New mining technique with big panels and stopes in deep mine

For the purpose to suit the bad mining technical conditions, such as deep imbed, gentle dip angle, and high initial stress in Dongguashan deposit, the stoping scheme was optimized. The new mining technique, with temporary curtain walls, large panels and stopes, was achieved as well. The deposit model, which was built through the DATAMINE, was led into FLAC^3D for numerical simulation. Based on these, the stabilities of pillars and stopes were analyzed. On the other hand, the impact of output stability by new scheme was verified with the help of optimization planning theory. The results show that stopes and curtain walls are safe when the width of temporary curtain walls between panels are 18 m. The length and width of stope increase to 78 m （82 m） and 18 m respectively, and those of panel increase to 300-500 m and 100 m respectively. The commercial test indicates that the new scheme can attain the aims of simpler production organization, better stope ventilation and work condition, smaller quantities of development and cutting, and 2/3 of equipments as before with the stable output. The pillar stoping technique is credible and valuable.     

大团山矿床采空区处理方法

采用岩石力学原理和方法,通过现场初始地应力实测、室内岩石力学性质试验和矿床开采全过程的三维有限元模拟,系统地分析了大团山矿床开采过程中采空区顶底板和矿柱的稳定性。结果表明,矿柱宽度小于２７．５ｍ时,矿柱将会发生失稳,增加矿柱宽度对采空区顶底板稳定性的影响并不明显。据此进一步提出了一套合理的空区处理方法,并被设计和生产所采纳     

滨海大型金矿床取消矿柱及房柱交替采矿的新工艺

针对三山岛金矿条件,研究了深部开采取消点柱的工艺技术。首先,调查测试了矿岩物理力学参数,并对矿岩质量进行了分级。其次,在详细分析上下盘及矿体的物理力学特性的基础上,对三山岛金矿深部开采取消矿柱进行了有限元数值模拟,研究得出-555m水平以下矿体的开采可全面取消矿柱。最后,结合矿床条件,提出了房柱交替式盘区上向分层充填采矿新工艺。工业试验结果显示,该新工艺大幅度提高了单位面积开采强度,对岩层扰动小,盘区生产能力大,矿石损失贫化小,获得了显著的经济效益。此外,对三山岛金矿由于深部开采而导致的地表沉降利用ANSYS软件进行分析,同时对岩层变形进行了监测。结果表明,三山岛金矿深部开采取消矿柱和采用房柱交替采矿新工艺后能够有效控制岩层变形,从而可实现滨海大型金矿床安全高效低贫损开采。     

Instantaneous and long-term deformation characteristics of deep room-pillar system induced by pillar recovery

The goaf may face a series of deformation and settlement problems when the room-pillar mining method is used to excavate ore and pillars in the deep strata. To this end, a deep room-pillar model with two levels was made, and the pillar recovery was carried out. The instantaneous deformation responses during the pillars recovery and the long-term settlements after the pillar recovery were analyzed. During the pillar recovery, different regions of surrounding rocks suffer from different dynamic disturbances which can be divided into three types, including (I) the combined action of blasting disturbance and unloading disturbance, (II) the sequential action of blasting disturbance and unloading disturbance, and (III) the action of unloading disturbance. After the pillar recovery, the settlement above the first recovering pillar is the largest, which has a traction effect on the settlement in other areas. The settlement process can be divided into two stages, stable displacement stage and unstable displacement stage. When the pillar-room system undergoes the unstable displacement stage, rock spalling and further cascading collapse will occur.     

Effects of pre-straining and coating on plastic deformation of aluminum micropillars

The plastic deformation of micropillars is known to be affected by whether dislocations can escape easily from the material volume, and the extent to which the dislocations mutually interact during the deformation. In this work, pre-straining and coating are used to modify the initial dislocation content and the constraints on the escape of dislocations. Aluminum micropillars in the size range from ～1 to ～6 μm, with or without thin coating by tungsten deposition and pre-straining by 7%, were compressed using a flat-punch nanoindenter to study their plasticity behavior. The results reveal very different behavior between the size regime of a few microns and that of ～1 μm. For pillars a few microns large, coating leads to significant strengthening, and pre-straining by 7% also produces a mild strengthening effect. The proof strength also exhibits good correlation with the square root of the residual dislocation density measured by transmission electron microscopy after deformation, indicating that strength in this size regime is controlled by dislocation interactions as in traditional Taylor hardening. Coating evidently helps retain dislocations inside the pillar, and pre-straining increases the initial dislocation content; both effects lead to more severe strain hardening during deformation. For smaller pillars ～1 μm in size, however, pre-straining results in softening, although coating still leads to strengthening, and the strength exhibits no correlation with the residual dislocation density, which remains close to the initial value even with coating. These suggest dislocation starvation in this small size regime and that strength is controlled by the availability of mobile dislocations. Coating cannot effectively trap dislocations inside the pillar, but can still strengthen the pillar, presumably because dislocation nucleation is more difficult at the coated surface.     

无间柱连续采矿法矿段回采的地压规律与控制技术

以某铜金属矿山为例,简介无间柱连续采矿法的技术思路和具体方案。运用能模拟开挖与充填的三维有限单元法程序,对无间柱连续采矿法 矿段回采的实际采矿过程进行数值分析,得出了无间柱连续采矿法的地压活动规律,提出相应的地压控制措施,为无间柱连续采矿法在试验矿山的应用和推广提供了依据。     

水平层状优势节理石灰岩采空区顶板破坏特征及其影响机制

为研究层状石灰岩采空区顶板的破坏特征及影响机制问题,在梅州某地下矿调研的基础上,构建采空区水平层状优势节理顶板力学模型,推导其应力分量表达式;结合M-C岩体强度准则,给出任意点岩体破坏判定值Z及其峰值数学式,分析顶板可能出现的变形破坏类型及失稳特征.结果表明:顶板的顶部、下部、两侧翼等位置出现4个判定峰值区域,依照Z值...     

露天与地下联合开采采空区稳定性分析

针对拉拉铜矿露天与地下联合开采的复杂情况,采用FLAC3D分析一定的隔离矿柱支撑下采空区围岩变形及破坏特征。依据岩石力学摩尔—库伦准则,采用FLAC3D内嵌的FISH语言定义了剪切安全度及拉伸安全度两种破坏判据。依据模拟结果,为施工设计提供理论依据。     

铝土矿采场矿石顶板承载机理与厚度优化

基于弹性薄板理论,分析矿石顶板破坏的主要规律,推导矿石顶板的厚度求解公式.研究结果表明:矿石顶板中心的拉应力是矿石顶板破坏的主要原因,根据该点的极限破坏条件推导出矿石顶板的厚度求解公式;以某铝土矿第10采场为工程案例,经过求解,该采场最优矿石顶板厚度为0.36 m,考虑安全系数为1.3,设计矿石顶板厚度为0.5 m;在...     

Size effects in the superelastic response of Ni54Fe19Ga27 shape memory alloy pillars with a two stage martensitic transformation

The superelastic behavior of Ni₅₄Fe₁₉Ga₂₇ shape memory alloy (SMA) single crystalline pillars was studied under compression as a function of pillar diameter. Multiple pillars with diameters between 10 μm and 200 nm were cut on a single crystalline bulk sample oriented along the [1 1 0] direction as the compression axis and that had undergone fully reversible two stage martensitic transformation, i.e. L2₁ austenite to 10M/14M modulated martensite and then to L1_o martensite. The results revealed an increase in the critical stress for stress-induced martensitic transformation and the yield strength of martensite with decreasing pillar size. The stress hysteresis also increased with the reduction in pillar size and the superelastic response started to diminish below 500 nm pillar diameter. Two-stage martensitic transformation was suppressed for pillar sizes of 1 μm and below, which were shown to exhibit a direct austenite to L1_o transformation. Such a change in the transformation pathway, i.e. from a two stage to one stage transformation, was also observed in bulk single crystals with increasing temperature. We demonstrated the absence of two stage transformation in bulk at high temperatures. This finding suggests that decreasing the sample size and increasing the temperature have similar effects on the superelastic response of NiFeGa SMAs that had undergone two-stage transformation and indicates that a reduction in pillar diameter decreases the transformation temperature due to the difficulty of martensite nucleation on small scales. The damping coefficients of the pillars were also calculated and the results highlighted that damping capacities higher than those of bulk metallic alloys can be achieved using submicron sized pillars.     

The deformation of Gum Metal through in situ compression of nanopillars

The name “Gum Metal” has been given to a set of β-Ti alloys that achieve exceptional elastic elongation and, with appropriate preparation, appear to deform by a dislocation-free mechanism triggered by elastic instability at the limit of strength. We have studied the compressive deformation of these materials with in situ nanocompression in a quantitative stage in a transmission electron microscope. The samples studied are cylindrical nanopillars 80–250 nm in diameter. The deformation pattern is monitored in real time using bright-field microscopy, dark-field microscopy or electron diffraction. Interesting results include the following: (i) nanopillars approach, and in several examples appear to reach, ideal strength; (ii) in contrast to conventional crystalline materials, there is no substantial “size effect” in pillar strength; (iii) the deformation mode is fine-scale with respect to the sample dimension, even in pillars of 100 nm size; (iv) shear bands (“giant faults”) do form in some tests, but only after yield and plastic deformation; and (v) a martensitic transformation to the base-centered orthorhombic α′′ phase is sometimes observed, but is an incidental feature of the deformation rather than a significant cause of it.     

Effects of size on the mechanical response of metallic glasses investigated through in situ TEM bending and compression experiments

Quantitative bending and compression tests on micropillars made of two different amorphous alloys, with tip diameters ranging from 93 to 645 nm, are performed in situ in a transmission electron microscope (TEM). Under microcompression each pillar shows an intermittent plastic flow accommodated by inhomogeneous shear banding. However, the individual shear banding events are strongly size-dependent, i.e. in larger pillars the deformation is controlled by nucleation of shear bands, but in smaller pillars it becomes propagation-controlled. On the other hand, the yield stress is essentially size-independent. Microbending tests show further advantages by amplifying size effects and minimizing artifacts. An interesting finding is that by microbending, a switch from highly inhomogeneous to fully homogeneous deformation is observed at an experimentally accessible size regime near 200 nm, whereas it is not accessible under microcompression, even at a sub-100 nm scale. These size effects are well interpreted by a micromechanical model, leading to a deformation map in the stress-size space. A physical picture of nanoscale shear localization process is also provided.     

Plastic deformation and residual stresses in amorphous silica pillars under uniaxial loading

We have carried out uniaxial compression of micron-scale amorphous silica pillars. We have measured load–displacement curves and observed the morphology of the pillars after unloading, providing strong evidence for large plastic deformations. Minor cracking is also observed, with a well-defined pattern. We find that the van Mises stress in compression is comparable to the intrinsic tensile strength of silica. Precise analysis of the deformation of the pillars has been carried out by finite element modeling (FEM) using the constitutive equation determined previously (G. Kermouche et al., Acta Materialia, 56 (2008) 3222), which quantitatively takes into account densification, shear flow and strain hardening. The residual stress distribution we predict by FEM matches the observed crack pattern well. Finally the calculated stress fields in pillar compression and cone indentation are compared. We propose an interpretation of the contrasts in terms of confinement.     

Loss of pseudoelasticity in nickel–titanium sub-micron compression pillars

Nickel–titanium (NiTi) is capable of undergoing pseudoelastic deformation wherein relatively large amounts of inelastic deformation are recovered upon load removal due to a martensitic phase transformation. This study investigates pseudoelastic as well as plastic deformation in sub-micron diameter NiTi compression pillars. Pillars ranging in diameter from approximately 2 μm to 200 nm were prepared using focused ion beam micro-machining of aged [1 1 1] single crystal NiTi. Results reveal pseudoelasticity in all samples tested with diameters between 2 μm and 400 nm, although permanent strain was introduced at relatively low strains compared to bulk. Decreased sample size generally showed a smaller stress–strain hysteresis, with a full loss of recoverable pseudoelastic strain for samples with a diameter smaller than 200 nm. In addition, plastic flow stress of the martensite was shown to be independent of sample diameter for the aged NiTi material. Lastly, it is observed that crystallographic orientation has a stronger influence on martensite plastic flow strength than pillar size.     

Optimization of mining method in subsea deep gold mines: A case study

The mining method optimization in subsea deep gold mines was studied. First, an index system for subsea mining method selection was established based on technical feasibility, security status, economic benefit, and management complexity. Next, an evaluation matrix containing crisp numbers and triangular fuzzy numbers (TFNs) was constructed to describe quantitative and qualitative information simultaneously. Then, a hybrid model combining fuzzy theory and the Tomada de Decisão Interativa Multicritério (TODIM) method was proposed. Finally, the feasibility of the proposed approach was validated by an illustrative example of selecting the optimal mining method in the Sanshandao Gold Mine (China). The robustness of this approach was demonstrated through a sensitivity analysis. The results show that the proposed hybrid TODIM method is reliable and stable for choosing the optimal mining method in subsea deep gold mines and provides references for mining method optimization in other similar undersea mines.     

基于正交规划的最优模锻工艺方案设计准则实验研究

分析了采用传统方法建立模锻工艺方案设计准则存在的问题,提出基于正交规划挖掘最优模锻工艺方案设计准则的思想.从影响轴对称锻件模锻工艺方案的诸多因素中选择轮毂的高和宽作为关键因子,进而针对这两个因子采用两因子两次组合正交规划法安排实验.并从判断模锻工艺方案优劣的多个因素中选择飞边金属消耗作为目标函数,在实验中实测该目标函数值.当轮毂的高和宽取某一固定值时,根据实验结果,从多个实验方案中选择使飞边金属消耗最小的工艺方案作为最优模锻工艺方案,从而获得最优模锻工艺方案设计准则.     

Enhancement of plasticity in Zr-based bulk metallic glasses electroplated with copper coatings

Electrodeposition was used to coat copper films on the surface of the BMG pillars (bulk metallic glasses) of Zr_52.5Cu_17.9Ni_14.6Al₁₀Ti₅ (Vit. 105) with the film thicknesses of 71.5 and 161.1 μm. The experimental results of the compression tests of the bare Vit. 105 pillars and the coated Vit. 105 pillars revealed that the copper costing increased the density of shear bands in the Vit. 105 pillars formed during the tests, resulting in the improvement of plasticity. The plastic strain was 6.1% for the coated pillars with a coating thickness of 161.1 μm, which is 3.59 times of 1.7% of the bare Vit. 105 pillars. The deformation of the copper films dissipated the strain energy and limited the propagation of shear bands, which led to the initiation and formation of multiple shear bands. The technique developed in this work provides an effective way to enhance the plasticity of BMGs at room temperature.     

湘西金矿深部采场稳定性计算机模拟分析

湘西金矿缓倾斜薄矿脉开采深度大， 地质情况复杂，存在一些未能完全解决的技术和理论难题。作者运用ＲＦＰＡ’９８ 数值模拟软件系统， 结合湘西金矿深部开采综合技术研究课题， 计算分析了深部采场的稳定性。计算结果表明： 在断层、裂隙发育的试验采场， 当采场跨度达到６ ｍ 以后， 顶板局部开始垮落；当跨度达到１０ ｍ ｍ 以后， 顶板中部发生冒顶事故。由此提出了相应的采场结构参数、顶板水压支柱支护、地压监测预报等综合地压控制措施。实际应用表明， 这些措施有效地维护了采场的稳定， 使回采作业安全、顺利地完成， 获得了理想的效果。     

基于正交试验的车顶盖板冲压工艺参数模拟研究

针对车顶盖板冲压成形后局部最小厚度和最大厚度能够反映材料开裂和起皱的趋势,通过正交试验和AutoForm冲压模拟软件相结合,采用单因素试验和正交试验,以厚度变化量为评价指标,研究了压边力、冲压速度、摩擦系数、凸凹模间隙和拉深筋宽度对厚度的影响规律。采用极差和方差分析,确定了各因素影响的主次顺序以及不同因素对厚度影响的显著性,获得了最优冲压工艺参数,最后以实际生产出的实物模型进行验证。结果表明:厚度变化量随着各因素数值的增大而逐渐降低;各因素对最小厚度影响的主次顺序和选取的数值为:冲压速度1500 mm·s~(-1)、摩擦系数0.15、凸凹模间隙0.63 mm、拉深筋宽度18 mm、压边力200 kN。     

Roof-crush strength improvement using rigid polyurethane foam

Recent bending tests show the effectiveness of rigid, polyurethane foam in improving the strength of automotive body structures. By using foam, it is possible to reduce pillar sections, and to reduce thicknesses or eliminate reinforcements inside the pillars, and thereby offset the mass increase due to the foam filling. Further tests showed that utilizing the foam filling in a B-pillar to reduce section size can save ~20 mm that could be utilized to add energy absorbing structures in order to meet the new interior head impact requirements specified by the federal motor vehicle safety standards (FMVSS) 201 Head Impact Protection upgrade.