WATER SUPPLY. BAKU (AZERBAIJAN)
In 2013, construction works began on the ultrafiltration plant in Ceyranbatan (Azerbaijan), with a treatment capacity of 520,000 cubic meters per day to meet the drinking water demand of Baku, the capital and most populous city of the country.
The water catchment was carried out through the execution of three submarine tunnels in Lake Ceyranbatan executed by jacking pipe with reinforced concrete pipes. Each pipeline had a length of 455 m and an internal diameter of 1,600 mm.
After the execution of each section, the submarine recovery of the tunnel boring machine used in the execution of the tunnels, AVN closed shield tunnel boring machine, was carried out. The execution of the inlet tunnels began in February 2014 and was completed in May 2015.
The companies involved in the execution of the tunnels and subsequent connection of the intake towers were, HidroLotus as the main contractor, Europea de Hincas Telemando S.A.U – Eurohinca for the execution of the tunnels and supervision of the submarine works, Piramida for the manufacture of the reinforced concrete pipes and Metear for the recovery of the tunnel boring machine and subsequent installation of the intake towers.
WHAT?
Three tunnels for the water catchment in Lake Ceyranbatan (Azerbaijan).
WHO?
Client
Azersu (State Water Company, Azerbaijan)
Microtunneling Contractor
HidroLotus (Joint Venture Hidro Group – Lotus)
Microtunneling Contractor
Eurohinca (Europea de Hincas Teledirigidas S.A.U.)
WHEN?
The inlet tunnels were executed between February 2014 and May 2015. The ultrafiltration plant came into operation at the end of October 2015.
WHERE?
Image 1: Absheron Peninsula, Azerbaijan.
WHY?
The three inlet tunnels of the Lake Ceyranbatan were designed to meet the growing demand for drinking water from the Absheron Peninsula, where both the country's capital, Baku, and other high-population satellite cities such as Sumqayit are located.
The treatment plant, ultrafiltration technology, has a daily treatment capacity of 520,000 m3.
Image 2: Orthophoto inlet tunnels of catchment in Lake Ceyranbatan.
HOW?
The execution of the three inlet tunnels was performed from the same launching shaft, executed by sheet piling and located about 50 m from Lake Ceyranbatan.
Image 3: Execution phase of the launching shaft and the pumping chamber.
The construction of the conductions was planned to be carried out in a trench, but during the development of the project this method was discarded to minimize the possible environmental impacts and above all not to affect the quality of the lake water during the execution of the new tunnel and intake towers. It is necessary to indicate that the projected tunnels were located very close to the pipeline in use for supply.
The jacking pipe was executied by tunnel boring machine (TBM) type hydroshield model AVN (Herrenknecht), a tunnel boring machine that would be recovery up to three times from the bottom of the lake to be able to execute all the sections.
One of the first challenges was to modify the original planned layouts to ensure an adequate load of earth on the pipeline and thus avoid the flotation of the pipe both during the execution phase and once the final design position and subsequent connection of the intake towers were reached.
For this, and for each section, a straight layout was made in elevation of descending slope to 4% (approximate length of 100 m) followed by a curve of radius 4,000 m and about 150 m in length to finish again in a straight section with a smoother downward slope of 0.3% until reaching the final length of the driving.
The layout in plan of the pipelines was straight as showed below.
Image 4: Straight layout of the inlet tunnels.
Below is the cross section, analogous for each section, and the levels above water level (awl) of those points of interest.
Image 5: Curved cross section of the inlet tunnels (elevation).
In this case, the entire length of the pipelines was made with trenchless technology, simply making a dry connection for each section in the launching shaft and being able to connect each section executed by jacking pipe with the pumping chamber located in the back of the reaction wall of the piles.
For the lining of the excavation, reinforced concrete pipes of 4 m in length and internal diameter 1,600 mm with a pipe wall 170 mm thick were used.
The design of the pipeline was carried out by Eurohinca including the design of the special pipes and the intermediate jacking stations (IJS). As for the special pipes, the so-called "Pipe 0", "Pipe 1" and the last pipe were designed. The first two were installed sequentially behind the TBM being necessary to carry out its recovery and to be able to make the connection of the intake tower in each of the pipes.
Image 6: Section showing the bulkhead between Pipe "0" and Pipe "1".
The "Pipe 0" served to eject both the TBM and the pipe itself through the action of hydraulic cylinders installed in the back of the TBM and in the back of the pipe itself.
The "Pipe 1" had installed a bulkhead with double function, first, to be able to flood the previous one, "Pipe 0", and to be able to compensate the hydrostatic pressure before the expulsion of the TBM and second, to be able to work dry inside the tunnel and to dismantle all the installations inside the tunnel without conditioning the recovery operations and subsequently to be able to make the connection between the conduction and the tunnel tower. Taking of each section.
At present, the "Pipe 0" is usually replaced by a recovery module, expressly for the recovery of the tunnel boring machine.
The last pipe had on its back a connection flange to connect each of the inlet tunnels with the pumping chamber.
As for the intermediate jacking stations, 4 stations were manufactured and installed in each section with a total length, once the cylinders inside were dismantled and the station closed, of 2.40 m.
One of every three pipes installed had 3 non-return valves, spaced 120 degrees, for the injection of bentonite into the back of the pipe during the execution of the excavation.
All the pipes had two types of gaskets, a primary type Harpoon or Delta type by its shape and another secondary type Block to guarantee the tightness of the conduction.
The manufacture of the pipe was done locally with a precast concrete company, Piramida, which, while familiar with all kinds of precast, including segment rings, lacked previous experience in the manufacture of reinforced concrete pipes.
As a guidance system, a conventional laser was used for the first meters of each section and then VMT's SLS system.
Another key to the project was the treatment of the ground in the back of the entrance sheet piles for each tunnel. The treatment consisted of performing a jet grouting over an area of 12 m in length (in the direction of the axis of the drive), 5 m wide and a depth of 2 m below the lower level of the TBM.
This minimized the risk of differential settlements in the first meters to the passage of the TBM and, on the other hand, cut the sheet piling in the entrance wall of each section.
Image 7: Section showing the TBM crossing the area of ground treatment (jet grouting).
Image 8: Connection works of the TBM.
Finally, one of the most delicate operations during the execution of underwater pipelines is the recovery of the TBM. In the specific case of the Ceyranbatan project, it was the first time that inlet tunnels were executed by means of jacking pipe and, therefore, the first time that an underwater recovery of a tunnel boring machine was carried out.
Once the TBM reaches the final position according to design, the dredging work begins to discover the TBM, carry out its expulsion and the subsequent lifting and transport to port.
Generally, dredging consists of clearing an area equal to the length of the TBM plus a couple of meters in front of the TBM and at least another additional meter to the width of the TBM on each side.
Once these works were completed, executed as well as the recovery operations by the Turkish company Metear, the TBM was prepared, making both the disconnections and connections necessary for the decoupling of the TBM and its subsequent lifting and transport to port and the connection of the recovery beam by divers.
To compensate the hydrostatic pressure existing at the recovery point and to be able to hydraulically expel the TBM, the flooding of "Pipe 0" was carried out by opening the feed and extraction valves of the machine pipe (first module of the TBM). Previously the TBM had been pressurized to a slightly higher pressure than the existing one, in this case, it was pressurized to 2.5 bar.
Once the rear section behind the TBM was flooded, the so-called "Pipe 0", hydraulic connections were made in the lock shield to allow the activation of the ejection cylinders installed at the rear of the TBM. Once these cylinders were actuated, the TBM was separated from the pipe and it was lifted for transfer to port and subsequent recovery of the TBM from land.
Image 9: Lifting work of the TBM after recovery.
Héctor Trigal
TUNNEL TECHNICAL DATA
Length
3 x 455 m (1,365 m)
Inner diameter
1.600 mm
Outter diameter
1.940 mm
Slope
Descending 4% at the entrance and 0.3% at the exit of the curve
Geology
Sands, clays and silts
Starting Level
16.5 m (awl)
Ending Level
8 m (awl)
Working Pressures
Up to 2 bar
TBM
Hydroshield AVN (Herrenknecht)
Intermediate Jacking Stations
4
BIBLIOGRAPHY
Técnicas de mejora y tratamiento del terreno aplicadas a la obra “construcción de 3 emisarios submarinos en el lago de Ceyrantaban, Azerbaiyán mediante tuneladora hidroescudo.
https://en.wikipedia.org/wiki/Jeyranbatan_Ultrafiltration_Water_Treatment_Plants_Complex
https://www.youPipe.com/watch?v=dd4gsmRebXk&ab_channel=EUROPEADEHINCASTELEDIRIGIDAS%2CS.A.