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Resources and Processing
Published in C. K. Gupta, Extractive Metallurgy of Molybdenum, 2017
In open pit operations, the ore is exposed by removal of overburden waste rock. The cut in the ore takes the form of benches that vary in height and width from mine to mine. The cycle of open pit extraction consists of drilling, blasting, loading, and haulage. Primary drilling consists of driving a vertical blasting hole into the ore. Secondary drilling and blasting may be required to break large boulders. Ore is loaded by mechanical shovels into rail cars or trucks, and haulage is by large trucks for short distances or by train for long distances. Skipways and belt conveyors are used at some mines for transporting ore to the mill site. Most molybdenum produced from open pit mines is that recovered as a by-product or coproduct from copper mines. The number of examples of open pit mines producing molybdenum as by-product with primary production of copper is large. There are only a few that produce molybdenum as a coproduct of copper. There are some open pit mines that are solely molybdenum producers. Examples given in Table 6 of the open pit mining operations producing molybdenum as the principle product and as by-product or coproduct illustrate this.
Earthworks
Published in Barry G. Clarke, Engineering of Glacial Deposits, 2017
Most glacial soils are suitable fill materials and have been extensively used as engineered fills for over 200 years. It may be necessary to remove boulders and zones of weaker and water-bearing materials during excavation. Fill selection will depend on its use; for example, fill for landfill liners must be able to achieve a low permeability when compacted. An engineered fill has to deal with changes in effective stress, water content and erosion during its life. This means that additional measures may be necessary to protect a fill from water. While the target density may be the maximum dry density, an allowance is made for the variation in water content and compacting effort using criteria set out in Figure 5.30. For example, for a fill to be used to support foundations and a fill in front of gravity retaining structures, the air voids content must not exceed 5% and the density must be at least 95% of the maximum dry density based on the heavy compaction method; between 5% and 10% air voids for embankments and other mass fills and a maximum dry density of at least 95% of the maximum dry density from the light compaction test. Figure 5.30 shows the more rigorous criteria for landfill liners where strength and permeability are critical.
Engineering properties of Newer Volcanics
Published in W. A. Peck, J.L. Neilson, R.J. Olds, K.D. Seddon, Engineering Geology of Melbourne, 2018
Identification of the size and frequency of boulders, knowledge of the joint spacing and how the material will break down under ripping are modern day practical considerations in bulk excavations with dozers. The frequency of boulders, their size and the best way to handle them will determine whether haulage on site by truck or scraper will be necessary and the type of loading to be employed.
Investigation on the morphological and mineralogical properties of coarse aggregates under VSI crushing operation
Published in International Journal of Pavement Engineering, 2021
Chonghui Wang, Hainian Wang, Markus Oeser, Mohd Rosli Mohd Hasan
Specifically, the procedure of boulders crushing starts by blasting natural stones and is followed by a series of multi-stage crushing and screening process, the excavator transfers the blasted rocks to a crusher located alongside the quarry wall, where the larger stones are consequently broken up into desired sizes. A jaw crusher is generally used as a primary or secondary stage of crushing, which contributes to size reduction of natural stone. In the next step, the particles are conveyed to secondary crushing for further reduction of grain size and modification on the morphological characteristics of aggregates. When referring to cone crushers, vertical shaft impactor (VSI), or horizontal shaft impactor (HSI) are normally regarded as secondary crusher, which indicates either of them can be applied for second crushing. The crushed rock is then either transferred directly to the next processing stage via conveyor belts or trucks. For the tertiary stage, the particles are further crushed by improving their shape qualities such as angularity and sphericity.
Prediction of fly-rock during boulder blasting on infrastructure slopes using CART technique
Published in Geomatics, Natural Hazards and Risk, 2021
Narayan Kumar Bhagat, Aditya Rana, Arvind K. Mishra, Madan M. Singh, Atul Singh, Pradeep K. Singh
Wyllie (1991) reported that a cut-slope created 20–30 years back should be stabilized considering poor construction practices and continuous degradation due to weathering. Rockfall or landslide along railways or highways in the hilly terrain is a frequent phenomenon. In one of the scientific study, Mignelli et al. (2014) reported that the rock slopes situated aside many kilometres of roads are prone to rockfalls and need proper mitigation Similar rockfall problems are also frequently observed along hundreds of kilometres of slopes aside railways and roadways in India which have caused several accidents and traffic delays (Mid Day News 2014; Ansari et al. 2015; Deccan Chronicle News 2019). Also, lots of rock excavations are in progress for upgrading infrastructures in the vicinity of existing railways and roadways. The rock excavation especially where isolated boulders are found in the slope mass need, safe removal considering the safety of railway tracks, overhead electric lines, signal posts, roadways and residential structures.
Glaciations at high-latitude Southern Australia during the Early Cretaceous
Published in Australian Journal of Earth Sciences, 2020
N. F. Alley, S. B. Hore, L. A. Frakes
The basal tillite has a sandy to silty matrix, is strongly bioturbated in the upper part and mildly so throughout and may exhibit cross-bedding. Large boulders are present, including of red porphyry and quartzite (a number of varieties), quartz, mafic rocks, schist, granite, siltstone and slate. Clast shape ranges from rounded to angular and clasts can be polished and facetted.