A new concept of pedogenic nodule formation in landscapes of the Russian Far East     

V. I. Roslikova 《Russian Journal of Pacific Geology》2008,2(4):370-376

The typification of ferromanganese nodules (FMN) formed in subaqueous and subaerial settings and in residual materials, as well as FMN localization in various sediments and soils, is discussed. The genetic diversity of morphologically similar FMN and the transformation of FMN-bearing complexes with changes in landscapes have been established.  相似文献   

New basis for the constitutive modelling of aggregated soils   总被引：1，自引：1，他引：0  

Azad Koliji  Laurent Vulliet  Lyesse Laloui 《Acta Geotechnica》2008,3(1):61-69

Natural and compacted soils are usually characterized by aggregation of particles. The mechanical behaviour of these materials depends on soil structure. The oedometric compression tests performed on aggregated samples presented here showed that these materials exhibit a yield limit depending not only on stress history and stress state but also on soil structure. Evidence is provided using the neutron tomography technique. These results revealed that soil structure modification occurs together with plastic deformations. The experimental results are used to propose a new state parameter to quantify the soil structure. Based on pore-scale experimental observations, an evolution law for this parameter is proposed as a function of associated plastic strains. Considering both soil fabric and inter-particle bonding effects, a new yield limit depending on stress state, stress history and soil structure is introduced for the aggregated soils. Accordingly, a new constitutive framework consistent with strain hardening plasticity is proposed to consider soil structure effects in the modelling of aggregated soils.  相似文献   

Changing grading of soil: effect on critical states   总被引：6，自引：3，他引：3  

David Muir Wood  Kenichi Maeda 《Acta Geotechnica》2008,3(1):3-14

Examples of situations are presented where the grading of a soil changes during its lifetime either by crushing of particles leading to an increase of fine material or by slow transport of fine particles with seepage leading to a decrease of fine material. Such grading changes influence the basic constitutive properties of the soil, in particular properties such as critical states which are dependent on the available range of densities of packing. Discrete element modelling is used to show the dependence of critical state conditions on grading and the way in which the particle assembly seeks out new critical state conditions as the grading changes.  相似文献   

RATIONAL UTILIZATION OF MOUNTAIN SOILS IN SOUTHEAST QINGHAI-XIZANG (TIBETAN)PLATEAU     

Li Mingsen 《地理学报(英文版)》1996,(4)

ISoil-fo~gEnvironmentandMainSoilTrocsThesoLItheastQinghai-Xizang(Tibetan)PlateauwheretheHengduanMoUnains,eastempartoftheThmalayanandNyainqentanglhamoUnainsarelocatedextendsfrom25'to34"Nand92'to1O5'Ewithanareaof5OO,OOOkm',oraboutone-fiffooftheentireQinghai-XiZangPlateau.ItisatransitionalzoneofdeePdisseCtedmoUntainseXtendingsoutheastWardpenpherallowlandsandwichedin-betWeenSichuanBasinandcentralYunnanPlateau.Whletheterrainofthesmponinclinestosoutheast,thealtitudeofthevaIleysraises…  相似文献   

EAR70、CLDAS和ERA Interim表层土壤温度在中国地区的评估     

单帅  师春香  沈润平  白磊 《气象科技》2021,49(6):830-837

本文利用2010—2015年2400多国家气象站逐小时观测数据对覆盖中国的EAR70、CLDAS和ERA Interim 3种表层土壤温度进行了评估和对比。结果表明：空间上CLDAS表层土壤温度精度最高（平均误差为-0.5 ℃，均方根误差为3.0 ℃，相关系数为0.96），受益于CLDAS高精度的陆面初始场，EAR70平均误差得到了改善；时间上ERA Interim再分析表层土壤温度在6:00和夏、秋季精度会明显下降，再分析表层土壤温度在数值较高时段表现出冷偏差，原因是模拟的土壤温度数值上升速度慢，对应的参数化方案有待改进。再分析表层土壤温度在东北地区冬季存在冷偏差，可能和积雪覆盖有关，陆面参数化方案也有待提高。在地形复杂的青藏高原地区，融合地面观测的CLDAS提高了大气驱动的质量进而改进了土壤的模拟。ERA Interim分辨率较粗不适合在青藏高原或者沿海地区使用，结合了CLDAS的EAR70在青藏高原精度提高。土壤表层温度的精度随着高精度的土壤状态初始场进入模式中时间延长会显著下降。因此，CLDAS的实时同化方式，能够有效提高在分析数据的精度。  相似文献   

施工顺序对软土地坪复合地基的影响探讨     

魏海涛  蔡智 《岩土工程技术》2021,(1)

场地回填土与搅拌桩施工顺序将直接影响软土地坪复合地基的处理效果,其中沉降控制是影响地坪安全运行的关键。以近海软土地区工业厂房水泥土搅拌桩复合地基工程为例,探讨了复合地基水泥土搅拌桩、回填土两种不同施工顺序的影响因素及相应处理效果;通过数值模拟试验,计算分析了不同填土厚度下两种工况的地基固结总沉降、施工沉降、工后沉降。结果表明,采用“先土后桩”的施工顺序的施工期沉降大于“先桩后土”,但工后沉降大大减小,提高了软土地坪地基处理效果,有利于处理后地坪的安全运行,验证了前述分析结论,为合理设计方案的确定提供了重要的参考依据。  相似文献   

船式支护在基坑中的应用     

何世达  徐忠  李燕枫 《岩土工程技术》2021,(1)

在深厚软土地区的基坑,对基坑底软土进行搅拌加固形成强度较高的底板而保证坑底稳定,侧壁采用支护桩支护保证侧壁的稳定使其不倾倒,支护桩与加固底板两者共同作用形成的船状结构支护体系类似轮船的船侧壁及船底板,以保证基坑的稳定。结合具体的工程实例,介绍了船式支护的侧壁及底板的设计方法。工程案例成功实施,监测结果表明,船式支护既可避免支护桩嵌固深度过长,又利于软土的土方施工及工程桩的保护,是安全可靠的,对类似工程有一定的参考意义。  相似文献   

用气象站地温资料计算多年平均土壤热流的初步结果   总被引：11，自引：3，他引：8  

董文杰  汤懋苍 《高原气象》1992,11(2):115-125

  相似文献   

饱和软土压缩曲线的“反常”现象     

冯铭璋  王兴涛 《上海国土资源》1990,(3):30-37

饱和软土压缩试验时,经常出现压缩曲线“反常”、压缩系数“倒大”的现象。它是土的原始结构发生破坏前后的不同压缩性的客观反映。饱和软土的结构力很微弱,唯质量好的原状土才能见到这种“反常”。应从成孔、取样、测试及资料整理等多个环节保证其工程意义。  相似文献   

A combined study of macroseismic data and focal mechanisms applied to the West-Bohemian earthquake,Czechoslovakia     

J. Zahradník  M. Antonini  G. Grünthal  J. Janský  D. Procházková  E. Schmedes  A. Špičak  J. Zedník 《Pure and Applied Geophysics》1990,133(1):53-71

The main shock of the West-Bohemian earthquake swarm, Czechoslovakia, (magnitudem=4.5, depthh=10 km) exhibits an irregular areal distribution of macroseismic intensities 6° to 7° MSK-64. Four lobes of the 6° isoseismal are found and the maximum observed intensity is located at a distance of 8 km from the instrumentally determined epicentre. This distribution can be explained by the energy flux of the directS wave generated by a circular source, the hypocentral location and focal mechanism of which are taken from independent instrumental studies. The theoretical intensity, which is assumed to be logarithmically proportional to the integrated squared ground-motion velocity (i.e.,I=const+log v ² (t)dt), fits the observed intensity with an overall root-mean-square error less than 0.5°. It is important that the present intensity data can also be equally well explained by the isotropic source. The fit was attained by means of a horizontally layered model though large fault zones and an extended sedimentary basin suggest a significant lateral heterogeneity of the epicentral region. The results encourage a broader application of the simple modelling technique used.  相似文献