Jurnal Puslitbang tekMira (Teknologi Mineral dan Batubara)
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PETROGRAPHIC ANALYSES OF COAL DEPOSITS FROM CIGUDEG AND BOJONGMANIK AREAS WITH REGARD TO THEIR UTILISATION
No full textGeological setting of the Cigudeg and Bojongmanik areas gives rise to the coal characteristics, par- ticularly due to the depositional environment and stratigraphic aspect. Those characteristics include lithotype, type and rank of the coals. The coals formed under wet-swamp condition to result in brighter lithotype and vitrinite-rich coal. By contrast, the coals formed under dry-swamp condition to result in duller lithotype and inertinite-rich coal. The Cigudeg coals contain clay minerals and quartz, whilst the Bojongmanik coals contain pyrite and calcite. These minerals are beneficial to interpret depositional environment of the coals. Ranks of the Bojongmanik coals are somewhat higher (lignite-subbitumi- nous C-B) that those of the Cigudeg coals (lignite-subbituminous B) according to the ASTM classifi- cation. These higher ranks are due to the thicker overburden on the Bojongmanik coals in terms of stratigraphic aspect. Regarding those petrographic characteristics, both coals are suitable for fuel of direct combustion for the small-scale and home industries that are available in the surrounding areas. Therefore, the coals can economically cope with the demand of those industries
COASTAL CHARACTERISTICS OF IRON SAND DEPOSITS IN INDONESIA
No full textCoastal features of Indonesia are controlled by the geology and geomorphology of the hinterland and the bordering adjacent marine environments. Tectonic instability manifested as frequent earthquakes combined with volcanic eruptions and sea level changes also affect Indonesian coastline. Unstable air and heavy rainfall zone known as intertropical convergence zone (ITC) which migrates to the north and south of the equator together with orographic factor of mountain ranges in Sumatra, Java and Nusatenggara are also controlling coastal landforms. Large sediment quantities resulted from a com- bination of deeply weathered rock in steep elevated hinterlands and frequent heavy rainfall are trans- ported to the coast and built extensive deltas and broad coastal plains. Iron sands in Sumatra, Java, Bali and Nusatenggara Islands are largely derived from denudation of andesite and old andesite forma- tion enriched in magnetite and ilmenite minerals. In certain cases periodic eruptions of active volca- noes supply fluvial sand to maintain the prograding shoreline. Wave regime in Indonesian coastal waters resulted from strong swells of Indian Ocean in the south and Pacific Ocean in the northeast has much influence various coastal features. Coastal zones especially the southern parts of the Neogene Sunda Banda magmatic arc are the area of potential and producing iron sand deposits which extend from northern Sumatra to eastern Indonesia. Beach sediments enriched in magnetic minerals of such coastal zones are typically black or grey. The iron sand deposits have been mined either by state company or by local people. Small scale mining helps to improve the economy of the commu- nity. Application of regulations and good guidances of these artisanal minings will not destructive to the natural environments
STUDY ON UTILIZING FLY ASH FOR CASTABLE REFRACTORY
No full textFly ash could be utilized as alumina and silica sources material. It could be treated by the following processes of demagnetisation, sinterization, grinding, mixing with crushed bricks as well as fired cement to create acid based on castable refractory. Sinterization changes alumina and silica signifi- cantly into mullite. The standard measurement of pyrometric cone equivalent (PCE) is used to under- stand the temperature resistance of the studied castable refractory based fly ash. The temperature resistance seems to increase after contacting with high temperature at longer time or repeatedly until reaching its Si-Al stabilization phase
DISPLACEMENT DISTRIBUTION MODEL OF ANDESITE ROCK MASS DUE TO BLASTING ACTIVITY USING FINITE ELEMENT METHOD
No full textIn mining operation, blasting is the most common method to disperse rocks. Blasting process does not only minimize rock fraction, but also produce less favourable energy for its surroundings. One of less favourable energies is ground vibration. The ground vibration will affect slope stability, because it will increase the driving force of the slope to collapse. Thereby, a research is needed to understand the influence of ground vibration in the slope stability. From the level of ground vibration influence on slope stability, it can be set the limit of the blasting process to keep the slope stable. Numerical method that used in this research is finite element method. One of its advantages is to accomodate time element in its calculations. Analysis results of this method are the displacements distribution model of the rock mass in static and dynamic conditions. On the track of A-A’, rock mass displacement took place at the crest of 6.6 mm (static condition) to 8.5 mm (dynamic condition). Likewise, the track of B-B’ line of 0.4 mm to 2.5 mm and line C-C’ from 0.6 mm to 2.0 mm. The safety factor value on the floor of the lines B-B ‘and C-C’ in the dynamic conditions is 1.3. This value is quite prone, so it needs a treatment at the mine slope in order not endanger workers’ safety, mining equipment and the surrounding buildings
