Restoring groundwater levels after tunneling: a numerical simulation approach to tunnel sealing decision-making

Tunneling is often unpopular with local residents and environmentalists, and can cause aquifer damage. Tunnel sealing is sometimes used to avoid groundwater leakage into the tunnel, thereby mitigating the damage. Due to the high cost of sealing operations, a detailed hydrogeological investigation should be conducted as part of the tunneling project to determine the impact of sealing, and groundwater modeling is an accurate method that can aid decision-making. Groundwater-level drawdown induced by the construction of the Headrace water-conveyance tunnel in Sri Lanka dried up 456 wells. Due to resulting socio-environmental problems, tunnel sealing was decided as a remedy solution. However, due to the expectation of significant delays and high costs of sealing, and because the water pressure in the tunnel may prevent groundwater seepage into the tunnel during operation, there was another (counter) decision that the tunnel could remain unsealed. This paper describes groundwater modeling carried out using MODFLOW to determine which option—sealed or unsealed tunnel—is more effective in groundwater level recovery. The Horizontal Flow Barrier and River packages of MODFLOW were used to simulate sealed and unsealed tunnels, respectively. The simulation results showed that only through tunnel sealing can the groundwater level be raised to preexisting levels after 18 years throughout the study area. If the tunnel remains unsealed, about 1 million m³/year of water conveyed by the tunnel will seep into the aquifer, reducing the operational capacity of the tunnel as a transport scheme. In conclusion, partial tunnel sealing in high-impact sections is recommended.

     

Application of K-means and PCA approaches to estimation of gold grade in Khooni district (central Iran)

Grade estimation is an important phase of mining projects, and one that is considered a challenge due in part to the structural complexities in mineral ore deposits. To overcome this challenge, various techniques have been used in the past. This paper introduces an approach for estimating Au ore grades within a mining deposit using k-means and principal component analysis (PCA). The Khooni district was selected as the case study. This region is interesting geologically, in part because it is considered an important gold source. The study area is situated approximately 60 km northeast of the Anarak city and 270 km from Esfahan. Through PCA, we sought to understand the relationship between the elements of gold, arsenic, and antimony. Then, by clustering, the behavior of these elements was investigated. One of the most famous and efficient clustering methods is k-means, based on minimizing the total Euclidean distance from each class center. Using the combined results and characteristics of the cluster centers, the gold grade was determined with a correlation coefficient of 91%. An estimation equation for gold grade was derived based on four parameters: arsenic and antimony content, and length and width of the sampling points. The results demonstrate that this approach is faster and more accurate than existing methodologies for ore grade estimation.     

Analyzing spatiotemporal land use/cover dynamic using remote sensing imagery and GIS techniques case: Kan basin of Iran

Land use/land cover (LU/LC) that are significant elements for the interconnection of human activities and environment monitoring can be useful to find out the deviations of saving a maintainable environment. Remote sensing is a very useful tool for the affair of land use or land cover monitoring, which can be helpful to decide the allocation of land use and land cover. Supervised classification-maximum likelihood algorithm in GIS was applied in this study to detect land use/land cover changes observed in Kan basin using multispectral satellite data obtained from Landsat 5 (TM) and 8 (OLI) for the years 2000 and 2016, respectively. The main aim of this study was to gain a quantitative understanding of land use and land cover changes in Kan basin of Tehran over the period 2000–2016. For this purpose, firstly supervised classification technique was applied to Landsat images acquired in 2000 and 2016. The Kan basin was classified into five major LU/LC classes including: Built up areas, garden, pasture, water and bare-land. Change detection analysis was performed to compare the quantities of land cover class conversions between time intervals. The results revealed both increase and decrease of the different LU/LC classes from 2000 to 2016. The results indicate that during the study period, built-up land, and pastures have increased by 0.2% (76.4 km²) and 0.3% (86.03 km²) while water, garden and bare land have decreased by 0, 0.01% (3.62 km²) and 0.4% (117.168 km²), respectively. Information obtained from change detection of LU/LC can aid in providing optimal solutions for the selection, planning, implementation and monitoring of development schemes to meet the increasing demands of human needs in land management.     

Hydrogeochemistry and geothermometry of the Jowshan thermal springs, Central Iran

Jowshan geothermal system comprises 6 thermal springs with outlet temperatures ranging from 39.3 to 46.6°C. The thermal water of these springs is presently used for swimming and as a treatment for rheumatism, sinusitis and skin diseases. The pH value of these springs is slightly acidic to neutral and the electrical conductivities about 1500 μS/Cm. The presence of many faults in the area, the alignment of all springs along the Sirch Fault and the similar chemical and isotopic composition of all springs in combination with the hydrogeological setting and geochemistry of water samples indicate that these springs are associated with deep circulation of meteoric water. According to this heating mechanism, meteoric waters infiltrate through fault openings to depth and after heating by geothermal gradient rise to the ground surface due to the hydraulic and buoyancy forces, a mechanism which is common in the southern parts of Iran. The use of various chemical geothermometers and mineral equilibrium states suggests a range of temperature about 50–90°C for the reservoir of Jowshan geothermal system.     

Utilization of waste coral for biodiesel production via transesterification of soybean oil

In the present study, the waste coral was utilized as a source of calcium oxide for transesterification of soybean oil into biodiesel (methyl esters). Characterization results revealed that the main component of the waste coral is calcium carbonate which transformed into calcium oxide when calcined above 700 °C. The Box–Behnken design of experiment was carried out, and the results were analyzed using response surface methodology. Calcination temperature, methanol– soybean oil molar ratio and catalyst concentration were chosen as variables. The methyl ester content (wt%) was response which must be maximized. A second-order model was obtained to predict methyl ester content as a function of these variables. Each variable was placed in the three low, medium and high levels (calcination temperature of 700, 800 and 900 °C; catalyst concentration of 3, 6 and 9 wt%; methanol-to-oil ratios of 12:1, 18:1 and 24:1). The optimum conditions from the experiment were found that the calcination temperature of 900 °C, catalyst concentration of 6 wt% and methanol-to-oil ratio of 12:1. Under these conditions, methyl ester content reached to 100 wt%. The waste catalyst was capable of being reused up to 4 times without much loss in the activity.     

Interacting new agegraphic dark energy in a cyclic universe

The main goal of this work is investigation of NADE in the cyclic universe scenario. Since, cyclic universe is explained by a phantom phase (ω<−1), it is shown when there is no interaction between matter and dark energy, ADE and NADE do not produce a phantom phase, then can not describe cyclic universe. Therefore, we study interacting models of ADE and NADE in the modified Friedmann equation. We find out that, in the high energy regime, which it is a necessary part of cyclic universe evolution, only NADE can describe this phantom phase era for cyclic universe. Considering deceleration parameter tells us that the universe has a deceleration phase after an acceleration phase, and NADE is able to produce a cyclic universe. Also it is found valuable to study generalized second law of thermodynamics. Since the loop quantum correction is taken account in high energy regime, it may not be suitable to use standard treatment of thermodynamics, so we turn our attention to the result of Li et al. (Adv. High Energy Phys. 2009: 905705, 2009), which the authors have studied thermodynamics in loop quantum gravity, and we show that which condition can satisfy generalized second law of thermodynamics.     

A multicriteria spatial decision support system for solving emergency service station location problems

Earthquakes occurring in urban areas constitute an important concern for emergency management and rescue services. Emergency service location problems may be formulated in discrete space or by restricting the potential location(s) to a specified finite set of points in continuous space. We propose a Multicriteria Spatial Decision Support System to identify shelters and emergency service locations in urban evacuation planning. The proposed system has emerged as an integration of the geographical information systems (GIS) and the multicriteria Decision-Making method of Preference Ranking Organization Method for Enrichment Evaluation IV (PROMETHEE IV). This system incorporates multiple and often conflicting criteria and decision-makers’ preferences into a spatial decision model. We consider three standard structural attributes (i.e., durability density, population density, and oldness density) in the form of spatial maps to determine the zones most vulnerable to an earthquake. The information on these spatial maps is then entered into the ArcGIS software to define the relevant scores for each point with regards to the aforementioned attributes. These scores will be used to compute the preference functions in PROMETHEE IV, whose net flow outranking for each alternative will be inputted in ArcGIS to determine the zones that are most vulnerable to an earthquake. The final scores obtained are integrated into a mathematical programming model designed to find the most suitable locations for the construction of emergency service stations. We demonstrate the applicability of the proposed method and the efficacy of the procedures and algorithms in an earthquake emergency service station planning case study in the city of Tehran.     

Kinetic modeling of carbon and nutrients removal in an integrated rotating biological contactor-activated sludge system

In this study, kinetics of biological carbon, nitrogen, and phosphorous removal from a synthetic wastewater in an integrated rotating biological contactor-activated sludge system was investigated. The experimental data obtained from varying four significant independent factors viz., hydraulic retention time, chemical oxygen demand for nitrogen to phosphorus ratio, internal recirculation from aerobic to anoxic zone and disks rotating speed were used for the process kinetic modeling. In order to obtain the bioprocess kinetic coefficients, Monod, first-order and Stover?CKincannon models were employed. As a result, Monod and Stover?CKincannon models were found to be the appropriate models to describe the bioprocess in the rotating biological contactor-activated sludge system as the determination coefficient for the first-order model obtained less than 0.79. According to the Monod model, growth yield, microbial decay rate, maximum specific biomass growth rate, and half-velocity constant coefficients were found to be 0.712?g VSS/g COD, 0.008/d, 5.54/d and 55?mg COD/L, respectively. From Stover?CKincannon model, the maximum total substrate removal rate constant and half-velocity constant were determined as 15.2, 10.98, 12.05?g/L?d and 14.78, 7.11, 6.97?mg/L for chemical oxygen demand, nitrogen and phosphorus removal, respectively. The kinetic parameters determined in this study can be used to improve the design and operation of the biological contactor-activated sludge system in full scale.     

Assessing flow paths in a karst aquifer based on multiple dye tracing tests using stochastic simulation and the MODFLOW-CFP code

Karst systems show high spatial variability of hydraulic parameters over small distances and this makes their modeling a difficult task with several uncertainties. Interconnections of fractures have a major role on the transport of groundwater, but many of the stochastic methods in use do not have the capability to reproduce these complex structures. A methodology is presented for the quantification of tortuosity using the single normal equation simulation (SNESIM) algorithm and a groundwater flow model. A training image was produced based on the statistical parameters of fractures and then used in the simulation process. The SNESIM algorithm was used to generate 75 realizations of the four classes of fractures in a karst aquifer in Iran. The results from six dye tracing tests were used to assign hydraulic conductivity values to each class of fractures. In the next step, the MODFLOW-CFP and MODPATH codes were consecutively implemented to compute the groundwater flow paths. The 9,000 flow paths obtained from the MODPATH code were further analyzed to calculate the tortuosity factor. Finally, the hydraulic conductivity values calculated from the dye tracing experiments were refined using the actual flow paths of groundwater. The key outcomes of this research are: (1) a methodology for the quantification of tortuosity; (2) hydraulic conductivities, that are incorrectly estimated (biased low) with empirical equations that assume Darcian (laminar) flow with parallel rather than tortuous streamlines; and (3) an understanding of the scale-dependence and non-normal distributions of tortuosity.