soil deformation moduli obtained from PLT     

Seyyed Mohammad Mousavi  Amir Hossein Alavi  Ali Mollahasani  Amir Hossein Gandomi 《Engineering Geology》2011,123(4):324

In this study, new empirical equations were developed to predict the soil deformation moduli utilizing a hybrid method coupling genetic programming and simulated annealing, called GP/SA. The proposed models relate secant (E_s), unloading (E_u) and reloading (E_r) moduli obtained from plate load–settlement curves to the basic soil physical properties. Several models with different combinations of the influencing parameters were developed and checked to select the best GP/SA models. The database used for developing the models was established upon a series of plate load tests (PLT) conducted on different soil types at various depths. The validity of the models was tested using parts of the test results that were not included in the analysis. The validation of the models was further verified using several statistical criteria. A traditional GP analysis was performed to benchmark the GP/SA models. The contributions of the parameters affecting E_s, E_u and E_r were analyzed through a sensitivity analysis. The proposed models are able to estimate the soil deformation moduli with an acceptable degree of accuracy. The E_s prediction model has a remarkably better performance than the models developed for predicting E_u and E_r. The simplified formulations for E_s, E_u and E_r provide significantly better results than the GP-based models and empirical models found in the literature.  相似文献   

Vitreous state in nature—Origin and properties     

Klaus Heide  Gerhard Heide 《Chemie der Erde / Geochemistry》2011,71(4):305-335

Vitreous materials are quite routinely found in natural settings. Most of them are aluminosilicates, which often occur in large deposits. Considering the geological formations in which naturally occurring vitreous aluminosilicates are found, they have generally remained stable for more than 1 Ma on the earth's surface, even in different geological and climatic environments. These non-crystalline solids played a very important role in the development of ancient human civilizations, long before the introduction of metallic tools. Today, however, the properties of natural glasses are of interest to mankind for completely different reasons. For example, industrial glasses are used today for encapsulating toxic wastes, especially radioactive waste, which remains active for centuries or more, in order to prevent the unwanted transfer of harmful materials to the environment. The chemical compositions of industrially produced glasses are in large part different from the compositions of natural glasses. Little is quantitatively known about the stability of industrial glasses over very long periods of time (>10,000 years). However, the physical and chemical stability of natural aluminosilicate glasses is known to extend over very long periods of time.The advancement of technological design to prevent or at least minimize the melt down of toxic waste during the encapsulation process is currently a major challenge, using glasses of natural chemical composition. Brecciated glass, which is found frequently in natural settings, provides a special clue to the possibility of producing vitreous solids by sintering glass fragments without melting the cullets. It is essential to prevent melting of the cullets because the melt has the potential of chemically reacting with the toxic waste.This paper summarizes the geological, chemical, and physical facts concerning naturally produced glasses, and seeks to establish a recognized database for further research in the domain of understanding the glass-forming processes that occur in nature. Furthermore, the authors hope to stimulate research into the utilization of natural resources that to solve the problem of storing of toxic waste safely.Major and trace element data have been collected over the past 100 years. These data constitute a sufficient basis for the chemical characterization of natural glasses. More information about the major elements is not required, in order to understand the chemical properties of these materials. On the other hand, large gaps in compositional data exist where other related components are concerned: e.g., in the case of “water-species”, with its different forms of bonding in silicates or oxygen (oxygen fugacity), CO₂-, sulphur - or hydrocarbons (methane)-, hydrogen-, chlorine-and fluorine-species. All these components have a significant impact on the properties of glasses, even when present only in minor quantities. Glass textures and crystal morphologies reflect the processes of nucleation and crystal growth in a glass-forming matrix during the cooling and reheating cycles which are currently not thoroughly understood. In nature, the processes that led to the formation of vitreous materials are very different from those used in the production of industrial glasses. The different genetic conditions under which glass formation occurs permit differentiation between magmatic and metamorphic vitreous solids. Sedimentary and biogenetic processes also contribute to the formation of non-crystalline solids.  相似文献   

循环冻融条件下安山岩和花岗岩的物理力学特性试验研究   总被引：5，自引：0，他引：5  

刘华  牛富俊  徐志英  林战举  许健 《冰川冻土》2011,33(3):557-563

结合青藏铁路块石护坡路基处于青藏高原特殊的气候条件,对用于青藏铁路护坡的两种主要岩石（花岗岩和安山岩）进行循环冻融试验.结果表明:两种岩石在经历了数次冻融循环后都出现了微细裂纹;声波监测表明,超声波速同冻融循环周期呈指数下降关系,显示了冻融循环对岩石风化的影响以及循环后岩石物理力学参数变化的趋势.结果说明,花岗岩的冻融...  相似文献   

长江源北麓河流域多年冻土区热融湖塘形成对高寒草甸土壤环境的影响   总被引：10，自引：7，他引：3  

王一博  吴青柏  牛富俊 《冰川冻土》2011,33(3):659-667

通过对长江源北麓河流域多年冻土区热融湖塘及湖塘影响周边条件下高寒草甸土壤理化性质的比较研究,结果表明:热融湖塘的形成对高寒草甸土壤环境产生了明显影响,热融湖塘形成对土壤质地、含水量、容重以及土壤养分等产生强烈改变,尤其表层土壤;土壤机质(SOM)、全氮(N)等化学物质和其他养分成分在不同退化的土壤中都有所改变.有机质和...  相似文献   

Reconstruction of sub-wavelength fractures and physical properties of masonry media using full-waveform inversion of proximal penetrating radar   总被引：1，自引：0，他引：1  

Claudio Patriarca  Sbastien Lambot  M.R. Mahmoudzadeh  Julien Minet  Evert Slob 《Journal of Applied Geophysics》2011,74(1):26-37

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福建第四纪活断裂岩石显微构造特征与孕震标志研究     

王洪涛  郑师春 《华南地震》2011,31(2):1-13

在福建第四纪活断裂调查研究基础上,进一步详细观察活动断裂面的擦痕、阶步、断层泥、蚀变程度的对比,并采集断面岩石切片,作显微构造观察,结合宏观断裂特征、震源机制解、地震破裂形迹,探讨宏、微观地震断裂破裂力学特性,试图为本区强震的中长期预测提供新的标志.  相似文献   

Experimental studies on the Danxia landscape morphogenesis in Mt.Danxiashan,South China     

ZHU Cheng  WU Li  ZHU Tongxin  HOU Rongfeng  HU Zhinong  TAN Yan  SUN Wei 《地理学报(英文版)》2015,25(8)

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Experimental research on physical properties of saline soil subgrade filler in Chaerhan region     

Yu Zhang  JianHong Fang  JianKun Liu  AnHua Xu 《寒旱区科学》2015,7(3):212-215

In order to improve the engineering stability of saline soil of high chloride content in the Chaerhan salt lake region, six typical characteristics saline soil samples were selected, and tests on their...  相似文献   

Influence of fines content on the anti-frost properties of coarse-grained soil     

TianLiang Wang  ZuRun Yue  TieCheng Sun  JinChuang Hua 《寒旱区科学》2015,7(4):407-413

This paper aims to determine the optimal fines content of coarse-grained soil required to simultaneously achieve weaker frost susceptibility and better bearing capacity. We studied the frost susceptibility and strength properties of coarse-grained soil by means of frost heaving tests and static triaxial tests, and the results are as follows:(1) the freezing temperature of coarse-grained soil decreased gradually and then leveled off with incremental increases in the percent content of fines; (2) the fines content proved to be an important factor influencing the frost heave susceptibility and strength properties of coarse-grained soil. With incremental increases in the percent content of fines, the frost heave ratio increased gradually and the cohesion function of fines effectively enhanced the shear strength of coarse-grained soil before freeze-thaw, but the frost susceptibility of fines weakened the shear strength of coarse-grained soil after freeze-thaw; (3) with increasing numbers of freeze-thaw cycles,the shear strength of coarse-grained soil decreased and then stabilized after the ninth freeze-thaw cycle, and therefore the mechanical indexes of the ninth freeze-thaw cycle are recommended for the engineering design values; and (4) considering frost susceptibility and strength properties as a whole, the optimal fines content of 5% is recommended for railway subgrade coarse-grained soil fillings in frozen regions.  相似文献   

Experimental study of the effects of non-uniformly distributed fine soil on mechanical properties of Shenyang–Dandong Railway coarse-grained soil     

QianMi Yu  JianKun Liu  JingYu Liu  DingJun Lv  TengFei Wang 《寒旱区科学》2015,7(5):503-512

The stress produced by repeated train loads decreases with increasing railway subgrade bed depth, and slightly weathered coarse particles of subgrade bed fillings can be broken at different levels under continuous load. Thus, the mass of fine soil, with a diameter of not more than 0.075 mm, is different at different depths. Fine soil is also sensitive to frost heave and thaw settlement. In order to study the effects of non-uniformly distributed fine soil on the mechanical properties of coarse-grained soil of the Shenyang-Dandong Railway, triaxial tests were conducted with three types of specimens, undergoing six freeze-thaw cycle numbers(0, 1, 3, 7, 9, 12) and three confining pressures(100, 200, 300 k Pa). The freezing temperature is-5 °C and the thawing temperature is +15 °C. The stress-strain behavior, static strength, resilient modulus, cohesive force and the angle of internal friction were measured for different tested specimens. As a result, the law of static strength and resilient modulus of different specimens following the increase of freeze-thaw cycles under three confining pressures is obtained. The changing law of cohesive force and friction angle of three specimens following the increase of freeze-thaw cycles is also calculated, and the different results of different specimens are also compared.  相似文献