A micro–macro investigation of the capillary strengthening effect in wet granular materials

Wet granular materials are three-dimensionally simulated by the discrete element method with water bridges incorporated between particles. The water bridges are simplified as toroidal shapes, and the matric suction is constantly maintained in the material. A comparison with experimental tests in the literature indicates that the toroidal shape approximation may be one of the best choices with high practicability and decent accuracy. Mechanical behaviours of wet granular materials are studied by triaxial tests. Effects of particle size distributions and void ratios are investigated systematically in this study. The hydraulic limit of the pendular state is also discussed. It gives the capillary cohesion function which is not only determined by the degree of saturation but also positively correlated to relative density and particle size polydispersity and inversely proportional to mean particle size. Furthermore, the capillary strengthening effect is also analysed microscopically in aid of the Stress–Force–Fabric relationship, mainly in fabric anisotropy, coordination number and stress transmission pattern, which revealed the micro-mechanisms of the additional effective stress induced by capillary effect.     

硅灰加固宁波软土的试验研究

为探索硅灰对软土的力学性质的影响,以宁波鄞州地区一种淤泥质黏土为试样,掺入不同量的硅灰,对硅灰加固土的力学性质和结构特征进行了测试。采用三轴不固结不排水剪切试验,测试分析了不同掺入量的硅灰加固土的应力应变关系,通过扫描电镜SEM照片分析了不同硅灰掺入量的硅灰加固土的结构特征。结果表明:(1)硅灰可以提高软土的黏聚力,黏聚力随着硅灰掺入量的增加而增大;(2)随着硅灰掺入量的增加,硅灰加固土的抗变形能力呈先增加后减小的趋势;(3)同一围压条件下,随着硅灰掺入量的增加,硅灰加固土的破坏偏应力逐渐增加;(4)随着硅灰掺入量的增加,硅灰加固土中大孔隙逐渐减少,小孔隙逐渐数量增加,孔径<1μm的小孔隙组分逐渐占优。     

黄陵背斜的构造几何形态及其成因探讨

黄陵背斜位于扬子克拉通的东缘,其核部出露的崆岭群被认为是扬子克拉通的基底岩石,并成为华南地质学研究的热点地区。从区域上看,黄陵背斜紧邻江汉盆地,东西两侧分别是荆当盆地与秭归盆地,黄陵背斜和周缘盆地构成明显的隆起—坳陷相互对应的构造。详细的野外观察和构造几何学的剖析表明,黄陵背斜的两翼西陡东缓,构成不对称背形的穹隆构造。在穹隆形成过程中,相应的岩石变形以顺层滑脱及相关的褶皱和小规模的逆冲断层为主,在早三叠世薄层灰岩、志留纪龙马溪组页岩、奥陶纪灰岩、寒武纪炭质灰岩以及震旦纪陡山沱组薄层灰岩广泛发育,并具有垂向缩短的重力滑脱特点,构造叠加关系指示了其形成于晚侏罗—早白垩纪之间。在构造变形分析的基础上,并深入探讨了黄陵背斜成因的3种可能的动力学背景。     

Reconstruction of hydrometeorological time series and its uncertainties for the Kaidu River Basin using multiple data sources

This paper tried to reconstruct the time series (TS) of monthly average temperature (MAT), monthly accumulated precipitation (MAP), and monthly accumulated runoff (MAR) during 1901–1960 in the Kaidu River Basin using the Delta method and the three-layered feed forward neural network with backpropagation algorithm (TLBP-FFNN) model. Uncertainties in the reconstruction of hydrometeorological parameters were also discussed. Available monthly observed hydrometeorological data covering the period 1961–2000 from the Kaidu River Basin, the monthly observed meteorological data from three stations in Central Asia, monthly grid climatic data from the Climatic Research Unit (CRU), and Coupled Model Intercomparison Project Phase 3 (CMIP3) dataset covering the period 1901–2000 were used for the reconstruction. It was found that the Delta method performed very well for calibrated and verified MAT in the Kaidu River Basin based on the monthly observed meteorological data from Central Asia, the monthly grid climatic data from CRU, and the CMIP3 dataset from 1961 to 2000. Although calibration and verification of MAP did not perform as well as MAT, MAP at Bayinbuluke station, an alpine meteorological station, showed a satisfactory result based on the data from CRU and CMIP3, indicating that the Delta method can be applied to reconstruct MAT in the Kaidu River Basin on the basis of the selected three data sources and MAP in the mountain area based on CRU and CMIP3. MAR at Dashankou station, a hydrological gauge station on the verge of the Tianshan Mountains, from 1961 to 2000 was well calibrated and verified using the TLBP-FFNN model with structure (8,1,1) by taking MAT and MAP of four meteorological stations from observation; CRU and CMIP3 data, respectively, as inputs; and the model was expanded to reconstruct TS during 1901–1960. While the characteristics of annual periodicity were depicted well by the TS of MAT, MAP, and MAR reconstructed over the target stations during the period 1901–1960, different high frequency signals were captured also. The annual average temperature (AAT) show a significant increasing trend during the 20th century, but annual accumulated precipitation (AAP) and annual accumulated runoff (AAR) do not. Although some uncertainties exist in the hydrometeorological reconstruction, this work should provide a viable reference for studying long-term change of climate and water resources as well as risk assessment of flood and drought in the Kaidu River Basin, a region of fast economic development.     

黑钨矿类质同象系列的红外光谱研究

本文是对黑钨矿类质同象系列研究的一个组成部分。测试结果表明在中红外区及远红外区的某些吸收谱带,其频率和强度的变化与黑钨矿中两端员组份FeWO_4和MnWO_4的相对含量有良好的线性相关关系。文中给出了频率变化的相关方程和相关图,并讨论了频率位移和强度变化的内部机制。     

中国上市公司的时空变化及机制研究

针对在中国地区发展不均衡的态势下,上市公司分布格局时空演变问题,该文对2009-2017年中国大陆各省上市公司的数量和总资产采用Local Moran’s I指数与Getis-Ord Gi*统计量进行研究,分析了中国大陆上市公司的空间分布格局和时间演变趋势,总结出中国上市公司相关指标的高值聚集和高低聚集分布格局、热点区域及其经济辐射能力。并且以北京、上海和广东为热点区域典型代表,从上市公司产业结构和区域经济发展两方面对时空变化机制的成因进行深入探讨。     

对GPS接收机测试评估的探讨

随着GPS的广泛应用和GPS产业的迅速发展，GPS厂家众多，生产的接收机类型更是数以百计，整个GPS接收机市场可以说是鱼目混珠，识别困难；大多数购买者只能听信厂家的技术指标，如何对GPS接收机的性能进行测试评估的意义显得很重要，本文基于此对GPS接收机测试评估展开探讨和研究。     

2.5-D DC Resistivity Modeling Considering Flexibility and Accuracy

We highlighted the flexibility of using unstructured mesh together with the local refinement by a resistivity model with complicated topography. The effect of topography is emphasized. Based on this, we calculated a specific class of layered models and found that the accuracy is not always satisfactory by utilizing the standard approach. As an improvement, we employed the layered earth as the reference model to calculate the wavenumbers. The comparison demonstrates that the accuracy is considerably improved...     

The Evolutionary History of Ore-forming Processes of Metallic Ore Deposits in Northern Guangxi1

Abstract The northern Guangxi region is an important rare metal, rare earth metal and polymetallic metallogenic province. In the region there exist five metallogenic series and two metallogenic subseries, whose metallogenesis shows features of polycyclic spiral evolution throughout the geological history. As far as various cycles are concerned, mantle-derived ore substances were reduced while crust-derived ore substances increased from early to late times; in the whole geological evolutionary history, mantle-derived substances decreased gradually while crust-derived ones increased. Meanwhile ore element associations became more and more varied. In terms of space, mineralization migrated from the old basement outwards, i.e. from west to east during the Precambrian, and from north to south during the Phanerozoic, and again from east to west during the Yanshanian.