Geostatistical Analysis for delineating sterile inclusions in Sidi Chennane' phosphatic series, Morrocco

The anomalies detected in phosphatic series of Sidi Chennane, one of phosphatic basins in Morocco, hinder the proper exploitation of phosphate levels and the assessing phosphate reserves seems incorrect. The purpose of this study was the evaluation of geostatistical methods for delimitation of these disturbances. To cover all the zones being able to be disturbed, we carried out, during the geophysical prospection in a parcel of 50 ha, 5151 resistivity measurements as horizontal profiling using the well-known Schlumberger array, in order to map the spatial distribution of  the sterile hardpan inclusions.Geostatistical tools were used to quantify the spatial correlation between apparent resistivity data. Semivariograms were obtained using a classical Matheron semivariogram estimator and fit to the experimental semivariograms obtained. We have selected those with the best fit in terms of sum of squared residuals (SSR).Geostatistical analysis was performed using the software VESPER 1.63. Spatial distribution maps were made by ordinary kriging, the qualitative interpretation of these maps reflects that the exponential model is found to be the best model representing the spatial variability of our geoelectric data. The qualitative interpretation of the kriged resistivity maps allows defining resistivity contrast, consequently we have delimited the crossing dominate area from a “normal” into a “disturbed” area. Models of the geology were successfully obtained from geostatical method, which help mapping the phosphate deposit inclusions and the estimations of phosphate reserves were improved and better constrained. ResumenLas anomalías detectadas en las series fosfóricas de Sidi Chennane, una de las cuencas fosfóricas de Marruecos, dificultan la explotación apropiada de los niveles de fosfato y hacen parecer incorrectos los cálculos de las reservas. El propósito de este estudio es la evaluación de los métodos geoestadísticos para la delimitación de estas anomalías. Para cubrir todas las zonas donde se pueden presentar estas alteraciones se llevaron a cabo,durante la exploración geofísica en una parcela de 50 hectáreas, 5151 medidas de resistividad con perfileshorizontales a través del conocido sondeo Schlumberger, con el fin de mapear la distribución espacial de las inclusiones estériles de la capa sólida.Se utilizaron herramientas geoestadísticas para cuantificar la correlación espacial entre los datos de resistividad. Se obtuvieron semivariogramas a través del tradicional estimador de semivariogramas Matheron y se adecuaron a los semivariogramas experimentales obtenidos. La selección se basó en aquellos que mejor se acoplaban en términos de la suma de cuadrados residuales (SCE). Los análisis geoestadísticos se realizaron con el programa VESPER 1.63. Los mapas de distribución espacial se hicieron por Kriging regular, y la interpretación cualitativa de estos mapas refleja que el modelo exponencial es el que mejor representa la variablilidad espacial de estos datos geoeléctricos. La interpretación cualitativa de los mapas de resistividad obtenidos por la técnica del Kriging permite definir el contraste de resistencia, lo que fija el área entre los estándares de “normal” y “Con Alteraciones”. Los modelos geológicos fueron obtenidos del método geoestadístico, lo que ayudó a mapear los depósitos de inclusiones de fosfato y mejoró las estimaciones de las reservas a través de una mejor definición de estas

Identification Of Collapsible Soils In Deroua (Morocco)

Deroua belongs to the Berrechid plain and it is characterized generally by a flat relief, formations from the quaternary and Pliocene age and unconformably on sedimentary formations of Cretaceous and Permian Triassic on shcists from the primaries. Several anomalies were detected in the buildings and pavement structures in different cities in the territory of the Berrechid plain, such as settlement, cracking or even sudden collapses. The presence of a water table with 1500 square kilometers in area, the climatology of the region and a major urban development are factors favoring collapsing soils. Thus, we conducted a series of geotechnical tests on four samples taken from Deroua, 10 km from the city of Berrechid to identify the nature of the soils of this city in order to study their behavior in unsaturated state. The results of Atterberg limits and the oedometer test, correlated with results of previous studies and bibliographical research confirm the hypothesis of collapsible soils. Therefore, the results will help to quantify and map the collapse of soils in Deroua, in order to establish a local hazards map that can be exploited by the urban agency

THE EFFECT OF SOIL DENSIFICATION ON THE ATTENUATION OF THE PHENOMENON OF SOIL LIQUEFACTION IN A PORT PROJECT IN MOROCCO

Morocco, which is in a seismically active zone, is currently experiencing a significant development in terms of the realization of development and infrastructure projects. Therefore, reflection on soil liquefaction problems during project design is essential. The densification of soils by vibro compaction is a recent process of soil treatment, its effect is to improve the geo mechanical characteristics of the soil in this case the relative density and subsequently the reduction of the potential for liquefaction, it is a technique soil improvement in the mass, it is closely linked to the grain size of the soil to be treated, its percentage of fines less than 10% (going to 0.08 mm <10%), this technique gives the treated soil sufficient cohesion to avoid large increases in pore pressures during the earthquake. This article aims, through the study of a real case, to evaluate the effectiveness of vibro compaction to improve the relative density of the soil and consequently the reduction of the risk of liquefaction of the treated soil. The work focuses on the analysis of the SPT tests carried out before treatment and on the CPT tests of control of the vibro-compactge works carried out after execution. This study showed that this process generates an effect of improvement of the relative density and reduction of the compaction by inducing a reduction of the risk of liquefactio

Enhancing Geophysical Signals Through the Use of Savitzky-Golay filtering method

En la cuenca de Sidi Chennane en Marruecos, existen inclusiones estériles de caliche que dificultan la extracción de las rocas fosfatadas y que son difíciles de detectar. La resistividad de los caliches excede un valor de 200 Ω-m contra 150 Ω-m para la roca fosfatada. Se realizó un trabajo de prospección eléctrica de tipo Schlumberger en una zona de 50 ha en la cuenca de fosfatos de Oulad Abdoun. Se obtuvieron modelos del perfil geológico mediante el filtro de Savitzky–Golay, y se logró localizar las inclusiones de caliche y las estimaciones de cálculo de las reservas de los fosfatos se encuentran muy circunscritas. doi: https://doi.org/10.1016/S0016-7169(14)70074-

The Observation and Modeling Contribution to Urban Geotechnical Works Projects: Al Boustane Clinic Extension, Rabat-Morocco

Starting each geotechnical work site needs a preparatory study and a pre-design. Both of them requisite an observation intervention before, in particular, those in urban sites. The purpose of this paper is to explain how observation combined with modeling makes it possible to manage the difficulty and complexity of this type of project, based on the observational method. Thus, a safe geotechnical structure requires a modeling based on observation investigation and site survey. In accordance with the site’s context, the model will be verified to see if the actual behavior is consistent with the design modeling. On this manner, we will detail this illustrated approach on several concrete geotechnical projects cases. This article will also include a case study of Alboustane clinic’s extension, in Morocco, to illustrate this method

Geophysical Investigations for Groundwater in Outita, Morroco, using ERT Method

Abstract—Morocco is a country in semi-arid to arid climate. Rainfall is irregular in time and space. Surface water undergoes very large fluctuations due to the hydraulicity of the year. Hence, the use of groundwater resources that play a very important role in supplying water to rural populations and irrigation. In this context a geophysical survey was carried out in Outita. The interpretation of ERT profiles oriented West-East showed a horst and graben structure and revealed the existence of water-bearing formations at depths of around 300m. To determine the lateral extent of these formations, two ERT profiles oriented in the North-South direction were carried out

Identification of formations of soil and subsoil using finite elements modeling

The Soil and subsoil survey are performed by direct and indirect methods. The direct methods are the investigations of field and laboratory while indirect methods are the geophysical methods. These allow, from one or more physical properties, to find out the underground's structure nondestructively. Geophysical methods for characterizing subsurface have long been used, in geotechnical, hydrogeological and environmental studies. For our study, we used the electrical resistivity's method. 52 geoelectric soundings VES was performed with a mesh of 500 m and electrodes distance between 1000 m and 3000 m. The interpretation of these VES allows the determination of the vertical succession of formations in place. In order to have a lateral facies variation, we used geostatistical methods for having adequate data that can be used in the input file of inversion's code Res2Dinv. The 2D images of the subsoil obtained confirm and complement the results of the correlations of oil drilling that are in this region. Thus, the study area also has a horst and graben structure. This study also allowed us to locate the sandstone formations that extend in two places along a North-South direction

Concrete lozenges impact on the slope erodibility

Water erosion is a natural phenomenon, the severity of which is related to several parameters depending on the raindrop impact, the characteristics of the soil and the level of human intervention. The risk of water erosion occurs in both drainage basins and road and rail slopes. Indeed, this phenomenon can be aggravated causing major gullies and landslides. The PK 94 of the Taourirte-Nador railway line, located in the oriental region of Morocco, whose slopes are formed by silt-clay formations experiencing intense erosion. The Moroccan experience for the slopes protection of water erosion knows the use of several methods in particular; concrete arcades and methods based on biological engineering. The objective is to contribute to this subject by proposing the use of concrete lozenges technique. It have the advantage of reducing both the area at risk of erosion and especially the length of slope which is an important factor in the Revised Universal Soil Loss Equation RUSLE used to quantify the quantities of soil eroded

Dam Foundation Treatment: High Stress Watetightness

By its dual function of consolidation and sealing, injection treatment is the most appropriate process to solve the majority of problems in the most diverse soils. Concerning a foundation, the use of this treatment makes it possible to reduce or eliminate karst risks by taking into account the geological implications of each region. However, its effectiveness is difficult to measure, especially when it comes to the treatment of a dam site where the waterthigtness of the foundation is essential for overall stability. A control of the parameters that regulate the injectability of the karst as well as a good knowledge of the karst environment allows the correct evaluation of the nature of the products and the methods of implementation of the grout curtain guaranteeing the safety of the structure. It is from this perspective that a statistical study of karst anomalies was carried out on the foundation of El Ghrass dam in order to define an adequate distribution of these karsts, which is essential for the determination of the pattern of injection (drilling spacing, alignments) necessary for the preparation of the quantities of the injection market