Progress and prospects of mining with backfill in metal mines in China

Mining is the foundation of modern industrial development.In the context of the“carbon peaking and carbon neutrality”era,countries have put forward the development strategy of“adhering to the harmonious coexistence of humans and nature.”The ongoing progress and improvement of filling mining technology have provided significant advantages,such as“green mining,safe,efficient,and low-carbon emission,”which is crucial to the comprehensive utilization of mining solid waste,environmental protection,and safety of re-mining.This review paper describes the development history of metal mine filling mining in China and the characteristics of each stage.The excitation mechanism and current research status of producing cementitious materials from blast furnace slag and other industrial wastes are then presented,and the concept of developing cementitious materials for backfill based on the whole solid waste is proposed.The advances in the mechanical characteristics of cemented backfill are elaborated on four typical levels:static mechanics,dynamic mechanics,mechanical influencing factors,and multi-scale mechanics.The working/rheological characteristics of the filling slurry are presented,given the importance of the filling materials conveying process.Finally,the future perspectives of mining with backfill are discussed based on the features of modern filling concepts to provide the necessary theoretical research value for filling mining.

Enhancing fly ash utilization in backfill materials treated with CO_(2)carbonation under ambient conditions

The environmental concerns resulting from coal-fired power generation that produces large amounts of CO_(2)and fly ash are of great interest.To mitigate,this study aims to develop a novel carbonated CO_(2)-fly ash-based backfill(CFBF)material under ambient conditions.The performance of CFBF was investigated for different fly ash-cement ratios and compared with non-CO_(2)reacted samples.The fresh CFBF slurry conformed to the Herschel-Bulkley model with shear thinning characteristics.After carbonation,the yield stress of the fresh slurry increased significantly by lowering fly ash ratio due to gel formation.The setting times were accelerated,resulting in approximately 40.6%of increased early strength.The final strength decreased when incorporating a lower fly ash ratio(50%and 60%),which was related to the existing heterogeneous pores caused by rapid fluid loss.The strength increased with fly ash content above 70%because additional C-S(A)-H and silica gels were characterized to precipitate on the grain surface,so the binding between particles increased.The C-S(A)-H gel was developed through the pozzolanic reaction,where CaCO_(3)was the prerequisite calcium source obtained in the CO_(2)-fly ash reaction.Furthermore,the maximum CO_(2)uptake efficiency was 1.39 mg-CO_(2)/g-CFBF.The CFBF material is feasible to co-dispose CO_(2)and fly ash in the mine goaf as negative carbon backfill materials,and simultaneously mitigates the strata movement and water lost in post-subsurface mining.

Calculation method of first collapse span with superhigh water material backfill mining

It is critical for the material to be of active supporting capacity before initial collapse ot mare root wltn supermgn water material backfill mining, and the maximum bending moment should be first calculated in order to determine the initial collapse span. In the light of principal of virtual work, the simple expression of deflection, bending moment of elastic clamped plate were deduced under the condition of vertical uniform distributed load, horizontal pressure and supporting by elastic foundation, and then, the maximal bending moment expression was derived too. At the same time, the influence degree on square clamped plate by adding horizontal pressure and elastic foundation were analyzed. The results show that the effect of horizontal pressure on maximal bending moment can be ignored when the value of horizontal pressure is two orders of magni- tude less than that of coeificient of elastic stiffness existing elastic foundation.

A New Mode of Coal Mining Under Buildings with Paste-Like Backfill Technology

The formation of the paste like backfill technology was introduced briefly in this paper. From the actual cases of coal mines, a new mode of coal mining under buildings with the technology was proposed. And its specificity was analyzed, and a further introduction to the full sand soil solidifying material was given. The main parts of the backfill system, such as the backfill preparation system, the pipeline transportation system, the backfill systems in fully mechanized mining faces and the backfill process, were presented emphatically.

Mass ratio design based on compaction properties of backfill materials

The backfill-mining mass ratio is the ratio of the mass of the backfill materials in the goaf to the mass of the produced raw coal during solid backfill mining and it is regarded as a direct control index of the backfill effect in solid backfill mining. To design the backfill-mining mass ratio in a solid backfill mining panel, the backfill-mining mass ratio was defined on the basis of the basic principle of solid backfill mining. In addition, the density-stress relationship of backfill materials under compaction was obtained for five types of materials to derive a design formula for backfill-mining mass ratio. Moreover, the 6304-1 backfill panel under the large-scale dam of Ji′ning No. 3 coal mine was taken as an engineering case to design the backfill-mining mass ratio. In this way, it is found that the designed backfill-mining mass ratio is 1.22, while the mean value of the measured backfill-mining mass ratio is 1.245. Besides, the maximum roof subsidence is only 340 mm which effectively guarantees the backfill effect in the panel and control of strata movement and surface subsidence.

A roof model and its application in solid backfilling mining

Through changing the axial load on backfilling material compaction test to reflect different overlying strata pressure on backfilling material, the stress-strain relations in the compaction process of backfilling material under the geological condition can be obtained. Based on the characteristic of overlying strata movement in backfill mining, a model of roof thin plate is established. By introducing the stress-strain relation in compaction process into the model and using RIZT method to analyze the bending deformation of roof, the bending deflection and stress distribution can be obtained. The results show that the maximum roof subsidence and maximum tensile stress occurring at the center are 255 mm and5 MPa, respectively. Tensile fracture of roof under the geological condition of Dongping Mine did not occur. The dynamic measurement results of roof in Dongping Mine verify the theoretical result from the aforementioned model, thereby suggesting the roof mechanical model is reliable. The roof thin plate model based on the compaction characteristic of backfilling material in this study is of importance to research on backfill mining theories and application of backfilling material characteristics.

Recovery of Mining Wastes in Building Materials: A Review

The use of materials from waste in buildings compensates for the lack of natural resources, solves the problem of waste management and provides an alternative technique for protection of the environment. There are a large number of industrial wastes that are used for full or partial replacement of raw materials in some construction materials. This review assesses mining waste in concrete as a substitute for aggregates and cement;in fired bricks as a substitute for soil;and in road backfill as a substitute for soil. This paper reviews some mining tailings, mine waste rocks and some slags obtained in the exploitation and/or processing of some ores including iron, gold, lead, phosphate, copper, coal, etc. Different physical properties, mechanical properties, chemical properties, heavy metal content, mineralogic composition, geotechnical properties and environmental properties (leaching test) of the mine wastes were examined. The physical, mechanical and environmental properties of the materials obtained by substitution of raw materials by mine waste were examined and compared to reference materials. Mining waste in cementitious materials offers good compressive strengths, while the porosity of the concrete and/or mortar is a factor influencing its toxicity. As for the waste in fired bricks, fired at a temperature of 900°C or more, it offers convincing compressive and flexural strengths. The few research studies obtained on the use of mining waste in road embankments have shown that mining waste can be used as a sub-base layer and backfill as long as it is not toxic. In addition, several other mining wastes require special attention as substitutes for raw materials in construction materials, such as coltan, cobalt.

不同加载速率下废石胶结充填体的力学特性及破裂特征研究

为研究不同加载速率与骨料粒径级配对废石胶结充填体的力学特性以及破裂特征变化规律;对不同骨料粒径级配的废石胶结充填体进行不同加载速率的单轴压缩试验,分析其力学特性的变化规律;并辅以声发射系统,研究废石胶结充填体内部裂纹的发展演化规律。结果表明:废石胶结充填体的单轴抗压强度与弹性模量随着加载速率的增大呈线性增长趋势;废石胶结充填体的单轴抗压强度与弹性模量随着骨料级配指数的增大呈现先增长后降低的趋势;随着骨料级配指数和加载速率的增大,试样破坏模式由张拉破坏逐渐转变为剪切破坏,破坏程度加剧,完整度降低;试样内部裂纹的发展演化总体分为压密阶段、弹性阶段、稳定扩展阶段及非稳定扩展阶段。

绿色矿山尾砂综合利用技术研究

四川某铅锌矿为建成无尾矿排放绿色矿山,将尾矿无害化处理,对其进行尾矿综合全利用研究。通过踏勘调研矿山技术条件,试验分析尾矿特性,拟定了全尾砂充填和分级细尾砂充填(粗尾砂建材化处理)2个方案。由于矿物磨矿碎胀性影响,采矿产生的采空区空间不能满足充填处置全部尾砂的需求,确定将全尾砂进行分级处理,分级界线74μm,粗粒级尾砂产率39.5%,以粗粒级尾砂脱水作为建筑用砂物料,细粒级尾砂浓密脱水作为充填骨料,从而实现尾矿零排放。根据细粒级尾砂特性,优选膏体仓储浓密机进行高效浓密脱水,并采用附近水泥厂的胶固粉进行分级细尾砂胶结充填。对2种利用方案进行经济成本分析可知,分级细尾砂充填每天可节省3422.1元,效果显著。该研究成果可为类似矿山建设无尾绿色矿山提供借鉴。

磷石膏协同多元固废制备矿山充填材料

为解决磷石膏利用率低、对环境危害大与低成本矿山充填材料研制的问题,本文以粉煤灰、钢渣、高炉矿渣为胶凝材料组分,协同磷石膏制备一种新型的磷石膏基矿山充填材料。通过抗压强度、流动度、凝结时间、浸出毒性和微观试验研究了充填材料的工程与环境特性。结果表明:所研制的矿山充填材料的抗压强度、流动度、凝结时间均能满足规范,达到工程应用需求;在养护28 d后,充填材料的重金属元素的浸出浓度都可以满足地下水Ⅲ级标准的要求,不会污染环境和危害人体健康。当钢渣和高炉矿渣的掺量逐渐增加时,抗压强度逐渐升高,流动度和凝结时间逐渐降低;充填材料中主要的水化产物是钙矾石和C—(A)—S—H凝胶,两者都为充填材料提供了主要的强度,且C—(A)—S—H凝胶可以包裹住重金属离子。

超高水材料在矿充填开采中的应用

随着矿产资源的不断开采,采空区的稳定性成为了重要问题,而超高水材料的出现为矿充填开采提供了一种新的解决方案,不仅能够迅速填补开采后的空洞,减少地质灾害发生的风险,还能有效提高矿产资源的回收率,进一步降低开采成本。本文主要探讨了在矿充填开采中超高水材料应用的相关内容,希望能够推动矿充填开采技术的创新与进步,并为矿资源的高效利用和环境保护做出积极贡献。

铝土矿高水材料逐巷充填矿柱回收技术及应用

奥家湾铝土矿采用房柱式采矿法,留设大量矿柱支撑顶板,采出率低,矿石损失量大。为安全回收铝土矿柱,理论分析了充填前后矿柱及充填体的应力分布状态,根据铝土矿体赋存特征及开采条件,提出了高水材料逐巷充填矿柱回收技术并开展了现场试验:将铝土矿柱划分多条采巷,开采完毕后采用水灰比为4∶1的高水充填材料与矸石胶结充实接顶,逐巷有序充填回收矿柱。为评估充填体力学性能,进行现场取样并开展实验测试。结果表明:充填体单轴抗压强度为2.84MPa,可有效支撑顶板,弱化矿柱应力集中程度,提高采场稳定性。本技术可安全回收矿柱,将矿石采出率提高至81%,同时能有效控制采后覆岩活动,且充填成本低,技术经济效益显著。

超高水材料充填减灾减损绿色开采理论与技术进展及展望

深部煤层安全高效开采与生态环境保护是当前煤炭资源绿色开采的重大难题之一。充填开采对于防治深井动力冲击灾害、减少地表下沉、保护生态环境具有显著成效,其中超高水材料水体积比高,充填开采具有工艺简单、适应性强、用料少、充填率高等特点,可有效解决地面环境保护与煤炭资源开采破坏之间的突出矛盾,符合煤炭资源减灾减损绿色智能开采新发展理念的要求。在总结充填开采技术研发背景与发展历程的基础上,阐明了超高水材料充填开采的技术原理、工艺流程及材料性能;重点从充填开采地表沉陷控制“充填体—煤柱”及“充填体—支架—煤体”协同承载等方面揭示了充填开采动力灾害防治机理;提出了减灾减损绿色开采动力灾害防治、智能化感知、地表形变监测与预计及充填装备智能化控制等关键技术,在山东义能煤矿成功进行了超高水材料充填开采实践,并实现了“三下”深部煤层安全高效智能绿色开采。为推进生态文明建设与环境保护,实现现代化矿井减灾减损绿色开采,展望了超高水材料充填开采研究方向为:深化深部超高水材料充填开采岩层控制基础理论、提高超高水材料充填开采技术智能化水平,创新超高水充填与煤系共伴生资源协同开采技术体系,联合超高水材料充填开采与碳捕获、封存及再利用技术,优化智能化绿色开采监测评估体系与方法,为实现深部资源绿色化开采提供科学依据。

煤矿微生物诱导碳酸钙沉积胶结充填开采技术研究

针对当前充填开采技术中水泥基胶结料存在的高排放和高耗能问题,将微生物诱导CaCO_(3)沉积(MICP)技术引入充填开采领域,研究了微生物胶结充填材料的力学性能,建立了基于MICP的微生物胶结充填开采技术体系。研究表明,拌和型和灌注型微生物胶结充填材料的强度随着营养液浓度和菌液用量的增加呈现先增大后减小的规律,平均强度分别为0.88 MPa和17.95 MPa;微生物充填材料内部的有效CaCO_(3)晶体是充填材料固结的关键,在拌和型试样中以方解石和球霰石的矿物形式存在,在灌注型试样中主要为方解石。微生物胶结充填开采技术的节能减排环境效益显著,特别是在当前环保需求和政策背景下,该技术具有科学价值和发展前景。

基于RSM-BBD法胶结充填材料配比优化及工程应用

针对煤层回采顶板垮落法产生的采煤固废堆放量大、长壁胶结充填开采中采充失衡等问题,内蒙古察哈素煤矿31采区采用连采连充巷式胶结充填采煤工艺,采用“隔三采一”的回采方式及“三强一弱”的充填模式。充填材料配比对充填成本与效果具有重要影响,针对原胶结充填材料中水泥消耗大、粉煤灰消纳少的问题,基于泰波理论确定矸石最佳粒径级配系数n为0.5,在此基础上,利用响应面法(RSM)优化材料配比。基于RSM-BBD (Box–Behnken Design)设计13组试验,建立充填体3、7及28 d单轴抗压强度与水泥质量分数X_(1)、粉煤灰质量分数X_(2)、固料质量分数X_(3)及3因素交互作用(水泥与粉煤灰交互作用X_(1)X_(2)、水泥与固料质量分数交互作用X_(1)X_(3)、粉煤灰与固料质量分数交互作用X_(2)X_(3))的回归模型,模型P值均小于10-4,模型可靠性强。试验结果表明:不仅单一因素对强度影响显著,且各因素的交互作用也对强度有一定的影响。强度随X_(1)与X_(3)的增加而增大,随X_(2)的增加先增大后减小,X_(1)对前期影响最显著,X_(3)对后期影响最显著,X_(2)对强度影响随龄期增长逐渐显著。X_(2)X_(3)对7 d强度影响显著,X_(1)X_(2)对28 d强度影响显著,X_(1)X_(3)对3、7和28 d强度均有显著影响。在X_(1)X_(3)对7、28 d强度的交互影响中,水泥与固料质量分数会相互促进两者对强度的增强作用,而在其他交互影响中,一因素的增加会对另一因素的影响效果起抑制作用。基于RSM确定合理配比为X_(3)取78%~79%, X_(2)取19%~20%;高强度充填时X_(1)取9%~10%,低强度充填时X_(1)取8%。察哈素煤矿303工作面共采出煤炭16.8万t,消纳矸石16.22万t,粉煤灰消纳增加量与水泥消耗减少量均达到1万t以上,大大节省了粉煤灰处理费用与水泥成本,具有良好的环境效益与经济效益。

梁家煤矿似膏体连采连充技术及工程实践

为解决梁家煤矿三下压煤问题,以2112工作面开采为工程背景,提出了短壁连采连充似膏体充填开采方法,优选了一种以炉渣、粉煤灰为主的似膏体充填材料配比,构建了由充填材料地面制备、井上下输送系统及短壁工作面连采连充一体化的绿色循环开采系统,并进行了地表变形控制效果预计及实测。方案应用结果表明:当粉煤灰质量占比65%、炉渣26%、水泥熟料7%、早强剂1%、减水剂1%和水胶比0.5时,粉煤灰-炉渣似膏体充填材料料浆浓度为66.7%,充填体单轴抗压强度可达到9 MPa,满足工程要求;梁家煤矿采用短壁连采连充开采方法,实测地表最大沉陷200 mm,地表控制在Ⅰ级损坏范围内,实现了不迁村建下安全高效开采。该技术在梁家煤矿的成功运用丰富了充填技术体系,可为其他矿井提供工程技术借鉴。

炉渣胶凝材料配比优选及充填体性能

这是一篇陶瓷及复合材料领域的论文。针对某铅锌矿全尾砂充填以水泥为胶凝材料成本过高和充填体后期强度低的问题,采用丰富的炉渣固废资源,开发低成本炉渣胶凝材料满足矿山充填体的质量需求。在对尾砂、炉渣和水泥熟料进行物化分析后,通过充填料浆坍落度实验和炉渣胶凝材料配比探索实验,确定满足流动性的料浆浓度为70%左右,炉渣与水泥熟料比值为2~4为较优配比区间;通过全面实验法探究了不同配比炉渣胶凝材料充填体强度,充填料浆的泌水率和凝结特性。结果表明:炉渣胶凝材料配比为炉渣添加量75%~80%,水泥熟料添加量20%~25%,充填体能够满足强度0.5~3.5 MPa,充填料浆泌水率小于5%的充填质量要求。

我国充填采煤技术回顾及发展现状

煤矿充填开采技术在固体废弃物处置、控制采煤沉陷、提高资源采出率和建设生态矿山等方面发挥着举足轻重的作用。自20世纪初至今,世界矿山充填开采技术已有百年的发展历史。根据资料分析,按照充填材料类型划分,20世纪矿山充填技术经历了废石干式充填、水砂充填、低浓度尾砂胶结充填和膏体充填4个发展阶段,回顾了当时我国充填采煤技术的应用和发展历程以及水砂充填、矸石自溜充填等主要充填工艺。21世纪以来,我国充填采煤技术取得了快速发展,形成了固体、膏体和超高水3种充填材料和应用于综采、连采工作面的2种充填工艺,固体废弃物利用种类、充填效果、机械化程度、整体技术水平大幅提升,对充填材料及其制备输送,工作面充填工艺特点进行了归纳总结,尤其是剖析了综采工作面充填的特点及生产效率制约因素,提出应从新型装备研发、临时护顶技术、充填空间高效密封措施等方面减少充填各环节时间。最后,结合实践效果,从充填采煤能力、地表下沉系数、充填开采增加成本、资源采出率和技术适用条件方面对固体充填综采、膏体充填综采、超高水充填综采、固体充填连采、膏体充填连采5种充填采煤方式进行了分析,为各矿选择适合自身的充填方式提供了依据。

脱硫石膏对赤泥-矿渣胶结充填料强度性能的影响

分别考察4种石膏(脱硫石膏、天然石膏、建筑石膏和分析纯石膏)对充填料试块的强度影响。研究结果表明:在养护7 d和28 d时掺入脱硫石膏的试块强度最高;脱硫石膏掺量对充填料试块强度有很大影响:当脱硫石膏相对掺量(质量分数)逐渐增加时,充填料试块强度增加,当掺量为19%时,充填料试块强度最大,再增加掺量则强度下降;掺有脱硫石膏相比掺有分析纯石膏的充填料产生强度更高,是由于它的溶解速率以及"离子氛"所致;水化产物有大量钙钒石、C—S—H凝胶以及霞石等成分。

煤矿井下高浓度胶结充填开采技术

为有效控制煤层开采引起的地表移动,进一步提高煤炭资源采出率,结合煤矿充填开采现状,提出煤矿高浓度胶结充填开采方法。运用相似模拟方法,从上覆岩层的移动形式、超前支承压力的影响范围、工作面周期来压强度及合理支架工作阻力等多个方面,研究了高浓度胶结充填开采工作面的矿压显现规律。以此矿压显现规律为依据,设计出与之相适应的充填开采液压支架和隔离支架,使之能够在形成较大充填空间的同时,减小工作面充填前顶板下沉量。同时阐述了高浓度胶结充填工作面布置形式及充填基本工艺,实现采煤和充填材料凝固平行作业,有效提高了工作面充填效率。