A new concept of backfill design—Application of wick drains in backfilled stopes

Backfilling represents an environmentally friendly mining waste disposal technique. It is increasingly used in underground mines all over the world. However, its primary purpose remains to improve ground stability and to reduce ore dilution. Previous investigations have shown that fill drainage plays a key role in backfill and barricade design. With a poor drainage system in the backfilled stope, the required dimension of barricade, which is constructed at the base of the stope near the drift entrance, has to be increased. A poor backfill drainage system can also lead to a significant increase in drainage waiting time and further reduction in mining productivity. In this paper, the drainage of conventional backfill design in backfilled stopes is briefly reviewed. For the first time, the application of the wick drain is introduced in the backfill within mine stopes. The drainage improvement from the introduction of the wick drain is illustrated using numerical modeling.     

大姚崩落采矿法借计算机模拟优选采场参数

目前大姚铜矿氧化矿采用的是底盘漏斗崩落采矿法。可是矿石损失值很高,虽然矿山做了大量工作,但是仍然不能将其降至设计的指标。鉴于目前的状况,为了掌握在矿山具体条件下崩落矿岩的流动规律;矿体产状、采场结构参数以及回采工艺与回贫指标之间的关系;以便为改进采矿方法、结构参数和回采工艺提供具有说服力的依据。展开了计算机模拟的最优化研究。论文说明了计算机模拟的试验方法并且分析了所获得的结果,提出了对实际生产具有指导意义的选择与建议。     

Strategic sill pillar design for reduced hanging wall overbreak in longhole mining

Steeply dipping, vein and tabular orebodies are traditionally extracted with longitudinal retreat mining methods such as Eureka and Avoca in a bottom-up sequence with delayed backfill. To increase productivity, sill pillars in the orebody are used to separate mining zones thus allowing production to take place simultaneously in two or more zones. While such mining methods are productive, they may be accompanied with high volumes of hanging wall overbreak causing significant unplanned ore dilution. In this work, it is shown through a mine design case study of a narrow vein deposit that a sill pillar could also play a significant role in limiting hanging wall overbreak. To demonstrate the role of sill pillar, a novel numerical modelling scheme is proposed to account for progressive stope wall overbreak. A numerical modelling approach of element death and rebirth is developed to allow for the detected stope overbreak to be immediately removed and replaced with backfill material before upper-level stope extraction. It is further shown that the average overbreak volume could be reduced by as much as 33% when the sill pillar is strategically placed in the lower half of a mine plan.     

冬瓜山矿体稳定性和岩石力学特性分析

通过对冬瓜山矿体岩石力学特性的分析,探讨了矿体特征及围岩性质、原岩应力、岩石物理力学性质、岩体的整体稳定性,以及矿岩构造条件、采场结构参数和采场回采顺序对巷道稳定性的影响.结果表明:冬瓜山矿体表现出软岩的性质,属于高应力软岩;冬瓜山矿体地应力场的分布规律可以作为矿山设计及岩体稳定性评价的依据;矿岩构造条件对矿床开采过程巷道的稳定性不会造成较大的影响;选择合适的采场结构参数和采场回采顺序,可减小对巷道稳定性的影响.     

东乡铜矿Ⅶ号难采矿体采场顶板控制技术

论述了后退或压气罐长锚索注浆法．对东乡铜矿Ⅶ号难采矿体采场进行了长锚索控顶试验，解决了该矿采场顶板控制的难题．     

Analysis of factors and countermeasures of mining subsidence in Kaiyang Phosphorus Mine

1 INTRODUCTION After useful mineral body has been mined and dragged out, mining goaf is formed and country rocks would probably lose original equivalence. When span of the goaf is long enough, even if the roof is hard and intact, the rock around the goaf would move towards the mining openings, and this movement would pass on to the adjoining rock mass until it reaches the surface and ground displacement can be observed. In other words, underground mining may cause ground cracks and surface…     

高大型采场全尾砂充填挡墙可靠性的力学分析

冬瓜山铜矿床埋藏距地表深达1000m,矿区构造应力复杂,属高地应力分布区域,采用大空场嗣后全尾砂胶结充填法开采．按充填料浆3种不同力学性质状态对充填挡墙进行了受力分析和计算,指出了影响充填挡墙可靠性的因素并提出了首采地段8#采场充填挡墙实施方案．     

预控顶下向分层全面采矿法试验研究

介绍了昆明理工大学与铜官山铜矿共同合作进行的预控顶下向分层全面采矿法试验研究，达到了提高生产能力、增加矿石回收率、降低贫化、减少采矿成本、增加矿山效益的目的．     

Evaluation of the use of sublevel open stoping in the mining of moderately dipping medium-thick orebodies

The flow of blasted ore during mining of moderately dipping medium-thick orebodies is a challenge. Selecting a suitable mining system for such ore bodies is difficult. This paper proposes a diamond layout sublevel open stoping system using fan blastholes with backfilling to mine such orebodies. To evaluate the performance of system the relationships between ore recovery and stope footwall dip angle, footwall surface roughness, drawpoint spacing and production blast ring burden were investigated. An ore recovery data set from 81 laboratory physical model experiments was established from combinations of the listed factors. Various modules in a back propagation neural network structure were compared, and an optimal network structure identified. An ore recovery backpropagation neural network (BPNN) forecast model was developed. Using the model and sensitivity analysis of the factors affecting the proposed open stope mining system, the significance of each factor on ore recovery was studied. The study results were applied to a case study at the Shandong Gold Group Jiaojia Gold Mine. The results showed that the application of a BPNN and sensitivity analysis models for ore recovery prediction in the proposed mining system and field experimental results confirm that the suggested mining method is feasible.     

考虑崩落矿岩非均匀度的低贫化放矿方式

分析了非均匀崩落矿岩在放矿过程中的流动特点以及无底柱低贫化放矿方式 .通过立体物理模拟放矿实验 ,对矿岩散体非均匀度对低贫化放矿方式截止放矿贫化率的影响进行了研究 ,并将研究结果应用到白银铜矿生产实践中 ,初步取得了良好的经济效益和社会效益     

Stability and reliability of pit slopes in surface mining combined with underground mining in Tonglushan mine

Slope stability is of critical importance in the process of surface-underground mining combination. The influence of underground mining on pit slope stability was mainly discussed, and the self-stabilization of underground stopes was also studied. The random finite element method was used to analyze the probability of the rock mass stability degree of both pit slopes and underground stopes. Meanwhile, 3D elasto-plastic finite element method was used to research into the stress, strain and rock mass failure resulting from mining. The results of numerical simulation indicate that the mining of the underground test stope has certain influence on the stability of the pit slope, but the influence is not great. The safety factor of pit slope is decreased by 0.06, and the failure probability of the pit slope is increased by 1.84%. In addition, the strata yielding zone exists around the underground test stope. The results basically conform to the information coming from the field monitoring.     

Numerical analysis of application for induction caving roof

New method for handling roof of the base successive mining is proposed, which is induction caving in the roof. The key is that it is made certain to the station of the space-time in the induction caving roof, as the stress is released with the mining process. And applying the catastrophe theory, the influencing factors of induction caving roof are studied in the emptied areas, such as the mechanical property of the surrounding rock, the area of the gob,the scope and dimension of tensile stress. The results show that the key factor is the area of the gob to the method of the induction caving roof. Then according to the geology and the ore characteristic, the three dimension FEM mechanical model is built in Tongkeng Mine, the laws of the tensile stress are analyzed to the space and the time in the roof with the mining, then it is rational design to the mine step and time of the handing the roof.     

东川面山连续分段空场采矿法通过放矿模拟试验选择合理采场结构参数

本文从东川面山现用分段空场采矿法所存在的问题——高贫损、低效率、不安全——出发,论证了连续分段空场采矿法的特点,并用正交放矿模拟试验设计方法来安排物理模型试验。对所取得具有代表性的数据和试验结果,进行分析、优选出为工业试验设计和生产应采取的合理采场结构参数的推荐值,和回贫指标的预报值。对该矿新采矿方法的设计、生产具有积极地指导作用。     

德兴铜矿品位参数优化

以德兴铜矿地质，采选和财务资料为基础，建立数模和综合技术经济模型，把矿山生产经营和经济运行等情况置于综合模型之内利用Ｌｏｔｕｓ１－２－３进行多方案树比的多目标决策优化分析，所得的结论可靠。     

Similar material simulation of time series system for induced caving of roof in continuous mining under backfill

With the help of similar material simulation test,time series system for induced caving of roof in continuous mining under complex backfill in ore body No.92 of Tongkeng Tin Mine was studied. According to the similarity theory,a two-dimensional similar simulation test-bed was constructed. The stress and displacement that change along with the advance of mining were acquired and analyzed automatically by data system. The processes of continuous mining of ore-block in 5 intervals and artificial induced caving of roof were simulated. The results of the test show that ore body remained as safety roof in thickness of 15 m guarantees the safe advance of stoping work face. Caving of safety roof puts in practice at the first two mining intervals when the third interval of continuous mining is finished,and one interval as the safety distance should be kept all the time between stopping and caving. While mining in the last interval,pre-slotting should be implemented first of all,and the roof of the last two mining intervals is caved simultaneously. Only this kind of time series system can be an efficient and safe way for induced caving of roof in continuous mining.     

块体理论及其在采场巷道稳定性分析中的应用

介绍了块体理论的基本原理及分析方法，并将该理论用于铜坑锡矿细脉带５７０水平下盘运输巷道顶板稳定性分析。将块体理论运用于地下矿山采场巷道的稳定性分析，不仅是对岩体结构分析法的补充，同时作为一种尝试，为正在发展与完善中的块体理论的应用开辟一个新的领域。     

Evaluation of the effect of geometrical parameters on stope probability of failure in the open stoping method using numerical modeling

Stress-induced failure is among the most common causes of instability in Canadian deep underground mines. Open stoping is the most widely practiced underground excavation method in these mines, and creates large stopes which are subjected to stress-induced failure. The probability of failure(POF)depends on many factors, of which the geometry of an open stope is especially important. In this study,a methodology is proposed to assess the effect of stope geometrical parameters on the POF, using numerical modelling. Different ranges for each input parameter are defined according to previous surveys on open stope geometry in a number of Canadian underground mines. A Monte-Carlo simulation technique is combined with the finite difference code FLAC3D, to generate model realizations containing stopes with different geometrical features. The probability of failure(POF) for different categories of stope geometry, is calculated by considering two modes of failure; relaxation-related gravity driven(tensile)failure and rock mass brittle failure. The individual and interactive effects of stope geometrical parameters on the POF, are analyzed using a general multi-level factorial design. Finally, mathematical optimization techniques are employed to estimate the most stable stope conditions, by determining the optimal ranges for each stope's geometrical parameter.     

Design of crown pillar thickness using finite element method and multivariate regression analysis

Minerals are now being extracted from deep mines due to drying up of resource in shallow ground. The need for suitable supports and ground control mechanisms for safe mining necessitates proper pillar design with filling technology. In addition, high horizontal stress may cause collapse of hanging wall and footwall rocks, hence designing of suitable crown pillars is absolutely necessary for imposing overall safety of the stopes. This paper provides a methodology for the evaluation of the required thickness of crown pillars for safe operation at depth ranging from 600 m to 1000 m. Analyses are conducted with the results of 108 non-linear numerical models considering Drucker-Prager material model in plane strain condition. Material properties of ore body rock and thickness of crown pillars are varied and safety factors of pillars estimated. Then, a generalized statistical relationship between the safety factors of crown pillars with the various input parameters is developed. The developed multivariate regression model is utilized for generating design/stability charts of pillars for different geo-mining conditions.These design charts can be used for the design of crown pillar thickness with the depth of the working,taking into account the changes of the rock mass conditions in underground metal mine.     

杨广寨急倾斜薄矿体近地表三角采场开采方法改进

急倾斜薄矿体露头附近开采时,常形成三角形不规则采场,采用普通浅孔留矿法回采存在一系列技术问题。针对杨广寨铅锌矿的具体情况,对采矿方案进行了优化,提出了矿房联络道通达地表的采准布置方案,并在矿山进行了采矿实验。结果表明,该采矿方法可减少大量采准工程,提高回收率及回采效率,降低采矿成本,具有较高的应用价值与经济效益。     

Numerical analysis of application for induction caving roof

New method for handling roof of the base successive mining is proposed, which is induction caving in the roof. The key is that it is made certain to the station of the space-time in the induction caving roof, as the stress is released with the mining process. And applying the catastrophe theory, the influencing factors of induction caving roof are studied in the emptied areas, such as the mechanical property of the surrounding rock, the area of the gob, the scope and dimension of tensile stress. The results show that the key factor is the area of the gob to the method of the induction caving roof. Then according to the geology and the ore characteristic, the three dimension FEM mechanical model is built in Tongkeng Mine, the laws of the tensile stress are analyzed to the space and the time in the roof with the mining, then it is rational design to the mine step and time of the handing the roof. Foundation item: Project(50490274) supported by the National Nature Science Foundation of China