CHINA MINE ENGINEERING

Abstract:This research simulated the large-scale pillarless continuous mechanized downward layered horizontal cut-and-fill mining process in Jinchuan Nickel 2# Mine and stress evolution analysis of the horizontal pillar during mining was focused. Results show that the stress is decreasing significantly as the horizontal pillar goes thinner in the multi-level mining process. There are both stress-releasing and stress concentration areas nearby the mining area. The result can be a good reference for the stress-releasing mining in deep mine.

Abstract:An iron mine is an ultra-large scale and ultra-deep one. Its ore body is particularly thick, thus the mining area is large. In order to ensure the safety of mining, it is planned that large strip pillars will be arranged between the panels, the numerical simulation method is used for a comparative study on the stress characteristics of the pillars, which mainly reveals the load-bearing function of the pillars in the panel. The results of the study can provide a reference for reserving and arranging pillars under similar mining conditions.

Abstract:The mining of deep-shaft metal mines is faced with severe ground pressure disaster, and greatly threatens the safety of underground operators and equipment. Drift advancement destroys the in-situ stress field of the deep protolith, and is under the risk of tunnel face rock burst caused by the redistribution of in-situ stress and the accumulation of high stress. This paper studies the tunnel face rock burst disaster prevention in the scenario of tunnel face rock burst during drift advancement in a deep-shaft and high ground stress mine. The mechanism of tunnel face rock burst and the idea of advance pre-splitting blasting for pressure relief blasting are put forward. The impact of advance pressure relief blasting depth on the pressure relief effect and the process scheme of tunnel face advance pressure relief blasting are analyzed, which is of vital importance to prevent rock burst disaster from happening hazards in front of the tunnel face, and offers reference to drift advancement in deep-shaft mines.

Abstract:The mining depth of mines in China has gone deeper and deeper. The renovation and expansion of mines are faced with the problem of production continuity. As deep mining continues, the main structures on the surface are often located in the monitoring range of rock displacement. In this paper, the FLAC3D software is used for numerical simulation on the mining of the ore body, and the surface subsidence data and deformation data of main vertical shafts are obtained. The simulation results show that after the mined deep ore body is filled, there is little influence on the stability of surface and main vertical shafts. Deep mining can ensure the safety of mine production, which provides a solid scientific evidence for continuous mine engineering works.

Abstract:An iron mine is a ultra-large scale and ultra-deep one. Its ore body is particularly thick, thus the mining area is large. In order to ensure the safety of mining, it is planned that large strip pillars will be arranged between the panels. In this paper, the numerical simulation method is used for a comparative study on the stress characteristics and plastic zone distribution of different schemes, with de-stress schemes taken at the upper, middle and lower parts of panel pillars, and in de-stress schemes lengths respectively of 60m, 120m, 180m and whole length at the upper part of the panel pillars. The study mainly reveals the load-bearing effects of the different de-stress schemes schemes. Its results can provide reference for de-stress schemes mining under similar mining conditions.

Abstract:In resent years, deep earth problems have exerted increasing influence on mine exploitation, raising widespread concern at home and abroad. High stress is the main source of deep earth problems. Though many achievements have been made in the research on prevention and control of hard rock burst due to high stress, the large deformation of soft rock caused by high stress remain a problem that troubles a great number of projects. Since Jinchuan No.2 mining area enters deep mining stage, it has been faced with various problems such as large deformation and high repair frequency of roadways. In this paper, based on the -650m ramp of Jinchuan No.2 mining area, numerical analysis is carried out on the supporting technology of high stress and large deformation roadways from the aspects of high geostress, strata structure and supporting conditions, and a multi-dimensional model is built to study the deformation rules and supporting technologies of roadways. The numerical analysis indicates that the roadways at the rock stratum controlled by horizontal stress fail in a mode of high-stress, whole section large deformation and instability; deformation rules are obviously reflected in the direction of main stress, where bottom heaving is caused due to the compressive stress and the failure features large range and long duration; bolt-grouting support shows good effect in control of bottom heaving and roadway convergence deformation, flexible support allows proper deformation, which can make the stress of surrounding rock adjusted and released.

Abstract:Considering the west vent shaft of Malanzhuang Iron ore mine is located in deep bedded deposit strata, a unique supporting structure is designed for the shaft collar by closely combining the construction scheme. As the result of trade-off study, the bolt-grouting support method was selected and successfully used in the construction of the shaft collar section. The unique supporting structure and construction scheme are the key to the successful construction of the west vent shaft collar.

Abstract:Jinchuan mining area has complex geotechnical conditions, where the fractured rock masses and high geostress have increased the difficulty in roadway support and the maintenance cost of roadways. In this paper, a systemic summary is made for the research achievements in roadway support of Jinchuan mining area, and based on years of engineering practice in such area, the widely used technology for reinforcement of the roadways surrounded by high stress fractured rocks in the mining area is concluded to provide reference for roadway support of similar mines.

Abstract:The influences of high altitude environment on people’s physical and mental health and the various occupational health and safety protection measures that should be taken in high altitude mine projects are analyzed and discussed by combining engineering construction practice, with the aim to provide reference for the construction management of other projects in high-altitude areas.

Abstract:The form of stockyard in a domestic aggregate project is analyzed herein. Characteristic stockyard types are summarized. An innovative matrix storage and conveying system is proposed to meet the complex requirements on stockyard, providing a favorable reference for its application in stockyards of bulk raw materials for coal, steel, non-ferrous and other industrial sectors.

Abstract:The strength of backfill is one of the key factors in the research of cut-and-fill mining technology, which directly affects the safety production and improvement of economic benefits of a mine. The evolution of mechanical properties of backfill under microwave heating is studied herein, which provides a new idea on improving the early strength of backfill. By orthogonal experiment, the influence pattern of each factor on backfill strength is studied and the influence level of each such factor is obtained, based on which the factors are arranged in a descending order as cement-sand ratio, density, power, heating time and microwave intervention time. With the increase of microwave power and microwave heating time, the strength of backfill shows a trend of raise followed by fall, and it decreases with the increase of microwave intervention time. The effect of microwave heating on strength improvement of backfill is more obvious in the backfill with higher cement-sand ratio and pulp density.

Abstract:In order to fully recover rich resources of Gongchangling underground mine and improve its economic benefits of production, it is necessary to update and optimize the existing mining methods. The study of physical-mechanical properties of ore is an important preliminary work in determining stope structural parameters and analyzing stope stability in the process of mine design. Based on earlier exploration results of the mine and lithology revealed in production practice, laboratory test on rock physical-mechanical property parameters were conducted on ore samples of 8 different lithology types from Gongchangling underground mine and plenty of parameters on rock physical-mechanical property have been obtained, which will provide basic data for later mining engineering design study.

Abstract:In order to study the influence of replacing natural sand with manufactured sand (M-sand) from basalt on the performance of high-strength concrete, six replacement rates (0%, 20%, 40%, 60%, 80% and 100%) are pre-set to test the concrete compressive strength, ultrasonic sound velocity and compression strain at each of these rates and study the influence of different replacement rates on the performance of high-strength concrete. The variation of shrinkage strain over age of the mixed-sand concrete is studied through polynomial fitting analysis on the variation data of JZ40 shrinkage strain over age. The test results show that the M-sand replacing natural sand as fine aggregate can lead to a slight reduction in the 7d, 28d and 56d compressive strength of the concrete, and when ultrasonic sound velocity is used as an indicator of the compaction of the mixed-sand concrete, more influence factors should be considered. When the replacement rate is less than 40%, the use of M-sand is beneficial to reducing shrinkage of concrete, and quartic function fitting can better reflect the variation of shrinkage strain over age of concrete.

Abstract:This paper analyzes the collapse mechanism and disaster characteristics of a high and steep slope controlled by rock structure. The adverse effect of rock structure on the slope is analyzed by stereographic projection method. The slope is easy to collapse under the external influence. The key parameters for slope stability calculation are determined by combining the regional empirical value and the forward and reverse calculation method; on this basis, the corresponding treatment measures are put forward.

Abstract:With the increasing geostress level faced by rock roadway (tunnel) engineering, the stability and maintenance of roadway are becoming a bigger challenge, and higher requirements are put forward for the understanding of unloading deformation characteristics of surrounding rock. It is necessary to master the deformation and failure mechanism of rock and surrounding rock under roadway (tunnel) excavation and unloading conditions. In view of this, based on the triaxial test system, polymethyl methacrylate is taken as a specimen to simulate the elastic stage of natural rock mass under secondary stress state, and explore the influence of roadway surrounding rock unloading in the elastic stage on the secondary stress state. The deformation of the specimen is solved by using the elastic deformation theory of natural rock mass under the condition of excavation and unloading, and compared with the test results. The results show that only elastic deformation occurs to the specimen during the test, and the deformation in the middle part is greater than that in the end; the larger the deformation of the surrounding rock near the tunnel wall, the less the deformation of the outer side of the specimen is than that of the inner side; the theoretical deformation value matches well with the experimental deformation value.

Abstract:The reasons for the abnormal supporting force and the abnormal sound from the support in the 2603 working face of a mine are analyzed by numerical simulation and field stress monitoring, and the treatment measures are formulated. The results show that after grouting solidification for fault area by using a 1000-meter directional drill, the support pressure of the working face basically tends to be stable without large fluctuation. The study results have guiding significance for the control of coal wall instability in other mines.

Abstract:The gob-side entry retaining technology is adopted for the 125220 belt conveyor entry of a coal mine in Shanxi Province, in order to study the engineering application of the technology, the entry surrounding rock is sampled to carry out a measuring test of mechanical parameters, followed by a FLAC3D based numerical simulation study by different cutting depths and angles. Finally, it is determined that the optimal cutting depth is 10m, the cutting angle is 10°, the spacing of cutting holes is 0.6m, the hole depth is 10m, the charging depth is 5m, the hole sealing is 3m, and a group of 10 holes is blasted at the same time. During the advance of stopping, the maximum displacement of the entry roof in the deep part is 176mm and in the shallow part is 78mm. The single hydraulic support used in the entry retaining section produces stress fluctuation, with the maximum value of 42MPa. The support measures are safe and reliable.

Abstract:The fractured rock stratum at large fault areas causes an overall poor stability and brings great difficulty in support of roadways crossing these areas. To solve the problem, a study is carried out on the 2309 return airway crossing the F19 fault of Cuijiagou coal mine. In the study, surface grouting technology is adopted for pre-reinforcement and anchor bolt+U-shaped steel for support of the airway at the fault area, followed by a 180d support effect monitoring of the airway roof. The results show that, compared with the 2311 haulage roadway without grouting reinforcement, the maximum displacement of the airway in the deep part is reduced by 60%, and by 70% in the shallow part. The airway at the reinforced area shows good integrality, without subsidence or large area collapse.

Abstract:The Yellow River Basin is the region with the largest scale of coal resource exploitation in China, the production safety risks of coal mining in this area should be paid attention to and studied. This paper collected and sorted out the data on technical conditions of coal mining in nine provinces of the Yellow River Basin, found out the typical indicators of production safety risks related to “Five Major Disasters in Coal Mining”, and then made a preliminary analysis and comparison of the production safety risks in each province. The study shows that the roof accident caused by rock burst in Shandong province has great production safety risk, and the coal mines in Sichuan and Henan province produce more coal dust; there are a lot of high gas mines in Sichuan and Shanxi, and a lot of coal and gas outburst mines in Henan; there are a large number of coal mines with spontaneous combustion tendency in Inner Mongolia and Shaanxi, and Henan has the most coal mines with extremely complex hydrogeological types. This study has made a beneficial attempt to analyze safety risks in coal production by using big data, and the results can provide reference for the formulation of coal safe production policies in the provinces in the Yellow River Basin.

Abstract:Through the detailed process mineralogical study of a certain low grade niobium ore, it can be found that the ore has complex structure, dominated by porphyritic structure and trachytic texture. It has such characteristics that the rock is composed of feldspar and pyroxene microlite; metal minerals and gangue minerals coexist and are mutually inclusive; the valuable element niobium is not found as an independent mineral but dispersed in pyroxene, feldspar, magnetite, amphibole, etc.; pyroxene is the main mineral for niobium recovery. Through beneficiation tests, the combined process of “magnetic separation for pre-concentration-rough concentrate leaching” was recommended for extracting the valuable element niobium from the ore; The leachate containing 87.44mg/L niobium can be obtained from this process and the recovery rate of niobium is 63.12%.

Abstract:With the deep mining of a certain gold mine, large deformation of roadway surrounding rock occurred, causing the fracture and caving of the roadway roof and the flaky and platy peeling of the two roadsides, showing a large area of support failure. In view of this phenomenon, support optimization design was carried out for the fractured roadway surrounding rock based on the loose circle theory. By measuring the surrounding rock loose circle, the loosening range is confirmed to be 1.5~2.0m. The supporting scheme of rock bolt+short anchor cable+metal mesh was adopted. Through engineering practice, the effect of roadway convergence and rock bolt stress is good, which can provide reference for mines with similar conditions.