Showing papers in "Arabian Journal of Geosciences in 2020"

Study on the surface particle distribution characteristics of silt with different moisture content

Abstract: Soil structure and particle distribution determine the action form of water and the distribution and movement form of water in the soil, which may cause many engineering and environmental problems, so it is of great significance to study the distribution form of soil particles under different moisture content. Taking the silt as the research object, the surface micro features of soil samples with the same dry density and different moisture content were collected, and the binarization analysis and particle statistics were carried out to study the action mode between water and particles. The results show that (1) moisture content has a certain impact on the micro features. With the increase of moisture content, the pores between soil particles gradually decrease, and the fractal dimension of surface particles also decreases. (2) In the case of the difference of specific surface area, the smaller the particle size, the more obvious the response to water. For this silt sample, the particles with a size of 0.03~0.05 mm are relatively stable. With the increase of moisture content, small particles flocculate to form large particles under a series of forces. (3) When the moisture content was 8.92% and 13.78%, the soil features changed significantly, which may be the critical moisture contents affecting the structural quality of the sample. (4) Advantage orientation of silt particles is 90°~105°, which may cause the soil mechanics characteristics of anisotropy. (5) The interaction model between water and soil particles is as follows: dissolution, the change of stress on particles, and the change of electrical double layer on the surface of soil particles.

Delineation of groundwater potential zones in Karha river basin, Maharashtra, India, using AHP and geospatial techniques

Abstract: Groundwater is a life-sustaining resource catering the daily water requirements of mankind, aids in industrial development, influences agricultural activity, and maintains the ecological balance. The present study was carried out in the Karha river basin, Maharashtra State, having an area of 1314.98 km2. In hydro-geological research, for the exploration of groundwater resources, the integration of remote sensing data and GIS plays a remarkable role in monitoring, assessing, and conserving groundwater resources for water resource management and development. A total ten thematic layers such as geomorphology, geology, land use/land cover, drainage density, slope angle, lineament density, rainfall distribution map, curvature, topographical wetness index, and soil map were integrated into a GIS platform, using the spatial analyst tool in Arc GIS 10.0 to delineate the Ground Water Potential Zones in Karha river basin area. The analytical hierarchy process (AHP) technique is used to determine the weighted value for each parameter and their sub-parameters, based on their relative importance of influencing factors for groundwater recharge. The final groundwater potential zonation map of the study area was categorized into four classes namely, poor, moderate, good, and excellent potential zones. The western part of the basin, particularly in Ghorawadi, Garade, and Saswad regions, have been identified as excellent potential zones for groundwater exploration. The result has shown about 21.96% (285.43 km2) and 28.82% (374.49 km2) of the study area falls under “excellent” and “good” groundwater potential zone, respectively, whereas about 10.81% (140.46 km2) area falls under the poor potential zone.

Effects of biochar on soil fertility and crop productivity in arid regions: a review

Abstract: Biochar, carbon-rich materials produced during the thermochemical processing of biomass, are receiving increased attention given their potential value as soil amendments Biochar are formed through pyrolysis processes—heating to several hundred degrees Celsius under oxygen-limited environments—and both the source feedstock and the reaction conditions affect the quality of the resulting chars Biochar can enhance soil physical and chemical properties and increase agricultural systems’ productivity through direct and indirect effects on crop growth and soil quality Biochar also may directly help mitigate climate change by sequestering stable carbon compounds in the soil and perhaps indirectly through increased C uptake by trees As the world faces growing challenges from soil degradation and climate change, biochar application to soils represents a potential pathway forward Although a large volume of literature exists regarding the use of biochar under favorable climatic conditions, information regarding biochar applications in semiarid and arid climates has been more limited Evidence of greater water holding capacity and reduced infiltration suggests these materials have potential to improve the productivity of such lands and provides a basis for considering its wider application in the arid environments such as Saudi Arabia Challenges and limitations for biochar use on a mass scale are also briefly discussed To move this technology forward, crop and soil scientists should involve economists and agricultural extension educators in studies that consider economic as well as biophysical implications for biochar’s application on a mass scale

Identification of groundwater recharge-based potential rainwater harvesting sites for sustainable development of a semiarid region of southern India using geospatial, AHP, and SCS-CN approach

Abstract: Groundwater recharge-based rainwater harvesting (RWH) is a standout among the most capable structures to reduce water deficit issues and to build the accessibility of water for sustainable development in the semiarid regions because of absence of precipitation and flighty precipitation patterns. The delineation of potential recharge zone (PRZ) with RWH and selection of sites cause a greater dispute for the water stakeholders because of deficient framework. The essential thematic layer such as land use/land cover, soil, geology, vadose zone, drainage density, slope, and runoff were used for delineation of PRZ and RWH sites. Analytical hierarchical process (AHP) was carried out by assigning different weights to different thematic layers to determining the PRZ and RWH sites. The present study endeavours to decide the suitable areas for RWH using Soil Conservation Service curve number (SCS-CN) based on surface runoff with geospatial techniques. The enlargement of water asset is proposed by the development of RWH structures such as farm pond (FP), percolation tank (PT), check dam (CD), and gully plug (GP) having 73.53% (358.08 km2) appropriate for FP, 8.62% (42 km2) reasonable for PT, 17.48% (85.16 km2) reasonable for CD, and 0.35% (1.71 km2) for GP of the present study region. Based on integrated mission of sustainable development specification, 20 PT, 11 FP, and 4 CD were identified having 85%, 90%, and 100% accuracy in agreement between existing structures and predicted potential site. The present study approach demonstrates the higher accuracy for identification of RWH at any scale with sustainable water resources development.

A GIS-based evaluation of hydrochemical characterisation of groundwater in hard rock region, South Tamil Nadu, India

Abstract: Groundwater is a major source for domestic and agricultural uses in Natham Taluk, Dindigul district, Tamil Nadu, India. The intention of this study is to determine the quality of groundwater for domestic and irrigation purposes in the hard rock region. Totally, 37 samples were collected and analysed for physical parameters that are pH, EC, TDS, TH, major cations and anions. Piper diagram shows that Ca-HCO3 and mixed Ca-Mg-Cl is the most prominent type of water. Gibbs diagram reveals that the higher concentrations of magnesium, sodium and potassium ions are accredited to geological sources such as rock-water interaction, ion exchange process and evaporation that are the major factors affecting the nature of groundwater. In view of irrigation indices, most of the sample locations are fit for irrigation use except magnesium hazard value. Additional statistical analysis, such as correlation and principal component analysis, was calculated using SPSS software. All results are indicated; weathering, rock-water interactions and anthropogenic activities are a significant factor that alters the existence of groundwater in the research area.

Water quality assessment along Tigris River (Iraq) using water quality index (WQI) and GIS software

Abstract: Most of the third world countries having rivers passing through them suffer from the water contaminant problem. This problem is considered so difficult to get the water quality within the standard allowable limits for drinking, as well as for industrial and agricultural purposes. This research aims to assess the water quality of the Tigris River using the water quality index method and GIS software. Twelve parameters (Ca, Mg, Na, K, Cl, SO4, HCO3, TH, TDS, BOD5, NO3, and EC) were taken from 14 stations along the river. The weighted arithmetic method was applied to compute the water quality index (WQI). The interpolation method (IDW) was applied in ArcGIS 10.5 to produce the prediction maps for 12 parameters at 11 stations along the Tigris River during the wet and dry seasons in 2016. The regression prediction was applied on three stations in the Tigris River between observed values and predicted values, from the prediction maps, in both seasons. The results showed that the regression prediction for all parameters was given the acceptable values of the determination coefficient (R2). Furthermore, the state of water quality for the Tigris River was degraded downstream of the Tigris River, especially at the station (8) in Aziziyah in the wet and dry seasons and increase degradation clearly at Qurnah (Basrah province) in the south of Iraq. This paper considers the whole length of the Tigris River for the study. This is important to give comprehensive knowledge about the contamination reality of the river. Such that it becomes easier to understand the problem of contamination, analyze it, and then find the suitable treatments and solutions.

A GIS-based statistical model for assessing groundwater susceptibility index in shallow aquifer in Central Tunisia (Sidi Bouzid basin)

Abstract: A comprehensive approach for assessing the shallow aquifer Susceptibility Index (SI) to pollution was proposed by combining the Vulnerability Index (VI) and Quality Index (QI) in Sidi Bouzid basin in Central Tunisia. Hydrochemical investigation showed that nitrate concentrations and total dissolved solid (TDS) values of the Mio-Plio-Quaternary (MPQ) aquifer in the study area were ranging from 14.3 to 111 mg/l and 1218 to 6202 mg/l successively. VI was first estimated using either a generic DRASTIC model or DRASTIC-LU model by adding land use (LU) factor, with preset factor weights; these weights were later adjusted using a single parameter sensitivity analysis (SPSA) or two different statistical methods: canonical analysis of principal coordinates (CAP) and partial least squares (PLS). Compared to the generic models, the weight of the factor impact of vadose zone (I) is equal to 5 remained the highest for all the other models, except for DRASTIC one using a CAP weight adjustment technique where the weight of I is equal to 1. DRASTIC-LU and DRASTIC-LU-CAP models predicted the widest (VILU − min=89, VILU − max=206) and narrowest (VILU − CAP − min=59, VILU − CAP − max=125) VI range, respectively. VI obtained by different weight adjustment techniques significantly correlated with nitrate concentrations with a significant correlation coefficient, higher than 0.50. Based on a model selection criterion, correlation between vulnerability indices and nitrate concentration, DRASTIC-LU-CAP may be recommended as the best model. QI was assessed by simply adding the concentration of some major elements ( $$ {Cl}^{-},{Na}^{+},{NO}_3^{-} $$, $$ {SO}_4^{2-} $$) and electric conductivity (EC) transformed into ordinal classes (1–5). Groundwater SI maps for both drinking and irrigation water generated into a GIS-based map showed that a great part of the study area had a high SI to pollution.

A groundwater potential zone mapping approach for semi-arid environments using remote sensing (RS), geographic information system (GIS), and analytical hierarchical process (AHP) techniques : a case study of Buffalo catchment, Eastern Cape, South Africa.

Abstract: Theme unsuitability is noted to have inhibited the accuracy of groundwater potential zones (GWPZs) mapping approach, especially in a semi-arid environment where surface water supply is inadequate. This work, therefore presents a geoscience approach for mapping high-precision GWPZs peculiar to the semi-arid area, using Buffalo catchment, Eastern Cape, South Africa, as a case study. Maps of surficial-lithology, lineament-density, drainage-density, rainfall-distribution, normalized-difference-vegetation-index, topographic-wetness-index, land use/land cover, and land-surface-temperature were produced. These were overlaid based on analytical hierarchical process weightage prioritization at a constituency ratio of 0.087. The model categorizes GWPZs into the good (187 km2), moderate (338 km2), fair (406 km2), poor (185 km2), and very poor (121 km2) zones. The model validation using borehole yield through on the coefficient of determination (R2 = 0.901) and correlation (R = 0.949) indicates a significant replication of ground situation (p value < 0.001). The analysis corroboration shows that the groundwater is mainly hosted by a fractured aquifer where the GWPZs is either good (9.3 l/s) or moderate (5.5 l/s). The overall result indicates that the model approach is reliable and can be adopted for a reliable characterization of GWPZs in any semi-arid/arid environment.

Influence of mine shallow roadway on airflow temperature

Abstract: With the increase of the depth of mining, the working environment of deep well is worse; in order to improve the working environment of deep mine, on the basis of a lot of practice, the idea of adjusting the temperature of the air flow in the mine was put forward. Take Jiaodong area as an example, on the basis of the model of surface temperature variation, the influence of surface temperature on the temperature of the mine has been established, obtaining the influence of surface temperature on the shallow layer of the mine area. In assumption of the roadway, the heat exchange process of the surrounding rock and the air flow in the shallow layer of the different seasons was analyzed, a model of the relationship between the geometry size of the roadway and the air temperature change was established, in order to control the temperature of the mine into the air temperature by using the shallow tunnel temperature effect and then to improve the working environment of the mine working environment to lay a theoretical foundation.

A comprehensive statistical assessment of drought indices to monitor drought status in Bangladesh

Abstract: In Bangladesh, drought has negative consequences on agriculture, environments, livelihood, and food security. However, a comprehensive statistical assessment of drought indices has rarely been found in the existing literature. To address this issue, firstly, this paper used daily temperature and precipitation data from the Bangladesh Meteorological Department (BMD) to calculate Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI). After that, we performed a statistical assessment, for instance, Pearson correlation coefficient, cross-correlation, cross-wavelet transform, and root mean square error, to identify the strengths of SPI and SPEI. Our findings showed that though both indices had a strong correlation with each other, SPEI performed better than SPI because evaporative demand has a positive impact on defining drought conditions in Bangladesh. Temperature and rainfall indices, for example, warm spell duration indicator (WSDI) and maximum amount of rain (Rx5day) that falls in five consecutive days, have been applied to find out the relationship between climate extremes and drought indices using cross-wavelet transform. Our results suggested that climate extremes such as WSDI and Rx5day have an influence on droughts in Bangladesh. Our results recommended that multi indices of drought assessment should be required in order to draw a robust conclusion.

The influence of water level fluctuation on the stability of landslide in the Three Gorges Reservoir

Abstract: In order to study the influence of water level fluctuation on the stability of landslide in the Three Gorges Reservoir (TGR), Xigouwan landslide was selected to be a research object to analyze its deformation mechanism as the fluctuation of the reservoir water level. Based on the long-term field monitoring of landslide, the evolution law of the surface has been studied. Based on the numerical simulation used by FLAC3D, five different water levels of TGR operating conditions are set, and the plastic zone, the factor of safety, change of displacement, and the seepage characteristics of the landslide were obtained to analyze the influence of water level fluctuation on the stability of landslide.

The propagation mechanism of an oblique straight crack in a rock sample and the effect of osmotic pressure under in-plane biaxial compression

Abstract: In this paper, the propagation mechanism of an oblique straight crack has been studied theoretically, which reveals its mechanical characteristics under in-plane biaxial compression. Firstly, the stress components away from the boundary are derived based on the superposition principle. The normal stress components are strengthened and shear stress component is restrained compared to the uniaxial condition. Then the relationship between stresses and stress intensity factors is analyzed, and the effect of stresses on the strength of cracked rocks is discussed. The analysis of wing crack growth shows that the reliable experimental results are very demanding for sample preparation. Based on Mohr-Coulomb criterion and Mohr’s stress circles, the failure mechanism of cracked rocks is analyzed, and the physical meaning of some formulas is vividly displayed. Moreover, we study the relationship between friction angle θ0 and angle β, which determines the minimum compressive strength of cracked rocks. There are evidences that the increase of crack opening width leads to β0 (a value of β) away from the theoretical value determined by sliding crack model, so that the role of stress σx can no longer be ignored. Theoretically speaking, for an initially closed crack, we find that, for the first time, both wing crack growth and shear compression failure are more likely to occur when the angle β between 22.5 and 45 degrees combining the statistical results of Barton and Choubey (Rock Mech Rock Eng 10:1–54, 1977). As for an initially open crack, the characteristics of stress intensity factors and circumferential stresses are also discussed, especially when σ1 equals σ3. Finally, we study the effect of osmotic pressure on stresses and stress intensity factors, the weakening of the properties of crack surfaces by water is also considered, and the mechanical behavior of a rock sample with an oblique straight crack changes dramatically.

Mechanical properties of limestone from Maixi tunnel under hydro-mechanical coupling

Abstract: The hydro-mechanical coupling often leads to both mechanical properties and stability deterioration during excavation of water-rich tunnel rock mass. Deformation and mechanical, fracture, and strain energy characteristics of limestone from Maixi tunnel in Guiyang (China) are investigated by hydro-mechanical coupling tests in this paper. Results show that the water pressure has a significant influence on the stress-strain curve, strength characteristics, and macro-fracture degree. The compaction stage is relatively prolonged and elastic phase is shortened. With increasing water pressure, average peak strength decreases exponentially and both average elastic modulus and deformation modulus decrease linearly. The larger the water pressure, the better the fragment uniformity, and fragment uniformity increases exponentially but decreases logarithmically with peak strength. Mercury-injection curve shows a rapid increase then develops gently; the pore volume per unit mass increases exponentially revealing that water pressure has a significant effect on the dissolution pores. Strain energy dissipation characteristics show that total strain energy, dissipation strain energy, and releasable strain energy decrease exponentially with increasing water pressure. Energy ratio Ud/Ut experiences a slow increase, then dramatic rise, and finally develops gently, but Ue/Ut goes through a negative development tend and its boundary points of water pressure are both 2 MPa and 4 MPa. Ud/Ut has a typical logistic function with water pressure reflecting the damage degree and sensitivity of dissipation strain energy to water pressure.

Estimation of solar radiation using neighboring stations through hybrid support vector regression boosted by Krill Herd algorithm

Abstract: Solar radiation is a basic input in many fields of studies and models. However, the low density of solar network stations; the improper distribution of these stations; high cost of purchasing, maintaining, and calibrating solar radiation measurement instruments; and frequent errors in the available data are the most important deficiencies in this regard. Thus, researchers are seeking for new and practical methods to estimate solar radiation accurately. The present study aimed to estimate the solar radiation values based on a new hybrid support vector regression model. To this aim, the solar radiation values of all eight target synoptic stations during 1974–2014 were estimated by using Krill-Herd hybrid algorithm (SVR-KHA) method based on support vector regression and implementing neighboring station data. Results indicated that the testing performance of SVR-KHA has a more precision and lower error for all target stations, compared with classical SVR. In addition, the best results were obtained for SVR-KHA3 hybrid model (Isfahan station). Further, the RMSE, MAPE, and R2 values for this model were 1.98 MJ/m2/day, 7.4%, and 0.93, respectively. In accordance with the results, Krill-Herd algorithm method coupled with support vector regression had a high performance and capability for solar radiation estimation in Iran. In other words, the hybrid SVR-KHA model is more flexible and has less error in modeling the nonlinear and complex systems. Finally, the new method of using neighboring stations can be regarded as an appropriate method for estimating nonlinear phenomenon such as solar radiation.

The use of RUSLE and GCMs to predict potential soil erosion associated with climate change in a monsoon-dominated region of eastern India

Abstract: Soil is one of the most important natural resources; therefore, there is an urgent need to estimate soil erosion. The subtropical monsoon-dominated region also faces a comparatively greater problem due to heavy rainfall with high intensity in a very short time and the presence of longer dry seasons and shorter wet seasons. The Arkosa watershed faces the problem of extreme land degradation in the form of soil erosion; therefore, the rate of soil erosion needs to be estimated according to appropriate models. GCM (general circulation model) data such as MIROC5 (Model for Interdisciplinary Climate Research) of CMIP5 (Coupled Model Intercomparison Project Phase 5) have been used to project future storm rainfall and soil erosion rates following the revised universal soil loss equation (RUSLE) in various influential time frames. Apart from that, different satellite data and relevant primary field-based data for future prediction were considered. The average annual soil erosion of Arkosa watershed ranges from 6 t/ha/year. The very high (> 6 t/ha/year) and high (5–6 t/ha/year) soil loss areas are found in the southern, south-eastern, and eastern part of the watershed. Apart from this, low (1–2 t/ha/year) and very low (< 1 t/ha/year) soil loss areas are associated with the western, northern, southern, and major portion of the watershed. Extreme precipitation rates with high kinetic energy due to climate change are favorable to soil erosion susceptibility. The results of this research will help to implement management strategies to minimize soil erosion by keeping authorities and researchers at risk for future erosion and vulnerability.

Physical simulation study of crack propagation and instability information discrimination of rock-like materials with faults

Abstract: In coal seam mining, fault structures are easy to activate, which poses a serious threat to the safety of the mine during use. Therefore, the identification of physical information before fault activation and the prediction of fault activation have important guiding significance and reference value for the safety of coal mine production. For this reason, this paper first developed rock-like materials for simulating faults and surrounding rocks. On this basis, simulation experiments on the activation process of different types of analogical fault were carried out. The results showed that the failure process of rock-like samples with analogical concealed fault and analogical conduction fault could be divided into three stages, but the failure characteristics of each stage were different. The rock-like sample with analogical concealed fault began to crack in the form of tensile cracks at the structural tip, accompanied by the partial release of strain energy, and the whole sample was stable. In the crack initiation stage of the analogical surrounding rock, the analogical surrounding rock became the main bearing zone, the weak area of the analogical surrounding rock produced a tensile crack, releasing a small amount of strain energy, and the sample remained in a stable failure state. The rock-like samples with analogical conduction fault began to crack at the interface between the analogical fault and the analogical surrounding rock in the form of a shear crack, which released part of the strain energy. The sample had a sliding trend, but it was stable as a whole. At the stage of crack generation and propagation, new shear cracks appeared at the interface, which were affected by the released and secondary accumulated strain energy; some of the strain energy was released, and the sample was basically stable. In the early stage of sliding instability, which is the key period to prevent fault activation, the stress change was relatively stable, and less strain energy was released. In the later stage, the new shear cracks were connected with the existing shear crack, and the sample underwent sliding instability failure, which released a large amount of strain energy.

A multi-criteria based SWOT analysis of sustainable planning for mining and mineral industry in Pakistan

Abstract: Lack of strategic planning in the mining and mineral industry (MMI) of Pakistan remains the core issue impeding the development of the industry. This study proposes and, respectively, prioritizes future strategies based on strengths–weaknesses–opportunities–threats (SWOT) analysis. The proposed strategies aim to foster the sustainable development of the MMI. An integrated approach is introduced to conduct the analysis. Initially, SWOT factors are identified through a literature survey and experts’ feedback. The importance of each element of SWOT analysis and underlying factors is quantified using fuzzy analytical hierarchy process (FAHP). Finally, the weightage obtained using FAHP is used in the fuzzy technique for order of preference by similarity to ideal solution (FTOPSIS) to rank, prioritize, and determine the best strategies for the future development of MMI. The FAHP results reveal that the strengths and weaknesses receive almost the same priority. It is found that the factors ‘enormous mineral potential’ and ‘demand for minerals’ can drive development in MMI, whereas governmental, organizational, and economic weaknesses place hurdles in the development. The results of FTOPSIS show that the need for new mineral policy development is recognized to be the most important factor, followed, respectively, by financial support to the industry, technological advancement, and human resource development.

Comparing performance of random forest and adaptive neuro-fuzzy inference system data mining models for flood susceptibility mapping

Abstract: Flood is one of the important destructive natural disasters in the world. Therefore, preparing flood susceptibility map is necessary for flood management and mitigation in a region. This research was planned to compare the performance of frequency ratio (FR), adaptive neuro-fuzzy inference system (ANFIS), and random forest (RF) models for flood susceptibility mapping (FSM) in the Gilan Province, Iran. First, a geospatial database included 220 flood locations and eleven effective flood factors (slope angle, aspect, altitude, distance from rivers, drainage density, lithology, land use, topographic wetness index (TWI), and stream power index (SPI)) were produced. According to flood locations, 30–70% of them were used for training and validation of the models, respectively. Afterward, the mean of Gini reduction was used to determine the priority of effective flood factors. Finally, the receiver operating characteristic (ROC) curve, area under the curve (AUC), was used to evauate and compare the performance of the models. The validation results of the models show that FR, ANFIS, and RF models had 68.6, 63.9, and 71.3% accuracy, respectively. In addition, distance from rivers, altitude, and drainage density was the most important factor for FSM in the study area. The finding of the current research proved a reasonable prediction performance for the models. Therefore, these models can be proposed for preparing FSM in similar climatic and physiographic areas and flood susceptibility maps can be used to manage floodplains in the study area.

Fluoride occurrence and human health risk from groundwater use at the west coast of Urmia Lake, Iran

Abstract: We investigated fluoride (F−) concentration and physicochemical features of groundwater in the Urmia coastal aquifer (northwest, Iran). Groundwater samples were collected during both dry (58 wells) and wet seasons (84 wells). Approximately 15 and 23% of the groundwater samples in the dry and wet seasons, respectively, exceeded the recommended F− value by WHO for drinking water (1.5 mg/L). High F− concentration in groundwater is mainly found in shallow wells. The cause of high F− concentration appears to be mainly caused by human activities. Agricultural fertilizers and industrial waste can result in rapid release of F− into the groundwater. Release of F− into the groundwater can, however, also be triggered by the interaction between rock and water. In the experimental area, high F− concentrations were found close to volcanic rocks. Health risks from exposure to F− in groundwater were analyzed for adults and children. Utilizing sensitivity analysis and Monte Carlo simulation, the uncertainties in the risk estimates were calculated. Sensitivity analyses showed that the most pertinent variables are F− concentration in drinking water, averaging time, exposure time, and ingestion rate of water. Children are more susceptible to the noncarcinogenic risk of F− in groundwater.

Nonlocal vibration analysis of Ti-6Al-4V/ZrO2 functionally graded nanobeam on elastic matrix

Abstract: In the present study, a nonlocal finite element method (FEM) is proposed to investigate the free vibration of functionally graded (FG) nanobeams resting on two parameters, the Winkler–Pasternak elastic foundation. Using the Eringen’s nonlocal elasticity theory, the Euler–Bernoulli beam model is implemented. The equations of motion are obtained by using Hamilton’s principle. Material properties of the beam vary in the thickness (height) direction based on the power law. The frequencies of functionally graded nanobeam are obtained for simply supported (S-S) boundary conditions with various values of power law exponent, small-scale (nonlocal) parameter, Winkler foundation parameter, and Pasternak foundation parameter. Vibration response of nano-scaled functionally graded beam resting on the Winkler–Pasternak elastic foundation is investigated via the nonlocal finite element method. A comparison of the numerical results of the present study with those from the open literature demonstrates a good agreement. Also, the difference between classical elasticity theory and nonlocal elasticity theory is discussed in this study.

Irrigation risk assessment of groundwater in a non-perennial river basin of South India: implication from irrigation water quality index (IWQI) and geographical information system (GIS) approaches

Abstract: Groundwater is an important natural resource for irrigation purpose in the non-perennial River basin (Shanmuganadhi) of South India. The present investigation was conducted to determine the groundwater suitability for irrigation purpose, using irrigation water quality index (IWQI) with the application of GIS. A total of 61 groundwater samples collected from the present study region were chemically analyzed such as TDS, EC, pH, Ca2+, Mg2+, Na+, K+, HCO3−, Cl−, and SO42−. Groundwater quality shows slight alkalinity (7.11–7.95). The Wilcox, USSL, and Doneen’s diagrams, and RSC, KR, and MHR indices indicate that maximum groundwater sampling locations fall under the unsuitable category for irrigation purpose. According to the classification of IWQI, 57% of the total groundwater samples belongs to the poor to unsuitable water quality types for irrigation. The spatial distribution of IWQI displays that 77.27% of the present study region comes under the vulnerable zones such as moderate restriction (51.99%, high restriction (23.10%), and severe restriction (2.18%) water quality for irrigation purpose. Therefore, the present study suggests the suitable treatment methods for increasing the soil permeability and thereby to improve the crop production.

Meteorological drought prediction using heuristic approaches based on effective drought index: a case study in Uttarakhand

Abstract: Monitoring and prediction of drought using standardized metrics of rainfall are of great importance for sustainable planning and management of water resources on regional and global scales. In this research, heuristic approaches including co-active neuro fuzzy inference system (CANFIS), multi-layer perceptron neural network (MLPNN), and multiple linear regression (MLR) were used for prediction of meteorological drought based on Effective Drought Index (EDI) at 13 stations located in Uttarakhand State, India. The EDI was calculated using monthly rainfall time-series data, and the significant input variables (lags) for CANFIS, MLPNN, and MLR models were derived using autocorrelation and partial autocorrelation functions (ACF and PACF) at 5% significance level. The predicted values of EDI obtained by CANFIS, MLPNN, and MLR models were compared with the calculated values based on root mean squared error (RMSE), Nash-Sutcliffe efficiency (NSE), coefficient of correlation (COC), and Willmott index (WI). The visual interpretation was also made using line diagram, scatter plot, and Taylor diagram (TD). The evaluation of results revealed that the CANFIS and MLPNN models outperformed than the MLR models for meteorological drought prediction at study stations. Also, the results of this research can be utilized for the decision-making of remedial schemes to cope with meteorological drought in the study region.

The improvement of ecological environment index model RSEI

Abstract: Protecting the ecological environment is an important goal of the world sustainable development. Rapid and quantitative evaluation of regional ecological environment is the technical support and necessary condition for this goal. The ecological environment index model (RSEI) which used to assess ecological environment is the most popular now. But it changed into two completely opposite models in the application. Most researchers choose which model to use based on the desired results. This article concludes the reason by studying the operating mechanism of the model and finds that it is the eigenvector direction in the principal component analysis causes this to happen. Taking Pingyu County as an example, this article calculates RSEI with Landsat 8 images in different periods in Google Earth Engine using the two existing models respectively and finds that two models show two opposite result trends in spatial distribution. Using any model to calculate the same image, the results are also opposite if changing the input order of the indicators. It is the eigenvector direction determines the spatial distribution by comparing and analyzing the eigenvector of each image and its corresponding RSEI. Then, this paper improves the model by fixing the eigenvector direction based on the actual effects on ecological environment of the four indicators, taking absolute values of the eigenvectors of NDVI and Wet which have a positive effect on the ecological environment and the opposite of absolute values of the eigenvectors of LST and NDSI which have a negative effect on the ecological environment, in order to improve the RSEI model. Using the improved model calculate each image, the results are consistently accurate. Furthermore, this paper also proposed a model for users who calculating the principal components through software where the eigenvector direction cannot be altered artificially. This paper proposes the improved model which is suitable for all users whether using software or conducting programming. The improved model is suitable for all images of any input order of the indicators. It provides the possibility of applying remote sensing big data to the ecological environment. At the same time, the study of the mechanism of the model provides a scientific basis for future scholars to calculate in batches.

Appraisal of heavy metal contamination in sediments of the Shitalakhya River in Bangladesh using pollution indices, geo-spatial, and multivariate statistical analysis

Abstract: Rapid urbanization and industrialization have aggravated heavy metal contamination in river sediments of the riverine ecosystem in developing countries like Bangladesh owing to their toxicity and persistence. Sediments are dynamic components and useful indicators to understand the level of contamination and their associated ecological risks in the aquatic environment. The study was conducted to investigate the heavy metal contamination in sediments for assessing the ecological risks of an urban river of Bangladesh using principal component analysis (PCA), Pearson’s correlation matrix, geo-accumulation index (Igeo), contamination factor (CF), contamination degree (CD), pollution load index (PLI), enrichment factors (EF), and potential ecological risk factor (RI). The ranges of Zn, Cr, Cu, Pb, and Cd in sediments were 42.22–99.55, 11.12–57.83, 7.98–53.31, 6.76–22.41, and 0.38–0.87 mg/kg, respectively. In the present study, heavy metal concentration in sediments followed the descending order of Zn > Cr > Cu > Pb > Cd, while the concentrations of Cu, Cr, and Cd were higher and the concentrations of Pb and Zn were lower than the toxicity reference value (TRV). Geoaccumulation index (Igeo) demonstrated that most of the sediment samples were unpolluted to moderately polluted. The PLI ranged from 0.334 to 1.209 that stated that sediments were moderately polluted by studied metals. The multivariate statistical analysis revealed that heavy metal contamination was influenced by multiple pollution sources. The extent of heavy metal pollution in the Shitalakhya River implies that the condition is much frightening to both the aquatic biota and inhabitants in the vicinity of the river.

Longitudinal study of land surface temperature (LST) using mono- and split-window algorithms and its relationship with NDVI and NDBI over selected metro cities of India

Abstract: This study was designed to compare the pattern of land surface temperature (LST) over four metro cities of India (Mumbai, Chennai, Delhi, and Kolkata) selected on a longitudinal basis in relation to the built-up and vegetation indices. Two different methods were employed for the retrieval of LST, i.e., mono-window algorithm (MWA) and split-window algorithm (SWA) on the Landsat 8 (OLI/TIRS) datasets, to analyze the spatial pattern of LST over selected cities in relation to normalized differential built-up index (NDBI) and normalized differential vegetation index (NDVI). The result shows that the LST was high over the densely built areas while low over the densely vegetated areas. The highest LST, NDBI, and NDVI were found in Mumbai, while Kolkata records the lowest LST and NDVI. Furthermore, the spatial analysis of LST shows that the LST was high in central parts of all cities except in the case of Delhi where some peripheral areas also record high LST. The comparison from in situ LST (field observations) reveals that the SWA has higher accuracy in the retrieval of LST in maritime areas like Mumbai and Chennai because it reduces the atmospheric effects, while the MWA has higher accuracy for inland areas like Delhi. The spatial relationships of LST with NDVI and NDBI show that vegetation cover has more impact on LST in Delhi while low in Chennai and Mumbai, and the built-up surfaces have a higher impact on LST in Chennai and Mumbai than Kolkata and Delhi.

The use of sodium chloride as strategy for improving CO2/CH4 replacement in natural gas hydrates promoted with depressurization methods

Abstract: Natural gas hydrates represent a valid opportunity in terms of energy supplying, carbon dioxide permanent storage and climate change contrast. Research is more and more involved in performing CO2 replacement competitive strategies. In this context, the inhibitor effect of sodium chloride on hydrate formation and stability needs to be investigated in depth. The present work analyses how NaCl intervenes on CO2 hydrate formation, comparing results with the same typology of tests carried out with methane, in order to highlight the influence that salt produced on hydrate equilibrium conditions and possibilities which arise from here for improving the replacement process efficiency. Sodium chloride influence was then tested on five CO2/CH4 replacement tests, carried out via depressurization. In relation with the same typology of tests, realised in pure demineralised water and available elsewhere in literature, three main differences were found. Before the replacement phase, CH4 hydrate formation was particularly contained; moles of methane involved were in the range 0.059–0.103 mol. On the contrary, carbon dioxide moles entrapped into water cages were 0.085–0.206 mol or a significantly higher quantity. That may be justified by the greater presence of space and free water due to the lower CH4 hydrate formation, which led to a more massive new hydrate structure formation. Moreover, only a small part of methane moles remained entrapped into hydrates after the replacement phase (in the range of 0.023–0.042 mol), proving that, in presence of sodium chloride, CO2/CH4 exchange interested the greater part of hydrates. Thus, the possibility to conclude that sodium chloride presence during the CO2 replacement process provided positive and encouraging results in terms of methane recovery, carbon dioxide permanent storage and, consequently, replacement process efficiency.

The EPIK multi-attribute method for intrinsic vulnerability assessment of karstic aquifer under semi-arid climatic conditions, case of Cheria Plateau, NE Algeria

Abstract: Karst aquifers supply an important freshwater resource for MENA (Middle East and North Africa) semi-arid regions. Their functioning conditions reveal often several contaminations. The Cheria carbonate aquifer (NE Algeria) has never had management tools to deal with the pollution of this resource. The outlining and protection of the vulnerable areas are essential to ensure the water purity and the consumer health. Based on the EPIK multicriteria analysis method, we aim in our study to assess the karstic aquifers intrinsic-vulnerability to contamination in the Cheria Plateau. This method has been already applied for contamination problems in Northeast Algeria. It uses a conceptual scheme that considers epikarst, protective cover, infiltration, and karst network as parameters. In addition, it also uses the interpolation of the geophysics data to define the conditioning attributes. The resulting vulnerability map categorizes all the basin vulnerable areas and the groundwater protection zones. Nearly 30% of the study area was judged as highly vulnerable to anthropogenic pollution, whereas around 10% is moderately vulnerable. These results confirm that the karst aquifer of the Cheria Plateau is severely polluted by chemical pesticides resulting from farming activity. In addition to the surrounding agricultural lands, the underground of Cheria city was found as extremely vulnerable to pollution (F < 19). Our study delimited boundaries for the karst aquifer protection zones and for an integrated resource management in this region. It recommends applying this method for comparable problems.

Groundwater quality assessment using random forest method based on groundwater quality indices (case study: Miandoab plain aquifer, NW of Iran)

Abstract: Miandoab plain aquifer, with 1150-km2 area, supplies a significant portion of the agricultural and drinking water demands of the area. In recent years, it has been faced with a significant decline in water level as a consequence of the deterioration of groundwater quality. Therefore, a scientific study of the groundwater resources in the study area for quantitative and qualitative management is necessary. One of the important indicators for assessing and zoning of the groundwater quality is the measurement of the concentrations of the ions and determining the groundwater quality index (GQI) by combining ion concentrations and their relationship with reliable standards. For this purpose, in October 2018, 75 water samples from the groundwater resources of the Miandoab plain aquifer were collected and chemically analyzed. To minimize the uncertainties, the fuzzy groundwater quality index was used by the fuzzification of the GQI method. Also, the random forest (RF) algorithms, as a learning method based on an ensemble of decision trees, were used for the assessment of groundwater quality. The RF technique has advantages over the other methods due to having high prediction accuracy, the ability to learn nonlinear relationships, and the ability to determine the important variables in the prediction. In the validation and comparison of methods, fuzzy groundwater quality index method with more accuracy is identified as a more reliable method in groundwater quality evaluation for drinking purposes. Based on the RFGQI results, 20, 16, 15, 26, and 23% of the Miandoab plain aquifer, respectively, has a suitable, acceptable, moderate, unsuitable, and absolutely unsuitable groundwater quality. Overall, the results of this study showed that the random forest method can be used as a reliable method for groundwater vulnerability, investigating and properly managing or monitoring of the aquifers.

Deformation and cracking characteristics of ring-shaped granite with inclusion under diametrical compression

Abstract: This paper presents the results of an experimental investigation on the deformation and cracking behaviors of ring-shaped granite specimens. Diametrical compression tests were conducted on ring-shaped granite specimens with inclusion and those without inclusion for comparison. The inclusion materials were of different strengths, stiffness, and sizes. Strain gauges (SGs) were amounted at the boundary of the hole to trace the strain evolutions, and digital image correlation (DIC) technique was used to identify the crack initiation and propagation process. The results indicated that the inclusion has a positive effect on the enhancement of the carrying capacity. The maximum carrying capacity of the specimen with low-strength inclusion decreases with increasing the inclusion diameter, while it first decreases and then increases when the inclusion diameter increases from 10 to 20 mm for the high-strength infilled specimens. The results of the strain evolutions analyzed by the SGs and DIC methods indicate that a lager hole diameter and a lower inclusion strength lead to a more intensive strain concentration around the hole. Due to the mismatch in the deformation at the rock–cement mortar interface, serious strain concentrations are induced, and hence leading to three types of failure, i.e., debonding between the interface, tensile crack in the granite, and tensile crack in the inclusion material.

Seismic hazard and risk assessment: a review of state-of-the-art traditional and GIS models

Abstract: The historical records of earthquakes play a vital role in seismic hazard and risk assessment. During the last decade, geophysical, geotechnical, geochemical, topographical, geomorphological, geological data, and various satellite images have been collected, processed, and well-integrated into qualitative and quantitative spatial databases using geographical information systems (GIS). Various types of modeling approaches, such as traditional and GIS-based models, are used. Progressively, seismic studies can improve and modify systematic models and standardize the inventory map of earthquake-susceptible regions. Therefore, this paper reviews different approaches, which are organized and discussed on various models primarily used to create an earthquake scenario focusing on hazard and risk assessment. The reviews are divided into two major parts. The first part is the basic principles, data, and the methodology of various models used for seismic hazard and risk assessment. In the second part, a comparative analysis in terms of the limitations and strengths of the models, as well as application variability is presented. Furthermore, the paper includes the descriptions of software, data resources, and major conclusions. The main findings of this review explain that the capability of machine learning techniques regularly enhances the state of earthquake research, which will provide research opportunities in the future. The model suitability depends on the improvement of parameters, data, and methods that could help to prevent future risk. This paper will help researchers further understand the models based on their strengths, limitations, and applicability.