Erosion wear at the bend of pipe during tailings slurry transportation:Numerical study considering inlet velocity,particle size and bend angle

Pipeline hydraulic transport is a highly efficient and low energy-consumption method for transporting solids and is commonly used for tailing slurry transport in the mining industry.Erosion wear(EW)remains the main cause of failure in tailings slurry pipeline systems,particularly at bends.EW is a complex phenomenon influenced by numerous factors,but research in this area has been limited.This study performs numerical simulations of slurry transport at the bend by combining computational fluid dynamics and fluid particle tracking using a wear model.Based on the validation of the feasibility of the model,this work focuses on the effects of coupled inlet velocity(IV)ranging from 1.5 to 3.0 m·s^(-1),particle size(PS)ranging from 50 to 650μm,and bend angle(BA)ranging from 45°to 90°on EW at the bend in terms of particle kinetic energy and incidence angle.The results show that the maximum EW rate of the slurry at the bend increases exponentially with IV and PS and first increases and then decreases with the increase in BA with the inflection point at 60°within these parameter ranges.Further comprehensive analysis reveals that the sensitivity level of the three factors to the maximum EW rate is PS>IV>BA,and when IV is 3.0 m/s,PS is 650μm,and BA is 60°,the bend EW is the most severe,and the maximum EW rate is 5.68×10^(-6)kg·m^(-2)·s^(-1).In addition,When PS is below or equal to 450μm,the maximum EW position is mainly at the outlet of the bend.When PS is greater than 450μm,the maximum EW position shifts toward the center of the bend with the increase in BA.Therefore,EW at the bend can be reduced in practice by reducing IV as much as possible and using small particles.

Experimental study on instability mechanism and critical intensity of rainfall of high-steep rock slopes under unsaturated conditions

Two critical factors,namely intense precipitation and intricate excavation,can trigger rock mass disasters in mining operations.In this study,an indoor rainfall system was developed to precisely regulate the flow and intensity of precipitation.A large-scale model experiment was conducted on a self-designed physical simulation experiment platform to investigate the failure and instability of high-steep rock slopes under unsaturated conditions.The real-time reproduction of the progressive failure process in high-steep rock slopes enabled the determination of the critical rainfall intensity and revealed the mechanism underlying slope instability.Experiment results indicated that rainfall may be the primary factor contributing to rock mass instability,while continuous pillar mining exacerbates the extent of rock mass failure.The critical failure stage of high-steep rock slopes occurs at a rainfall intensity of 40 mm/h,whereas a rainfall exceeding 50 mm can induce critical instability and precipitation reaching up to 60 mm will result in slope failure.The improved region growing segmentation method(IRGSM)was subsequently employed for image recognition of rock mass deformation in underground mines.Herein an error comparison with the simple linear iterative cluster(SLIC)superpixel method and the original region growing segmentation method(ORGSM)showed that the average identification error in the X and Y directions by the method was reduced significantly(1.82%and 1.80%in IRGSM;4.70%and 6.26%in SLIC;9.45%and 12.40%in ORGSM).Ultimately,the relationship between rainfall intensity and failure probability was analyzed using the Monte Carlo method.Moreover,the stability assessment criteria of rock slope under unsaturated condition were quantitatively and accurately evaluated.

Using cemented paste backfill to tackle the phosphogypsum stockpile in China:A down-to-earth technology with new vitalities in pollutant retention and CO_(2) abatement

Phosphogypsum(PG),a hard-to-dissipate by-product of the phosphorus fertilizer production industry,places strain on the biogeochemical cycles and ecosystem functions of storage sites.This pervasive problem is already widespread worldwide and requires careful stewardship.In this study,we review the presence of potentially toxic elements(PTEs)in PG and describe their associations with soil properties,anthropogenic activities,and surrounding organisms.Then,we review different ex-/in-situ solutions for promoting the sustainable management of PG,with an emphasis on in-situ cemented paste backfill,which offers a cost-effective and highly scalable opportunity to advance the value-added recovery of PG.However,concerns related to the PTEs'retention capacity and long-term effectiveness limit the implementation of this strategy.Furthermore,given that the large-scale demand for ordinary Portland cement from this conventional option has resulted in significant CO_(2) emissions,the technology has recently undergone additional scrutiny to meet the climate mitigation ambition of the Paris Agreement and China's Carbon Neutrality Economy.Therefore,we discuss the ways by which we can integrate innovative strategies,including supplementary cementitious materials,alternative binder solutions,CO_(2) mineralization,CO_(2) curing,and optimization of the supply chain for the profitability and sustainability of PG remediation.However,to maximize the co-benefits in environmental,social,and economic,future research must bridge the gap between the feasibility of expanding these advanced pathways and the multidisciplinary needs.

基于微震多参数的大规模岩体垮塌前兆特征研究

微震监测技术能进行工程岩体失稳垮塌前兆特征的辨识和分析,对于地质灾害预警防控具有重要意义。本文基于已有室内岩石受压损伤破坏声发射实验规律,通过开展现场微震多参数定量分析,探究了柿竹园矿山6·21大爆破诱发山体滑移垮塌的前兆特征。大爆破诱发微震事件的b值和空间分形维数表现出下降趋势,b值急剧下降和分形维数降到最低可作为工程岩体失稳垮塌的前兆特征。此外,能量指数和累计视体积的变化可以分别表征应力和应变的变化。能量指数快速下降和累计视体积持续增加的组合特征反映了岩体的失稳状态。经过多个失稳破坏阶段后岩体发生最终的失稳垮塌。该案例表明微震监测能为工程岩体失稳垮塌的预警和防控提供重要信息,也为涉及爆破作业的诸多地质工程活动的安全监测提供了参考。

Particle simulation of the failure process of brittle rock under triaxial compression

In order to investigate the failure process of brittle rock under triaxial compression through both experimental and numerical approaches, the particle simulation method was used in numerical simulations and the simulated results were compared with those of the experiment. The numerical simulation results, such as fracture propagation, microcrack distribution, stress-strain response, and damage patterns, were discussed in detail. The simulated results under various confining pressures （0-60 MPa） are in good agreement with the experimental results. The simulated results reveal that rock failure is caused by axial splitting under uniaxial compression. As the confining pressure increases, rock failure occurs in a few localized shear planes and the rock mechanical behavior is changed from brittle to ductile. Consequently, the peak failure strength, microcrack numbers, and the shear plane angle increase, but the ratio of tensile to shear microcracks decreases. The damage formation during the compression simulations indicates that the particle simulation method can produce similar behaviors as those observed through laboratory compression tests.

Temperature variation characteristics in flocculation settlement of tailings and its mechanism

Rapid flocculation and settlement(FS)of mine tailings is significant for the improvement and development of the filling process,whereas the settlement velocity(SV)of tailings in FS has been recognized as a key parameter to evaluate the settlement effect.However,the influence of temperature on the SV and its mechanism have not been studied.FS experiments on tailings with various ambient temperatures were carried out.The SVs of tailings with a solid waste content of 10wt%and an anionic polyacrylamide content of 20 g·t^−1 were measured at different temperatures.The SV presented an“N”-shaped variation curve as the temperature changed from 5 to 40℃.The mechanism of these results can be explained from the perspective of the electric double-layer repulsive force,molecular dynamics,and the polymer flocculation principle,as revealed from the scanning electron microscopy of floc particles.The findings will be beneficial in the design of tailings dewatering processes and save costs in the production of cemented paste backfill.

Surface property variations in flotation performance of calcite particles under different grinding patterns

基于料层粉碎工作方式,高压辊磨制备的矿物颗粒具有区别于其他磨矿方式制备颗粒的表面特性,对矿物浮选会产生较大的影响。本文研究了高压辊磨、颚式破碎、干式球磨、湿式球磨及湿式棒磨下方解石纯矿物颗粒的浮选行为,并通过比表面积、粒径分布、原子力学显微镜、表面电子能谱及动电位等手段表征了不同磨矿方式制备颗粒的表面特性以揭示其浮选机理。结果表明:当磨矿细度较低时,相比于其他磨矿方式高压辊磨制备的方解石颗粒在油酸钠和十二胺体系均能够获得更好的浮选指标;由磨矿方式导致的矿物颗粒比表面积、粒度分布、表面粗糙度、Fe^(3+)沾染物、键合能及Zeta电位差异是其浮选行为差异化的主要原因。

Physiological responses of people in working faces of deep underground mines

The research studied the influences of high temperature, high pressure, high humidity, noise and other harmful factors in mining conditions on the people health and safety, and investigated the impacts of confined environmental on human physiology factors, including temperature, humidity, noise, pressure,toxic and harmful gases in terms of environmental characteristics in underground mines and an artificial intelligence system for simulation of the environment in a confined space of deep mines. Our results show that the systolic pressure, diastolic pressure, mean pressure, heart rate, respiratory rate, typing test speed and memory level percentage are negatively correlated with temperature value, and positively correlated with humidity value; the human temperature and weight are positively correlated with temperature value, and negatively correlated with humidity value. This research lays the foundation for the study of interaction between the deep confined space environment and safety behavior.

An Innovative Non-Pillar Coal-Mining Technology with Automatically Formed Entry: A Case Study

A non-pillar coal-mining technology with an automatically formed entry is proposed,which reduces the waste of coal resources and the underground entry drivage workload.Three key techniques in this technology cooperate to achieve automatic formation and retaining of the gob-side entry,and to realize nonpillar mining.Constant-resistance large deformation(CRLD)support ensures the stability of the entry roof;directional presplitting blasting(DPB)separates the entry roof and the gob roof;and a blockinggangue support system(BGSS)integrates the caved rock material as an effective entry rib.An industrial test was conducted to verify the engineering effects of these key techniques.The field application results showed that the retained entry was under the pressure-relief zone due to the broken-expansion nature of the caved rock mass within the DPB height.After going through a provisional dynamic pressure-bearing zone,the retained entry entered the stability zone.The final stable entry meets the requirements of safety and production.The research results demonstrate the good engineering applicability of this technology.By taking the framework of the technology design principles into consideration and adjusting the measures according to different site conditions,it is expected that the proposed non-pillar coal-mining technology can be popularized on a large scale.

Characteristics of mineral element content of alpine vegetation in permafrost region on Qinghai-Tibetan Plateau

The content characteristics of 16 elements （Al, Ca, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Sr, and Zn） in 23 plant species collected from the Qinghai-Tibetan Plateau permafrost region were investigated using ICP-OES. Results show that the average contents of Ca, K, Mg, Fe and P were higher than 1,000 mg/kg, those of Al, Na, Zn and Cr ranged between 10-1,000 mg/kg and those of Cu, Li, Pb and Mo were less than 10 mg/kg. The levels of Al, Ca, K, Mg and Na were within the scope of the reported terrestrial plant element content, those of Sr, Fe and Cr were higher than the average of the terrestrial plants and the maximum content of Max was higher than the upper limit of the reported Mn content. The main character of the element content was of the Ca〉K type, however, in terms of Cyperaeeae species the element content character was K〉Ca type. The contents of Ca, Li, Mg and Sr in Gramineae and Cyperaeeae species were higher than those in other species and the contents of Ca, K, Mg, Fe, E A1 and Na in all collected plants were higher than those of other elements. Zn had weak variability with the lowest coefficient （i.e., 7.81%）, while other elements had strong variability. The ratio of maximum content to minimum content indicated Ca and K had less change than other elements in the Qinghai-Tibetan Plateau permafrost region. Element content of alpine vegetation in the Qinghai-Tibetan Plateau permafrost region mainly shows a positive correlation, among which the correlation coefficient between Al and Pb, Al and Fe, Mo and Cr, Pb and Fe, Sr and Li were higher than 0.9, and negative correlation had no statistical signifi- cance. The correlation between Al and Fe, Mg, Mn in the Qinghai-Tibetan Plateau permafrost region were consistent with that reported in Kunlun Mountains.

Micro-macro evolution of mechanical behaviors of thermally damaged rock:A state-of-the-art review

The influence of thermal damage on macroscopic and microscopic characteristics of different rocks has received much attention in the field of rock engineering.When the rocks are subjected to thermal treatment,the change of macroscopic characteristics and evolution of micro-structure would be induced,ultimately resulting in different degrees of thermal damage in rocks.To better understand the thermal damage mechanism of different rocks and its effect on the rock performance,this study reviews a large number of test results of rock specimens experiencing heating and cooling treatment in the laboratory.Firstly,the variations of macroscopic behaviors,including physical parameters,mechanical parameters,thermal conductivity and permeability,are examined.The variations of mechanical parameters with thermal treatment variables(i.e.temperature or the number of thermal cycles)are divided into four types.Secondly,several measuring methods for microstructure,such as polarizing microscopy,fluorescent method,scanning electron microscopy(SEM),X-ray computerized tomography(CT),acoustic emission(AE)and ultrasonic technique,are introduced.Furthermore,the effect of thermal damage on the mechanical parameters of rocks in response to different thermal treatments,involving temperature magnitude,cooling method and thermal cycle,are discussed.Finally,the limitations and prospects for the research of rock thermal damage are proposed.

温度和pH值对全尾砂膏体流变特性的影响

本文研究了在不同温度和pH值条件下,温度和pH值对全尾砂膏体流变特性的影响及其影响机制。在不同温度和pH值的条件下制备全尾砂膏体,温度控制分别设置在10,20,30,40和50℃,pH值控制分别设置为3,7和13。对制备完成的全尾砂膏体进行流变剪切试验、热重实验(TG&DTG),傅立叶变换红外光谱实验(FT-IR)和扫描电子显微镜分析(SEM)。研究结果表明,温度对全尾砂膏体的流变特性有显著影响,而pH值对全尾砂膏体的流变特性的影响相对较小。在相同的pH值条件下,较高温度(超过20℃)的全尾砂膏体易产生较高的剪切应力、屈服应力和表观黏度,但过高的温度(50℃)无法达到更高的表观黏度。在同一温度、pH值为3和13时的非中性环境下,全尾砂膏体的剪切应力和表观黏度较中性条件都有所增强。相同温度下(低于50℃),pH值的升高会导致全尾砂膏体产生两种不同的屈服应力和表观黏度曲线。微观分析表明,全尾砂膏体的流变特性受温度和pH值的影响,温度和pH值会影响全尾砂膏体中水泥的水化过程、水化速率及水化产物的空间结构。

温度和龄期对砾石砂胶结充填体物理力学性能的影响

深部矿山胶结充填体在未来数十年里将不可避免地会暴露在20~60℃的环境温度中。本文制备了两种砾石砂胶结充填体,即棒磨砂胶结充填体(CRB)和戈壁砂胶结充填体(CGB),并分别在不同温度(20℃、40℃、60℃)和龄期(3 d、7 d、28 d)条件下进行了养护;然后,基于室内试验探索了温度和龄期对CRB和CGB物理力学特性的影响效应。结果表明:1)温度和龄期对充填体物理力学特性的影响主要取决于水化产物量和胶结结构密实度,温度对早期充填体热膨胀性和超声性能的影响更为显著;2)温度和龄期对CGB抗压强度的促进作用要强于CRB,随着温度的升高,试样的压缩破坏形式由X-共轭剪切破坏转变为拉伸破坏,试样的完整性得到了显著改善;3)同样CGB的抗剪性能普遍优于CRB,温度对充填体抗剪强度的影响较龄期要弱,但剪切变形和剪切面破坏形态与温度密切相关。

基于基团贡献法和热力学第二定律模型对有机朗肯循环(ORCs)工质的评估（英文）

基团贡献(GC)法一般用于预测有机物的热力学属性参数,但对过程指标的预测能力有限,如热力循环过程的效率。本文发展了一种结合GC 法和有机朗肯循环(ORC)热效率解析模型的方法,可以高效快速地估算有机朗肯循环的热效率,从而在某种程度上克服GC 方法的局限性。利用GC 法与ORC热效率解析模型,筛选了60 多种用于中低温有机朗肯循环的有机工质。首先,运用GC 方法预测了60 多种有机工质的临界温度Tc,临界压力Pc,潜热r,液体的定压比热容c 等热力学属性。其次,基于由热力学第二定律推得的ORC 解析模型,可直接由GC 法预测的热力学参数直接确定ORC 的输出功wout 和热效率η等性能指标。计算结果表明,与NIST 数据相比,本文采用的GC 模型具有足够的精度来估算热力学参数(Tc,Pc,r,c,wout,η的平均相对误差分别为4.45%,9.29%,5.85%,11.5%,10.8%,2.9%)。其中热效率的平均相对误差最小(约为2.9%),且所有预测值的误差在0~24%的范围内。本研究表明GC 方法与ORC 解析模型结合,不仅提供了一种估算热效率的直接方法(无需状态方程),并且提供了一种快速准确的方法来评估有机工质的热力学性能。本文研究成果也为指导基于GC 法的ORC 有机工质计算机辅助设计提供借鉴。

不同剪切方向作用下矿石-充填体耦合试样剪切行为的温度效应

为了理解深部高水平应力条件下温度对矿石-充填体耦合结构体剪切特性的影响效应,分别对不同温度(20,40,60°C)下棒磨砂胶结充填体(CRB)和矿石-充填体耦合试样(OCRB)开展直剪试验,并对不同剪切方向作用下OCRB的剪切行为及AE特征参数进行比较分析。结果表明:温度对CRB剪切性能的影响主要取决于其微观结构和主要矿物相特性,且在40°C时的性能相对较优;OCRB的剪切变形较CRB增加了“峰值波动阶段”,且与AE特征参数有良好的相关性,温度对OCRB的剪切强度既可以是正面影响也可以是负面影响,这取决于温度值大小和剪切作用方向;沿轴向(D1)方向OCRB的剪切性能明显优于垂直于轴向(D2)方向的,矿石-充填体耦合结构(即采场)的共同承载性能与环境温度和主应力方向密切相关。

Trace Metal Concentration in Two Matrices in an Urban Subtropical River

This study investigates the concentration of metals namely aluminium, manganese and cobalt in two matrices: sediment and fish organs (whole muscle stomach tissue, gills, liver and kidney) in an urban river, Mukuvisi River, Zimbabwe. River bed sediments and fish samples were collected simultaneously at five sites over seven months (September 2008-April 2009). Concentrations of aluminium, manganese and cobalt in the selected fish organs and sediment were estimated using the Flame Atomic Absorption Spectrometry (FAAS). Water limnochemical aspects, dissolved oxygen, pH, temperature and conductivity were measured concomitantly at each site. Aluminium had significantly higher mean concentrations and bioconcentration factors in both sediments and fish tissues relative to cobalt and manganese. Cobalt and aluminium were detected in all fish tissues, whilst manganese was not detected in muscle and liver. Significant differences in bioconcentration factors for the metals in organs of the same fish species analysed in this study show differences in metal assimilation. Metal specific river rehabilitation methods need to be applied for the future restoration of the ecological integrity of Mukuvisi River.

Effect of magnetic field on elements segregation in electroslag ingot

In order to improve the production efficiency of electroslag remelting process and the solidification quality of electroslag ingot,a novel electroslag furnace with electromagnetic stirring was designed and the effects of external magnetic field and different electrical parameters on electroslag remelting process were studied.The distribution of carbon,chromium,phosphorus and compactness in electroslag ingot was analyzed through original position analysis apparatus.Results show that the external magnetic field accelerates the remelting of consumable electrode.Under the condition of remelting voltage of 34 V and current of 1500 A,the remelting rate of metal consumable electrode increases from 20 to 27 mm min−1 when the magnetic induction intensity of 62×10^(−4) and 108×10^(−4) T is applied.However,the remelting current decreases from 1500 to 1100 A under the condition of constant remelting rate and remelting voltage,thereby reducing the energy consumption.The effect of external magnetic field on the segregation of different elements in electroslag ingot is different.Under the experimental conditions,the carbon segregation is unremarkable,but the phosphorus segregation is improved when the electromagnetic force generated by the interaction between the external magnetic field and the remelting current is small.However,the excessive electromagnetic force aggravates the segregation of carbon and phosphorus.With the increase in electromagnetic force,the chromium segregation gradually increases.

Determination of activity interaction parameters of Nb in Fe-C-Nb melts at 1873 K

The interaction parameters of Nb in Fe-C-Nb melts at 1873 K were measured using the chemical equilibrium method.The Fe-C melts were equilibrated with the CaO-MgO-Al_(2)O_(3)-NbO_(2) slags under a controlled oxygen potential for 24 h.In addition to acting as the protective gas,argon was adopted to control the oxygen potential.Based on the data obtained in the experiments,the activity interaction parameters were obtained by the multiple linear regression method.The first-order interaction parameters e_(Nb)^(C)and e_(Nb)^(Nb)are determined to be−0.035 and−0.134,respectively.The second-order interaction parameters r_(Nb)^(C),r_(Nb)^(Nb,C),and r_(Nb)……(Nb)are determined to be 0.011,−0.0063,and 0.0023,respectively.The thermodynamic data obtained are more reliable than those in previous publications for the Fe-C-Nb system when the Nb content range was 0.92-4.62 wt.%.

Separation/degradation behavior and mechanism for cationic/anionic dyes by Ag-functionalized Fe_(3)O_(4)-PDA core-shell adsorbents

High-performance adsorbents have been well-studied for the removal of organic dye pollutants to promote environment remediation.In this study,an Ag nanoparticle-functionalized Fe_(3)O_(4)-PDA nanocomposite adsorbent(PDA-Fe_(3)O_(4)-Ag)was synthesized,and the adsorption/separation performance of commonly used cationic and anionic organic dyes by the PDA-Fe_(3)O_(4)-Ag adsorbent were assessed.Overall,PDA-Fe_(3)O_(4)-Ag exhibited a significantly higher adsorption capacity for cationic dyes compared to anionic dyes,the highest of which was more than 110.0 mg/g(methylene blue(MB)),which was much higher than not only the adsorption capacities of the anionic dyes in this study but also other dye adsorption capacities reported in the literature.The dye adsorption kinetics data fitted well to both the pseudo second-order kinetics model and the Langmuir isotherm model,suggesting a monolayer-chemisorption-dominated adsorption mode.Thermodynamics analysis indicated that the adsorption process was both endothermic and spontaneous.Furthermore,the PDAFe_(3)O_(4)-Ag adsorbent achieved high photodegradation removal rates of the dyes,especially neutral red(NR)and methyl orange(MO),which were 91.2%and 87.5%,respectively.With the addition of PDA-Fe_(3)O_(4)-Ag,the degradation rate constants of NR and MO increased from 0.08×10^(−2)and 0 min^(−1)to 2.11×10^(−2)and 1.73×10^(−2)min−1,respectively.The high adsorption and photocatalytic degradation performance of the PDA-Fe_(3)O_(4)-Ag adsorbent make it an excellent candidate for removing cationic and anionic dyes from the industrial effluents.