To reduce the accumulation of coal gangue and steel slag, a mixture of lime-steel slag-coal gangue for pavement base was prepared. Six groups of lime-steel slag-coal gangue mixtures were designed using a uniform design method. The 7 d unconfined compressive strength, 180 d compressive resilience modulus and 180 d splitting tensile strength tests, the freeze-thaw cycles, and the wet and dry cycles were carried out to study the mechanical properties, frost resistance and water stability. The expansion effect of f-CaO in steel slag on the mixtures was investigated by water immersion. SEM was used to explore microscopic changes in the mixtures. The field application of coal gangue mixture was carried out for two years. The results show that the regression equations obtained by the uniform test have high accuracy. With the increase of lime in the mixture, the mechanical strength, frost resistance, and water stability of the mixtures were first enhanced and then decreased. With the increase of steel slag, the unconfined compressive strength increased, the compressive resilience modulus increased at first and then decreased, the splitting tensile strength decreased, the BDR value decreased, and the strength loss of water stability increased gradually. The internal structure of the mixtures is stable and has good frost resistance. There is no obvious microscopical difference before and after freeze-thaw cycles. The immersion expansion rate of the mixtures was far less than 1.5 %.
The article presents the results of analysis of thermal operation and hearth lining melting of blast furnaces of various designs on the basis of information from the system of monitoring of thermal operation and hearth lining melting – mathematical model “Hearth” developed in Iron and Steel Institute NAS of Ukraine (ISI NASU). Realization of continuous monitoring of the hearth melting in blast furnaces made it possible to estimate the effect of using “ceramic cup” in terms of the value of heat losses of the hearth and coke consumption for their compensation. It is established that the value of specific heat loss per unit volume of blast furnace in blast furnaces with a “ceramic cup” ~ 0,4-0,7 kW/m3, in blast furnaces without it ~0,9-1,1 kW/m3. Ceramic cup gives savings of about 1 kg/t-HM of coke.
Mining engineering. Metallurgy, Materials of engineering and construction. Mechanics of materials
Zirconium (Zr) alloy is widely used in the nuclear industry due to its low thermal neutron absorption cross-section and excellent mechanical properties. The texture easily formed in the hcp-structured α-Zr determines its service performance. To analyze the texture evolution and deformation mechanism during cold rolling, the Zr-2.5Nb alloy was rolled to various reductions in two directions (rolling direction (RD) and transverse direction (TD)) at two deformation temperatures (room temperature (RT) and cryogenic temperature (CT)). A combined approach of experimental observation and crystal plasticity simulation was employed to systematically investigate the texture evolution and deformation mechanism under cold rolling. The TD-spread elliptical texture is formed in α-Zr during RD-rolling, while the disc-shaped basal texture is produced during TD-rolling. The prismatic slip has no effect on the texture type. The basal slip leads to the formation of strong basal texture. The pyramidal <c+a> slip causes the basal poles to tilt toward RD. Both prismatic and basal slips lead to the formation of the TD-spread elliptical texture with double peaks. At RT, the final FND of RD-rolling is similar to that of TD-rolling, a similarity that is caused by basal slip. The Kearns factors of normal direction (ND) is recorded as FND. At CT, {10 1‾ 2} and {112‾ 1} twinning play an important role in the early stage of deformation. Compared to TD-rolling at RT, the relatively inactive basal slip results in lower texture intensity during TD-rolling at CT. This study deepens our understanding of the texture evolution and deformation mechanisms of Zr alloy.
Horizontal well fracturing stimulation is currently the most core technical means to achieve efficient development of unconventional coalbed methane resources. Although good on-site results have been achieved, there are still some problems such as unclear the goal of fracturing stimulation, unclear the adaptability of the main horizontal well fracturing technology and lack of evaluation methods for fracturing effects. In order to further improve the production and development benefits of fractured horizontal wells, this article based on the viewpoint of “unblock and channeling”that has achieved significant results in the southern part of the Qinshui Basin and has been verified by practice, combined its requirements for fracturing on high-rank coal reservoir and the characteristics of the original natural pores and fractures in the high-rank coal reservoirs in the southern part of the Qinshui Basin, referred meanwhile to the evaluation experience of previous fracturing, selected seven key indicators: Types and quantity of fracturing operation curves for each section of the horizontal well, average operating pressure, instantaneous shut-in pressure, accident type and occurrence rate, Pressure at the moment of initial gas production, Current bottomhole flowing pressure and daily gas production (Production time is more than one year), and comprehensive average stable gas production, proposed an evaluation method for the fracturing effect. Furthermore, combined with on-site comparative experiments, a study on the adaptability of the main horizontal well fracturing technology will be conducted to determine the upper limit and shortcomings of the main fracturing technology’s stimulation capacity. The results show: With the increase of burial depth and geo-stress, the difficulty of coal reservoir stimulation has shifted from easy to filter out, prone to excessive opening of natural fractures near the wellbore, making it difficult to create dominant main fracturing fractures, to difficulty in gradually opening natural fractures around the dominant main fracturing fractures, insufficient opening of secondary fractures, and difficulty in transporting fracturing sand, making it easy for desanding and sand-block.Due to the excessive pressure loss along the wellbore, the bottom sealing drag fracturing technology is unable to meet the needs of “unblocking and channeling”fracturing stimulation at depths of more than 1 000 meters.The continuous tubing fracturing technology has the problem of insufficient carrying capacity for fracturing sand after at depths exceeding 1 200 meters.The bridge shooting combined fracturing technology can not only meet the needs of the “Unblocking and Channeling” fracturing stimulation of coal reservoirs with a depth of 1 250 meters, but also has the potential to further increase the scale of fracturing stimulation, which can meet the construction and implementation of the“unblocking and channeling”fracturing stimulation of coal reservoirs under deeper conditions. The research provides important basis and support for the rational selection and upgrading of fracturing technologies in the southern part of the Qinshui Basin and other coalbed methane blocks at home and abroad.
At present, there are few studies on the phase transition during the thermocompression plastic deformation of magnesium alloy. In this study, the evolution model of thermal compression plastic of AZ31 magnesium alloy was constructed by molecular dynamics, and the phase transition relationship between HCP and FCC at different thermal compression rates was studied. By combining GLEEBLE thermal compression experiment with transmission electron microscopy experiment, high-resolution transmission electron microscopy images were taken to analyze the transition rules between HCP and FCC during plastic deformation at different thermal compression rates, and the accuracy of molecular dynamics analysis was verified. It is found that the slip of Shockley's incomplete dislocation produces obvious HCP →FCC phase transition at low strain rate and base plane dislocation at high strain rate, which makes the amorphous phase transition of HCP→OTHER more obvious, which provides theoretical guidance for the formulation of forming mechanism and preparation process of magnesium alloy.
Abstract The flow of fluid through the porous matrix of a reservoir rock applies a seepage force to the solid rock matrix. Although the seepage force exerted by fluid flow through the porous matrix of a reservoir rock has a notable influence on rock deformation and failure, its effect on hydraulic fracture (HF) propagation remains ambiguous. Therefore, in this study, we improved a traditional fluid–solid coupling method by incorporating the role of seepage force during the fracturing fluid seepage, using the discrete element method. First, we validated the simulation results of the improved method by comparing them with an analytical solution of the seepage force and published experimental results. Next, we conducted numerical simulations in both homogeneous and heterogeneous sandstone formations to investigate the influence of seepage force on HF propagation. Our results indicate that fluid viscosity has a greater impact on the magnitude and extent of seepage force compared to injection rate, and that lower viscosity and injection rate correspond to shorter hydraulic fracture lengths. Furthermore, seepage force influences the direction of HF propagation, causing HFs to deflect towards the side of the reservoir with weaker cementation and higher permeability.
Lara Moreno, Endzhe Matykina, Kiryl A. Yasakau
et al.
The aim of the present study is to evaluate the effect of alloy processing and composition as well as the pH control and testing medium on the in vitro corrosion performance of MgZnCa systems for biodegradable implants. The grain size and secondary phases were analyzed by optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Scanning kelvin probe force microscopy (SKPFM) was used to analyze the Volta potential values of the second phases. The corrosion performance of the three alloys was evaluated by electrochemical and hydrogen evolution methods in α-MEM with and without organic species (i.e. complete and inorganic α-MEM). Two strategies were followed to evaluate the influence of the pH on the corrosion behavior: daily solution replacement and CO2 flow based pH control. For all the materials, the organic medium accelerates the corrosion process. Constant pH maintained by CO2 flow through the medium results in considerably higher corrosion rates for all alloys. The impact of pH is lesser on the as-cast alloys due to the barrier effect of the secondary phases, particularly pronounced in the Mg1Zn1Ca alloy which showed the lowest corrosion rate. The wrought Mg0.5Zn0.2Ca alloy that lacks the refined secondary phase network and exhibits high number of twins undergoes accelerated uniform corrosion under constant pH conditions.
In response to the current challenges of high water pressure and easy conduction in kilometer deep wells, we propose the “hydrophobic pressure reduction, slurry reinforcement” mine water control technology, which requires slurry materials with “high strength, strong stability, easy flow, low cost” and other properties. “High strength” can be achieved by adding nano-reinforced materials. “Strong stability” can be achieved by preferentially selecting easy-to-consolidate and difficult-to-disperse raw materials and adjusting the mixing conditions. “Stable flow” can be achieved by adjusting the particle size of added raw materials and increasing the interfacial friction. “Low cost” can be achieved by using existing large-scale industrial and mining solid waste products that are in urgent need of treatment, supplemented by a small amount of additives. In view of the above problems, this paper aims at reinforcing the coal seam floor with slurry, and takes the large-scale utilization of industrial and mining wastes as the direction. By using waste tire rubber particles, fly ash and clay as the main materials, supplemented with a small amount of admixtures, the orthogonal test method is used to carry out experimental research on the basic performance of solid waste slurry filling materials. The effects of different rubber particle admixtures and admixtures were analyzed in the paper, and their effects on the flowability, mechanical properties, stability in mine water environment, impermeability and microstructural properties of the grouted stone body were derived. The research results show that when rubber particles are mixed with 20%, fly ash with 65%, clay with 15%, and nano-silica with 1% of solid powder, the flow of the grouted slurry is 293 mm, the 28 d compressive strength of the grouted stone body is 11.7 MPa, and the seepage pressure of the stone body is 0.8 MPa, and the obtained test results can meet the demand of field grouting reinforcement, which is useful for The obtained test results can meet the demand for on-site grouting reinforcement, which has scientific reference value for large-scale bottom slab fracture grouting reinforcement and also provides reference for large-scale utilization of solid waste products.
To quantitatively analyze the mechanisms of graded distribution and refinement of electromagnetic separation technology, in situ Al–Mg2Si graded materials were prepared using traveling magnetic field. Simulation and experiment were both carried out to analyze the effect of traveling magnetic field on the distribution and size of Mg2Si phase. Simulation results show that 6A excitation current density achieves the best effect of graded distribution. Experiments results show traveling magnetic field changed the distribution of Mg2Si in the alloy from uniform to graded distribution and refined the size of primary Mg2Si particle from 16 μm to 10 μm at the outer region on the cross-section. The mechanism of refinement was quantitatively analyzed, the refinement of Mg2Si particle results from stirring and crushing by magnetic field without promoting nucleation. The graded distribution mechanism is attribute to the resultant force acting on Mg2Si particle, which promote Mg2Si particle distributed near the outer region and graded distribution. Hardness distribution on the cross-section is consistent with the volume fraction distribution of Mg2Si.