Disturbance failure mechanism of highly stressed rock in deep excavation:Current status and prospects

This article reviews the current status on the dynamic behavior of highly stressed rocks under disturbances.Firstly,the experimental apparatus,methods,and theories related to the disturbance dynamics of deep,high-stress rock are reviewed,followed by the introduction of scholars’research on deep rock deformation and failure from an energy perspective.Subsequently,with a backdrop of highstress phenomena in deep hard rock,such as rock bursts and core disking,we delve into the current state of research on rock microstructure analysis and residual stresses from the perspective of studying the energy storage mechanisms in rocks.Thereafter,the current state of research on the mechanical response and the energy dissipation of highly stressed rock formations is briefly retrospected.Finally,the insufficient aspects in the current research on the disturbance and failure mechanisms in deep,highly stressed rock formations are summarized,and prospects for future research are provided.This work provides new avenues for the research on the mechanical response and damage-fracture mechanisms of rocks under high-stress conditions.

Separation of Pd and Pt from highly acidic leach liquor of spent automobile catalysts with monothio-Cyanex 272 and trioctylamine

Platinum group metals(PGMs),especially Pd,Pt,and Rh,have drawn great attention due to their unique features.Direct separation of Pd and Pt from highly acidic automobile catalyst leach liquors is disturbed by various factors.This work investigates the effect of various parameters including the acidity,extractant concentration,phase ratio A/O,and diluents on the Pd and Pt extraction and their stripping behaviors.The results show that the Pd and Pt are successfully separated from simulated leach liquor of spent automobile catalysts with monothioCyanex 272 and trioctylamine(TOA).Monothio-Cyanex 272 shows strong extractability and specific selectivity for Pd,and only one single stage is needed to recover more than 99.9% of Pd,leaving behind all the Pt,Rh,and base metals of Fe,Mg,Ce,Ni,Cu,and Co in the raffinate.The loaded Pd is efficiently stripped by acidic thiourea solutions.TOA shows strong extractability for Pt and Fe at acidity of 6 mol·L^(–1) HCl.More than 99.9% of Pt and all of the Fe are extracted into the organic phase after two stages of countercurrent extraction.Diluted HCl easily scrubs the loaded base metals(Fe,Cu,and Co).The loaded Pt is efficiently stripped by 1.0 mol·L^(–1) thiourea and 0.05–0.1 mol·L^(–1) Na OH solutions.Monothio-Cyanex 272 and TOA can realize the separation of Pd and Pt from highly acidic leach liquor of spent automobile catalysts.

Petroleum coke as reductant in co-reduction of low-grade laterite ore and red mud to prepare ferronickel: Reductant and reduction effects

Petroleum coke is industrial solid wastes and its disposal and storage has been a great challenge to the environment. In this study, petroleum coke was utilized as a novel co-reduction reductant of low-grade laterite ore and red mud. A ferronickel product of 1.98wt% nickel and 87.98wt% iron was obtained with 20wt% petroleum coke, when the roasting temperature and time was 1250°C and 60 min, respectively. The corresponding recoveries of nickel and total iron were 99.54wt% and 95.59wt%, respectively. Scanning electron microscopy-energy dis- persive spectrometry (SEM-EDS) analysis showed metallic nickel and iron mainly existed in the form of ferronickel particles which distrib- uted uniformly at a size of approximately 30 μm with high purity. This study demonstrated that petroleum coke is a promising reductant in the co-reduction of laterite ore and red mud. Compared to other alternatives, petroleum coke is advantageous with reduced production cost and high applicability in anthracite-deficient areas.

Loading capacity and emulsification phenomena of HREE extraction by dialkylphosphinic acids with different β,γ,δ-substituents

The relationship between dialkylphosphinic acid structure and their loading capacity for HREEs and emulsification phenomena has rarely been studied.In this paper,we took Lu extraction as an example to study the effect of β,γ,δ-substituents of dialkylphosphinic acids on their loading capacity and anti-emulsification performance for HREEs.To discuss conveniently,the dialkylphosphinic acids were classified into two groups:β-substituent group(P208,INET-1,P218,USTB-1 and P227)and γ,δ-substituent group(P218,P2132 and Cyanex 272).For β-substituent group extractants,their loading capacities are in the order P208(299.7 mg/L)≈INET-1(299.5 mg/L)>P218(270.8 mg/L)>>USTB-1(163.1 mg/L)>P227(151.4 mg/L),while their anti-emulsification/gelation performances are just in the opposite order P227>USTB-1>P218>P208≈INET-1 under the studied conditions.For γ,δ-substituent group extractants,their loading capacities are in the order P218(270.8 mg/L)>P2132(192.3 mg/L)>Cyanex272(131.7 mg/L),while the anti-emulsification performance of P218 is better than those of P2132 and Cyanex 272.The loading capacity data given in the parentheses are obtained through repeatedly extracting Lu from ~4×10^(-4)mol/L of Lu aqueous feed solution with initial pH of 2.40 by 0.01 mol/L extractant at phase ratio A/O of 1:1.

The role ofβ,γ,δ-substituent of dialkylphosphinic acids in HREE extraction and separation behaviors

Heavy rare earth element(HREE)separation has always been a great challenge.The kind of dialkylphosphinic acids is recognized as the third generation of organophosphorous acid extractants.However,detailed relationship betweenβ-substituent(especially when it changes from H to methyl,and further to ethyl)and their extraction behaviors and selectivity for HREEs have rarely been reported.Besides,there are also few reports on effect ofγ,δ-substituent on HREE extraction and separation.In this paper,we synthesized five and collected two dialkylphosphinic acids with differentβ,γ,δ-substituents(from H to ethyl).These extractants were divided into two groups to discuss their extraction behaviors and selectivity for HREEs:β-substituent group(P208,INET-1,P218,USTB-1 and P227)andγ,δ-substituent group(P218,P2132 and Cyanex 272).To evaluate and compare their extractabilities,P507 was used as a reference and Tm,Yb,Lu were extracted with 0.01 mol/L of these extractants from single Tm,Yb and Lu solutions(~4×10^(-4)mol/L)at different initial pH.Besides,pH_(0.5)(Tm),pH_(0.5)^(Yb)and pH_(0.5)^(Lu)values and their differences(ΔpH_(0.5)^(Tm-Yb),ΔpH_(0.5)^(Yb-Lu),ΔpH_(0.5)^(Tm-Lu))for each extractant were given to roughly evaluate their separation performance for Tm,Yb and Lu.To further investigate the selectivity of these extractants for HREEs,Tb,Dy,Ho,Er,Tm,Yb and Lu were extracted from their mixed solution with initial pH of 4.00 at phase ratio A/O of 2:1,1:1 or 1:2.Their HREE separation performance is mainly discussed based on the adjacent HREE separation factors(β_(N+1/N))and their average value(β_(Tb-Lu)).

Changes in underflow solid fraction and yield stress in paste thickeners by circulation

The trouble-free and efficient operation of paste thickeners requires an optimal design and the cooperation of each component.When underflow discharging is suspended,alleviating the vast torque that the remaining solids within the thickeners may place on rakes mainly lies in the circulation unit.The mechanism of this unit was analyzed,and a mathematical model was developed to describe the changes in underflow solid content and yield stress.The key parameters of the circulation unit,namely,the height and flow rate,were varied to test its performance in the experiments with a self-designed laboratorial thickening system.Results show that the circulation unit is valid in reducing underflow solid fraction and yield stress to a reasonable extent,and the model could be used to describe its efficiency at different heights and flow rates.A suitable design and application of the circulation unit contributes to a cost-effective operation of paste thickeners.

岩石超声特性与加载应力关系及在深部开采中面临的挑战

地应力测量是矿山进入深部采矿后需要开展的一项重要工作,高效的地应力测量方法对于确定围岩的稳定性具有重要意义。岩石的超声特性是其物理力学性质、宏细观结构及受力状态等因素的综合体现,以波速为关键参数的声学信息与围岩的应力状态、变形、细观结构、实验条件等因素具有显著的关联性。以众多专家学者研究成果为基础,从波速−应力−应变关联性,考虑岩性、孔隙结构等内在因素影响,以及围压、温度等外界因素影响,波速数学模型四方面介绍了岩石声学特性的研究现状,提出了应力作用下考虑温度因素影响的应力−温度耦合波速关系方程,最后结合深部开采发展需求提出了关于岩石声学−应力研究发展的建议方向。

基于图像识别技术的膏体微观结构纹理特征分析（英文）

胶结充填膏体(CPB)、砂浆及混凝土等水泥基材料的力学强度取决于其微观结构,如孔隙数量、孔径及结构,颗粒及骨架的排列形态等。对于该类材料的力学强度与其孔隙结构(如孔径及其分布)的关系研究目前已有很多,但与微观形态特征或纹理特性的相关性研究较少。纹理是一种反映图像中同质现象的视觉特征,体现了物体表面共有的内在属性,包含了物体表面结构组织排列以及它们与周围环境的联系,是量化微观形态特性的有效方法。在统计分析中,灰度共生矩阵(GLCM)纹理和Tamura纹理是表征纹理特征的最具代表性方法。本研究以3种不同质量浓度膏体制备的充填体试块为样本,养护至指定龄期后经单轴抗压强度试验获得其力学强度,再对试块断面进行电镜扫描(SEM)获得其微观结构图像;基于图像识别/分析技术提取SEM图像的纹理特征参数,分析纹理特性与SEM图像参数(放大倍数)间的关系,筛选出有效的SEM图像样品;分析各纹理参数与膏体浓度的相关性,识别出与膏体浓度呈正相关的纹理参数,并验证该纹理参数与力学强度存在严格的相关关系。

单轴压缩下热处理花岗岩的损伤特征:来自主/被动超声技术的见解

为了探明热处理对花岗岩损伤破裂的影响,对室温(25℃)及热处理(200,300和400℃)花岗岩试样进行单轴压缩试验,并采用主动超声和被动声发射监测技术研究试样的损伤特征。研究结果表明:与未进行热处理的试样相比,试样经200℃处理后单轴抗压强度(UCS)无明显变化,经300℃处理后UCS增加12.65%,经400℃处理后UCS降低4.97%。随着热处理温度由25℃升至400℃,试样初始P波速度由4909 m/s逐渐降低至3823 m/s,未加载时花岗岩试样的波速各向异性ε由0.03增至0.09。随着轴向荷载增加,ε受预存裂纹(包括热致裂纹)和应力诱发裂纹影响,在裂纹闭合阶段和不稳定开裂阶段迅速增大。超声波主频幅值在垂直方向(轴向)随应力增大而增大,在水平方向随应力增大而减小。此外,经热处理后试样的声发射事件定位震级减小,低频事件和高振幅事件增多。然而,没有足够的证据表明400℃以下的热处理对声发射时序特征、震源位置和b值有显著影响。