In Niger, irrigated agriculture constitutes the main alternative for meeting family needs. It is within this framework that the state and its partners have adopted strategies to promote irrigated production sites. Thi...In Niger, irrigated agriculture constitutes the main alternative for meeting family needs. It is within this framework that the state and its partners have adopted strategies to promote irrigated production sites. This study was carried out on the Konni irrigated perimeter, the objective of which is to analyze the physical state of hydraulic infrastructures and their operation before the rehabilitation of the said perimeter. The methodology adopted consisted, first of all, of documentary research focused on data relating to this scope and our theme to properly guide the collection of data in the field. The field phase was then followed with an observation of hydraulic infrastructures one by one in order to assess their condition. Thus, the collected data was processed and analyzed. The results of this study show a notable deterioration of hydraulic infrastructure which affected the operating yield of the study area, with the development of barely 700 ha out of 1226 ha planned by the basic study for off-season production (57%). Bathymetric measurements showed that the volume of sediment that accumulated in the Zongo Dam is 1.2 million m3, which reduces its initial capacity from 12 million m3 to 10.8 million m3 after 43 years of service. The expansion joints of the feed canal are all in poor condition. 90% of the total length of the tertiary canals are degraded, 82.32% of the panels of the main canal C are degraded and 17.68% are cracked. All crossing structures are blocked between the RN1 and the Zongo dam. Based on this critical situation, it would be essential to consider rehabilitation work on all infrastructure in order to restore the hydraulic and even agronomic performance of the Konni irrigated area.展开更多
The spiral assembly steel structure, a newly developed retaining wall for the rapid excavation of small-sized foundation pits in unsaturated soil, is presented. This new type of retaining structure is prefabricated in...The spiral assembly steel structure, a newly developed retaining wall for the rapid excavation of small-sized foundation pits in unsaturated soil, is presented. This new type of retaining structure is prefabricated in the factory and is assembled on site in the excavation of a pit. This retaining structure is composed of several prefabricated steel structural units, in which the adjacent steel structural units are joined with connectors. Each steel structural unit has one steel pipe in the radial direction and is welded to a single piece of steel plate. After full installation in situ, the retaining structure becomes a cylindrical steel structure. With the protection afforded by this new type of retaining structure, excavation work can be completed within 24 h to a depth up to 5 m. In order to verify the reliability and effectiveness of this new retaining structure, field construction tests were conducted in Beijing, China. The test construction was monitored. The monitoring program included measuring stress in the structure, lateral earth pressure, and lateral deformation of the surrounding soil. The monitoring data from the field test were compared with the theoretical results. The results show that the proposed new structure is reliable and effective.展开更多
文摘In Niger, irrigated agriculture constitutes the main alternative for meeting family needs. It is within this framework that the state and its partners have adopted strategies to promote irrigated production sites. This study was carried out on the Konni irrigated perimeter, the objective of which is to analyze the physical state of hydraulic infrastructures and their operation before the rehabilitation of the said perimeter. The methodology adopted consisted, first of all, of documentary research focused on data relating to this scope and our theme to properly guide the collection of data in the field. The field phase was then followed with an observation of hydraulic infrastructures one by one in order to assess their condition. Thus, the collected data was processed and analyzed. The results of this study show a notable deterioration of hydraulic infrastructure which affected the operating yield of the study area, with the development of barely 700 ha out of 1226 ha planned by the basic study for off-season production (57%). Bathymetric measurements showed that the volume of sediment that accumulated in the Zongo Dam is 1.2 million m3, which reduces its initial capacity from 12 million m3 to 10.8 million m3 after 43 years of service. The expansion joints of the feed canal are all in poor condition. 90% of the total length of the tertiary canals are degraded, 82.32% of the panels of the main canal C are degraded and 17.68% are cracked. All crossing structures are blocked between the RN1 and the Zongo dam. Based on this critical situation, it would be essential to consider rehabilitation work on all infrastructure in order to restore the hydraulic and even agronomic performance of the Konni irrigated area.
基金Project(41202220)supported by the National Natural Science Foundation of ChinaProject(20120022120003)supported by the Research Fund for the Doctoral Program of Higher Education,China+1 种基金Project(2652012065)supported by the Fundamental Research Funds for the Central Universities of ChinaProject(2013006)supported by the Research Fund for Key Laboratory on Deep Geo Drilling Technology,Ministry of Land and Resources,China
文摘The spiral assembly steel structure, a newly developed retaining wall for the rapid excavation of small-sized foundation pits in unsaturated soil, is presented. This new type of retaining structure is prefabricated in the factory and is assembled on site in the excavation of a pit. This retaining structure is composed of several prefabricated steel structural units, in which the adjacent steel structural units are joined with connectors. Each steel structural unit has one steel pipe in the radial direction and is welded to a single piece of steel plate. After full installation in situ, the retaining structure becomes a cylindrical steel structure. With the protection afforded by this new type of retaining structure, excavation work can be completed within 24 h to a depth up to 5 m. In order to verify the reliability and effectiveness of this new retaining structure, field construction tests were conducted in Beijing, China. The test construction was monitored. The monitoring program included measuring stress in the structure, lateral earth pressure, and lateral deformation of the surrounding soil. The monitoring data from the field test were compared with the theoretical results. The results show that the proposed new structure is reliable and effective.
