Effects of particle size on crushing and deformation behaviors of rockfill materials

Strength and deformation behaviors of rockfill materials,key factors for determining the stability of dams,pertain strongly to the grain crushing characteristics.In this study,single-particle crushing tests were carried out on rockfill materials with nominal particle diameters of 2.5 mm,5 mm and 10 mm to investigate the particle size effect on the single-particle strength and the relationship between the characteristic stress and probability of non-failure.Test data were found to be described by the Weibull distribution with the Weibull modulus of 3.24.Assemblies with uniform nominal grains were then subjected to one-dimensional compression tests at eight levels of vertical stress with a maximum of 100 MPa.The yield stress in one-dimensional compression tests increased with decreasing the particle size,which could be estimated from the single-particle crushing tests.The void ratio-vertical stress curve could be predicted by an exponential function.The particle size distribution curve increased obviously with applied stresses less than 16 MPa and gradually reached the ultimate fractal grading.The relative breakage index became constant with stress up to 64 MPa and was obtained from the ultimate grading at the fractal dimension(a?2:7).A hyperbolical function was also found useful for describing the relationship between the relative breakage index and input work during one-dimensional compression tests.     

Reconstruction of nearshore chemical conditions in the Mesoproterozoic: evidence from red and grey beds of the Yangzhuang formation,North China Craton

ABSTRACT

Mesoproterozoic red beds near ancient coasts have not aroused extensive interest. A new geochemical study of the alternating red and grey dolostones from the Yangzhuang Formation provides a better understanding of the redox conditions of nearshore sedimentary environments. In this contribution, whole-rock samples are characterized by positive correlations of rare earth elements (REE) vs. Th and Fe_T vs. Th and flat-type REE distribution patterns, indicating massive terrigenous input, which is considered to be inherited from felsic rocks. Relatively high (Fe_mag+Fe_ox)/Fe_T and Fe³⁺/Fe²⁺ ratios in red beds indicate more oxidized conditions in supratidal environments compared with the lower oxygen contents in intertidal environments. Under these two distinct chemical sedimentary conditions, acetic acid-leached red and grey samples both have HREE-depleted distributions, suggesting significant freshwater invasion. Moreover, limited terrigenous redox-sensitive elements (RSEs) can reach the coast where the red beds are deposited, whereas relatively high RSE enrichment factors originating from shallow oceans are recorded in grey beds. In the Mesoproterozoic, limited oxidative weathering, shallow seawater desalination, and low organic production occurred near the coast. Meanwhile, a prolonged period of low Mo and U availability preserved in carbonate minerals confirmed that marine oxygen levels failed to satisfy the deposition of offshore red beds. During the regression, potentially exposed sediments connected to atmospheric oxygen guaranteed the oxidation of iron and the formation of red beds, and these events were coupled with negative δ¹³C_carb shifts in the Yanliao rift zone.     

俄罗斯贝加尔湖北部 Yoko-Dovyren 层状纯橄岩-橄长岩-辉长岩地块: 结构、成分以及作为矿物原材料的用途

Yoko-Dovyren层状纯橄岩-橄长岩-辉长岩地块位于西伯利亚克拉通南部的一处褶皱构造框架中(俄罗斯贝加尔湖地区北部)。该地块的结构在其厚度最大的中部得到了着重研究。剖面底部主体成分为斜长橄榄岩,并依据内部的堆晶成分变化从下往上可分为五个主要的地层序列:纯橄岩→橄长岩→橄榄辉长岩→橄榄辉长苏长岩→石英辉长苏长岩以及含易变辉石的辉长岩。该地块的矿化包括铜-镍矿化、低硫型富铂族元素(PGE)矿化以及铬铁矿化等。另外,该地块也含多种非金属矿物原材料,如硼矿化、透辉石、各种镁质硅酸盐岩等。它们也包括纯橄岩、异剥橄榄岩和橄长岩,并以较高的品质产出,有望采掘加工成为建筑材料(水泥、混凝土、沥青混凝土和建筑陶瓷)。综合利用矿物原材料可增加矿床价值,并有助于建设环保型采矿工作体系。     

High‐Precision Cd Isotope Measurements of Soil and Rock Reference Materials by MC‐ICP‐MS with Double Spike Correction

This study presents a high‐precision Cd isotope measurement method for soil and rock reference materials using MC‐ICP‐MS with double spike correction. The effects of molecular interferences (e.g., ¹⁰⁹Ag¹H⁺, ⁹⁴Zr¹⁶O⁺, ⁹⁴Mo¹⁶O⁺ and ⁷⁰Zn⁴⁰Ar⁺) and isobaric interferences (e.g., Pd, In and Sn) to Cd isotope measurements were quantitatively evaluated. When the measured solution has Ag/Cd ≤ 5, Zn/Cd ≤ 0.02, Mo/Cd ≤ 0.4, Zr/Cd ≤ 0.001, Pd/Cd ≤ 5 × 10^?5 and In/Cd ≤ 10^?3, the measured Cd isotope data were not significantly affected. The intermediate measurement precision of pure Cd solutions (BAM I012 Cd, Münster Cd and AAS Cd) was better than ± 0.05‰ (2s) for δ^114/110Cd. The δ^114/110Cd values of soil reference materials (NIST SRM 2709, 2709a, 2710, 2710a, 2711, 2711a and GSS‐1) relative to NIST SRM 3108 were in the range of ?0.251 to 0.632‰, the δ^114/110Cd values of rock reference materials (BCR‐2, BIR‐1, BHVO‐2, W‐2, AGV‐2, GSP‐2 and COQ‐1) varied from ?0.196‰ to 0.098‰, and that of the manganese nodule (NOD‐P‐1) was 0.163 ± 0.040‰ (2s, n = 8). The large variation in Cd isotopes in soils and igneous rocks indicates that they can be more widely used to study magmatic and supergene processes.     

Nitrogen Mass Fraction and Stable Isotope Ratios for Fourteen Geological Reference Materials: Evaluating the Applicability of Elemental Analyser Versus Sealed Tube Combustion Methods

Thirteen commercially available silicate reference materials (RM) and one in‐house reference material, eleven of which have no previously published values, were analysed for nitrogen mass fraction and isotopic ratios with an Elemental Analyser (EA), and a Sealed Tube Combustion line, coupled to a continuous flow isotope ratio mass spectrometer (IRMS). These materials ranged from < 10 μg g^?1 to 1% m/m nitrogen mass fractions and δ¹⁵N of ?0.5 to +19.8‰. Existing nitrogen RM BHVO‐2, MS#5 and SGR‐1b were used to assess the accuracy of the data from the sealed tube combustion line, which was found to be in good agreement with existing published values. In contrast, the EA‐IRMS failed to fully liberate nitrogen from all silicate rocks and minerals (achieving a mean of 44 ± 10% nitrogen yield) resulting in kinetic fractionation of isotope values by ?1.4‰ on average. Therefore, sealed tube combustion is better suited for analyses of silicate‐bound nitrogen. The EA worked reliably for organic samples, but care should be taken when using the EA for silicate nitrogen research. Moving forward, it is recommended that BHVO‐2, Biotite‐Fe, FK‐N and UB‐N be used as quality control materials as they appear to be most reproducible in terms of nitrogen mass fraction (relative error < 10%, 1s), and isotopic composition (< 0.6‰, 1s).     

复合载体夯扩桩工艺在吉林省的应用

复合载体夯扩桩工艺是将地基处理与地基施工合二为一的一种地基加固处理新技术,是一种性价比高的桩型,承载力与其它桩型相比较高,得到建筑界的好评,取得了显著效果。笔者通过两个工程实例的对比,论述该方法的特点、施工工艺及检测结果。     

多肽类生物活性物质的非核糖体合成机理

遗传信息通过信使核糖核酸、转运核糖核酸和核糖体转变成蛋白质的过程是分子生物学的基石。但是 ,许多多肽类生物活性物质是通过非核糖体途径合成的 ,只有非核糖体多肽合成酶系参与。非核糖体多肽合成酶系是一类多功能蛋白质复合体 ,能识别、激活、转运氨基酸底物并按特定顺序合成多肽。非核糖体多肽合成酶系同时具有酶和模板功能 ,因此被称为蛋白质模板。由于底物大部分是稀有氨基酸 ,经由该途径合成的多肽类生物活性物质种类繁多。了解多肽非核糖体合成机理有助于寻找多肽类生物活性物质 ,有利于通过人工操作非核糖体合成酶系生产多肽类药物。近年来的研究已经使人们初步了解了多肽非核糖体合成的机理。本文将介绍非核糖体合成酶系组成、结构和多肽非核糖体合成过程     

山东省焦家金成矿带大比例尺成矿预测中地质模型的研究与应用

根据焦家金成矿带的矿床空间定位规律、分布规律，矿体赋存规律，对焦家金成矿带深部大中型金矿体进行了预测，共圈定了11处A级靶区，矿体25个，总计预测金矿资源量（334）约600t，为该成矿带已探明储量的168％。     

Does a representative volume element exist for fatigue life prediction? The case of aggregate composites

In a previous work, discrete modeling and a statistical approach were used to quantify the minimal representative volume element (RVE) size for aggregate composites, such as bituminous materials in the linear elastic regime (Comput. Mater. Sci. 2005; 33 :467–490). In this paper, the discrete model is extended to strain‐softening behavior under cyclic loading. The existence of a RVE for fatigue life prediction is numerically proved and its minimal size is determined. It is found that it is much larger than the minimal RVE size in the elastic regime. Copyright © 2007 John Wiley & Sons, Ltd.     

湘西董家河铅锌矿地质特征及成矿物质来源探讨

湘西董家河铅锌矿区赋存于陡山沱组下部(Zd)微晶白云岩中,顶板为黑色炭质板岩,底板为南沱组冰碛层,矿体产状、矿石矿物组合、矿石组构反映成矿受沉积成岩和后期构造热液活动的双重控制,成矿温度低(130°~170℃),属典型的低温沉积改造型矿床。矿床经历了沉积成岩和后期热液改造阶段,硫、铅、碳氧同位素组成表明成矿物质主要来源于下伏地层和围岩,部分物质来源于深部基底变质岩。