Earth Sciences

In southern Tunisia, the lack of permanent surface water, associated with drought conditions, leads to an endless abstraction from the limited low renewable multi-layered aquifer system of Système Aquifère du Sahara Septentrional containing two principal aquifers, the complex terminal and the Continental Intercalaire (CI) multi-layered systems. The deepest aquifer embodies the low-enthalpy thermal resources of Southern Tunisia. The thermo-mineral surface manifestations of the conductively heated waters reveal the complexity of the geotectonic history of the region and create oases systems in net contrast to the desertic landscape of the Chotts region. As agriculture constitutes the principal economic activity in the studied area and as it is currently threatened by thermal water quality degradation, the present hydrogeological investigation aims for a characterization of the CI thermal resources on the basis of a critical quality evaluation. Thus, different geothermometry approaches have been applied to characterize the low-enthalpy thermal field showing a temperature ranging from 27 to 72 °C. The application of cations geothermometers owns to different temperature estimations ranging from 28 to 202 °C. Based on Na +-Mg 2+-K + , K +-Mg 2+-Ca 2+ and HCO 3 −-Cl −-SO 4 2− geoindicators, the CI thermal resources refer to immature waters characterized by MI varying from − 0.5 to 0.19. The assessment of groundwater chemical composition based on a Durov diagram proves that CI thermal water is governed by mixing between different water bodies with relative abundance of Na + , Cl − , and SO 4 2− elements. According to D'Amore genetic diagram and meteoric genesis indices, the analyzed groundwater derived from deep circulation in sandy formations. The water quality can change along fluid migration pathways expressed by scattered isotopic and chemical data and a number of mixing ratios. Most changes in the background CI composition result from continuous pumping that modifies natural flows and increase quality degradation.

The purpose of the present study was to compare the prediction performances of three statistical methods, namely, information value (IV), weight of evidence (WoE) and frequency ratio (FR), for landslide susceptibility mapping (LSM) at the east of Constantine region. A detailed landslide inventory of the study area with a total of 81 landslide locations was compiled from aerial photographs, satellite images and field surveys. This landslide inventory was randomly split into a testing dataset (70%) for training the models, and the remaining (30%) was used for validation purpose. Nine landslide-related factors such as slope gradient, slope aspect, elevation, distance to streams, lithology, distance to lineaments, precipitation, Normalized Difference Vegetation Index (NDVI) and stream density were used in the landslide susceptibility analyses. The inventory was adopted to analyse the spatial relationship between these landslide factors and landslide occurrences. Based on IV, WoE and FR ...

Several sinkhole collapses were occurred in the many sites in urban areas and/or their rural periphery; in NE Algeria, in the last few years. The abrupt collapse causes damages to properties, infra-structures, and even lives. The most spectacular oneoccurred in February 2009 inside the Cheria city, Northwest of Tebessa department, with a diameter of more than a hundred meters. This abrupt collapse is due to a sudden rupture of the roof of a large underground karst cavity. It caused panic-stricken among the population living near the crater. In order to investigate the origin of this phenomenon, we combine several geophysical and geotechnical methods, such as Ground Penetrating Radar, Electrical Resistivity Tomography, Standard Penetration Test, Mechanical Drill Core, Cave Survey Photogrammetry, etc. It appears that each method may provide specific information. Their comparison allows to precise the results itself, the limits and the application field of each. Consequently a number o...

Several types of instabilities can menace the personnel and equipment in the open cast mines. Their kinematicis dependent commonly on the nature, the structure, the fracturing and the strength of the rock mass. A scientific assessment vis-a-vis their equilibrium is suggested. For this task a considerable amount of field work must already carrying out to supply the necessary data ie: geometric, mecanic and geologic parameters. The main purpose of this research is identifying different modes of slope failures that may develop on the career “ENOF” of Jebel Gustar, by a multi-step analysis. For this task, i) a structural analysis; ii) an estimation of the rock mass and discontinuity mechanical properties, iii) a rating of the rock mass quality, iv) and a numerical simulation of the stability are procedurally used. The results matched well with the field observations. They proved the poor stability of the career, showing a typical example of a bad slope-design. The application of such ap...

Slope failures (SF) in mountainous terrain often occur during or after heavy rainstorms, resulting in the loss of life and damage to the natural and/or built environment. Assessing areas susceptible to SF is essential for land use planning in threatened areas. This article presents an didactic basedanalysis of the potential contribution to geo-spatial approaches for predicting SF qualitative exposure in mountainous environment. Its main aim is to assess the impact of the geologic, geomorphic, rainstorms, and anthropogenic factors in the initiation of SF in Zaarouria region. 219 events (1996-2016) were inventoried through images interpretation and field surveys and were compared to the physical parameters of the terrain to give a SF susceptibility index value using a simplified model. Vulnerability and risk maps are also established. The Standard deviation classification was used to delineate various susceptibility, vulnerability and risk zones, namely, nil, low, moderate and high. Field data on SF were employed to evaluate and validate the susceptibility zonation map. The results of this study demonstrate that SF are largely governed not only by geoenvironmental conditions but also by human activities, mainly roads and construction.

This study aimed to assess landslide susceptibility by employing certainty factors model (CF) to select the causative factors for landslide susceptibility mapping in Upstream of Jeneberang River, South Sulawesi. Indonesia. The landslide causative factors were: soil, slope angle, aspect, elevation, lithology, land use, distance to the river, drainage density, and precipitation. For validation purpose, landslide inventory map was randomly partition into two groups, 30% for the validation and 70% for the training. Landslide susceptibility maps were produced by logistic regression using original factor (all nine factors) and selected factor (four factors with positive CF value). The result of certainty factor analysis shows CF value is positive for elevation, land use, slope and drainage density. The accuracy of two landslide susceptibility maps were evaluated by calculating the area under the curve of Receiver Operating Characteristic (ROC) curves. The result shows the the success rate curve for nine factor map (80.2%) is higher than four factor map (78%). But in case of closeness between success rate curve and predictive rate curve, certainty factors model has a closer distance. In this study, effect analysis studies show how the accuracy changes when the input factors are changed.

Purpose. To analyze the sliding from the geotechnical point of view and to identify the plausible causes that influence it. Methodology. To analyze the sliding from the geotechnical point of view and to identify the plausible causes that influence it, our study follows the following chronological order. Firstly, a feedback reconstructs the slip from the geotechnical point of view; a backanalysis is required to confirm the surface failure. Next, a check will be made of the surface failure through the finite differ ence method and using the shear strength reduction by finite difference method (SSRFD). A parametric study on the influence of the geometric parameters is performed to see the influence of the latter on the stability. The plausible cause that has directly influenced this sliding is shown. findings. This paper considers the application of three methods: limit equilibrium method (LEM), finite element method (FEM) and finite difference method (FDM) to perform back analysis and find out the layer of slope failure in an open pit mine. originality. Three different approaches LEM, FEM and FDM were used to perform the backanalysis the rock mass properties and to investigate the slope failure mechanism and the accuracy of this method in mining engineering field. Practical value. This study has illustrated that noncompliance with the art, open pit mining standards and early planning of the mining method can most often lead to critical situations and catastrophic results. The back analysis of the slip site allowed us to reconstruct the break already observed and to draw maximum lessons on the mode, location and mechanical parameters that triggered this break.

This paper presents a GIS-based method for landslide susceptibility (LS) assessment using slope-movement inventory and field data. The study has been carried out along A1-Highway (A1-H) in Hanif region as this road section is threated by several types of mass wasting. This hilly zone is known by their landslides sensitive terrains in the North of Algeria. The terrain data are collected from a Géologic map, satellite imageries, digital elevation model, rainfall data, field suveys and ancillary data. In this paper Frequency Ratios (FR) based on bivariate statistical method are evaluated by comparing the observed landslides to their controlling factors. The product of the linear summation of the FR values was a landslide susceptibility index (LSI) map. It was categorized using the natural breaks classification method. The resultant LS zonation map delineates the area into five hierarchic zones. The results confirms that the angle of the slope, plays the most role in wasting especially ...

Purpose. Several natural and anthropogenic factors control the hydro-geochemical behavior of groundwater. These factors influence on the quality, even the suitability of this resource for drinking. The main purpose of our study is the application of multivariate statistical methods to compile the mechanisms of mineralization acquisition in confined aquifers. Methods. The adopted method measures the chemical evolution of Ca+2, Mg+2, Na+, K+, HCO-3, Cl-, SO4-2, NO-3, NO-2, NH+4, and PO4-3 using an atomic-absorption spectrometer. The content of nitrogen and dissolved oxygen is measured using a spectrophotometer. Temperature (T°), electrical conductivity (EC), pH and dissolved oxygen are determined using a multi-parameter system. Findings. The main results show that 28 water samples from the Mio-Plio-Quaternary aquifer of the Gadaïne-Ain Yaghout plain have chemical facies of chloride, sulfate-calcium and chloride-magnesium types. Originality. The originality of the study is in the demon...

The hydrogeochemical and isotopic compositions of groundwaters of the Mio-Plio-Quaternary (MPQ) aquifer of the El Eulma area, Northeast Algeria were examined to determine the main factors controlling groundwater chemistry and salinity as well as its hydrogeochemical evolution. Groundwater occurs in different water-bearing formations belonging to Quaternary, Neogene, Upper Cretaceous and Jurassic age. Different geochemical interpretation methods were used to identify the geochemical characteristics. Groundwater of the MPQ aquifer has the highest salinity values (564.5≤total dissolved solids≤2,333 mg/L) in the study area due to the impact of saltwater of Chotts and/or Sebkha "Bazar" and agricultural activities. Plotting data in a Piper diagram showed 18 O and display an isotopic signature close to that of meteoric water with d-excess values indicating present-day precipitation over the region and reflect the contribution of vapour masses from Mediterranean Sea and Atlantic origin. The isotopic features suggest that most of the groundwaters at the study area result from mixing between recent recharge and an older component recharged under climatic conditions cooler than at present.

The hydrodynamic of the multi-aquifer system (the Continental Intercalaire " C.I " and the Complex Terminal " C.T ") of the North Gafsa basin is largely determined by tectonics (Tebessa-Gafsa fault). The composition of groundwater is controlled by complex reactions at gas-liquid-solid "mineralogical composition of associated rocks" interfaces, which depend on the natural surrounding and potential anthropogenic impact. The hydrochemical data (major ion geochemistry) indicate that these groundwaters are characterized by the dominance a Ca-Mg-HCO 3 /SO 4 and Na-Cl-NO 3 water types. Geochemical pattern is mainly controlled by the

Climate change is having short-and long-term impacts on surface and groundwater in the northern part of the African continent. This has led to a wide range of consequences that have added pressure on the groundwater systems in this part of the world. Among such pressures, we can cite the mal-distribution and the irregularity of precipitation and ice, flooding, evaporitic sediments input by the drainage net, water degradation, mud stagnation in dams, dead tranche, drought, decreasing of the natural recharge and increasing of the groundwater abstraction, conflict between trans-boundary waters, desertification, imbalance between the regions, migration, revolution, socioeconomic imbalance, etc. Actually, watermonitoring networks indicate noticeable hydrogeologic variations and a rise of the groundwater salinity. It was confirmed by the geochemical analysis of water resources that showed scattered data between the northern part characterized by low mineralized groundwater (TDS ranging 0.4-3 g/l) and the southern area where the salinity ranges from 2.5 to 90 g/l. The obtained values are far above the permissible limits for both human consumption, agricultural and tourist activities. These effects, when compounded, are anticipated to worsen the situation and to constitute veritable threats for social and economic development in these regions of North Africa (Morocco, Algeria, Tunisia, Libya, Egypt, etc.). The potential solutions consist of taking urgent to utilize the intelligent technology (bio and nano-technology), policies relevant policies to manage water resources, and the engagement of private, civil, and international sectors if a major crisis is to be averted (collective effort).

Heavy rainfall in Aïn Draham province in the NorthWestern of Tunisia lead to the formation of some landslides which could poses danger to lives and properties. The geological outcrops of the region mainly consist of Numidian flysch rocks. In this study, field based 15 undisturbed samples were taken, from 11 boreholes drilled in 4 landslide points, to understand the real behaviour of soils when landslides occur. For this purpose, the geotechnical characterization of all samples was carried out. The grain size distribution shows that the clay and silt fractions prevail. The clay fraction ranges between 4% and 64% with an average of 40.4%, the silt fraction ranging from 19% to 71% averaging 39.8% and the sand fraction was between 6% and 44% with an average of 19.8%. The Casagrande plasticity chart indicates that 33.3% of samples were in the high plasticity group (CH group) and 66.6% having a medium to low plasticity. The water content varies between 12% and 31%. The direct shear strength test shows that the cohesions values range from 41 KPa to 77KPa and the internal friction angle values range widely from 12° to 27°. A statistical approach was taken to determine the most important factors responsible for the decrease of the cohesion and friction angle which are in charge of slope failure. For this, a correlation matrix of all soil properties was done. The coefficients of correlation show that the clay fraction is the most correlated parameter to the cohesion with an index of-0.872. Unfortunately, the internal ACCEPTED MANUSCRIPT friction angle is very low correlated to all geotechnical parameters. The clay fraction, as the most correlated to the cohesion, and the water content, which depends on rainfall (landslide triggering factor), were considered as two independent parameters for the establishment of a multiple linear and non-linear regression models of the cohesion. The multiple linear model showed that the cohesion decrease with the increase of water content and especially the increase of clay fraction with coefficients of-0.083 and-0.441, respectively. The non linear model showed that the cohesion decrease exponentially and linearly with the increase of the clay fraction and water content, respectively. The statistical study of the effect of geotechnical parameters on the landslide triggering, shows that the clay formations and also the increases of soils clay fraction by alteration phenomena is the crucial factor in landslides genesis. During rainfall the increase of the water content of clayey soils decreases the shear strength of soils more and more.

The Sidi Bouzid and El Hjal Wadi basins together comprise one of the most important agricultural regions in Central Tunisia. Exploitation of the groundwater in this region is increasing exponentially. In this work, hydrochemical characteristics and the analytic hierarchy process (AHP) were used to assess the suitability of the groundwater in the aquifer for use in irrigation. Concentrations of total dissolved solids in the groundwater ranged from 1500 to 5000 mg/L. The most abundant chemical species in the water were SO 4 2− and Cl − , with mean concentrations of 1010 mg/L and 641 mg/L, respectively. The high levels of these species can be explained by sulfate mineral dissolution and the leaching of evaporitic formations into the groundwater flow. Quality criteria weighting using the AHP was employed to generate a map of groundwater suitability for irrigation. This method categorized water samples as either excellent, good, or permissible for irrigation based on the Water Quality Index (WQI). Most of the water samples (76.5%) in the study area were found to contain water that would be good for irrigation, although the groundwater quality deteriorated towards the areas with low elevation.

Trepça mine was opened by traverbank from the First Tunnel and then through the central well to the depths of XI-th horizont (from 760m up to 12m), 11 horizonts were developed with vertical distance of 60m, while in the above part of the mines, between quotes 760m and 610m, 4 horizonts are developed with vertical spacing every 35m. The mine is about 750m deep and wide 2500m with an average of 20 mining bodies, which, in the horizontal cut have a size of 300 to 3000m2. In this paper it was analyzed the stability of the security plates of the ore in the "Trepça" mine in Stantërg, which are formed in ore during primary use. In the general part, will be given knowledge from the geological aspect of the mine and detailed knowledge on the exploitation systems of the mineral resource.

The rock fragmentation reflects the degree of control of blasting. Despite the accuracy of screening analysis to determine the size distribution of blasted rocks, this technique remains complex and long because of the large volume of blasted rocks. The digital image processing method can overcome these constraints of accuracy and speed. Our method uses the empirical model of KuzRam and numerical method (Digital image processing) through two image processing software’s (WipFrag and Split-Desktop) to analyze the particle size distribution of rocks fragmented by explosives in Jebel Medjounes limestone quarry. The digital image processing is based on the photography of the pile of blasted rock analyzed using image processing techniques. The objective of this work is to evaluate and compare the results obtained for each blast from the two methods and to discuss the similarities and differences among them. Three different blasts with the same design were analyzed through the two methods. ...

Despite efforts to protect the hydrosystems from increasing pollution, nitrate (NO3−) remains a major groundwater pollutant worldwide, and determining its origin is still crucial and challenging. To disentangle the origins and fate of high NO3− (>900 mg/L) in the Sidi Bouzid North basin (Tunisia), a numerical groundwater flow model (MODFLOW-2005) and an advective particle tracking (MODPATH) have been combined with geostatistical analyses on groundwater quality and hydrogeological characterization. Correlations between chemical elements and Principal Component Analysis (PCA) suggested that groundwater quality was primarily controlled by evaporite dissolution and subsequently driven by processes like dedolomitization and ion exchange. PCA indicated that NO3− origin is linked to anthropic (unconfined aquifer) and geogenic (semi-confined aquifer) sources. To suggest the geogenic origin of NO3− in the semi-confined aquifer, the multi-aquifer groundwater flow system and the forward and...

The neo-tectonic research is interested in the study of the movements of Earth's crust in recent geological times. It could explain the deformation mechanisms that lead to the structuring of drainage catchments. The Morsott-Tebessa-Youkous (Chabro) collapsed basin corresponds to a subsiding depression framed by brittle structures and filled with thick deposits. Our work aims to unveil the neo-tectonic activity and reconstruct the morphometric evolution of the landscape and the drainage network of the basin. For this task, our investigation applies a quantitative analysis of geomorphic indices extracted from the DEM of the study area. We used a GIS-based approach to compile seven morphometric factors namely Integral Hypsometry (HI), the Sinuosity of mountain fronts (Smf), the Valley Floor width to height ratio (VF), the Asymmetry Factor (AF), Basin Shape index (BS), and the topography (T). All these thematic parameters were processed in a Geo-database to calculate the study area's Relative Tectonic Activity Index (IRAT) as a result. The IRAT map was categorized into three classes. The result highlighted the distribution of relative tectonic activity in the region and unveiled some unknown faults. It associated the sinuosity of rivers and the deformation of the substratum with active tectonic anomalies. This research work succeeded in drawing up a new scheme of the neo-tectonic activity and morphostructural evolution in the collapsed basin.