Stochastic Modeling Approach for the Evaluation of Backbreak due to Blasting Operations in Open Pit Mines

Backbreak is an undesirable side effect of bench blasting operations in open pit mines. A large number of parameters affect backbreak, including controllable parameters (such as blast design parameters and explosive characteristics) and uncontrollable parameters (such as rock and discontinuities properties). The complexity of the backbreak phenomenon and the uncertainty in terms of the impact of various parameters makes its prediction very difficult. The aim of this paper is to determine the suitability of the stochastic modeling approach for the prediction of backbreak and to assess the influence of controllable parameters on the phenomenon. To achieve this, a database containing actual measured backbreak occurrences and the major effective controllable parameters on backbreak (i.e., burden, spacing, stemming length, powder factor, and geometric stiffness ratio) was created from 175 blasting events in the Sungun copper mine, Iran. From this database, first, a new site-specific empirical equation for predicting backbreak was developed using multiple regression analysis. Then, the backbreak phenomenon was simulated by the Monte Carlo (MC) method. The results reveal that stochastic modeling is a good means of modeling and evaluating the effects of the variability of blasting parameters on backbreak. Thus, the developed model is suitable for practical use in the Sungun copper mine. Finally, a sensitivity analysis showed that stemming length is the most important parameter in controlling backbreak.     

Some metal concentrations in the edible parts of Tridacna maxima, Red Sea, Egypt

The concentrations of Ca, some essential (Fe, Zn, Mn, and Cu) and non-essential nutritive elements (Cd, Pb, and Ni) were measured in the edible parts (mantle and adductor muscles) of Tridacna maximx collected from south Quseir City (Red Sea). The general trend of metal contents of the different parts follows the order; Ca > Fe > Zn > Pb > Mn > Cu > Cd > Ni. The tissues before cooking recorded the highest average concentrations of Cu, Pb, Fe, Cd, Mn, and Ni (2.658, 5.250, 34.375, 1.464, 3.207, and 0.886 ppm, respectively) relative to tissues after cooking and the water of cooked tissues (WCT). The total cooked tissues recorded higher average contents of Zn and Ca (17.282 and 1,114.679 ppm) than the uncooked tissues. Calcium recorded the highest concentration in the ECT of adductor and mantle muscles (2,081.126 ± 177.39 and 1,893.326 ± 394.28 ppm). Mantle recorded higher concentrations of Pb, Mn, Ni, and Ca (7.489 ± 4.65, 4.241 ± 1.13, 0.980 ± 0.60, and 1,039.362 ± 177.42 ppm, respectively) than adductor muscle before cooking. Ca concentration levels in the WCT increased after cooking tissues especially in adductor muscles. This may attributed to the liberation of larger amount of calcium in ionic form in water. The clams may have intracellular regulatory mechanisms to keep their concentrations in equilibrium, subsequently; the recorded metal concentrations are in the safe limits for human consuming, where these concentrations did not exceed the clam’s capacity of regulation.     

Spectral gamma‐ray logs and palaeoclimate change? Permian–Triassic,Persian Gulf

Spectral gamma ray (SGR) logs are used as stratigraphic tools in correlation, sequence stratigraphy and most recently, in clastic successions as a proxy for changes in hinterland palaeoweathering. In this study we analyse the spectral gamma ray signal recorded in two boreholes that penetrated the carbonate and evaporate‐dominated Permian–Triassic boundary (PTB) in the South Pars Gasfield (offshore Iran, Persian Gulf) in an attempt to analyse palaeoenvironmental changes from the upper Permian (Upper Dalan Formation) and lower Triassic (Lower Kangan Formation). The results are compared to lithological changes, total organic carbon (TOC) contents and published stable isotope ( δ ¹⁸O, δ ¹³C) results. This work is the first to consider palaeoclimatic effects on SGR logs from a carbonate/evaporate succession. While Th/U ratios compare well to isotope data (and thus a change to less arid hinterland climates from the Late Permian to the Early Triassic), Th/K ratios do not, suggesting a control not related to hinterland weathering. Furthermore, elevated Th/U ratios in the Early Triassic could reflect a global drawdown in U, rather than a more humid episode in the sediment hinterlands, with coincident changes in TOC. Previous work that used spectral gamma ray data in siliciclastic successions as a palaeoclimate proxy may not apply in carbonate/evaporate sedimentary rocks. Copyright © 2014 John Wiley & Sons, Ltd.     

The impact of the spatial variability in bottom roughness on tidal dynamics and energetics,a case study: the M 2 surface tide in the North European Basin

A modified version of the 3D finite-element hydrostatic model QUODDY-4 is used to quantify the changes in the dynamics and energetics of the M ₂ surface tide in the North European Basin, induced by the spatial variability in bottom roughness. This version differs from the original one, as it introduces a module providing evaluation of the drag coefficient in the bottom boundary layer (BBL) and by accounting for the equilibrium tide. The drag coefficient is found from the resistance laws for an oscillatory rotating turbulent BBL over hydrodynamically rough and incompletely rough underlying surfaces, describing how the wave friction factor as well as other resistance characteristics depend on the dimensionless similarity parameters for the BBL. It is shown that the influence of the spatial variability in bottom roughness is responsible for some specific changes in the tidal amplitudes, phases, and the maximum tidal velocities. These changes are within the model noise, while the changes in the averaged (over a tidal cycle) horizontal wave transport and the averaged dissipation of barotropic tidal energy may be of the same orders of magnitude as are the above energetic characteristics as such. Thus, contrary to present views, ignoring the spatial variability in bottom roughness at least in the North European Basin is only partially correct: it is valid for the tidal dynamics, but is liable to break down for the tidal energetics.

     

The Āhangarān lead-silver deposit,SE-Malāyer,West Central Iran

The hangarn Pb-Ag deposit is located 20 km ESE of Malayer in West Central Iran. The area is covered by lower Jurassic slates, phyllites and quarzitic sandstones and lower Cretaceous carbonates. An important sedimentary hiatus (which occurs all over Central Iran) with a disconformity surface separates the Jurassic and Cretaceous sediments. The area is situated on the Sanandaj-Sirjan structural zone which is characterized by NW striking regional metamorphism and volcanism in Mesozoic to early Tertiary time, by plutonism in late Mesozoic to early Tertiary, and by Alpine tectonism in Tertiary to present times. The geometry and geochemistry of the ore bearing units in the hangarn area are reported. The ore matter occurs as scattered patches in flat and thin lenses of sandy-dolomite interbedded in the lower Cretaceous carbonates, and as fracture and karst fillings in the same lenses. The ore matter (Pb, Zn, Cu, Fe) may have originated from periodic exhalations, which may have entered the sea water contemporaneous with periodic volcanic activities in the early Cretaceous time (Golpygn area). It may have been transported by means of sea water to the shore lines. Here the metallic ions were precipitated by biochemical agents as alternating flat sheets within carbonates. Later geologic evolution (tectonic and circulating groundwater etc....) may have recrystallized and/or remobilized locally some of the ore matter to its present position.     

Experimental Study on the Sand of Bandar-e Anzali Using Shaking Table

Geotechnical and Geological Engineering - Due to the economic and tourist importance of Bandar-e Anzali coastal zone and also the high seismic risk in this area, this article provides an...     

Water Curtain System Pre-design for Crude Oil Storage URCs: A Numerical Modeling and Genetic Programming Approach

In this paper the main criteria of the water curtain system for unlined rock caverns (URCs) is described. By the application of numerical modeling and genetic programming (GP), a method for water curtain system pre-design for Iranian crude oil storage URCs (common dimension worldwide) is presented. A comprehensive set of numerical simulations is performed using the finite element based commercial software (COMSOL 5.1) where the results are used as database for genetic programming. Describing equations of water inflow to the filled and empty caverns and water production rate of water curtain boreholes are generated using GP. By equating the proposed equations to each other, water curtain system can be pre-designed. Relative error of the generated GP equations shows their ability and accuracy. Applying a standard regression coefficient method, sensitivity analysis of parameters related to water curtain performance and water inflow to the caverns is performed as well. The results help the design of the water curtain system for crude oil storage caverns worldwide.     

The impact of the spatial variability in bottom roughness on tidal dynamics and energetics, a case study: the M 2 surface tide in the North European Basin

A modified version of the 3D finite-element hydrostatic model QUODDY-4 is used to quantify the changes in the dynamics and energetics of the M ₂ surface tide in the North European Basin, induced by the spatial variability in bottom roughness. This version differs from the original one, as it introduces a module providing evaluation of the drag coefficient in the bottom boundary layer (BBL) and by accounting for the equilibrium tide. The drag coefficient is found from the resistance laws for an oscillatory rotating turbulent BBL over hydrodynamically rough and incompletely rough underlying surfaces, describing how the wave friction factor as well as other resistance characteristics depend on the dimensionless similarity parameters for the BBL. It is shown that the influence of the spatial variability in bottom roughness is responsible for some specific changes in the tidal amplitudes, phases, and the maximum tidal velocities. These changes are within the model noise, while the changes in the averaged (over a tidal cycle) horizontal wave transport and the averaged dissipation of barotropic tidal energy may be of the same orders of magnitude as are the above energetic characteristics as such. Thus, contrary to present views, ignoring the spatial variability in bottom roughness at least in the North European Basin is only partially correct: it is valid for the tidal dynamics, but is liable to break down for the tidal energetics.     

Geology and geochemistry of D–O–C isotope systematics of the Qolqoleh gold deposit, Northwestern Iran: Implications for ore genesis

The Qolqoleh gold deposit is located in northwestern part of the Sanandaj–Sirjan metamorphic belt, northwestern Iran. Igneous and sedimentary units exposed in the area have undergone greenschist metamorphism. The area was affected by a NE–SW trending shear zone and subsequent deformation. Two different types of mineralization are distinguished in the Qolqoleh gold deposit based on geological–structural conditions indicated by microtextural analysis: ductile and then brittle. Ore-forming processes are divided into three stages: Early (I), Middle (II) and Late (III), which include quartz–pyrite (I), sulfides and gold (II) and carbonate veinlets (III), respectively. The stage I fluids are characterized by δ¹⁸O = 15.5‰ at 440 ºC, and are thought to be deep-sourced metamorphic waters; the stage III fluids, with δ¹⁸O = 1.6‰, are shallow-sourced meteoric waters; whereas, the stage II fluids, with δ¹⁸O = 13.1‰, are a mixture of deep-sourced metamorphic and shallow-sourced meteoric fluids. Based on comparisons of the D–O–C isotopic systematics, the ore-forming fluids with characteristic high δ¹⁸O and δ¹³C and low δD originated from metamorphic devolatilization of Cretaceous volcano-sedimentary (felsic to mafic metavolcanic rocks–shale–carbonate–carbonaceous chert) sequences, locally rich in organic matter. During late Cretaceous continental collision of the Afro-Arabian continent and the Iranian microcontinent, a crustal slab consisting of felsic to mafic metavolcanic rocks, carbonate, shale and carbonaceous chert was underthrust northwards beneath the central Iranian microcontinent along the Zagros fault. During further contraction, deformation was localized in reverse oblique-slip structures with vergence toward south; shear zones generally follow contacts between more competent and less competent rock units. Metamorphic devolatilization of this underthrust slab is the source of the ore-forming fluids that generated the Au ore belt, which includes the Qolqoleh gold deposit.