CHINA MINE ENGINEERING

Abstract:Making sure the length of stemming in the bore hole which can keep an effectively exvacation. What’s more, the relative calculating theory didn’t consider the acceleration change which must be disparate with the reality. This paper will improve the calculation considering the previous methods as well as combine with the actual works to select the proper calculating range, which shows that the improved method is basically consistent with the previous project experience, confirming the rationality of this method.

Abstract:A tailings dam is constructed by gravel with one-step constructed method in two phases. Before the second phase of the project, the physical and mechanical properties of the dam gravel were systematically tested, which provided a theoretical basis for the stability evaluation and analysis of the dam heightening project. On-site sampling and particle analysis showed that the dam material was well-graded gravel. At the same time, based on the dry density index detected on site, large-scale triaxial shear tests of this gravel under different consolidation and drainage conditions were carried out indoors. The test results show that the cohesion c is 20kPa and the friction angle φ is 31.8° for CD test， the cohesion c is 8kPa and the friction angle φ is 29.2° for CU test, the cohesion c is 107kPa and the friction angle φ is 4.0° for UU test.

Abstract:The 3102 return airway is protected by 6m coal pillar, and the 3-1 coal seam mined in the adjacent 3101 working face is spontaneous combustion coal seam. Due to the influence of lateral pressure in goaf and tunneling, the deformation of coal pillar in the 3102 return airway is large. In order to ensure the safety of roadway driving and avoid spontaneous combustion of residual coal in adjacent goaf, the evolution law of fissures in coal pillar is analyzed through simulation analysis and field observation. The results show that with the gradual expansion of the fissures in the coal pillar in the 3102 return airway, and there are through-fissures in the coal pillar, the fissures in the coal pillar can be divided into four areas. The research results provide reference for adopting targeted fissures blocking technology in mines.

Abstract:According to the actual construction situation of a mine in alpine region, the safety and stability of high and steep rock slope under freezing and thawing cycles are analyzed by means of field measurement, laboratory test, SVOffice software simulation and limit equilibrium theory analysis. The experimental simulation and field verification show that when the temperature difference is about 50℃, the influence of freeze-thaw cycle on rock mass is mainly reflected in strength decrease and fissure increase of shallow rock mass, and the freezing depth is less than 8m. According to the actual situation of a mine with high and steep slope, the limit equilibrium theory analysis show that the overall safety factor of the slope is reduced by 2.1%-5.2% compared with that before freezing and thawing, and the influence of freezing and thawing cycle on the overall slope stability is light.

Abstract:In this paper, an open-pit mine in DRC is taken as an experimental site. Firstly, the data of previous blasting shock and related lithology and geology information are analyzed. Secondly, under the condition of the same parameters such as hole depth, hole spacing, charge and packing, the blasting with shock damping ditch, pre-splitting blasting and blasting without shock damping measures are carried out respectively. The blasting shock data are collected, processed and analyzed, and the shock damping effect of pre-splitting blasting is studied. The results show that pre-splitting blasting can reduce the shock peak value by more than 13% compared with normal blasting; the closer the measuring point to the blasting center, the greater the shock damping effect of pre-splitting blasting, viz. the closer the protected building to the blasting works, the better the shock damping effect of pre-splitting blasting; and pre-splitting blasting has less shock damping effect than blasting with shock damping ditch.

Abstract:This paper analyzes the main problems existing in the deep shaft mining of a gold mine in South Africa. Combined with Phase II project under implementation, the mining scheme is adjusted according to the change of vein thickness and occurrence, thus reducing dilution rate, improving recovery rate and realizing continuous mining. Meanwhile, the technological measures such as deep shaft mining sequence, structure parameters, stope ventilation and cooling, drainage and ground pressure management are also expounded.

Abstract:In order to improve the purity of bentonite, sodium polyacrylate, sodium pyrophosphate and sodium hexametaphosphate are used as dispersants to study the reagent influence on the dispersion behavior of bentonite ore. The yield and montmorillonite content influence are analyzed under different particle size conditions. The results show that under different dispersants conditions, the yield and the montmorillonite content at 70μm particle size are less affected; under different dosages of dispersant, those at -70μm particle size are less affected, while those at partial particle sizes are greatly affected.

Abstract:Liaoji gold mine is located in the northeast wing of Bihenying dome in the Qinglong-Luoping mineralization belt in the northern Golden Triangle of Yunnan, Guizhou and Guangxi. According to the mineralization model with structural alteration variant (SBT) as the core established by gold prospecting in southwestern Guizhou, the gold orebodies occurring in SBT have been found through drilling engineering verification. The gold resources preliminarily discovered are in small deposits. The host rocks are mainly breccia tuff, breccia tuffaceous basalt, breccia limestone and breccia claystone. The hydrothermal alteration closely related to gold mineralization mainly includes limonitization, silicification and pyritization. Gold mainly exists in silicate minerals and sulfides in the form of encapsulated gold, with an average share of 37.52% and 35.90% respectively. The gold in strongly weathered to moderately weathered ores mainly exists in the form of free gold.

Abstract:With the increasing mining depth, the ground pressure increases, which leads to the difficulty increase of roadway support. In order to solve the problem of deep high-stress surrounding rock support, this paper uses COMSOL software to carry out numerical simulation of surrounding rock stress distribution in both primary rock roadway section and prestressed grouted anchor support roadway section, and the simulation results show that prestressed grouted anchor technology can effectively control the stress concentration of roadway roof and the instability of roof rock. Prestressed grouted anchor technology is applied to the support of 11034 haulage roadway in a mine, proving that it can effectively solve the problem of surrounding rock support of deep high-stress roadway.

Abstract:Through FLAC^3D simulation of 8102-3 working face before and after passing through 5102 empty roadway, the stress, displacement and plastic zone distribution of the roadway are analyzed by using crib, bolt and filling support respectively. The surrounding rock stability of empty roadway is good and the supporting effect is the best with filling support. High-water materials are used to construct along the 5102 empty roadway from west to east in turn, with a spacing of 30~50m. After the filling support is completed, it can be seen from monitoring the hydraulic support resistance in 8102-3 working face that the filling support in the empty roadway can ensure the safe mining of the working face.

Abstract:The dynamic pressure load of the mined out area above makes the advancing of fully mechanized coal faces difficult. To solve this problem, a case study was made of the 31201 work face, 3-1# coal seam. As the pressure is great during advancement, and as large areas of over-burdened supports often occur, the duration and length of periodic pressure steps in different areas, as well as the energy released were monitored, and a pressure occurrence pattern was thus developed. Based on the pressure pattern, oriented drilling and blasting was used to relieve the pressure caused by the concentrated pillars in the mine-out area above. According to the field data, when 31201 work face was passing the area of concentrated pillars, roof stability was greatly enhanced and pressure was reduced markedly, with no over-burdened supports; the average periodic pressure step and duration were 8.65m and 2.3m respectively. The scope and severity of surface cracks were also greatly reduced, and the goal of “bringing roof movement under control and relieving roof pressure step by step” was realized.

Abstract:The high dust concentration during fully mechanized sublevel caving mining has become an unfavorable factor restricting the efficient and safe mining of the mine. In order to reduce the dust concentration in fully mechanized mining face, according to the geological conditions of 5108 mining, this paper analyzes the long-hole low-pressure water-filling technology, the effect of coal seam water content improvement and dust prevention after short-hole medium-pressure water-filling in working face. According to the analysis results, this paper puts forward that the water-filling technology combining long-hole low pressure and short-hole medium pressure is applied in 5108 fully mechanized sublevel caving faces. The results show that the coal seam content increases from 2.43% to 5.45%, with an increase of 124.3%. The dust concentration in the working face was reduced to 24mg/m³, which indicates remarkable dust reduction effect by water-filling.

Abstract:The Jilong Mountain Gold Mine in Hubei Province has a lot of unfinished levels, and the stopes are scattered. Consequently, a number of ventilation issues occurred, including fresh air contamination, reversed, stagnant, and disordered air flow, and air leakage. To address these issues, after verifying the total air flow, a number of measures were taken in the deep underground ventilation system: adding another fan station, replacement by two fans of the same specs, relocating the fan stations. These measures have improved the ventilation, protected personnel health, prevented ventilation accidents such as smoke poisoning, and lifted production efficiency.

Abstract:The causes of conveyor belt misalignment are first analyzed and summarized, and a simulative study is conducted of the correction performance of ADAMS self-aligning idler rolls. The study reveals that: (1) Belt conveyor misalignments occur as a result of a number of factors, including: imbalanced belt load, mal-functionary idlers and pulleys. (2) The correction performance of self-aligning idlers is quite strong when their flip is within 12°, but declines notably when the flip is greater than 12°. (3) In field application, therefore, belt misalignment should be controlled within a small range. When the misalignment is great, human interference is required to limit the misalignment impact. The study can serve as a useful reference for the handling and prevention of belt conveyor misalignments in mine shafts.

Abstract:The main shaft hoist system is powered by #1 and #2 electric current closed loop drive systems. The #2 rectifier panel could start when the electric current was under 1000A. However, as the current increased to 1800A, a “fast-acting fuse” alarm was registered, with one fast-acting fuse blown out, followed by abnormal sound of the motor. An investigation was made and the rectifier panel and the main drive system were checked. The wave forms of both primary and secondary sides of the panel were measured. Judging from the wave aberration, the 6RA70 digital speed regulating device was found to be broken, as the pulses distributed to the six sets of thyristors were uneven. Consequently the thyristors were unable to change phases normally, and the DC EMF and AC voltage were in series aiding, forming a short circuit, which blew out the fast-acting fuse.

Abstract:To reduce the great vibration caused by the conventional blasting in the Jinduicheng stopes above the Dongchuan River tunnel, which is quite close to the stopes, digital electronic detonators were adopted and proper hole-to-hole and row-to-row blasting delays needed to be determined. Vibration was measured both inside the tunnel and on the working platform. A test was done comparing the different delays of digital electronic detonators and high precision blasting caps. Through studying the vibration wave profiles and other vibration data, the optimal short delay was determined to minimize the vibration. A blasting method that best controls the blasting vibration is thus found, to ensure the operation safety of the Dongchuan River Tunnel. As the result indicates, when the hole to hole delay is set at 30ms and row-to-row delay at 75ms, the blasting vibration frequency can be improved, reducing the vibration intensity by 22.7% as compared with the effect by conventional blasting. The test result serves as a good reference for further attenuating the blasting vibration in advanced stages of the Jinduicheng open-pit mine.

Abstract:To improve the safety level of belt conveyors, it was proposed to use heat detectors: optical fiber heat detectors were installed along the conveyor to detect temperature abnormality and locate the fire position; sprinkling units were then activated corresponding to the fire locations, to prevent any conveyor induced fire from deteriorating. The article also elaborates on the working principles, composition, and field application of the heat-detector-based fire protection system. The study serves as a reference for the fire protection of other mine transport systems.

Abstract:The mineral grade of a deposit is an important yardstick for the evaluation of a mine. The ultra-high-grade value has a major effect on the resource estimation of precious and non-ferrous metallic mines, and in turn affects project valuation, hence a key issue to consider in project acquisition. Current practices of handling ultra-high-grade values include average multiples and probability plot. Each of the two has its own merits. This paper is a study of the two methods by comparing their estimation results, providing a reference for Chinese investors in acquiring overseas mines.

Abstract:As low-voltage installations are numerous and various in type and power in a certain plant, selecting 380V as the LV distribution voltage has a number of drawbacks: including overly short power supply distance, large cable demand, considerable distribution-induced power loss. In contrast, using 660V as the distribution voltage is conducive to reducing distribution power loss and non-ferrous metal usage, hence more environmentally friendly. The paper is a case study of the LV power voltage selection process. Using the flotation plant of a certain non-ferrous metal mineral processing plant as an example, the paper demonstrates the merits of using 660V as the LV distribution voltage, compares the 660V and 380V options, and also proposes some basic principles guiding the selection of 380V and 660V as LV distribution voltages.

Abstract:Due to structural zone and deep high-stress, the surrounding rock of some underground roadways is broken or deformed, leading to support difficulty. Through theoretical analysis and field test, this paper puts forward a high-strength grouted anchor support scheme, finalizes technical parameters and puts it into application by combining with actual conditions. And the application effect is judged through field investigation and deformation observation. The results show that the high-strength grouted anchor support technology can effectively improve the self-bearing capacity, integrity and strength of surrounding rock, and effectively control the deformation of roadway, which provides a reference for the control of broken roadway surrounding rock under similar conditions.

Abstract:The mined-out areas of a metallic mine, complemented by karst caves, made the construction of the pile foundations of a bridge above very difficult and resulted in poor piles. To ensure file construction quality, it was proposed to inject concrete into the mined-out areas and the karst caves in question, and to use steel sleeve pipes to ensure the quality of foundation bore holes. After these measures were taken, foundation quality tests showed that all the piles were of Class I, hence very successful. This attempt thus brings useful experience to operations under similar circumstance.