Bulkhead Works Executed by BAUER Lebanon
The Jannah Dam, located on the Nahr Ibrahim River about 30 km North-East of Beirut, is designed as a massive arch gravity dam to store 38 Million m3 of water to feed the areas of Byblos, Beirut and its suburbs. The maximum height of the dam above the foundation level is 162 m.
The deep excavation to the dam foundation level is supported by an arch-shaped bulkhead.
The bulkhead, executed as overlapped rows of diaphragm walls (d-walls), was successfully completed in February 2019.
The executed concept is coming from Bauer.
The bulkhead (diaphragm) walls with a total area of about 3,610 m² were constructed, utilizing Bauer BC 40 cutter, in alluvial deposits, mostly in zones with noticeable permeability, which aggravated the challenges related to the locally encountered artesian conditions.
The three parallel running overlapped diaphragm walls, each with a wall thickness of 120 cm, are connected by a capping beam. The d-walls on the upstream and downstream side were executed first. Subsequently the diaphragm wall in the center. During the execution of the diaphragm wall in the center, the BAUER BC 40 cutter cutted continuously in the d-walls on the upstream and downstream side. The result is a homogeneous, friction-locked block.
Despite the challenges faced, with considerable full-face rock excavation to reach and block the assumed cavities, the bulkhead construction works were finished ahead of the schedule to the full satisfaction of the client.
|| MINISTRY OF ENERGY AND WATER (Lebanon)
||ANDRADE GUTIERREZ ENGENHARIA S.A.
|| ARTELIA Eau Environment
The installed diaphragm walls provides the necessary stabilization during the deep excavation to reach the dam foundation level. The d-walls extends over a length of approx. 80 m.
Approximately 3,610 m² diaphragm walls were constructed with a nominal thickness of 1,2 m (U/S). The bulk head is designed to support maximum excavation depth of 36m.
The bulkhead diaphragm walls were constructed in a relatively heterogeneous soil condition:
- Alluvial deposits: sandy clay, clayey sand, gravel and cobbles. containing chert / basalt and boulder
- Competent rock (embedment stratum): Limestone (so-called Dolostone) up to 60 MPa
The works were executed by utilizing one BAUER cutter unit BC 40.
The execution of the diaphragm walls was another pioneer work in Lebanon, being the first bulkhead diaphragm wall on dams in specialized geotechnical works in the country.