基于核磁共振的脆硬性泥页岩水化损伤演化研究

为研究脆硬性泥页岩水化后细观结构的损伤演化特征,利用核磁共振技术对不同浸泡时间的脆硬性泥页岩试样进行测量,得到不同浸泡时间的试样质量变化、横向弛豫时间T2谱分布以及核磁共振成像。结果表明：水化作用会对岩石内部产生损伤,岩样吸水率在最初的8 h内变化相对较大,1 d后相对接近稳定,之后变化不明显。随着浸泡时间的延长,微裂缝在水化的作用下快速扩展、贯通使岩样表面产生明显裂纹。核磁共振T2谱图和成像结果表明,水化作用使岩样微观结构重新分布,T2曲线信号幅度发生明显的变化,并随着浸泡时间的延长而增加。整个水化损伤分为3个阶段：大尺寸孔隙裂纹发展阶段;小孔隙产生、大尺寸孔隙裂纹加剧扩展;小孔隙加剧产生扩展、大尺寸孔隙裂纹归并贯通至水化破坏阶段。核磁共振图像显示同一块岩样在不同浸泡时间的内部微观结构分布,动态地显示岩石的水化损伤过程。     

Bounding the required sample size for geologic site characterization

The proposed objective of limited sample geologic site characterization is to minimize the chance of unknown and unexpected extremes. This problem proves to be extremely difficult when the data are spatially correlated. A generalization of the classical one-sided nonparametric tolerance interval, based upon the statistical concept of associated random variables, establishes a rigorous, almost distribution-free, tool for computing the minimum required sample size for site characterization. An upper bound on the required number of samples follows from a heuristic measure for the quantity of information in a spatially dependent sample; the measure presented is the equivalent number of uncorrelated samples and is calculated using an estimated variogram. An empirical check of the upper and lower bounds, using more than 2 million simulations and seven real data sets produces a heuristic rule for quantifying the required number of samples.This paper was presented at Emerging Concepts, MGUS-87 Conference, Redwood City, California, 13–15 April 1987.     

Sampling variation of principal components

The convenience of reducing the dimension of a data matrix by principal component analysis invites substantive interpretation of the coefficients of the components. To test the consistency of component coefficients, 10 samples of approximately 25, 50, 100, and 200 items each were randomly drawn, with replacement, from a source sample consisting of 2086 subalkaline asalt analyses. From each sample principal components were calculated using 9 major oxides as variables. Although the eigenvalues are remarkably consistent, both across and within sample size groups, the coefficients of the eigenvectors are subject to considerable sample variance. It is sometimes assumed that the coefficients of the components calculated from small samples are well enough known to be used in detailed petrological interpretation. Our results indicate that the validity of this assumption should be tested in each specific research even when rather large samples are used. The testing procedure used here is suitable of a sufficiently large reservoir of sample items is available; in the absence of such a reservoir complete simulation could be used.     

不同颗粒尺寸条件下MICP固化砂土的试验研究

通过选取3种不同颗粒尺寸的砂样进行微生物诱导碳酸钙（MICP）注浆试验,对同一尺寸试验组分别进行8、10、12次胶结液灌注,结合细菌吸附率、流出液Ca2+浓度、试样渗透系数、碳酸钙含量、孔隙结构和最终加固效果等数据,探讨了颗粒尺寸对MICP加固砂土的影响。试验结果表明,细菌吸附率与颗粒尺寸间存在一定联系,颗粒尺寸越大,细菌吸附量相对越少;同时颗粒尺寸会影响试样固化过程及孔隙结构的发展,颗粒尺寸较小的试样能留住更多的营养物质;固化过程中,颗粒尺寸较小的砂样由于孔隙较小、渗透系数小等原因,试样上部易形成淤堵,从而导致试样加固效果不均;大颗粒尺寸的试样,孔隙较大、持水能力弱,产生的碳酸钙含量偏低并在试样下部堆积,从而导致加固效果较差。     

Particulate trace metal speciation in stream sediments and relationships with grain size: Implications for geochemical exploration

Sediment samples were collected from streambeds in an undisturbed watershed in eastern Quebec (Gaspé Peninsula). Two sampling sites were located on a stream draining an area of known mineralization (Cu, Pb, Zn) and two on a control stream. The sediment samples were separated into 8 distinct size classes in the 850 μm to <1 μm size range by wet sieving, gravity sedimentation or centrifugation. Each sediment subsample was then subjected to a sequential extraction procedure designed to partition the particulate heavy metals into five fractions: (1) exchangeable; (2) specifically adsorbed or bound to carbonates; (3) bound to Fe-Mn oxides; (4) bound to organic matter; (5) residual. The following metals were analyzed in each extract: Cu, Pb, Zn; Fe, Mn.Comparison of samples from the mineralized area with control samples revealed the expected increase in total concentrations for Cu, Pb and Zn. Non-detrital metals were mainly associated with Fe oxides (specifically adsorbed; occluded) and with organic matter or resistant sulfides. For a given sample, variation of trace metal levels in fractions 2 and 3 with grain size reflected changes in the available quantities of the inorganic scavenging phase (FeOx/MnOx); normalization with respect to Fe and Mn content in fraction 3 greatly reduced the apparent dependency on grain size.The results of this study suggest that a single reducing extraction (NH₂OH.HCl) could be used advantageously to detect anomalies in routine geochemical surveys. A second leaching step with acidified H₂O₂ could also be included, as the trace metal concentrations in fraction 4, normalized with respect to organic carbon content, also showed high {anomaly/background} ratios.     

Capturing the complete stress–strain behaviour of jointed rock using a numerical approach

This paper presents the results of a series of numerical experiments using the synthetic rock mass (SRM) approach to quantify the behaviour of jointed rock masses. Field data from a massive sulphide rock mass, at the Brunswick mine, were used to develop a discrete fracture network (DFN). The constructed DFN model was subsequently subjected to random sampling whereby 40 cubic samples, of height to width ratio of two, and of varying widths (0.05 to 10 m) were isolated. The discrete fracture samples were linked to 3D bonded particle models to generate representative SRM models for each sample size. This approach simulated the jointed rock mass as an assembly of fractures embedded into the rock matrix. The SRM samples were submitted to uniaxial loading, and the complete stress–strain behaviour of each specimen was recorded. This approach provided a way to determine the complex constitutive behaviour of large‐scale rock mass samples. This is often difficult or not possible to achieve in the laboratory. The numerical experiments suggested that higher post‐peak modulus values were obtained for smaller samples and lower values for larger sample sizes. Furthermore, the observed deviation of the recorded post‐peak modulus values decreased with sample size. The ratio of residual strength of rock mass samples per uniaxial compressive strength intact increases moderately with sample size. Consequently, for the investigated massive sulphide rock mass, the pre‐peak and post‐peak representative elemental volume size was found to be the same (7 × 7 × 14 m). Copyright © 2015 John Wiley & Sons, Ltd.     

Constituent material properties and clast-size distribution of volcanic breccia

Volcanic breccia is a representative heterogeneous rock. As a preliminary study for determining its mechanical properties in laboratory and field experiments, its material properties and structural features were described. Three-dimensional clast-size distribution was also estimated for the study site using the theory of stereology. With this distribution determined, a numerical simulation was performed to investigate the relationship between the volumetric proportion of clasts in a sample and the areal proportion and maximum length of clasts on a lateral surface of the sample. The following observations were made: (1) coefficients of variation for volumetric proportion are dependent on the size of the sample, and became large when the size of the sample is small; (2) samples with a small coefficient of variation can be selected at any size if a restriction is placed on the ratio, D_max/D₀, of the maximum length of clasts to the size of the sample; and (3) the volumetric proportion of clasts in each sample can be estimated from the observed areal proportions within an error range that depends on the whole volumetric proportion.     

结构面粗糙度统计测量最小样本数确定方法

由于结构面粗糙度具有各质异性、各向异性、非均一性和尺寸效应等特征，结构面粗糙度系数（JRC）取值具有不确定性，工程中广泛采用统计方法来分析结构面粗糙度性质，然而以往研究往往忽略样本数不足对统计结果的影响。针对结构面粗糙度统计测量时无法确定合理样本数的问题，分别提出基于变异系数级比分析及简单随机抽样原理的最小样本数确定方法。以实际工程岩体结构面表面数据为研究对象，对比分析两种方法在系列尺寸下确定的统计测量最小样本数。实例分析表明：小尺寸样本的变异系数（CV）值明显大于大尺寸样本，且CV值随取样尺寸的增大而减小，取样尺寸为10～50 cm的CV值基本稳定在0.31～0.47之间，取样尺寸为60～100 cm的CV值基本稳定在0.21～0.31之间；最小样本数与取样尺寸基本满足幂函数关系，且最小样本数随取样尺寸的增大而减少；系列尺寸下级比分析方法在允许误差为±2%时确定的最小样本数与简单随机抽样原理在最大允许误差为10%、置信度为95%时计算的最小样本数是一致的，相似度大于0.997。该研究方法可为工程岩体中定量获取结构面粗糙度统计测量最小样本数提供依据，保证了JRC（结构面粗糙度系数）统计测量结果的准确性，对工程岩体稳定性评价中结构面力学参数的准确获取具有重要意义。     

堆石料缩尺方法的分形特性及缩尺效应研究

采用6种不同缩尺方法将同一条现场级配曲线缩制成不同的数值模拟级配曲线,建立以不同粒径范围内颗粒数为测量数的分形模型,研究了颗粒级配分布的分形特性;基于颗粒流方法,生成与级配曲线相对应的6组数值试样进行双轴压缩试验,研究了缩尺方法对数值试样宏观力学特性及细观力学响应的影响;并讨论了颗粒级配分布的分形特性与数值试样力学特性之间的关系。结果表明：采用不同方法缩尺后数值试样的颗粒级配分布具有分形特性,分维数D为1.463～1.783;随着缩尺方法相似比尺M的增大,数值试样中细颗粒数量增多,粗细颗粒的充填关系得到改善,力学特性逐步提高;颗粒级配分布分维数D与数值试样力学特性指标之间存在较好的线性关系。     

微量陨石激光熔样稀有气体测定方法

微量陨石激光熔样稀有气体测定方法是一种可以在微米尺度上对几毫克陨石样品进行准确稀有气体同位素分析的方法,克服了传统全岩熔融法在测量时存在样品用量大、前处理过程复杂和样品稀有气体分布不均导致不同组分的宇宙射线暴露历史无法进一步区分等问题。但是由于该方法所用样品体积小和样品用量低,要求实验室具有超低本底的稀有气体提取系统,目前国内在微量陨石稀有气体分析技术方面尚处于起步阶段。本文采用金刚石激光样品窗成功研制了超低本底的气体提取系统,通过系统体积标定和天平称量误差、热本底、干扰元素、质量歧视及质谱灵敏度等参数的校正,在中国科学院地质与地球物理研究所建立了微量陨石激光熔样稀有气体测定方法,并对毫克级微量钙长辉长无球粒陨石Millbillillie粉末标样进行了稀有气体同位素含量和比值测定,计算获得准确一致的宇宙暴露年龄。该方法的建立,将为我国迅速发展的比较行星学和深空探测提供重要技术支撑。     

电感耦合等离子体质谱法测定砂岩型铀矿样品中分步提取的铀

本文研究地质样品中铀形态的分析方法及应用技术,以进一步说明铀形态分析在地球化学找矿中的重要作用。该方法参考Tessier流程,将样品中的铀分为可交换离子态、碳酸盐结合态、铁锰氧化物结合态、硫化物及有机物结合态和结晶态,分别提取,提取溶液用高分辨率电感耦合等离子体质谱仪进行测量。设计的形态提取配方具有良好的可选择性和可重复性,经过国家标准物质、国际形态标准物质和人工模拟样品验证,证明形态提取试剂配方适合所定义的形态分析。通过对实际样品(总量铀为635μg/g)验证表明,碳酸盐结合态铀提取结果的可重复性最好(RSD为2.6%),其次为硫化物及有机物结合态铀(RSD为4.0%)、结晶态铀(RSD为6.0%)和铁锰氧化物结合态铀(RSD为6.1%),可交换离子态铀提取结果的可重复性最差(RSD为26%)。碳酸盐结合态铀与结晶态铀之比,可以用于反映地下铀矿的存在概率。     

泰思肯集成矿物分析仪对岩矿样品精细扫描中不同实验条件的对比研究

泰思肯集成矿物分析仪(TESCAN Integrated Mineral Analyzer,简称TIMA)是基于扫描电子显微镜、加载多个X射线能谱仪和其他探测器、自动识别矿物并成像的分析系统。TIMA已广泛应用到岩石学、矿物学、地球化学、石油、古生物等地球科学领域中,特别是在针对矿物成分和结构复杂、粒径细小的地质样品以及数量大且样品重复性高的实验需求时,它具备分析快速并且能获得统计学数据的优势。为了达到分析测试目的,同时节约成本,选择最佳的实验条件至关重要,但相关研究往往被忽视。因此,本文以陕西省略阳县铧厂沟金矿床中的含金矿化黄铁绢英岩样品为例,使用TIMA在不同扫描模式和分析类型以及多种实验参数设置条件下,对样品进行了分析测试,比较了测试结果的矿物相组成数据、小区域矿物相图和元素分布图的图像质量以及矿物颗粒粒径等统计数据。研究结果表明,影响TIMA分析质量的主要因素为背散射像素间距、能谱测试点间距以及X射线采集计数;实验条件的选择主要取决于样品的矿物成分、粒径和测试分析的目的。     

Microdiamond grade as a regionalised variable – some basic requirements for successful local microdiamond resource estimation of kimberlites

Microdiamonds offer several advantages as a resource estimation tool, such as access to deeper parts of a deposit which may be beyond the reach of large diameter drilling (LDD) techniques, the recovery of the total diamond content in the kimberlite, and a cost benefit due to the cheaper treatment cost compared to large diameter samples. In this paper we take the first step towards local estimation by showing that micro-diamond samples can be treated as a regionalised variable suitable for use in geostatistical applications and we show examples of such output. Examples of microdiamond variograms are presented, the variance-support relationship for microdiamonds is demonstrated and consistency of the diamond size frequency distribution (SFD) is shown with the aid of real datasets. The focus therefore is on why local microdiamond estimation should be possible, not how to generate such estimates. Data from our case studies and examples demonstrate a positive correlation between micro- and macrodiamond sample grades as well as block estimates. This relationship can be demonstrated repeatedly across multiple mining operations. The smaller sample support size for microdiamond samples is a key difference between micro- and macrodiamond estimates and this aspect must be taken into account during the estimation process. We discuss three methods which can be used to validate or reconcile the estimates against macrodiamond data, either as estimates or in the form of production grades: (i) reconcilliation using production data, (ii) by comparing LDD-based grade estimates against microdiamond-based estimates and (iii) using simulation techniques.

     

煤样粒度对煤的视相对密度测定影响探讨

煤是由有机物质和无机物质混合组成,由于自身的特殊性质,影响煤的视相对密度测定因素很多,如样品制备、温度控制、空白试验等。按照GB/T6949-1998《煤的视相对密度测定方法》要求,煤样粒度采用10~13mm,即使严格按照国标制样化验,仍出现化验数据与实际情况不符的现象。大量的对比实验表明:煤样粒度对测试结果影响明显,其中采用4~6mm和6~10mm2个粒级进行煤视相对密度测定实验,结果发现重复性限好。考虑到4~6mm粒度的煤样在涂蜡时容易崩解破裂并易粘蜡屑等缺点,故建议用6~10mm粒度代替国标中的10~13mm粒度进行煤视相对密度的测定。     

Fractionation of U,Th, Ra and Pb from boreal forest soils by sequential extractions

To determine the mobility of natural radionuclides in boreal forest soil, a five-step sequential extraction procedure was carried out on soil samples taken from various depths down to 3 m on Olkiluoto Island, Finland, where there are plans to construct a spent nuclear fuel disposal repository in the bedrock. The extracted fractions studied were exchangeable, acid-soluble, reducible, oxidizable and tightly bound. It was found that the extractability of most of the radionuclides studied was dependent on the sample grain size and depth. All the elements were concentrated in the smallest grain size samples (<0.063 mm). The extraction behaviour of Th, however, did not vary with sample depth, and only about 10% of the Th was extracted by the time of the final extraction step. Stable Pb and ²¹⁰Pb, as well as Ba and Ra concentrations were strongly correlated in the extractions. Radium and Ba were leached more readily than the other elements; approximately 17% of the total Ra was found in the first fraction extracted, representing exchangeable ions. Uranium was more mobile in the topsoil horizons than in the lower horizons. In the topsoil samples, an average of 51% of the extractable U was leached in the second extraction step, representing the elements soluble in weak acids, whereas only 13% of the U in the subsoil samples was extracted in this step. This is probably due to changes in soil redox conditions lower down the soil profile. The extraction behaviour of Pb and Fe also suggests the presence of more reducing conditions in the deeper soil horizons, because the percentage of extractable Pb and Fe in the oxidizable fraction increased with sample depth.     

A Bounding Surface Plasticity Model for Intact Rock Exhibiting Size-Dependent Behaviour

A new constitutive model for intact rock is presented recognising that rock strength, stiffness and stress–strain behaviour are affected by the size of the rock being subjected to loading. The model is formulated using bounding surface plasticity theory. It is validated against a new and extensive set of unconfined compression and triaxial compression test results for Gosford sandstone. The samples tested had diameters ranging from 19 to 145 mm and length-to-diameter ratios of 2. The model captures the continuous nonlinear stress–strain behaviour from initial loading, through peak strength to large shear strains, including transition from brittle to ductile behaviour. The size dependency was accounted for through a unified size effect law applied to the unconfined compressive strength—a key model input parameter. The unconfined compressive strength increases with sample size before peaking and then decreasing with further increasing sample size. Inside the constitutive model two hardening laws act simultaneously, each driven by plastic shear strains. The elasticity is stress level dependent. Simple linear loading and bounding surfaces are adopted, defined using the Mohr–Coulomb criterion, along with a non-associated flow rule. The model simulates well the stress–strain behaviour of Gosford sandstone at confining pressures ranging from 0 to 30 MPa for the variety of sample sizes considered.     

大型原位直剪试验设备改进研制与应用

大型原位直剪试验的试样尺寸大,对土体扰动小,是获取岩土体强度参数的有效方法。中国科学院武汉岩土力学研究所在参考室内、现场两用大型直剪仪后,又改进研制了一套大型原位剪切设备。与传统原位直剪设备不同,该设备采用上、下两个刚性剪切盒,可完成尺寸为50 cm×50 cm×41 cm,最大粒径为5 cm的原位土体试样的剪切试验。该直剪设备组装方便,采用高精度传感器可自动采集数据,更适合于复杂的现场试验环境。介绍了该设备的结构组成、工作原理、技术优点。结合实例详细介绍了大型原位直剪试验的试验方法及注意事项。将此大型原位直剪设备应用于向家坝库区两个滑坡现场试验,得到了滑坡滑带、滑体的原位抗剪强度参数,分析了不同试样大型原位直剪试验剪切曲线的特点,进一步论证了该直剪设备的优良工作性能。     

Analysis of size effects on the geomechanical parameters of intact granite samples under unconfined conditions

A total of 28 uniaxial compressive strength tests were performed on cylindrical Blanco Mera granite samples with diameters ranging between 14 and 100 mm, with results indicating that this granite undergoes a significant reverse size effect: the UCS increases as sample diameter increases up to 54 mm, but thereafter decreases. It was also found that the results tend to be more scattered for smaller sample diameters. We also found an apparent correlation between Young’s modulus and sample diameter. It was not possible to draw any clear conclusions regarding the variability in Poisson’s ratio with sample size. With respect to crack initiation and crack damage stresses, the behaviour of the tested samples also indicates a reverse effect. This research would suggest that the traditionally assumed decrease in strength as sample size increases does not hold for granite samples with diameters below 54 mm.     

Thermal conductivity measurements of road construction materials in frozen and unfrozen state

A series of thermal conductivity measurements for various materials was performed in a large climate chamber. The size of the chamber allowed the preparation of relatively large samples in a controlled thermal environment. Three types of thermal sensors were used: (1) two needle probes; (2) a grid of temperature sensors, evenly distributed inside the sample; (3) two additional thermal probes, which were simplified versions of an instrument originally developed for measuring thermal properties of the ice/dust mixture expected to exist at the surface of a comet nucleus. They consist of a series of individual temperature sensors integrated into a glass fibre rod. Each of these sensors can be operated in an active (heated) or passive (only temperature sensing) mode. The following sample materials were used: fine-grained reddish sand, coarse-grained moist sand, gravels with various grain size distributions from < 1 cm up to about 6 cm, and for comparison and calibration pure water (with convection suppressed by adding agar-agar), compact ice, and compact granite. Of particular interest are the measurements with composite samples, like stones embedded in an agar-agar matrix. We describe the evaluation methods and present the results of the thermal conductivity measurements.     

Rapid Determination of Trace and Ultra Trace Level Elements in Diverse Silicate Rocks in Pressed Powder Pellet Targets by LA‐ICP‐MS using a Matrix‐Independent Protocol

A simple, single sample preparation involving pressed rock powder pellets was utilised to determine the trace and ultra trace abundances of petrogenetically important elements including high field‐strength elements and REEs by laser ablation‐ICP‐MS. One of the elements predetermined by XRF spectrometry served as an internal standard. The influence of sample preparation parameters (grain size, pellet compactness and amount of binding media) on analytical performance was also investigated, including sample homogeneity issues at the laser sampling scale. Line scanning with a high repetition frequency (20 Hz) and large beam diameter (200 μm) ensured ablation from a larger sample surface area, eliminating issues related to sample heterogeneity. A median grain size of about 10 μm for silicate rock powders was found to be sufficiently representative at this scale of laser sampling. Granitic rocks or samples containing resistant minerals such as zircon needed extra grinding to achieve grain sizes down to < 5 μm for better precision for elements that are concentrated in these phases. Using ¹³⁷Ba as an internal standard, reasonable accuracies within 15–20% for most of the high mass trace elements were achieved; in the case of low mass elements, it may deviate up to 40%. Precision of measurements rarely exceeded 15% RSD.