Titanium‐in‐biotite thermometry in porphyry copper systems: Challenges to application of the thermometer

Empirical geothermometer dealing with Ti solubility in the Fe‐Mg biotites was originally proposed for biotites in graphitic, peraluminous metapelites containing ilmenite or rutile that equilibrated roughly at 4–6 kbar. Given that biotites are abundant in the porphyry copper systems, this geothermometer has frequently been used for the determination of magmatic–hydrothermal temperatures in the porphyry copper systems. Common associations of porphyry copper deposits (PCDs), that is, low Al content of biotite, biotite chloritization (causes the biotite to become more magnesian and to lose Ti), and biotite formation by amphibole replacement, as well as disequilibrium, local equilibrium, or re‐equilibration of biotites, especially through potassic alteration, may provide significant uncertainty in the temperatures estimated a by Ti‐in‐biotite geothermometer. In addition, besides the calibration range of thermometer for pressure (400–600 MPa), the temperatures of major sulfide precipitation in PCDs (>~400°C) does not fit with the temperature range of thermometer calibration (480–800°C). Worth noting, as confirmed by fluid inclusion data in the Sarkuh PCD, regardless of presence of mineralogical requirements, obtained temperatures of sulfide mineralization using Ti in biotite thermometer could be overestimated. This may be due to the difference between general conditions of sulfide mineralization and calibration range of Ti in the biotite thermometer for pressure and temperature, as well as the metaluminous nature of biotites in PCDs.     

Support system suggestion based on back-analysis results case study: Babolak water conveyance tunnel

Determining in-situ soil or rock geotechnical properties is a difficult task for a design engineer. Back analysis is a helpful technique for evaluating soil property by considering and measuring the convergence of an underground opening. Back analysis was performed by matching numerical modeling results with the measured tunnel convergence. The main purpose of this study was to determine optimum rock mass properties using back analysis in order to suggest the best and most economical support system. Accordingly, the difference between measured and calculated convergence values was minimized by using an error function (objective function). In this paper, through the parameters obtained from back analysis, a support system based on a set consisting of shotcrete, wire mesh, and lattice girder was suggested for the Babolak water conveyance tunnel in Mazandaran, Iran. Therefore, the suggested design was based on decreasing shotcrete thickness from 25 to 20?cm and eliminating of rock bolts.     

Biomonitoring of Ni and V Contamination Using Oysters (Saccostrea cucullata) at Lengeh Port,Persian Gulf,Iran

Vanadium and nickel are two important indicators of oil pollution. Lengthy exposure to these elements causes serious harmful effects in human health, different harsh allergies being examples. The accumulation of two heavy metals (Ni and V) in sediment and the soft and hard tissues of Saccostrea cucullata were analyzed at three sampling sites along the coast of Lengeh Port, Persian Gulf. Results indicated at all the sampling sites; the Ni levels in soft tissues (STs) were higher than in the shells (SHs) and sediments, whereas the V levels were higher in the sediments. In addition, meaningful relationship (r = 0.65; p < 0.05) was observed across Ni levels in ST of S. cucullata and sediment, while for V concentrations a strong relationship (r = 0.83; p < 0.01) was found in SH of S. cucullata and sediment. This indicates that ST and SH of oyster can be considered as a biomonitoring agent for Ni and V levels, in coastal waters, respectively. The exposure of the consumer is compared directly to minimal risk level and provisional maximum tolerable daily intake. Result indicated that levels of Ni and V were within the safety limits for human consumption.     

Impact of local site conditions on portfolio earthquake loss estimation for different building types

This article presents a sensitivity analysis investigating the impact of using high-resolution site conditions databases in portfolio earthquake loss estimation. This article also estimates the effects of variability in the site condition databases on probabilistic earthquake loss ratios and their geographical pattern with respect to structural characteristics of different building types. To perform the earthquake loss estimation here, the OpenQuake software developed by Global Earthquake Model is implemented in Clemson University’s supercomputer. The probabilistic event-based risk analysis is employed considering several notional portfolios of different building types in the San Francisco area as the inventory exposure. This analysis produces the stochastic event sets worth for 10,000 years including almost 8000 synthetically simulated earthquakes. Then, the ground motion prediction equations are used to calculate the ground motion per event and incorporate the effect of five site conditions, on amplifying or de-amplifying the ground motions on notional building exposure locations. Notional buildings are used to account for various building characteristics in conformance with the building taxonomy represented in HAZUS software. The HAZUS damage functions are applied to model the vulnerability of various structural types of buildings. Finally, the 50-year average mean loss and probabilistic loss for multiple values for probability of exceedance (2, 10, 20, and 40%) in 50 years are calculated, and the impact of different site condition databases on portfolio loss ratios is investigated for different structural types and heights of buildings. The results show the aggregated and geographical variation of loss and loss ratio throughout the region for various site conditions. Comparing the aggregated loss and loss ratio, while considering different databases, represents normalized differences that are limited to 6% for all building taxonomy with various heights and for all PoEs. However, site-specific loss ratio errors are significantly greater and in some cases are more than 20%.     

Numerical evaluation of liquefaction-induced damages in composite breakwaters and its application for performance-based improvement design

Breakwaters provide a calm sea basin for ships and protect harbor facilities by reflecting wave energy toward the open sea area. Their performance under environmental loadings is the main concern for coastal engineers. Liquefaction susceptibility of loose sediments of seabed threatens performance of these structures. The article investigates soil liquefaction effects on the seismic performance of Iran liquefied natural gas (LNG) composite breakwater. Performance-based design method, considering both grade of the breakwater and acceptable level of damages, was selected as design philosophy. Liquefaction-induced damages to the breakwater were determined by numerical analysis. Since the obtained level of deformations did not meet allowable damages, soil improvement against liquefaction was considered. Different improvement patterns were proposed based on distribution of pore pressure ratio (r_u) beneath the breakwater to control its seismic performance. This investigation revealed that the most important area for soil improvement is located near the toes of breakwater to control the slope instability and performance of the breakwater.     

Landslide susceptibility assessment by Dempster–Shafer and Index of Entropy models,Sarkhoun basin,Southwestern Iran

Landslides are natural disasters often activated by interaction of different controlling environmental factors, especially in mountainous terrains. In this research, the landslide susceptibility map was developed for the Sarkhoun catchment using Index of Entropy (IoE) and Dempster–Shafer (DS) models. For this purpose, 344 landslides were mapped in GIS environment. 241 (70%) out of the landslides were selected for the modeling and the remaining (30%) were employed for validation of the models. Afterward, 10 landslide conditioning factor layers were prepared including land use, distance to drainage, slope gradient, altitude, lithology, distance to roads, distance to faults, slope aspect, Topography Wetness Index, and Stream Power Index. The relationship between the landslide conditioning factors and landslide inventory maps was determined using the IoE and DS models. In order to verify the models, the results were compared with validation landslide data not employed in training process of the models. Accordingly, Receiver Operating Characteristic (ROC) curves were applied, and Area Under the Curve (AUC) was calculated for the obtained susceptibility maps using the success (training data) and prediction (validation data) rate curves. The land use was found to be the most important factor in the study area. The AUC are 0.82, and 0.81 for success rates of the IoE, and DS models, respectively, while the prediction rates are 0.76 and 0.75. Therefore, the results of the IoE model are more accurate than the DS model. Furthermore, a satisfactory agreement is observed between the generated susceptibility maps by the models and true location of the landslides.     

Coupling of solid deformation and pore pressure for undrained deformation—a discrete element method approach

This paper presents a numerical scheme for fluid‐particle coupling that uses the discrete element method by taking into consideration solid deformation and pore pressure generation. A new water particle element is introduced to calculate pore water pressure due to porosity changes. The water particle element has the same size and shape as the solid element and experiences the same amount of deformation. On the basis of the effective stress principle at the element contact, the total force is equal to the sum of the force transmitted through the solid element contact and the water particle force due to pore water pressure. Analytical solutions of traditional soil mechanics problems, such as isotropic compression and consolidated triaxial undrained test, are used to quantitatively validate the proposed model. The numerical results show good agreement between the model and the analytical solutions. The model therefore provides an effective method to calculate pore pressure in a porous medium in discrete modeling.     

An alternative method for density variation modeling of the crust based on 3-D gravity inversion

In this paper we are proposing an alternative method for determination of density variations of the crust from constrained inversion of the terrestrial gravity data. The main features of the method can be summarized as follows: (i) Constructing a band-pass filter to remove the long and short wavelength signals from the terrestrial gravity data. (ii) Using an iterative method for stabilization and solution of the inverse problem. The mentioned regularization method is first validated by simulated gravity data and next the methodology is used for development of a new regional density variation model of the crust in three layers based on real gravity data in geographical area of Iran. Application of the band-pass filter to the latter data resulted the residual gravitation variations in the range of − 300 to 50 (mGal) which next based on the iterative method resulted following ranges for residual densities: −120 to 40 (kg/m³) in first layer, −40 to 40 (kg/m³) in second layer, and − 40 to 40 (kg/m³) in third layer.     

The Positive Effects of Nanoclay on the Hydraulic Conductivity of Compacted Kahrizak Clay Permeated With Landfill Leachate

This study evaluates the effect of nanoclay on permeability, swelling, compressive strength, and cation exchange capacity of a compacted Kahrizak landfill clay liner. The results show that 4% nanoclay significantly reduces permeability (3 × 10^?9 to 7.74 × 10^?11 cm/s in neutral, 3.66 × 10^?9 to 7.9 × 10^?10 cm/s in acidic, and 3.25 × 10^?9 to 5.24 × 10^?10 cm/s in alkaline condition), and increases compressive strength (by 36.28%) and the percentage of swelling (from 16.67 to 41.82, 23.33 to 45.45, and 15 to 38.18 at pH 7, 4.8, and 9, respectively) compare to raw clay samples. Moreover, the results of cation exchange capacity tests show that adding 4% nanoclay to the Kahrizak clay, permeated with landfill leachate, helps the sample maintain its mono‐valent ions between layers and remains dispersed. The results of SEM and XRD analyses show that by adding nanoclay, nanoclay clusters are formed in the sample; as a result, the interlayer spacing decreases which makes it remain dispersed. XRF analyses also demonstrate that by adding nanoclay to the mixture, the permeability and therefore, the amount of heavy metals which can penetrate into it decreases. The results justify the construction of clay barriers with nanoclay in order to prevent leachate penetration, and consequently reduce the operation costs.