EVALUATION OF THE STABILITY OF A TEMPORARY PILLAR WHEN MIINING ORE HORIZONS WITH BACKFILLING AND CAVING

A method is proposed for mining thick and flat ore deposits at great depths in conditions of a decline in the value of extracted mineral raw materials. It is found that safe mining with solidifying backfill and caving is achieved by determining the parameters of stable spans of rooms, in place of which artificial supports and temporary ore pillars are formed. These pillars are recovered with a lag behind room-and-pillar mining by caving of ore and enclosing rocks. It is shown that, depending on the type of geomechanical model of geomedium and orientation of the initial natural stresses acting in the rock mass relative to the mining front, the field of application of the mining system is limited by the depth and parameters of excavation. Predictive areas of possible rock failure are determined applicably to rock masses with different degree of disturbance.

Technological Adaptation of Internal Dumping to the Operating Mode of Open Pit when Developing Inclined and Steeply Dipping Coal Seams Strata

With surface mining of inclined and steeply dipping coal deposits, the so-called deeping longitudinal mining methods with a gradual deepening of mining from the surface to the final depth are widely spread, while orienting the mining front along the strike line of the seams (strata). When using such mining methods, the volumes of internal dumping are limited or completely absent; there is a peak-like increase in overburden volumes and transportation distance, the land resources disturbing proceeds at a progressive pace. In this regard, it is obvious that an important production task is to find technological solutions and methods to develop coal deposits that reduce the environmental hazard and increase resource conservation in mining by placing overburden in the mined-out space while reducing the area for external dumps and disturbing the earth's surface. If this is not foreseen at the present time, then all coal surface mines in the coming decades will be limited by their own external dumps of overburden, and their further development will be problematic.

Portable Raman Spectrometer for In Situ Analysis of Asbestos and Fibrous Minerals

Asbestos inhalation is associated with fatal respiratory diseases and raises concerns from the perspective of workplace safety and environmental impacts. Asbestos and asbestos-like minerals naturally occur in rocks and may become airborne when outcrops or soils are disturbed by anthropic activities. In situ detection of these minerals is a crucial step for the risk evaluation of natural sites. We assess here whether a portable Raman spectrometer (pRS) may be used in the identification of asbestos and asbestos-like minerals at the mining front during exploitation. pRS performance was tested at three geologically different mining sites in Italy and New Caledonia and compared with a high-resolution micro-Raman spectrometer (HRS). About 80% of the overall in situ analyses at the mining front were successfully identified by pRS, even when intermixed phases or strongly disaggregated and altered samples were analyzed. Chrysotile and tremolite asbestos, asbestos-like antigorite, and balangeroite were correctly detected during surveys. The major difficulties faced during in situ pRS measurements were fluorescence emission and focussing the laser beam on non-cohesive bundles of fibers. pRS is adequate for discriminating asbestos and asbestos-like minerals in situ. pRS may support risk assessment of mining sites to better protect workers and environment.

Experimental Study on Lateral Permeability Evolution of Sandstone under Seepage-Damage Coupling

To analyze the internal pore evolution law of aquifer rock in a coal mining front under the coupling effect of stress and seepage and the influence on the water inrush performance of the working face, research on the working face was conducted to improve the RTR-1000 high-temperature and high-pressure rock triaxial mechanical testing system, using hollow cylindrical and complete sandstone samples and by considering the stress change law in the actual mining process as the reference loading path. At the initial stage of loading, the permeability of sandstone demonstrates a rapid downward trend within a small range of stress change, with a decline rate of 50%. At lower permeabilities, the fluctuation is small; the plastic and failure stages are transient, and the relationship curve between the horizontal permeability and the axial confining pressure of sandstone is divided into compaction, multiple fluctuations, surrender, and failure. In several stages, the sandstone lateral permeability experiment under the coupling effect of stress and seepage demonstrates that the permeability of the aquifer in the coal mining front is significantly reduced after the original rock stress is disturbed by mining, suggesting that the water inrush calculation of the traditional water-flowing fractured zone and caving zone aquifer rock permeability experiment is inaccurate. Further research can deepen the stress and seepage coupling evolution process under the action of working face water inrush.

Parameters of Transition from Deepening Longitudinal to Continuous Lateral Surface Mining Methods to Decrease Environmental Damage in Coal Clusters

The present paper deals with an original way to reduce the environmental damage caused to land and air resources by surface coal mines with external dumping, due to the transition to internal dumping with filling the worked out space of the surface mine with overburden. The basic principle of the proposed idea is the transition from the deepening longitudinal mining method for the development of inclined and steep coal seam strata to lateral ones. This article substantiates the choice of technology for a block-and-layer continuous lateral mining method, including the construction of a first-stage pit, the use of a combined transport and direct dumping technology for moving overburden to an internal dump when mining blocks using draglines. The advantage of the presented technology, along with filling the internal capacity of the surface mine field with overburden, is the possibility of leveling the relief within the boundaries of the pit allotment and the implementation of reclamation as the mining front moves forward, without waiting for the dump to be completely filled in the boundary contours. Attention is also paid to the economic benefits of block-layer technology and the continuous lateral mining method, in the transition to which the overburden transporting costs can be significantly reduced, while the limitations of the proposed method’s implementation concern specific coal deposits that make up a small part of the fields being developed today by surface mining.

Justification of multi-section clay storage parameters on the pit internal dump during the integrated use mining of placer deposits

Purpose is an establishment of efficient parameters of a multi-section man-made deposit at the pulp clays storage on the surface of internal pit dumps during the development of placer deposits. The analytical research method was used to establish the main parameters of man-made deposits sections depending on their width and depth. A graphical research method was used to establish the downtime duration between formation of the first and second sections of the man-made deposit. It is established that division of the man-made deposit into five sections parallel to the mining front reduces time period till start of its operation from 8 to 5 years for it thickness 10 m and from 7 to 5 years at thickness 20 m. However, a significant disadvantage is the increassd number of sections in the man-made deposit from 2 to 5 is an increase in the volume of construction work from 0.27 to 1.11 million m3 at thickness 10 m, and from 0.53 to 2.15 million m3 at thickness 20 m, which confirms the necessity to find an effective number of sections in the man-made deposit and their parameters. The dependence between beginning of the works on filling the man-made deposit and the width of its first section delays start of the filling works, but too small width causes downtime at transiting from the first section to the second one. Efficient width of the man-made deposit first section is established, in which downtime is reduced from 7 years to 5.8 years, and volume of raw materials located outside the pit is reduced by 0.1 - 0.5 million m3 depending on the width of the first section. A method is proposed for determining an effective width of the first section in a two-section man-caused deposit, in which occurs while filling the sections. It is established that effective width of the first section oin the two-section man-made deposit with thickness of 10 m and with parameters of a typical pit development at mining of titanium-zirconium deposit is 241 m.

Evaluation of Effect of the Excavator Cycle Duration on its Productivity

Hydraulic excavators currently used at open pit mines, in particular backhoes, are more maneuverable, mobile and have more digging capabilities than rope shovels. This makes them suitable for a variety of conditions: top and bottom digging, loading lower, higher and at the standing level. The variants of mutual arrangement of the excavator and the dump truck, respectively, affect the duration of the excavator cycle, which, in turn, directly affects the productivity of the excavator. This article evaluates changes in the productivity of an excavator, depending on its angle of rotation and options for digging and loading. It is determined that the smaller the swing angle of an excavator, the greater its impact on productivity. Based on the executed calculations relative decrease in productivity (in percent from the most optimum variant) is established. Results of work can be used at planning of open pit mining for the purpose of definition, for example, speed of mining front movement at change of parameters of an excavator face and a type of a digging and loading.

Sistem Dewatering Air Panas Tambang Bawah Tanah Toguraci PT. Nusa Halmahera Minerals

The development of the Toguraci Underground Mine was begun in 2011 with the ore production started in 2012. The amount of water continued to increase in the Underground Mine at the beginning of 2014 which became problem that effected the activities of mining. The increase of hot water Toguraci underground mining effected to the safety for workers who are exposed to hot water, ventilation problems and equipment that are submerged in hot water. Tuguraci mine has two dewatering systems, namely dewatering systems on the surface and dewatering systems in underground mines. The handling of surface water comes from pumping underground to surface where water discharge is around 400 L / s with the temperatures ranging from 70°C while water treatment in underground mines includes decreasing water heading levels and pumping water from underground mines to the surface. The increase water entering heading development and stoping can be overcome by changing the surface dewatering system by using water cooling, while underground mining is done by changing the pipeline from the polypipe to the steel pipe and to reduce water entering the mining front is doned by drill holes for installing submersible pumps and replacing Oddesse pump to the Schlumberger pump which is more resistant to high temperature hot water, as long as mining operations take place 48 borehole drilling has been done with 11 borehole flowrate below 5 l / s and 37 borehole with flow rate above 5 l / s, and a water drop of around 77 meters