Prospects of the method of stepwise crushing as a source of information on the fluid phase of rocks and minerals

This paper illustrates opportunities provided by the method of stepwise crushing for the investigation of the fluid phase of geologic objects. Owing to the efficient separation of gases from fluid inclusions of different generations trapped during mineral growth and/or subsequent alteration (metasomatic and hydrothermal), stepwise crushing allows us to obtain the isotopic characteristics of end-members and, thus, reliably establish the source and evolution of fluids in magmatic and postmagmatic processes; this method provides clues to a better understanding of interaction of global reservoirs, such as the mantle, crust, and atmosphere. The importance of information obtained by this method is exemplified here by the results of the investigation of mantle rocks and minerals from various geologic environments (MORB, SCLM, and carbonated mantle). It was shown that the multi-isotope approach yields most comprehensive data on the genetic features and evolution of the fluid phase. The importance of combining isotope geochemical and microthermometric fluid inclusion data is demonstrated by the example of a mantle xenolith of garnet lherzolite from the Jetty Oasis. Together with the microthermometric investigation of fluid inclusions and developing laser techniques for opening of individual inclusions, the method of stepwise crushing provides a means for solving one of the most important practical problems—obtaining information on the geochemical features and physicochemical parameters of mineral-forming (and ore-forming) processes.     

Shear sliding failure of the jointed roof in laminated rock mass

Summary The jointed roof in laminated rock mass may be capable of self-support and sustaining transverse load and can be analysed by the voussoir beam notation. There are three main failure modes of a voussoir beam structure: crushing in the high stress areas, buckling without localised material failure and shear sliding along the joints. Previous studies on the voussoir beam have concentrated on the crushing failure mode, assuming that the voussoir beam would not fail by shear sliding prior to reaching its crushing strength. However, the possibility exists that the voussoir beam may collapse by shear sliding along the joints with a strength much lower than that predicted by the estimation method for crushing failure, depending upon the joint properties. Hence the stability analysis of a jointed roof without considering the shear sliding failure may lead to disastrous consequences. In this paper a numerical and experimental study has been carried out to analyse the shear sliding failure of voussoir beams containing vertical and inclined joints with one or more mid joints. Equations for verification of shear sliding are proposed and effects of the voussoir beam geometry and material properties on the shear sliding failure are also discussed.     

A combined method to model grain crushing with DEM

This paper presents a combined method to model grain crushing effects with discrete element method.This method combines the two most commonly used concepts to model grain crushing in DEM,i.e.the replacement method and the agglomerate method,so that it is both accurate and efficient.The method can be easily implemented.The performance is shown by several DEM simulations of biaxial tests.Particles with different crush-abilities are modeled.DEM simulation results with and without grain crushing are compared and discussed.The change of grain size distribution due to grain crushing is also investigated.     

基于线性拟合的颗粒材料破碎状态表征

在荷载等因素作用下发生颗粒破碎是岩土材料的固有属性,选择合适的颗粒破碎状态表征指标是颗粒破碎问题研究中首先要解决的问题。基于颗粒破碎导致细颗粒含量增加,级配曲线抬升并趋向于分形的客观事实,提出了利用级配曲线的拟合直线的斜率和相关系数的变化规律描述颗粒破碎状态及其演化的新方法。在该基础上,提出了表征颗粒破碎状态的破碎分形指数及破碎分形相关性指数的概念,阐述了二者随颗粒破碎的发展规律。与试验结果对比表明,提出的状态指标与试验结果能够很好的吻合,颗粒破碎状态存在明确的对应关系,能够表征颗粒破碎难易程度及其发展趋势,为研究颗粒破碎问题提供了新思路。     

堆石料单粒强度尺寸效应的颗粒流模拟方法研究

围绕堆石料单粒强度尺寸效应的颗粒流模拟方法展开研究。首先,基于FISH二次开发建立了堆石料的随机不规则单粒模型,充分考虑堆石料的形状特征和破碎现象;然后,建立了堆石料单粒强度尺寸效应的等效模拟方法,以单粒强度随其粒径的变化规律为基础,推导了堆石料模型中细观黏结强度与堆石料等效粒径的负指数经验公式;其次,基于建立的数值模型对堆石料的室内单粒压缩试验进行仿真模拟,验证数值模型的正确性和合理性,并对较大粒径堆石料的单粒强度进行模拟预测,突出数值试验的优势;最后,基于建立的数值模型对相同粒径不同形状特征堆石料的单粒强度分布特征进行模拟研究。研究结果表明：（1）堆石料内部缺陷含量和尺寸随粒径增加对其单粒强度所产生的尺寸效应,可通过堆石料模型中细观强度参数随粒径折减进行等效模拟;（2）形状特征对堆石料的破裂机制具有重要影响,方形颗粒为压剪破裂,单粒强度较高,而随机不规则颗粒和圆形颗粒为拉剪或劈裂,单粒强度相对较低;（3）拉剪或劈裂条件下,堆石料形状越不规则,其单粒强度的离散程度越高,反之则离散程度越低。相关研究成果可为进一步研究荷载作用下堆石体内各粒径段堆石料的破碎量奠定基础,从而更加真实地反映堆石体的级配演化规律。     

Grain-size distribution of subglacial till and its realtion to glacial scrushing and abrasion

A subglacial till formed from a sandstone bedrock has a variable grain-size distribution which reflects its variable genesis. Glacial comminution processes were simulated by artificial mill experiments with fragments of the sandstone bedrock. Pure crushing caused disintegration along mineral boundaries into separate minerals, most mineral grains retaining their primary size during the crushing process. Abrasion produced cracks across the minerals and resulted in silt-sized rock flour. The experiments indicate that most of the sand-sized till material formed as a result of crushing, while the silt is mainly the result of abrasion. The sand and silt are both regarded as components resistant to further glacial comminution, but are formed by different comminution processes. By considering also the coarser till material, the general principles of glacial breakdown of resistant rocks from boulders to sand or silt can be illustrated. A matrix index and an abrasion index based on the mill experiments distinguish well between genetically different subglacial till types     

Multidimensional spectrum estimation for nonstationary processes

A spectrum estimation method for multidimensional nonstationary processes has been developed. The estimation method has been applied to a nonstationary two-dimensional random field. The numerical findings show that the results of the estimations are about what can be expected from a multidimensional estimation for a nonstationary process.     

矿石崩落块度的三维建模技术及块度预测

以金川集团Ⅲ矿区为研究对象,根据现场不连续面参数调查结果,利用Monte Carlo模拟方法,产生不连续面综合数据库。然后确定构成岩块的节理面数量、建立三维坐标系统中节理面方程、确定构成岩块的顶点和每个顶点的坐标,并计算岩块的体积、判别岩块的形状特征,从而对矿石崩落块度进行预测。矿石的崩落块度直接影响采场的底部结构设计、出矿设备的选择、二次破碎、炸药消耗的估算等。经过模拟得出的崩落块度预测结果为: 等效尺寸大于0.9 m的块体筛上累积体积百分比为38.2 %,大于1.3 m的块体筛上累积体积百分比为17.2 %。     

多块体形状堆石体碾压颗粒破碎数值模拟

通过6种典型堆石块体的形状近似,分别采用两种接触本构模型建立了多块体形状堆石体离散元数值模型,研究堆石体在碾压荷载作用下的颗粒破碎过程,建立颗粒破碎的量化计算方法,分析碾压前、后堆石级配曲线的变化,讨论接触本构模型和颗粒形状对块体破碎的影响。模拟结果显示,碾压荷载下堆石颗粒以张拉破碎为主,随着碾压遍数的增加,局部开始出现剪切破碎;提出的颗粒破碎量化计算方法,在大粒径范围对粒径变化幅度预测偏大,但级配曲线整体趋势与实测结果比较吻合;相比较于接触连接模型,平行连接模型与现场碾压试验结果更接近。6种块体形状的数值结果显示,随着形状系数的增加,在其他条件不变的情况下颗粒破碎率逐渐降低,其中类长方形块体在碾压荷载作用下颗粒破碎最明显。相比较于纯圆颗粒或者单一非圆颗粒,采用的6种颗粒形状建立的堆石体振动碾压离散元模型,更接近现场实际情况。     

Cone crusher chamber optimization using multiple constraints

The chamber geometry is one of the key factors that influences the performance of a cone crusher. The design of the chamber geometry should take product quality and crushing efficiency into account. In this paper the kinematics of rock material in a crushing chamber, as interparticle breakage occurs, has been analyzed and the chamber division is achieved. Based on the chamber division and a population balance model, the method for chamber geometry design is presented. Combining the empirical model for predicting particle shape with the size distribution model, a flakiness prediction model is proposed. With the size reduction model and flakiness prediction model as constraints, an optimization of the crushing chamber is achieved. Finally, the validity of the crushing chamber optimization model has been verified by an appropriate prototype test.     

Quantification of particle crushing in consideration of grading evolution of granular soils in biaxial shearing: A probability‐based model

A probability‐based model is presented to estimate particle crushing and the associated grading evolution in granular soils during isotropic compression and prepeak shearing in biaxial tests. The model is based on probability density functions of interparticle and intraparticle stress (ie, particle normalized maximum shear stress and particle average maximum shear stress) derived from discrete element method simulations of biaxial tests. We find that the probability density functions of normalized maximum shear stress are dependent on the current sample grading, implying coupling effects between particle crushing and sample grading such that the particle crushing is affected by the current sample grading, and the grading change is also dependent on the current particle crushing extent. To incorporate these coupling effects into the model, particle crushing and grading change are calculated for each load increment, in which the crushing probability of a particle during any loading increment is denoted as the corresponding increment of probability of the internal maximum shear stress exceeding its maximum shear strength. The model shows qualitative agreement with published experimental data. The effects of the model parameters, including initial porosity, particle strength, initial grading, and crushing mode, on the calculated results are discussed and compared with previous studies. Finally, the strengths and limitations of the model are discussed.     

A constitutive model for granular materials with grain crushing and its application to a pyroclastic soil

A constitutive model for granular materials is developed within the framework of strain–hardening elastoplasticity, aiming at describing some of the macroscopic effects of the degradation processes associated with grain crushing. The central assumption of the paper is that, upon loading, the frictional properties of the material are modified as a consequence of the changes in grain size distribution. The effects of these irreversible microscopic processes are described macroscopically as accumulated plastic strain. Plastic strain drives the evolution of internal variables which model phenomenologically the changes of mechanical properties induced by grain crushing by controlling the geometry of the yield locus and the direction of plastic flow. An application of the model to Pozzolana Nera is presented. The stress–dilatancy relationship observed for this material is used as a guidance for the formulation of hardening laws. One of the salient features of the proposed model is its capability of reproducing the stress–dilatancy behaviour observed in Pozzolana Nera, for which the minimum value of dilatancy always follows the maximum stress ratio experienced by the material. Copyright © 2002 John Wiley & Sons, Ltd.     

矿山地质环境治理中坚硬岩石削坡方法比较和优化

对各种岩性的山体进行削坡减载是矿山地质环境治理项目中的重要工程。以江苏省某地矿山环境治理项目为例,对高边坡坚硬石体削坡的“露岩爆破法”、“膨胀剂破碎法”、“二氧化碳致裂法”、“机械破碎法”4种方法进行了比较和优化,在分析了该工程的施工重点、难点的基础上,选用“二氧化碳致裂法”施工,取得了良好的效果。详细介绍了工程的施工工艺、施工过程等,总结了相关经验,对用“二氧化碳致裂法”施工进行了进一步的思考。     

Grain crushing in geoscience materials-Key issues on crushing response,measurement and modeling:Review and preface

Grain crushing is commonly encountered in deep foundation engineering,high rockfill dam engineering,railway engineering,mining engineering,coastal engineering,petroleum engineering,and other geoscience application.Grain crushing is affected by fundamental soil characteristics,such as their mineral strength,grain size and distribution,grain shape,density and specimen size,and also by external factors including stress magnitude and path,loading rate and duration,degree of saturation,temperature and geochemical environment.Crushable material becomes a series of different materials with the change in its grading during grain crushing,resulting in a decrease in strength and dilatancy and an increase in compressibility.Effects of grain crushing on strength,dilatancy,deformation and failure mechanisms have been extensively investigated through laboratory testing,discrete element method(DEM)modelling,Weibull statistics,and constitutive modelling within the framework of the extended crushing-dependent critical state theory or the energy-based theory.Eleven papers summarized in this review article for this special issue addressed the above issues in grain crushing through the advanced testing and modelling.     

Grain Size Effect of Calcite on Calcination: A Case Study from Afyon (Western Turkey)

Limestones have been one of the major economic sources in state’s economy and becoming more and more important in recent years. They are mainly exploited for crushed stone, dimension stone and micronized calcite production including lab-grade CaO with high purity. Although some of the applications require fairly simple value-adding processes such as crushing and/or sizing, some may require rather complicated processes such as calcination and coating.     

322矿田铀矿床原地破碎浸出地质技术评估

本文从原地破碎浸出法采矿要求出发，对322铀矿田碎裂蚀变花岗岩型铀矿床（点）的地质构造、岩／矿石物质成分、矿石结构、铀的赋存形式、岩／矿石物理力学参数、矿体形态、产状、规模及矿床水文地质条件进行了研究；通过原地爆破筑堆试验及一系列铀矿的柱浸工艺试验，获得了大量原地破碎浸出参数；运用原地破碎浸出法适用性评价模型对其进行了评价，认为该矿田碎裂蚀变花岗岩型铀矿床适宜采用原地破碎浸出法开采。     

馏化法处理垃圾新工艺探讨

为了适应环保部门提出的更高的环保要求,减少因焚烧垃圾产生的CO2含量,从而达到节能减排的目标,在大量实验和计算研究的基础上,提出了采用馏化法处理垃圾的新工艺。馏化法主要是垃圾中的炭质不参加燃烧,不产生CO2和CO,不破坏空气中的主要成分,做到无害生产。馏化法处理垃圾的设备由喷淋系统及滚动筛、不锈钢输送带、隧道式烘干炉及馏化炉、烘干焦化炉、粉碎机、液压成型机等组成。主要的配套工艺有垃圾干馏炭化制砖工艺和垃圾三角条幅填海工程工艺。该馏化法处理垃圾解决了减少CO2排放问题,而炭渣填海方法做到零污染、全利用效果,具有客观的经济效益。     

Multiscale estimation of the Freundlich adsorption isotherm

Adsorption plays an important role in water and wastewater treatment. The analysis and design of processes that involve adsorption rely on the availability of isotherms that describe these adsorption processes. Adsorption isotherms are usually estimated empirically from measurements of the adsorption process variables. Unfortunately, these measurements are usually contaminated with errors that degrade the accuracy of estimated isotherms. Therefore, these errors need to be filtered for improved isotherm estimation accuracy. Multiscale wavelet based filtering has been shown to be a powerful filtering tool. In this work, multiscale filtering is utilized to improve the estimation accuracy of the Freundlich adsorption isotherm in the presence of measurement noise in the data by developing a multiscale algorithm for the estimation of Freundlich isotherm parameters. The idea behind the algorithm is to use multiscale filtering to filter the data at different scales, use the filtered data from all scales to construct multiple isotherms and then select among all scales the isotherm that best represents the data based on a cross validation mean squares error criterion. The developed multiscale isotherm estimation algorithm is shown to outperform the conventional time-domain estimation method through a simulated example.     

基于PFC2D岩石颗粒破碎强度和能量的分形模型

颗粒的破碎强度随着粒径的增大而减小,即颗粒破碎的尺寸效应,分形模型为解释固体颗粒破碎的尺寸效应提供了可行的方法。根据岩石颗粒破碎时的分形特征,采用Sammis破碎准则,通过模拟分析得出岩石颗粒破碎能量和强度的分形模型,建立和验证用分维D来表示岩石颗粒破碎的能量和强度准则,得出并验证了岩石颗粒破碎分维的确定方法。利用离散元软件PFC2D的黏结颗粒模型BPM（Bonded Particle Model）模拟了小孔隙率n=0.12和大孔隙率n=0.3,即密实和松散两种情况。其中小孔隙率采用在模型上添加小颗粒的新方法,分别做了400组粒径不等的数值模拟试验,从粒径与破碎强度、破碎能量之间的关系和应力-应变曲线3个方面进行了统计,验证了岩石颗粒破碎强度与分维D的理论关系为σ_f∝dD-3,并得出颗粒破碎时的能量和与分维D之间的关系为E_f∝dD-1。验证了分形理论在分析颗粒破碎的尺寸效应中的较好应用,为确定岩石颗粒的破碎强度和岩石堆砌体剪切强度提供新的方法和参考意见。     

考虑土石料颗粒破碎和密度变化的次塑性本构模型建模方法

试验和现场观测都发现高土石坝的坝料在高压及湿化作用下会发生显著的颗粒破碎,颗粒破碎会改变土石料的级配曲线和密度,因而影响其后继力学行为,因此,土石料的颗粒破碎是当前岩土工程领域的研究热点。为了模拟土石料在高压及湿化作用下发生显著的颗粒破碎现象,以及循环加载中的颗粒破碎与应力诱导各向异性随动硬化共同影响下土石料的变形,本文提出了一个建模方法,考虑土石料颗粒破碎和密度变化的影响。所建议的次塑性本构模型在经过试验资料的验证后可用于动力有限元数值计算。