基于正交有限元的矿柱动态模糊可靠性分析

地下矿体开采过程中矿柱的稳定性不仅具有随机性而且具有模糊性,考虑矿岩、混凝土材料参数及矿柱内应力的随机模糊性,提出了用动态模糊可靠度分析矿柱稳定性的新概念。通过多次正交试验有限元计算,得到矿体在每个开采施工步骤过程中功能函数值,并通过正交多项式拟合矿柱功能函数,从而建立矿柱单元在不同的开采施工步骤时的概率密度函数和模糊失效隶属度函数,求解矿柱单元在不同开采施工步骤时的模糊失效概率和模糊可靠度指标,获得了矿柱的模糊可靠性曲线。采用该方法对哈尔滨某钼矿Ⅰ号矿体上向水平充填采矿方案进行计算和分析,结果表明动态模糊可靠度能较好地反映矿体开采全过程的矿柱稳定性变化状况,为优化矿区开采方案和指导矿山安全生产提供了依据。     

深井矿山联合开采交错区地压显现时空规律研究

为了研究矿山联合开采的地压显现规律,以夏甸金矿为例,其矿体中浅部采用崩落法开采,跨度超过300 m,而两翼采用充填法开采.采用数值模拟与现场监测方法,综合分析了深部联合开采交错区的应力、位移等时空规律.数值模拟结果表明：无底柱分段崩落法与上向水平分层充填法联合开采时,崩落采空区下方应力集中数值较大,矿体两翼略小,交错区应力值最高.地压动态监测发现,无底柱分段崩落法区的顶板沉降位移与巷道水平收敛位移普遍大于上向分层充填法,但围岩二次应力的变化要略小于上向分层充填法,联合开采区域在整体上处于稳定状态.研究实现了多参量联合动态监测,为深部开采过程中地压显现的有效监测预警提供了有效手段,具有良好的推广示范效应.     

基于中厚板理论的深部崩落转充填隔离矿柱稳定性分析

在金属矿山崩落转充填开采过程中,隔离矿柱作为浅部向深部延伸的衔接部分,其合理尺寸的留设对于实现矿山安全高效回采具有重要意义.针对内蒙古某铅锌矿深部崩落转充填开采这一实际情况,对水平隔离矿柱建立了厚板力学模型.考虑到连续板联结处的弯矩不可忽略,基于中厚板理论推导得出了对边简支对边固支条件下的应力表达式.采用前处理软件HyperMesh构建矿区高精度六面体网格模型,并将矿区三维地质模型导入有限差分软件FLAC~(3D)之中,以705中段及上部围岩塑性区体积为依据近似得出作用在隔离矿柱之上的均布荷载,并应用最大拉应力理论计算出隔离矿柱安全厚度为20 m.利用数值模拟软件分析了所留水平隔离矿柱的力学行为及其稳定性.结果表明:隔离矿柱沉降值与塑性区均控制在容许范围之内,稳定性良好,验证了所留隔离矿柱厚度的合理性.     

上向分层进路充填采矿法在木利锑矿的应用

采用分层崩落法对木利锑矿主矿体进行回采,存在地表陷落、机械化程度低、贫化率较大、通风条件差和坑木消耗大等问题。针对以上问题,设计采用了上向分层进路充填采矿法对主矿体进行回采,并在矿山进行了采矿实践,结果表明该采矿方法可克服以上缺点,获得了较好的经济效益,对同类矿山的生产具有一定的指导意义。     

框架式大跨度矿房开采技术

新桥硫铁矿采用两步回采的分段空场嗣后充填法,回采其呈框架式布置的矿柱,矿房,由于矿房跨度大大超过矿柱宽度,且矿柱充填质量较差,使第二步矿房回采难度加大,在矿房回采试验中,作者根据数值分析结果,采用了分区爆破,最后暴露充填体的开采技术,使大跨度矿房回采获得了成功,取得了显著的经济效益,也为类似条件矿山的开发提供了经验。     

尾砂胶结充填体与岩体耦合作用机理研究

充填法开采被广泛应用于隐患资源2次开采中,研究充填体与岩体耦合作用机理,对充分利用矿产资源、保护地表建筑物、延长矿山服务年限等方面具有十分积极的作用.以程潮铁矿西区选厂下遗留矿柱2次开采为研究背景,通过对尾砂胶结充填体的无侧限单轴抗压正交力学试验,得到了不同灰砂比、不同浓度、不同龄期参数与充填体单轴抗压强度的曲线关系和多参数线性回归方程式,同时分析了影响充填体抗压强度的主次因素.最终依据充填体与岩体能量匹配原则,通过数值模拟并充分考虑回采中爆破震动对采场稳定性的影响,得出最优充填方案.     

彭山锡矿采场稳定性的模型试验

彭山锡矿系一投产不久的新矿山,初步设计采用房柱法回采。由于矿岩地质条件的复杂多变性,原设计的矿房矿柱尺寸难以维持采场在回采期间的安全稳定性.为此,矿山急需提供具体条件下的合理尺寸,作为单体设计与施工的理论依据,同时希望摸清回采期间采场顶板与矿柱的应力分布与变化规律,摸清回采期间顶板围岩与矿柱的变形与破坏机制.根据以上要求,笔者采用相似材料模型模拟去对该矿Ⅳ—1矿体的房柱法采场的稳定性问题进行了研究,并从相似材料选择,测试元件制作、制模工艺和数据处理等方面探讨了提高模拟置信度的有关措施。     

基于采矿环境再造的空区顶板-矿柱系统协同作用

为研究空区系统动态演化过程中的协同稳定规律,运用三维有限元3D-σ,以某具体工程实际为背景进行了空区顶板-矿柱系统协同作用研究,得出各模拟方案顶板-矿柱系统安全率、塑性区和应力场的分布;探索了空区系统协同处理模式力学响应;从协同理念出发,为保证后续矿体安全开采提出块石充填采矿环境再造技术进行矿体原有环境修复方案.有限元研究结果表明:协同发展具有条件性,当顶板跨度为15 m、20 m、30 m时对应协同矿柱结构尺寸为3 m、4.5 m和6 m,空区系统顶板为大理岩、玄武岩时极限暴露面积指标分别为1000 m2、1600 m2;以现有方式进行后续矿体开采,应力集中现象明显,顶板最大拉应力为3.496 MPa,低于围岩极限强度,安全率为0.924,低于临界状态;在块石充填环境改造后,最大拉应力降至1.655 MPa,安全率为1.229,应力场、安全率明显改善,能确保后续矿体开采期间系统协同稳定.     

矿柱结构的可靠性设计

考虑岩体的各种力学参数,几何尺寸以及外部荷载作用的随机性和变异性,本文应用结构可靠度理论对矿柱结构进行可靠性设计,不仅考虑了矿柱强度和矿柱应力的均值大小,同时也考虑了它们的离散程度,克服了传统的单一安全系数的缺陷。用矿柱结构的可靠摭来评价矿柱结构稳定性,概念上更明确,合理。     

某矿山Ⅲ号矿体采空区安全性评价

为保证某矿山Ⅲ号矿体＋138m 中段部分残留矿柱回采工作的顺利进行,需对采空区的安全性进行评价.通过对＋138m 中段采空区进行实地调查并取样试验,获得了采空区和矿柱的空间分布形态及矿岩力学参数.在此基础上,利用有限差分软件FLAC3D及经典力学理论对采空区顶板及采场预留间柱的稳定性进行分析.结果表明,＋138m 中段采空区总体上处于较稳定状态,除局部区域安全度略有不足之外,其他区域整体上安全度较高,因此在合理的回采方案下回收部分残留矿柱是安全可行的.     

Dynamic failure risk of coal pillar formed by irregular shape longwall face:A case study

Irregular shape workface would result in the presence of coal pillar, which leads to high stress concentration and possibly induces coal bumps. In order to study the coal bump mechanism of pillars, static and dynamic stress overlapping(SDSO) method was proposed to explain the impacts of static stress concentration and tremors induced by mining activities. The stress and deformation in surrounding rock of mining face were analyzed based on the field case study at 1303 workface in Zhaolou Coal Mine in China.The results illustrate that the surrounding rock of a workface could be divided into four different zones,i.e., residual stress zone, stress decrease zone, stress increase zone and original stress zone. The stress increase zone is prone to failure under the SDSO impact loading conditions and will provide elastic energy for inducing coal bump. Based on the numerical modelling results, the evolution of static stress in coal pillar as the size of gob increasing was studied, and the impact of dynamic stress was investigated through analyzing the characteristics of tremor activities. The numerical results demonstrate the peak value of vertical stress in coal pillar rises from about 30 MPa with mining distance 10 m to 52.6 MPa with mining distance 120 m, and the location of peak stress transfers to the inner zone of coal pillars as the workface moves forward. For the daily tremor activities, tremors with high energy released indicate high dynamic stress disturbance on the surrounding rock, therefore, the impact of dynamic stressing is more serious during workface extension period because the tremor frequency and average energy after workface extension are higher than those before the workface extension.     

Surrounding rock control of gob-side entry driving with narrow coal pillar and roadway side sealing technology in Yangliu Coal Mine

Gob-side entry driving can increase coal recovery ratio, and it is implied in many coal mines. Based on geological condition of 10416 working face tailentry in Yangliu Coal Mine, the surrounding rock deformation characteristics of gob-side entry driving with narrow coal pillar is analysed, reasonable size of coal pillar and reasonable roadway excavation time after mining are achieved. Surrounding rock control technology and effective roadway side sealing technology are proposed and are taken into field practice. The results showed that a safer and more efficient mining of working face can be achieved. In addition, results of this paper also have important theoretical significance and valuable reference for surrounding rock control technology of gob-side entry driving with narrow coal pillar under special geological condition.     

Mechanisms of support failure and prevention measures under double-layer room mining gobs – A case study: Shigetai coal mine

In the practice of mining shallow buried ultra-close seams, support failure tends to occur during the process of longwall undermining beneath two layers of room mining goaf (TLRMG). In this paper, the factors causing support failure are summarized into geology and mining technology. Combining column lithology and composite beam theory, the key stratum of the rock strata is determined. A finite element numerical simulation is used to analyze the overlying load distribution rule of the main roof for different plane positions of the upper and lower room mining pillars. The tributary area theory (TAT) is adopted to analyze the vertical load distribution of each pillar, and dynamic models of coal pillar instability and main roof fracture are established. Through key block instability analysis, two critical moments are established, of which critical moment A has the greater dynamic load strength. Great economic losses and safety hazards are created by the dynamic load of the fracturing of the main roof. To reduce these negative effects, a method of pulling out supports is developed and two alternative measures for support failure prevention are proposed: reinforcing stope supports in conjunction with reducing mining height, or drilling ground holes to pre-split the main roof. Based on a comprehensive consideration of economic factors and the two categories of support failure causes, the method of reinforcing stope supports while reducing mining height was selected for use on the mining site.     

Subsidence over room and pillar retreat mining in a low coal seam

The objective of this paper is to study the behavior of a low thick and low depth coal seam and the overburden rock mass. The mining method is room and pillar in retreat and partial pillar recovery. The excavation method is conventional drill and blast because of the small production. The partial pillar recovery is about 30% of the previous pillar size, 7 m × 7 m. The roof displacement was monitored during retreat operation; the surface movement was also monitored. The effect of the blasting vibration on the final pillar strength had been considered. Due to blasting, the pillar reduced about 20%. The consequence is more pillar deformation and roof vertical displacement. The pillar retreat and ground movement were simulated in a three-dimensional numerical model. This model was created to predict the surface subsidence and compare to the subsidence measured. This study showed that the remaining pillar and low seam reduce the subsidence that was predicted with conventional methods.     

Coal pillar mechanics of violent failure in U.S. Mines

This paper seeks to enhance the understanding that the horizontal stresses build up and release during coal pillar loading and unloading(post-failure) drawing upon three decades of observations, geomechanical monitoring and numerical modeling in bump-prone U.S. mines. The focus is on induced horizontal stress in mine pillars and surrounding strata as highly stressed pillars punch into the roof and floor, causing shear failure and buckling of strata; under stiff stratigraphic units of some western US mines, these events could be accompanied by violent failure of pillar cores. Pillar punching eventually results in tensile stresses at the base of the pillar, facilitating transition into the post-failure regime; this transition will be nonviolent if certain conditions are met, notably the presence of interbedded mudstones with low shear strength properties and proper mine designs for controlling seismicity and dynamic loads. The study clearly shows high confining stress build-up in coal pillars resulting in up to twice higher peak vertical stress and high strain energy accumulations in some western US mines in comparison with peak stresses predicted using common empirical pillar design methods. It is the unstable release of this strain energy that can cause significant damage resulting from pillar dilation and ground movements. These forces are much greater than the capacity of most common internal support systems, resulting in horizontal stressinduced roof falls locally, in mines under unremarkable far-field horizontal stress. Attention should be placed on pillar designs as increasing support density may prove to be ineffective. This mechanism is analyzed using field measurements and generic finite-difference stress analyses. The study confirms the higher load carrying capacity of confinement-controlled coal seams in comparison with structurally controlled coal seams. Such significant differences in confining stresses are not taken into account when estimating peak pillar strength using most common empirical techniques such as those proposed by Bieniawski and Salamon. While using lower pillar strength estimates may be considered conservative,it underestimates the actual capacity of pillars in accumulating much higher stress and strain energies,misleading the designer and inadvertently diminishing mine safety. The role of induced horizontal stress in mine pillars and surrounding strata is emphasized in coal pillar mechanics of violent failure. The triggering mechanism for the violent events is sudden loss of pillar confinement due to dynamic loading resulting from failure of overlying stiff and strong strata. Evidence of such mechanism is noted in the field by observed red-dust at the coal-rock interfaces at the location of coal bumps and irregular, periodic caving in room-and-pillar mines quantified through direct pressure measurements in the gob.     

Application of HEMS cooling technology in deep mine heat hazard control

This paper mainly deals with the present situation, characteristics, and countermeasures of cooling in deep mines. Given existing problems in coal mines, a HEMS cooling technology is proposed and has been successfully applied in some mines. Be-cause of long-term exploitation, shallow buried coal seams have become exhausted and most coal mines have had to exploit deep buried coal seams. With the increase in mining depth, the temperature of the surrounding rock also increases, resulting in ever increasing risks of heat hazard during mining operations. At present, coal mines in China can be divided into three groups, i.e., normal temperature mines, middle-to-high temperature mines and high temperature mines, based on our investigation into high temperature coal mines in four provinces and on in-situ studies of several typical mines. The principle of HEMS is to extract cold energy from mine water inrush. Based on the characteristics of strata temperature field and on differences in the amounts of mine water inrush in the Xuzhou mining area, we proposed three models for controlling heat hazard in deep mines: 1) the Jiahe model with a moderate source of cold energy; 2) the Sanhejian model with a shortage of source of cold energy and a geothermal anomaly and 3) the Zhangshuanglou model with plenty of source of cold energy. The cooling process of HEMS applied in deep coal mine are as follows: 1) extract cold energy from mine water inrush to cool working faces; 2) use the heat extracted by HEMS to supply heat to buildings and bath water to replace the use of a boiler, a useful energy saving and environmental protection measure. HEMS has been applied in the Jiahe and Sanhejian coal mines in Xuzhou, which enabled the temperature and humidity at the working faces to be well controlled.     

Pillar design and coal burst experience in Utah Book Cliffs longwall operations

Longwall mining has existed in Utah for more than half a century. Much of this mining occurred at depths of cover that significantly exceed those encountered by most other US longwall operations. Deep cover causes high ground stress, which can combine with geology to create a coal burst hazard. Nearly every longwall mine operating within the Utah's Book Cliffs coalfield has been affected by coal bursts. Pillar design has been a key component in the burst control strategies employed by mines in the Book Cliffs.Historically, most longwall mines employed double-use two-entry yield pillar gates. Double-use signifies that the gate system serves first as the headgate, and then later serves as the tailgate for the adjacent panel. After the 1996 burst fatality at the Aberdeen Mine, the inter-panel barrier design was introduced.In this layout, a wide barrier pillar protects each longwall panel from the previously mined panel, and each gate system is used just once. This paper documents the deep cover longwall mining conducted with each type of pillar design, together with the associated coal burst experience. Each of the six longwall mining complexes in the Book Cliffs having a coal burst history is described on a panel-by-panel basis.The analysis shows that where the mining depth exceeded 450 m, each design has been employed for about 38000 total m of longwall panel extraction. The double-use yield pillar design has been used primarily at depths less than 600 m, however, while the inter-panel barrier design has been used mainly at depths exceeding 600 m. Despite its greater depth of use, the inter-panel barrier gate design has been associated with about one-third as much face region burst activity as the double-use yield pillar design.     

Deformation and failure study of surrounding rocks of dynamic pressure roadways in deep mines

In order to understand the change rules of stress-displacement in surrounding rocks of dynamic pressure roadways in deep mines and to obtain a theoretical basis for analyses of roadway stability and designs of support,we established a coupling equation of adjacent rock strength,mining stress and supporting resistance on the basis of an elastic-plastic theory of mechanics.We obtained an analytical solution for stress and displacement distribution of elastic and plastic regions in surrounding rock of dynamic pressure roadway..Based on this theory,we have analyzed the changes in stress-displacement in elastic and plastic regions of surrounding rocks of dynamic pressure roadways in the Haizi Coal Mine.The results show that:1) radial and tangential stress change violently within the first 4 m from the inner surface of a roadway after excavation;radial stress increases while tangential stress decreases within a range of about 6 m from the inner surface of the roadway as a function of q3;2) radial and tangential stress increase with an increase in the mining pressure coefficient k;the increase in the rate of tangential stress is greater than that of radial stress;3) the radial displacement of the inner surface of roadways decreases with an increase in q3,provided that k remains unchanged.     

Rock burst laws in deep mines based on combined model of membership function and dominance-based rough set

Rock bursts are spontaneous, violent fracture of rock that can occur in deep mines, and the likelihood of rock bursts occurring increases as depth of the mine increases. Rock bursts are also affected by the compressive strength, tensile strength, tangential strength, elastic energy index, etc. of rock, and the relationship between these factors and rock bursts in deep mines is difficult to analyze from quantitative point. Typical rock burst instances as a sample set were collected, and membership function was introduced to process the discrete values of these factors with the discrete factors as condition attributes and rock burst situations as decision attributes. Dominance-based rough set theory was used to generate preference rules of rock burst, and eventually rock burst laws analysis in deep mines with preference relation was taken. The results show that this model for rock burst laws analysis in deep mines is more reasonable and feasible, and the prediction results are more scientific.     

Practical assessment of rock damage due to blasting

Blasting is the most cost effective methodology to break rock for mining or civil engineering applications.A good production blast will break only the rock that is needed to be removed, leaving the host rock with minimal damage. The control of rock damage due to blasting is very important when it comes to mine or construction design, safety, and cost. Damage to the host rock due to a production blast could result in failures, overbreak and unstable ground. Knowing how far the fractures generated by a production blast will go into the host rock is a valuable tool for engineers to design a safe highwall while keeping the actual excavation close to the design. Currently, there are several methods available to predict damage due to blasting. The accuracy of many of these methods is questionable, and in most cases, the methodologies over predict the results. This often leads to inefficient mines and poor construction works. When the current methodologies are reviewed, each one presents sound approaches, but in many cases they also lack consideration of other variables that, according to the authors, need to be included when predicting blast damage. This paper presents a practical methodology to assess the rock damage from blasting by combining other methodologies. The proposed method allows consideration of more variables when compared to available methods, resulting in a more accurate rock damage assessment. The method uses the estimation of the generated levels of peak particle velocity with the distance from a production blast presented by Persson and Holmberg, the peak particle velocity damage ranges proposed by Forsyth and the relationship between the static compressive strength and dynamic compressive strength of rocks from Liu. The new methodology was validated using the data published in a large-scale study performed in granite by Siskind.