The integral design method embodies empirical, analytical and observational approach to the underground excavation design. The application of the integral method for solving stability problems at the underground excavations of the Bekhme Dam project in Iraq is presented in the paper.
La methode integrale des etudes reuni t les approches empirique, analytique et d"observation de l"etude des galeries. Cet article decrit la mise en oeuvre de la methode integrale dans la solution des problèmes de stabilite des fouilles souterraines dans le cadre de l"etude de Bekhme Dam en Iraq.
Die Integralprojektierungsmethode verbindet einen empirischen Zutritt, analytischen Zutritt und Beobachtungszutritt in Tunnelprojektirung. In den Artikel ist die Verwendung der Integralmethode dargestellt, die bei der Solution des Stabilitatsprobleme der unterirdischen Ausgrabungen auf Bekhme Dam Projekt in Iraq benutzt ist.
The Bekhme Dam project, in Northeast Iraq, has been officially dubbed "The project of the Nineties" because of the magnitude of the work involved in its construction. Quantities are estimated to 10 Mm3 of surface excavation and 2.5 Mm3 of underground excavation. In addition, 3Mm3 of concrete and 25,000 t of steel will be used.
At the beginning of the-tunnel excavation works, the employer had not as yet appointed the designer, and the documentation only consisted of the conceptual design which defined geometry of the underground structures and the concrete linings thickness, without analysis of stability and temporary protection of the underground excavation. The investigation works executed up to that moment focused on the part of the rock massif that is located in the dam zone and there were practically no data for the remaining part of the massif, except for the geological prospection results.
According to recommendations given by international experts, the employer insisted that the excavation support design be made parallel to the excavation with respect to the real rock mass state to be defined at the heading.
The integral design method was proposed (Stojković, 1986) and accepted as it enables such design procedure.
As to its morphology, the dam zone is a canyon of the Great Zab River which flows from northeast to southwest and is perpendicular to the strike of the structure. The underground works that will be studied in this paper are located at the left side of the dam zone.
At the dam location, cretaceous sediments are represented by carbonate rocks: limestones and dolomites and by marly rocks: marls with intercalations of marly sandstones.
From the structural aspect, the dam is located at the northeast wing of the anticline. The anticline is of northwest-southeast strike, i.e. it is almost perpendicular to the river flow and to the tunnel direction.
(Figure in full paper)
As presented in the characteristic engineering geological cross section (fig. 2), the eight following rock types can be distinguished according to their engineering and geological properties:
Bedded marls with intercalations of marly sandstone,
Breccia limestone, karstified, clayey,
Thin-layered marly limestone, very jointed, interbedded with clay,
Massive limestones and dolomites