Model test and stress distribution law of unsymmetrical loading tunnel in bedding rock mass

The exit section of Duck River Tunnel owns characteristics of bedding geology and unsymmetrical loading terrain. A centrifugal model test concerning the destruction process of Duck River Tunnel is conducted. Test results are concluded as follows: The surrounding rock at the bottom of the right sidewall is the first to be destroyed; the fracture planes in surrounding rock on both left and right side lead to the ground surface; the rupture angles are different from homogenous rock mass. Results of numerical model are consistent with the test results. For doing some comparative study, numerical models of homogeneous and bedding rock mass are respectively established. Conclusions are summarized from numerical analysis as follows: The stress distribution law of bedding surrounding rock is basically similar with that of homogeneous surrounding rock, while the stress value of bedding surrounding rock is larger than that of homogeneous rock. Meanwhile, the surrounding rock stress of the structural plane increases or decreases by leaps and bounds, and the stress intensity at the bottom of right sidewall is the highest as well as the surrounding rock, there is also the most easily destructible, which is the same as the test result. The research results have significant reference value to similar projects.     

水进砂研究进展

水进砂在水进过程中被侵蚀、淘洗、搬运,其沉积特征明显有别于背景砂体,表现出明显的穿时性。水进砂的发现完善了层序地层学理论,同时它在油气储存运移、原油物性预测以及油气勘探开发方面也有重要价值。本文从砂体的性质、来源、所处背景砂体的环境以及发育的构造条件4个方面对水进砂进行了分类,并总结了具代表性的形成机制：地层响应模型、水进型三角洲模型、海侵—海退模型、水动力模型、下切谷模型和潮汐改造的沙脊模型。近年来,相关学者在传统沉积学的基础上,又运用水动力学、遗迹学和不整合面识别等比较独特的方法对水进砂进行了研究。未来水进砂的研究工作将不再局限于海相砂体中,同时将运用更精细的方法对水进砂进行更深入的研究。     

Significance,Progress and Tasks of New-type Urbanization Research

Urbanization is the most prominent comprehensive geographical process based on human activities in the surface of the Earth, with obvious interdisciplinary characteristics. In recent years, new urbanization has become an important frontier issue both at home and abroad. Urbanization is also one of the most important frontier interdisciplinary directions and one of the key research areas of geosciences. Future Earth, the United Nations Sustainable Development Goals (SDGs) and the International Geographical Union’s Commission on Geography for Future Earth:Coupled Human-Earth Systems for Sustainability (IGU-GFE) all emphasize coupling relationship between urbanization and human-earth system and sustainable development. Based on the discussion of significance of urbanization research in interdisciplinary fields, this paper reviewed the progress of urbanization research and put forward challenges and opportunities of urbanization research, and its objectives and tasks. It is recommended to play the role of the multi-disciplinary cross-cutting characteristics and strengthen the scientific and technological support and basic research depth of urbanization in interdisciplinary fields. To face the international research frontier and meet China's major needs, we proposed the top-level design and scientific and technological layout for urbanization research as soon as possible so as to improve the influence, the right to speak and the initiative of China's urbanization research in the world and play the scientific and technological support role of basic research better to serve the country’s strategic needs.     

上地幔不相容元素的显交代作用

通过矿物微区成分和图象分析，研究了在金伯利岩中发现的多种氧化物矿物的成分、结构特点及其相互关系．指出富含硅酸盐不相容元素的地幔流体交代、熔融先期形成的矿物以及充填作用，形成了近年来我国和南非金伯利岩中发现的多种新矿物相，包括沂蒙矿系列、蒙山矿系列、Ｋ－Ｃｒ柱红石、阿玛科矿、Ｚｒ－Ｔｉ氧化物（锆钛矿）、ＲＥＥ－Ｔｉ氧化物（铈钛矿）等．这些新矿物高度富集了Ｋ，Ｂａ，Ｃａ，Ｓｒ，Ｔｉ，Ｚｒ，ＲＥＥ等不相容元素．研究表明不相容元素的显交代作用可分早、中、晚３个阶段，各阶段不相容元素的富集程度、温压条件及流体的动力学特征等既有明显的差异性，又有一定的继承性     

从上地幔相关的交代钛氧化物矿物研究看中国及南非金伯利岩地球化学性质的相似性

通过对山东蒙阴金伯利岩中富含硅酸盐不相容元素的锶钛铁矿族（ＬＩＭＡ系列）、磁铁铅矿族（ＨＡＹＩ系列）矿物及其相关的钛氧化物矿物的探针成分分析，对比南非Ｄｅｂｅｅｒｓ，Ｊａｇｅｒｓｆｏｎｔｅｉｎ及Ｂｕｌｔｆｏｎｔｅｉｎ等地金伯利岩区的相似矿物研究，发现这类矿物的产出、相互关系及化学成分非常相近，与共生的金云母、碱性闪石等含水矿物一起，反映了富Ｋ，Ｂａ，Ｔｉ，Ｚｒ，Ｎｂ，ＲＥＥ等不相容元素的流体对先前亏损的方辉橄榄岩的交代作用．ＬＩ－ＭＡ，ＨＡＹＩ系列矿物是流体对镁钛铁矿、铬尖晶石等的继承交代产物．不相容元素的局部富集还可形成一些罕见的矿物相，如ＲＥＥ－Ｔｉ及Ｚｒ－Ｔｉ氧化物．与之相关的呈海绵边或基质、空洞充填产出的钙钛矿、富锰钛铁矿、富锰锌尖晶石、柱红石、铬阿玛科矿等，则与碳酸盐化及金伯利岩岩浆晚期不相容元素的浓聚有关．对这类矿物化学成分及相互关系的研究，不但从微观角度揭示了不相容元素在部分上地幔岩石中的富集，提供了卷入交代流体的总成分目录，而且表明南非和山东金伯利岩地球化学性质的相似性     

Exploring variations in upper ocean structure for the last 2 Ma of the Nansha area by means of calcareous nannofossils

A great number of calcareous nannofossils have been found in the deep-sea sediments of 2.32 Ma at ODP Site 1143 located in the Nansha area, the southern South China Sea. The number of coccoliths varies from about 0.5×10⁶ up to almost 53×10⁶ coccoliths/g sediment, with an average of 16×10⁶ coccoliths/g sediment. The accumulation rate of total coccoliths varies from 1×10⁶ to 278×10⁶ coccoliths/cm² ka. The nannofossil assemblages are usually dominated by a lower-photic species-Florisphaera profunda, of which the average percentage is about 70% in all samples. The absolute abundance and the accumulation rate of nannofossils as well as the percentage ofF. profunda display significant oscillations on two different time scales. One is the fluctuation coincident with the glacial-interglacial cycle, and the other is the long-term changes on a time scale longer than 100 ka. Six evolutionary stages of calcareous nannofossils could be divided for the last 2.32 Ma, from which we can reconstruct the changes in the depth of nutricline of the Nansha area. In this paper, the possible mechanism resulting in these variations is also discussed.     

Mathematical Model of the Geothermal Water Resources in the South Hot Spring System in Chongqing

INTRODUCTION Southhotspring,smallhotspringandQiaokou barepresent,betweenthem,thegeothermalwaters ofthesouthhotspringsysteminthesouthhotspring anticlineinChongqing.Thesouthhotspringanti clineisageothermalwaterstoragesystem.Itex tendsfromnorthtosouthinthecentralpartof Chongqing.Itis45kmlongfromsouthtonorthand2kmwide.Thesouthhotspringandsmallhot spring,inthemiddleoftheanticline,arewell known touristattractionsfortheirgeothermalwaters.Ex cessiveexploitationledtoagradualdeclineinthewa terlev…     

Evolution of soil properties on stabilized sands in the Tengger Desert, China

The spatial and temporal patterns of pedogenesis on stabilized dunes at Shapotou, northwestern China, were studied on the time sequences of 0, 18, 35 and 43 years. The spatial pattern of soil formation was estimated by measuring the thickness of accumulated sand fractions on the stabilized dune surface and by analyzing the characteristics and properties of soil. The results showed that the environment of soil formation and circulation of soil material were influenced in the processes of shifting-sand fixation, and the mean soil particle size changed from >0.2 to <0.08 mm in 0–20 cm soil depth with the succession from cultivated plants to natural vegetation. The capacity of available soil water increased fivefold. Deep infiltration of water in soil no longer occurred due to the increase in soil water capacity and the change of redistribution of soil water in profiles. Soil microorganisms evolved from simple to complex. Interaction of these processes obviously brought about accumulation of soil fertility, evolution of soil profiles and development of the profiles towards aripsamments. The difference of micro-topography is closely related to redistribution of material and energy in soil formation.     

Forcing mechanism of the Pleistocene east Asian monsoon variations in a phase perspective

The variations of the Earth’s geometry (ETP) pre-dominate climate changes such as monsoon on the Earth[1], serving as its external forcing. The loess/ paleosol sequence in Central China provides a good record of terrestrial deposition to study the evolution of the east Asian monsoon[2―4]. However, the deep sea deposition, due to its high resolution dating and abun-dant climate proxies, should be able to provide more climatic information in the geological time, such as the forcing mechanis…     

Study of the Stacking Sequences of an Irregular Mixed-Layer Illite/Smectite (I/S) Clay Mineral—with a Discussion on the Existence of Minerals with Two-Dimentional Lattice and One-Dimentional Quasi-Lattice

There are two aspects in the study of irregular mixed-layer clay minerals: one is the kinds and ratios of their basic structural unit layers and the other is the junction probabilities of the unit layers. Irregular mixed-layer illite/smectite clay minerals (I/S) are widespread in nature. While studying the clay minerals from the Permian-Triassic (P/T) boundary bed, the authors found that I/S clay minerals are developed in all P/T boundary clay layers in areas from the northwest to southeast of China. Systematic mineralogical studies of the I/S clay minerals from Hunan, Hubei, Sichuan and Zhejiang were made by means of X-ray, infrared spectroscopic, electron microscopic and chemical analyses and a deepened study of the stacking sequences of their structural unit layers was conducted by the MacEwan one—dimentional direct Fourier transform. It was found that the stacking of the illite and smectite crystal layers along the c axis can be derived from Fibonacci sequences. Hence, the authors propose that such I/S clay minerals are possessed of two—dimentional crystal lattice and one—dimentional quasicrystal lattice.