Numerical predictions of the behaviour of soft clay with two anisotropic elastoplastic models     

Paulo J. Venda Oliveira  Luís J.L. Lemos 《Computers and Geotechnics》2011

The numerical predictions obtained with the Melanie and MIT-E3 models are compared. Firstly, the performance of the constitutive models is checked against undrained triaxial tests. The models are then used to replicate the behaviour of an embankment built on soft clay. The numerical results are compared with the field data in terms of settlements, lateral displacements and excess pore pressures. Additionally, the numerical predictions are also analysed in terms of yield area, contours of vertical effective stresses, horizontal effective stresses and shear stresses and in terms of effective stress paths.  相似文献   

中国钼矿主要矿集区及其资源潜力探讨   总被引：18，自引：0，他引：18       下载免费PDF全文

黄 凡陈毓川  王登红袁忠信 陈郑辉 《中国地质》2011,38(5):1111-1134

钼矿是中国的优势矿种之一,在全国范围内均有分布。矿床成因类型以斑岩型、矽卡岩型和热液脉型为主,成矿时代以中生代和新生代为主。新世纪,随着科技进步,钼的应用领域逐渐扩大,带动了中国钼矿的勘探和开采工作,取得了一系列找矿新突破,特别是在非传统的钼矿产区发现了许多大型和超大型钼矿,使中国钼矿资源量有了大的突破,基本上改变了过去"南钨北钼"的原有格局。本文在广泛搜集资料的基础上,总结了中国钼矿资源特点,并综合考虑岩浆、构造、地层、流体、成矿时代等因素,初步将中国钼矿划分为17个大的矿床集中区(矿集区),简单介绍了矿集区的基本地质特征和成矿特征,给出了几个最重要矿集区的区域成矿模式,同时根据已有资料和找矿新进展,对主要钼矿矿集区进行了资源潜力分析,并对中国钼矿找矿工作提出了建议。  相似文献   

利用方式对东北黑土粘土矿物组成的影响   总被引：1，自引：0，他引：1  

郑庆福  赵兰坡  冯君  王鸿斌  李春林 《矿物学报》2011,31(1):139-145

土地利用方式是影响土壤可持续利用的重要因素。粘土矿物是土壤重要的活泼物质,会受利用方式的影响而发生改变。为了揭示利用方式对土壤粘土矿物的影响,对不同利用方式下的东北黑土进行土壤理化特性及粘粒XRD分析。结果表明:荒地、旱田(大豆)、旱田(玉米)、水田利用的土壤矿物颗粒的风化依次增强,伊利石的含量和结晶度也依次降低。经水田利用后的黑土,粘土矿物的演变过程为:云母→伊利石→蛭石和绿泥石。定量结果表明黑土水田利用会出现蛭石绿泥石化现象。综合说明旱田利用会使土壤结构破坏以及水土流失加剧,而水田利用则能较好的协调土壤理化性质,可较大程度的改良土壤。  相似文献   

坡缕石粘土固定辣根过氧化酶处理硝基酚废水     

舒林  彭书传  刘海波  鲍腾  刘文静 《岩石矿物学杂志》2011,30(6):1063-1068

以坡缕石粘土、淀粉、水玻璃为原料,研究了固定化酶载体的制备工艺,探究了固定化酶载体在辣根过氧化酶(HRP)降解硝基酚废水中的作用,并探讨了反应时间、酶浓度、H2O2及硝基酚浓度对降解效果的影响。结果表明,固定化酶载体的最佳制备工艺为:水玻璃12%,淀粉20%,煅烧温度550℃,煅烧时间2 h;固定化酶对硝基酚的去除效果明显高于原酶;固定化酶去除水中硝基酚的最佳反应条件为:反应时间1.5 h,加酶量150 U,H2O2浓度0.12%,硝基酚浓度100 mg/L;固定化酶重复使用7次后对硝基酚的去除率仍高于60%。  相似文献   

The influence of freeze-thaw cycles on the granulometric composition of Moscow morainic clay   总被引：2，自引：0，他引：2  

Ze Zhang  Vadim V. Pendin  WenJie Feng  ZhongQiong Zhang 《寒旱区科学》2015,7(3):199-205

The freeze-thaw cycling process considerably changes the composition,structure,and properties of soils.Since the grain size is the most important factor in determining soil characteristics,our current research primarily aims to investigate dynamic changes of the soil fraction when exposed to freeze-thaw conditions.We observed two series of Moscow morainic clayey specimens(g QmII):(I) the original series,and(II) the remolded series.We subjected each series of soil specimens to different frequencies of freeze-thaw cycles(3,6,20,and 40 cycles),and we used granulometric tests to analyze both series before and after exposure to freeze-thaw conditions.As a result of our experiments,the granulometric compositions tended to be distributed evenly after 40 freeze-thaw processes(i.e.,content of fraction for 0.1–0.05 mm was increased after 40 freeze-thaw cycles) because the division of coarse grains and the aggregation of fine grains were synchronized during the freeze-thaw process.The soil grains in both series changed bi-directionally.In the original series,changes of the sand grains were conjugated with the clay grains,and in the remolded series,changes of the sand grains were conjugated with the silt grains,because potential energy difference caused the division and aggregation processes to relate to the counteraction process.The even distribution of soil grain size indicated the state of equilibrium or balance.The granulometric compositions were altered the most during the sixth freeze-thaw cycle,because the coefficient of the intensity variation of the grain fineness(Kvar) had its maximum value at that time.  相似文献   

楚科奇海盆M04柱晚更新世以来沉积古环境记录   总被引：1，自引：0，他引：1  

章伟艳  于晓果  刘焱光  金路  叶黎明  许冬  边叶萍  张德玉  姚旭莹  张富元 《海洋学报》2015,37(7):85-96

对"中国第五次北极科考"采自楚科奇海盆的M04柱进行粒度、冰筏碎屑、黏土矿物、岩心XRF扫描、沉积物颜色分析,初步建立了楚科奇海盆晚更新世MIS4期以来的沉积地层框架。MIS4期以来,楚科奇海盆M04柱沉积物粒度和黏土矿物组成具有明显的冰期/间冰期变化特征,冰期沉积物粒度分布以双峰态为主,由洋流搬运和海冰搬运沉积组分组成,伊利石含量高、高岭石含量低;间冰期沉积物具有三峰态粒度分布特征,由海冰搬运、洋流搬运和冰山搬运沉积组分组成,伊利石含量低、高岭石含量高。通过M04柱黏土矿物组合类型与北冰洋边缘海盆的表层沉积物黏土矿物组合类型对比表明,晚更新世以来楚科奇海盆沉积环境发生显著变化:温暖的间冰期受波弗特涡流驱动,波弗特海为研究区的物源输入提供了主要贡献;寒冷的冰期表层环流呈反向输运,细颗粒物源碎屑以东西伯利亚海的输入为主。  相似文献   

我国西北夏季风边界千年尺度变化的证据--来自盐池和猪野泽盐类矿物分析结果   总被引：1，自引：0，他引：1  

李育  张成琦  周雪花  王岳 《沉积学报》2015,33(3):524-536

我国夏季风西北缘是响应长尺度气候变化最为敏感的区域之一, 但夏季风边界变化与千年尺度气候变化之间的关系尚不明确, 相关研究仍缺乏足够证据。夏季风西北缘湖泊沉积物中盐类矿物种类与含量的时空变化, 有助于推测气候变化特征。盐池和猪野泽分别位于祁连山北麓的河西走廊中段和东段, 是研究长时间尺度亚洲夏季风影响区西北边界变化的关键区域。研究全新世千年尺度下, 夏季风西北边界的变化对夏季风西北缘气候变化过程的影响, 对明确季风边缘区千年尺度季风变化机制, 预测未来长尺度气候变化有重要意义。因此, 本文选择盐池古湖泊盐池剖面(YC), 猪野泽青土湖01、02剖面(QTH01、QTH02)等三个剖面, 开展全新世千年尺度下, 亚洲季风西北边界地区湖泊沉积物盐类矿物时空变化对比研究。结果显示:QTH01、QTH02剖面盐类矿物以碳酸盐为主, 硫酸盐类矿物仅零星出现, 而YC剖面硫酸盐类矿物含量相对较高, 同时出现了氯化物型矿物, 全新世气候特征整体较猪野泽更为干旱。末次冰期和早全新世, 三个剖面受季风输送水汽影响明显, 碳酸盐类矿物能较好沉积, 季风边界在这一时期向北扩张, 推进到祁连山中段地区;中全新世QTH01、QTH02剖面受夏季风影响减弱, 湖泊退缩, 碳酸盐类矿物含量达到峰值, YC剖面则表现出极端干旱的气候特征, 硫酸盐类矿物因“盐效应”含量下降, 此时夏季风西北部水汽输送边界位于石羊河流域和盐池流域之间;晚全新世盐池和猪野泽均以风成沉积为主, 气候干旱, 碳酸盐类矿物难以保存, 硫酸盐和氯化物矿物含量出现高值, 说明夏季风西北边界进一步向南迁移。综上所述, 盐类矿物含量变化能良好反应夏季风西北缘全新世气候变化特征, 同时证明, 在全新世千年尺度上, 夏季风西北边界在盐池流域和石羊河流域之间存在变化。  相似文献   

矿物学文献中未定名矿物的编码系统:国际矿物学协会新矿物与命名和分类委员会“未定名矿物”小组报告     

傅小土  杨主明 《矿物学报》2015,35(2):276-278

国际矿物学协会新矿物与命名和分类委员会(IMA-CNMMN)的未定名矿物小组(SUM),开发了一个编码系统,对已经发表但尚未定名的矿物进行编码。在文献中存在两类未定名矿物。一是"有效"未定名矿物,是指未定名矿物没有对应的已知矿物种,但如果它们有其他产地或能够在其他样品中被发现,那么已发表的相关矿物描述允许得到认可。二是"无效"未定名矿物,是指未定名矿物已经有对应的已知矿物种;或者相关矿物描述不足以获得认可。未定名矿物的名单是由IMA保管。该编码系统提供了一个永久的UM号码。中国的矿物学文献的数量和重要性有必要用中文阐述未定名矿物的编码系统。  相似文献   

粉质黏土堤防漫溢溃决试验          下载免费PDF全文

魏红艳  余明辉  李义天  吴松柏 《水科学进展》2015,26(5):668-675

为研究粉质黏土堤防漫溢溃决破坏过程及其对水流要素和土体性质的响应规律,以河道流量、筑堤土体含水率和孔隙率为变量,在弯道水槽中开展了9组堤防漫溢溃决概化试验.通过试验发现,粉质黏土堤漫溢溃决溃口发展过程可分为垂向侵蚀和横向扩宽两个阶段,垂向侵蚀阶段以"陡坎"后退为主要形式;筑堤土体含水率与孔隙率不仅影响了溃口垂向侵蚀以及横向扩宽速度,而且决定了溃口最终形态,河道流量主要影响堤防溃口的横向扩宽速度;溃口处流速以及下游水位变化受溃口高度的制约.拟合得到土体黏聚力与土体含水率、孔隙率的相关关系式;通过试验数据提出了由土体黏聚力和水流参数表达的"陡坎"侵蚀后退速度计算公式,证明具有一定合理性.  相似文献   

Diffusive mass exchange of non‐reactive substances in dual‐porosity porous systems – column experiments under saturated conditions          下载免费PDF全文

Bastian Knorr  Piotr Maloszewski  Florian Krämer  Christine Stumpp 《水文研究》2016,30(6):914-926

Diffusive mass exchange into immobile water regions within heterogeneous porous aquifers influences the fate of solutes. The percentage of immobile water is often unidentified in natural aquifers though. Hence, the mathematical prediction of solute transport in such heterogeneous aquifers remains challenging. The objective of this study was to find a simple analytical model approach that allows quantifying properties of mobile and immobile water regions and the portion of immobile water in a porous system. Therefore, the Single Fissure Dispersion Model (SFDM), which takes into account diffusive mass exchange between mobile and immobile water zones, was applied to model transport in well‐defined saturated dual‐porosity column experiments. Direct and indirect model validation was performed by running experiments at different flow velocities and using conservative tracer with different molecular diffusion coefficients. In another column setup, immobile water regions were randomly distributed to test the model applicability and to determine the portion of immobile water. In all setups, the tracer concentration curves showed differences in normalized maximum peak concentration, tailing and mass recovery according to their diffusion coefficients. These findings were more pronounced at lower flow rates (larger flow times) indicating the dependency of diffusive mass exchange into immobile water regions on tracers' molecular diffusion coefficients. The SFDM simulated all data with high model efficiency. Successful model validation supported the physical meaning of fitted model parameters. This study showed that the SFDM, developed for fissured aquifers, is applicable in porous media and can be used to determine porosity and volume of regions with immobile water. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献