膏体充填中挡墙安全性分析

In underground mining, there has been an increasing use of “cemented paste” for the backfilling of stopes. As this cemented paste backfill (CPB) enters the stope as a fluid, shotcrete barricades are often used to retain the fill material during and after the filling operations. However, failures of barricades have been reported around the world in recent years. This paper presents an analytical solution based on the elastic thin plate theory for calibrating the design of shotcrete barricades in underground mines using CPB. This solution was used to determine the quantitative relationships between the lateral loading from the paste and the barricade response during the backfilling process. The results show that the proposed solution agrees well with in situ data. According to the actual barricade responses, the acceptable tensile stress and an analysis method of cracks development are proposed. The proposed solution has practical significance for underground mines.     

Stability Control of Underground Construction

<正>This paper presents the reason for instability of underground construction.In order to know failure mechanism during the whole construction process,a research framework of multi-scale based on experiments and numerical analysis is established.Some promising aspects in the topics of stability control are also given in the paper.     

尾砂膏体充填体在冲击载荷作用下的长期力学行为及特性

Cemented tailings backfill (CTB) structures are important components of underground mine stopes. It is important to investigate the characteristics and dynamic behavior of CTB materials because they are susceptible to disturbance by dynamic loading, such as excavation and blasting. In this study, the authors present the results of a series of Split–Hopkinson pressure bar (SHPB) single and cyclic impact loading tests on CTB specimens to investigate the long-term dynamic mechanical properties of CTB. The stress–strain relationship, dynamic strength, and dynamic failure characteristics of CTB specimens are analyzed and discussed to provide valuable conclusions that will improve our knowledge of CTB long-term mechanical behavior and characteristics. For instance, the dynamic peak stress under cyclic impact loading is approximately twice that under single impact loading, and the CTB specimens are less prone to fracture when cyclically loaded. These findings and conclusions can provide a new set of references for the stability analysis of CTB materials and help guide mine designers in reducing the amount of binding agents and the associated mining cost.     

Long-term mechanical behavior and characteristics of cemented tailings backfill through impact loading

Cemented tailings backfill(CTB) structures are important components of underground mine stopes. It is important to investigate the characteristics and dynamic behavior of CTB materials because they are susceptible to disturbance by dynamic loading, such as excavation and blasting. In this study, the authors present the results of a series of Split–Hopkinson pressure bar(SHPB) single and cyclic impact loading tests on CTB specimens to investigate the long-term dynamic mechanical properties of CTB. The stress–strain relationship, dynamic strength, and dynamic failure characteristics of CTB specimens are analyzed and discussed to provide valuable conclusions that will improve our knowledge of CTB long-term mechanical behavior and characteristics. For instance, the dynamic peak stress under cyclic impact loading is approximately twice that under single impact loading, and the CTB specimens are less prone to fracture when cyclically loaded. These findings and conclusions can provide a new set of references for the stability analysis of CTB materials and help guide mine designers in reducing the amount of binding agents and the associated mining cost.     

Geomechanical design of a room and rib pillar granite mine

The geomechanical and stability design of an underground granite mine located in Canal San Bovo (Trento district, Northeastern Italy) was described. The exploitation of the granite, which is used in the ceramic industry, was carried out by the rooms and rib pillars method. The rooms are 12 m wide while the pillars are 11 m wide and they cross the main discontinuity set of the rock mass in the perpendicular direction. To verify the stability condition of an underground mine, it is necessary to carry out the calculations that are able to check both the local and global stability of the rock mass. In the studied example, this approach has been applied with the development of analytical and numerical parametric analyses and it has permitted to get the best orientation and to design the size of rooms and pillars.     

Research on droplet formation and dripping behavior during the electroslag remelting process

A better understanding of droplet formation and dripping behavior would be useful in the efficient removal of impurity elements and nonmetallic inclusions from liquid metals. In the present work, we developed a transparent experimental apparatus to study the mechanisms of droplet formation and the effects of filling ratio on droplet behavior during the electroslag remelting (ESR) process. A high-speed camera was used to clearly observe, at small time scales, the droplet formation and dripping phenomenon at the slag/metal interface during a stable ESR process. The results illustrate that a two-stage process for droplet formation and dripping occurs during the ESR process and that the droplet diameter exhibits a parabolic distribution with increasing filling ratio because of the different shape and thermal state of the electrode tip. This work also confirms that a relatively large filling ratio reduces electricity consumption and improves ingot quality.     

Review on aggregation of acid extractants in solvent extraction of metal ions: remark on the general model

The aggregation behavior of various acid extractants in the solvent extraction systems of metal ions is re-examined and explained according to knowledge obtained in recent work. The conclusions are as follows. (1) Complexes formed by the extractants and metal ions can form reversed micelles in organic diluents, depending on the microstructures of the complexes. The dimers of the acid extractant cannot percolate to the metal-extractant aggregates, and the acid-salt complexes are always formed in the aggregates. The reversed micelles or the W/O microemulsions formed by different species cannot be associated with each other to form a unified aggregate. (2) In solvent extraction systems, hydration of the extractants and metal ions can be considered as the driving force of forming reversed micelles. (3) Information of the first approach to the insight of the bicontinuous microemulsion of NaDEHP shows that various components in the aqueous phase behave confined and very similar to the typical AOT/n-heptane W/O microemulsions. (4) In the extraction of lanthanide ions by the W/O microemulsion of sodium naphthenate, the saponification is a process of forming reversed micelle or W/O microemulsion, while the extraction step is a process of destroying reversed micelles or W/O microemulsion droplets.     

养护湿度对充填体性能的影响规律

Cemented paste backfill (CPB), a mixture of tailings, binder, and water, is widely and extensively used for the recovery of mineral resources, the prevention of ground subsidence, and the management of mine waste. When installed, the CPB is subjected to complex environmental conditions such as water content, temperature, and power, which have a significant impact on its efficiency. Thus, this study conducts a series of laboratory programs, including investigation of moisture, temperature, stress–strain relation, and microstructure to show the effect of curing humidity on the CPB behaviors. The results obtained indicate that ambient humidity can have a dramatic effect on CPB in terms of its macro performance of internal relative humidity, temperature and strength, as well as the micro expression. Typical examples of these effects on CPB include an increase in curing humidity, which favors binder hydration, and then an increase in hydration materials, temperature and peak stress in the CPB. The results obtained will lead to a better understanding of CPB’s responses to various environmental conditions.     

Effect of curing humidity on performance of cemented paste backfill

Cemented paste backfill(CPB), a mixture of tailings, binder, and water, is widely and extensively used for the recovery of mineral resources, the prevention of ground subsidence, and the management of mine waste. When installed, the CPB is subjected to complex environmental conditions such as water content, temperature, and power, which have a significant impact on its efficiency. Thus, this study conducts a series of laboratory programs, including investigation of moisture, temperature, stress–strain relation, and microstructure to show the effect of curing humidity on the CPB behaviors. The results obtained indicate that ambient humidity can have a dramatic effect on CPB in terms of its macro performance of internal relative humidity, temperature and strength, as well as the micro expression. Typical examples of these effects on CPB include an increase in curing humidity, which favors binder hydration, and then an increase in hydration materials, temperature and peak stress in the CPB. The results obtained will lead to a better understanding of CPB's responses to various environmental conditions.     

全尾砂膏体充填材料早期强度、性能改善及稳定性分析

High-density tailings, small cementitious materials, and additives are used for backfill materials with poor early compressive strength (ECS), which may greatly affect the mining and backfill cycle, to prepare paste backfill materials (PBMs) with a high ECS. The effects and mechanisms of different early strength agents on the property of PBM are investigated. The action mechanism of additives on the properties of PBM is also analyzed through X-ray diffraction, scanning electron microscope, and energy dispersive spectrometry. Results show that the effects of single-component additives 1, 3, and 6 are better than those of the other additives, and their optimal dosages are 3wt%, 1wt%, and 3wt%, respectively. The optimum multicomponent combinations are 1wt% of additive 1 and 1.5wt% of additive 6. The ECS of the paste with additive 10 increases to a greater extent than that of the other pastes because of the synergistic action of additive 1 with additive 6. The hydration product of Ca(OH)₂ is consumed, and more C–S–H gels are generated with the addition of additives to paste. Tailings particles, ettringite crystals, and gels intertwined with one another form a dense net-like structure that fills the pores. This structure can significantly improve the ECS of PBM.     

Advances in Tube Hydroforming - An Enabling Technology for Low-Mass Vehicle Manufacturing-Material, Lubrication, Loading, Simulation Issues, and Alternatives

The tube hydroforming process (THF) has recently found a wide application opportunity in the automotive industry, and is of increasing interest to other industries as well. The increased interest stems from the fact that, through the THF process, manufacturers are able to produce complex, consolidated,lightweight parts with reduced number of post-processing than through alternative metal forming techniques.In order to fully realize the benefits of this technology, various aspects have been under investigation in academia and industry world-wide. In this paper, effect of loading path, incoming material variation, and lubrication on the robustness of the hydroforming process and final part specifications are summarized based on previous experimental and computational work. In addition, the simulation of hydroforming and examples are presented in comparison with experimental findings. Briefly, results emphasized the importance of the loading path design whereas material variation within the experimentally tested range was not found to be significantly effective on the final part specifications. Selection of a lubricant for hydroforming of a frame rail part was presented demonstrating several aspects of lubrication selection methodology. Results of friction experiments show that only thickness, axial feeding, and force measurements are good indications of lubricant performance as these are found to be strongly discriminative.     

Processing investigation and optimization for hybrid thermoplastic composites

A thermoplastic based composite material is suitable for automobile and aerospace applications. The recyclability of thermoplastic and clean processing further enhance its use. The only limitation encountered in using this material is its high-melt viscosity. Various techniques have been developed to overcome this problem. Commingled materials are one of such methods adopted for making proper use of thermoplastic. A major problem observed during the use of a commingled material is its de-commingling, wherein, the uniform distribution of fiber and thermoplastic yam gets disturbed and affects the final quality of the composite. The effects of the braiding process on laminate quality were investigated. Flat plaques were produced by braiding the commingled yam, using a 48-carrier braiding machine. The braids (and control woven samples) were subsequently heated and consolidated in a nonisothermal compression molding operation. Prior to the manufacture of the ‘best quality’ plaques, a series of moldings were produced under different consolidation conditions, to study the dependence of properties on the process variables. This enabled a processing window to be established for each material and helped to separate the respective effects of yam handling, textile processing, and consolidation on laminate properties.     

Basic rules for rheologic forging process of semisolid alloy

Semisolid mold forging is a major type of semisolid processing, which is different from neither traditional mold forging nor traditional permanent casting. However, processing defects are often seen in work pieces because of lacking available rules for the process design and control. Some basic rules for the process design and control, simply named the shortest flowing length, pressure filling and the minimum uplifting mold pressure, are advanced in the paper based on amount of researches and experiments. The equations to determine the major process parameters are given out such as the filling pressure, forming pressure and locking mold pressure for the process design and control. The rules and equations are experimentally proved available and applicable by several actual work pieces produced by the semisolid forging process.     

Early-age strength property improvement and stability analysis of unclassified tailing paste backfill materials

High-density tailings, small cementitious materials, and additives are used for backfill materials with poor early compressive strength(ECS), which may greatly affect the mining and backfill cycle, to prepare paste backfill materials(PBMs) with a high ECS. The effects and mechanisms of different early strength agents on the property of PBM are investigated. The action mechanism of additives on the properties of PBM is also analyzed through X-ray diffraction, scanning electron microscope, and energy dispersive spectrometry. Results show that the effects of single-component additives 1, 3, and 6 are better than those of the other additives, and their optimal dosages are 3 wt%, 1 wt%,and 3 wt%, respectively. The optimum multicomponent combinations are 1 wt% of additive 1 and 1.5 wt% of additive 6. The ECS of the paste with additive 10 increases to a greater extent than that of the other pastes because of the synergistic action of additive 1 with additive 6. The hydration product of Ca(OH)_2 is consumed, and more C–S–H gels are generated with the addition of additives to paste. Tailings particles,ettringite crystals, and gels intertwined with one another form a dense net-like structure that fills the pores. This structure can significantly improve the ECS of PBM.     

3 D structure parameterization design and modeling for irregular structure of stope bottom

Stope mining design is a very important and complicated task in daily production design and technical management of an underground mine.Based on workface technology and human-computer interaction technology, this study introduces a method of 3D parametric design for the irregular struc-ture of stope bottoms, and focuses on solving technical problems in surface modeling of stope bottom structure.Optimization of the minimum span length algorithm ( MSLA) and the shortest path search algorithm ( SPSA) is conducted to solve the problem of contour-line based instant modeling of stope bottom structures, which makes possible the 3D parametric design for irregular structure of stope bot-tom.Implementation process and relevant methods of the proposed algorithms are also presented. Feasibility and reliability of the proposed modeling method are testified in a case study.In practice, the proposed 3D parameterization design method for irregular structure stope bottom proves to be very helpful to precise 3D parametric design.This method is capable of contributing to improved efficien-cy and precision of stope design, and is worthy of promotion.     

Evolution of plant reproduction: From fusion and dispersal to interaction and communication

Based on the existing data concerning the evolution of the sexual reproduction, it is argued that the processes of sex differentiation and interactions play a key role in evolution. From the beginning environment and organism are unified. In a changing dynamic environment life originates and the interaction between life and environment develops from simple to more complex organisms. Sexual reproduction is introduced after the origin of meiosis and is a key process in evolution. The asexual reproduction process prepares to dispersal. Sexual reproduction process adds the genome renewal and the gamete-gamete interaction. Reproduction and dispersal are connected and the process of reproduction has similarities between asexual and sexual reproduction. Unicellular algae develop the physiological and morphological sex differentiation. Sex differentiation is connected with the way of dispersal. The step to multicellular plants introduces cell isolation after meiosis and by the stay on the mother plant within a cell or organ, plant-cell apoplastic interaction originates and by prolonged stay the plant-plant interaction. This stay influences the type of dispersal. A life cycle with alternation of generations and two moments of dispersal permits plants to go on land. In ferns a shift in the moment of sex differentiation to meiospore happens and the stay of the macrospore leads to the seed plants. In water all types of sexual reproduction, interactions and the alternation of generations are prepared and these are used to conquest land. On land the biotic dispersal is realized. The phylogeny of sexual reproduction reveals that the sex differentiation and interaction are the main causes in the evolution of sexual reproduction. Sexual reproduction shows interactions during gamete fusion, between organism and environment and in multicellular plants between organisms. With respect to other types of interaction as in symbiosis or the nutrient chain, interaction is considered as an important action which is based on a persisting cooperation and points to a push during evolution. The push is expressed as communication： the driving force in the evolution. Based on the interactions between organisms and interactions between organisms and the dynamic environment, communication is considered as a driving force leading to the evolution as explained in the development of plant reproduction. Consequences for reproduction, its regulation and the process of evolution are discussed.     

Numerical simulation on reho-diecasting mould filling of an automobile master brake cylinder

An apparent viscosity model of semi-solid A356 aluminum alloy has been developed and the software Castsofl6.0 coupled with the model has been used to simulate the mould filling of an automobile master brake cylinder with the semi-solid A356 aluminum alloy slurry. The simulation results are in agreement with the practical filling process, indicating that the apparent viscosity model is feasible and can be used to simulate the mould filling of the semisolid A356 aluminum alloy slurry and can be used to optimize the filling process and the design of dies. A higher injection pressure, a higher ingate flow velocity of the semi-solid slurry, and a higher slurry temperature are advantageous to the mould filling of the automobile master brake cylinder.     

Hydration kinetics of cementitious materials composed of red mud and coal gangue

To elucidate the intrinsic reaction mechanism of cementitious materials composed of red mud and coal gangue (RGC), the hydration kinetics of these cementitious materials at 20°C was investigated on the basis of the Krstulovi?–Dabi? model. An isothermal calorimeter was used to characterize the hydration heat evolution. The results show that the hydration of RGC is controlled by the processes of nucleation and crystal growth (NG), interaction at phase boundaries (I), and diffusion (D) in order, and the pozzolanic reactions of slag and compound-activated red mud–coal gangue are mainly controlled by the I process. Slag accelerates the clinker hydration during NG process, whereas the compound-activated red mud–coal gangue retards the hydration of RGC and the time required for I process increases with increasing dosage of red mud–coal gangue in RGC.     

Improving the electrical performance of resistive switching memory using doping technology

In this paper, improvements of resistive random access memory (RRAM) using doping technology are summarized and analyzed. Based on a Cu/ZrO2/Pt device, three doping technologies with Ti ions, Cu, and Cu nanocrystal, respectively, are adopted in the experiments. Compared to an undoped device, improvements focus on four points: eliminating the electroforming process, reducing operation voltage, improving electrical uniformity, and increasing device yield. In addition, thermal stability of the high resistance state and better retention are also achieved by the doping technology. We demonstrate that doping technology is an effective way of improving the electrical performance of RRAM.     

On time-domain methods for milling stability analysis

As a basic and advanced machining technique,the high-speed milling process plays an important role in realizing the goal of high performance manufacturing.From the viewpoint of machining dynamics,obtaining chatter-free machining parameters is a prerequisite to guaranteeing machining accuracy and improving machining efficiency.This paper gives an overview on recent progress in time domain semi-analytical methods for chatter stability analysis of milling processes.The state of art methods of milling stability prediction in milling processes and their applications are introduced in detail.The bottlenecks involved are analyzed,and potential solutions are discussed.Finally,a brief prospect on future works is presented.