The Agadez city is built on the faulted and fractured sandstones formation of the“Agadez Sandstones”,which deposit in unconformity on the Precambrian basement of the Aïr Mountain.The present study focuses on th...The Agadez city is built on the faulted and fractured sandstones formation of the“Agadez Sandstones”,which deposit in unconformity on the Precambrian basement of the Aïr Mountain.The present study focuses on the geotechnical risk assessment and geological origin of building fracturation in Agadez city.A methodological approach integrating measurement of fractures planes affecting the buildings and their statistical analysis has been implemented.Statistical analysis of obtained data showed that in 100 fractured buildings,about 3%buildings are at risk of collapse(very high risk),64%buildings are fractured(medium risk of collapse),and 34%buildings are cracked(lower risk of collapse).These results showed as well that the nature of the material(rheology)influences the buildings fracturation.Indeed,the buildings made from cement are more easily fractured than buildings made from clay materials.Statistical analysis of fracture planes reveals that the geotechnical risk associated with buildings fracturation propagates in NW-SE,corresponding to the major directions of risk propagation,mainly dipping in northwest sectors(zones)of the Agadez city.The interpretation of geological and geophysical data combined to those obtained in the case of this study,reveals that the risk associated with buildings fracturation in Agadez city is caused by geological seismic events and or anthropogenic activities(explosive firing on the uranium mining sites like Somaïr and Cominak).展开更多
This study tries to highlight the role of magnetic and seismic data in the prevention of building cracking, which constitutes a geotechnical risk in Agadez City. This city is built on the faulted and fractured sandsto...This study tries to highlight the role of magnetic and seismic data in the prevention of building cracking, which constitutes a geotechnical risk in Agadez City. This city is built on the faulted and fractured sandstone formations of the “Agadez Sandstones Formations”, which were deposited in unconformity on the basement of the Aïr Mountain. This study focuses on the prevention of geotechnical damages related to building cracking in the Agadez region through geophysical methods, which are well known for investigating tectonic structures and their directions on the surface and subsurface. A methodological approach integrated the seismic and magnetic data interpretation combined with field measurement on the cracked building and its underlying substratum, represented by Agadez sandstones and basement. The extraction of seismic lineaments from the West African seismic map showed the seismic directions oriented NW-SE (N135˚ to N160˚), passing through the studied area. The structural interpretation of the magnetic map shows that the Agadez region is also affected by the subsurface lineaments mainly oriented in NW-SE (N135˚) directions, which are similar to the identified seismic lineaments in the same zone. A structural study carried out on the Agadez sandstones and the underlying basement showed that faults and fractures oriented N120˚ to N165˚ affect both the basement of the Aïr Mountains and the sandstone formations on which the city of Agadez is built. These observations showed that building cracking in the Agadez region has a higher propagation tendency according to the directions ranging from NW-SE (N135˚) to NNW-SSE (N165˚). Therefore, the building’s cracking has a stronger propagation component according to these mean directions that are not recommended for building. To prevent and reduce the risks related to building cracking in Agadez region, it is highly recommended to build in the minor directions of cracking propagation, which correspond to NE and SW directions.展开更多
Irrigation is considered a means of intensifying agriculture.It helps to increase productivity while securing it against the risks of drought.It is a means of combating poverty and hunger,which are especially endemic ...Irrigation is considered a means of intensifying agriculture.It helps to increase productivity while securing it against the risks of drought.It is a means of combating poverty and hunger,which are especially endemic in West Africa.The technical study for the development of a site for the creation of an irrigated area is made up of different phases including the plot,the sizing of the irrigation network,the sizing of the pumping station(s),the dimensioning of the drainage network and the circulation and protection networks.The design of the developments takes into account a certain number of essential elements,including the planned crops,the irrigation system,the nature of the soil,the topography of the land,and the availability and quality of water.The objective of this study carried out in the north of Niger(Agadez)is the design of a Californian network where the hydraulic dimensioning of a solar pumping station and irrigation pipes will be carried out.The methodology adopted is first a series of visits for the collection of climatic,agronomic,topographical and technical data,then an exploitation of the data collected and finally,the writing of this article.The study shows that the developed site covers an area of 12 ha,including 48 plots of 0.25 ha.It had a modern layout and a Californian irrigation system.The results of this technical study propose a 270m deep borehole connected to a 54.4 KWC solar pumping system and a 66 KVA emergency generator of the J66 soundproof hooded SDMO brand serving as water supply sources for the developed site.A Grundfos esp 60-1730 kW pump ensures water extraction.Water is transported to the network via supply pipes with a diameter of 200 mm and distribution pipes whose diameters vary between 160-200 mm.展开更多
文摘The Agadez city is built on the faulted and fractured sandstones formation of the“Agadez Sandstones”,which deposit in unconformity on the Precambrian basement of the Aïr Mountain.The present study focuses on the geotechnical risk assessment and geological origin of building fracturation in Agadez city.A methodological approach integrating measurement of fractures planes affecting the buildings and their statistical analysis has been implemented.Statistical analysis of obtained data showed that in 100 fractured buildings,about 3%buildings are at risk of collapse(very high risk),64%buildings are fractured(medium risk of collapse),and 34%buildings are cracked(lower risk of collapse).These results showed as well that the nature of the material(rheology)influences the buildings fracturation.Indeed,the buildings made from cement are more easily fractured than buildings made from clay materials.Statistical analysis of fracture planes reveals that the geotechnical risk associated with buildings fracturation propagates in NW-SE,corresponding to the major directions of risk propagation,mainly dipping in northwest sectors(zones)of the Agadez city.The interpretation of geological and geophysical data combined to those obtained in the case of this study,reveals that the risk associated with buildings fracturation in Agadez city is caused by geological seismic events and or anthropogenic activities(explosive firing on the uranium mining sites like Somaïr and Cominak).
文摘This study tries to highlight the role of magnetic and seismic data in the prevention of building cracking, which constitutes a geotechnical risk in Agadez City. This city is built on the faulted and fractured sandstone formations of the “Agadez Sandstones Formations”, which were deposited in unconformity on the basement of the Aïr Mountain. This study focuses on the prevention of geotechnical damages related to building cracking in the Agadez region through geophysical methods, which are well known for investigating tectonic structures and their directions on the surface and subsurface. A methodological approach integrated the seismic and magnetic data interpretation combined with field measurement on the cracked building and its underlying substratum, represented by Agadez sandstones and basement. The extraction of seismic lineaments from the West African seismic map showed the seismic directions oriented NW-SE (N135˚ to N160˚), passing through the studied area. The structural interpretation of the magnetic map shows that the Agadez region is also affected by the subsurface lineaments mainly oriented in NW-SE (N135˚) directions, which are similar to the identified seismic lineaments in the same zone. A structural study carried out on the Agadez sandstones and the underlying basement showed that faults and fractures oriented N120˚ to N165˚ affect both the basement of the Aïr Mountains and the sandstone formations on which the city of Agadez is built. These observations showed that building cracking in the Agadez region has a higher propagation tendency according to the directions ranging from NW-SE (N135˚) to NNW-SSE (N165˚). Therefore, the building’s cracking has a stronger propagation component according to these mean directions that are not recommended for building. To prevent and reduce the risks related to building cracking in Agadez region, it is highly recommended to build in the minor directions of cracking propagation, which correspond to NE and SW directions.
文摘Irrigation is considered a means of intensifying agriculture.It helps to increase productivity while securing it against the risks of drought.It is a means of combating poverty and hunger,which are especially endemic in West Africa.The technical study for the development of a site for the creation of an irrigated area is made up of different phases including the plot,the sizing of the irrigation network,the sizing of the pumping station(s),the dimensioning of the drainage network and the circulation and protection networks.The design of the developments takes into account a certain number of essential elements,including the planned crops,the irrigation system,the nature of the soil,the topography of the land,and the availability and quality of water.The objective of this study carried out in the north of Niger(Agadez)is the design of a Californian network where the hydraulic dimensioning of a solar pumping station and irrigation pipes will be carried out.The methodology adopted is first a series of visits for the collection of climatic,agronomic,topographical and technical data,then an exploitation of the data collected and finally,the writing of this article.The study shows that the developed site covers an area of 12 ha,including 48 plots of 0.25 ha.It had a modern layout and a Californian irrigation system.The results of this technical study propose a 270m deep borehole connected to a 54.4 KWC solar pumping system and a 66 KVA emergency generator of the J66 soundproof hooded SDMO brand serving as water supply sources for the developed site.A Grundfos esp 60-1730 kW pump ensures water extraction.Water is transported to the network via supply pipes with a diameter of 200 mm and distribution pipes whose diameters vary between 160-200 mm.
