Abstract
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.
Highlights
The watertightness of dams is generally ensured by the construction of an injection curtain under the structure called « grout curtain » [1]
In particular the watertightness of El Ghrass dam is a rather complex problem since it is entirely located in the limestones of the Aaleno-Bajocian seating of a karst activity which may endanger the stability of the foundation, and makes it difficult to choose the injection parameters and especially the mesh and the extension of the sealing veil, that must be adapted to the nature of the foundation [2]
A statistical study will refine the design of the grout curtain to better intercept karst anomalies and define the right mesh and inclination of the injections wells, a device that will guarantee a good waterproofing of the dam foundation [9]
Summary
The watertightness of dams is generally ensured by the construction of an injection curtain under the structure called « grout curtain » [1]. In particular the watertightness of El Ghrass dam is a rather complex problem since it is entirely located in the limestones of the Aaleno-Bajocian seating of a karst activity which may endanger the stability of the foundation, and makes it difficult to choose the injection parameters and especially the mesh and the extension of the sealing veil, that must be adapted to the nature of the foundation [2]. The old folded Granitic Paleozoic outcrop can be seen at 5 Km south of the site and 10 Km further north, it is associated to the Triassic clays and basalts forming a waterproofing barrier and on which is overlying the Jurassic dolomitic limestone series affected essentially by a faulting tectonic. The Mio-Pliocene and Quaternary formations form the last overlaps on the previous series
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