1st International Congress on Tunnels andUunderground Structures in South-East Europe „USING UNDERGROUND SPACE“ April 7-9, 2011, Dubrovnik, Croatia Construction of two underground stations in Almaty city - Republic of Kazakhstan (Design&Build) Milomir PAVLOVIĆ Dipl.Ing., Inter-koop, Belgrade, Serbia, [email protected] Zoran JOKSOVIĆ Dipl.Ing., DuoDEC Belgrade, Serbia, [email protected] Summary: Construction of two underground stations of the first phase of first metro line in the city of Almaty, Republic of Kazakhstan, is presented in this professional work. Almaty metropolitan was constructed under very complex construction conditions (geology, traffic, configuration, seismic, climate etc.). Metro stations, constructed by Energoprojekt are underground stations placed at great depths of 40 and 70 m. Construction method was modified NATM, without anchors, but with pipe roofing. Company "Energoprojekt", from Belgrade, Serbia, has joined the project since 2006 as the only foreign construction company. For less than four years, "Energoprojekt" built two underground stations. As there were no accurate designs, the contract was Design&Build type. Design service, (existing design check and adjustments, main design for NATM structures, structural analysis, shop-drawings and design site supervision), was provided by DuoDec, specialized consulting company form Belgrade, Serbia. Keywords: metro station, NATM, top heading, invert, construction stages 1. About metro in Almaty Almaty is the largest city in Republic Kazakhstan, with 1.5 million population. As the former capital of Kazakhstan and the first city of a million in that region, by Soviet standards, in 1983 it was decided to build a metro. Building of metro lasted until 1996, when the collapse of the Soviet Union and the fall of the economy, caused the suspension of works. Until that moment, the preliminary design and preparation works for about 4.0 km. of parallel transport tunnels for the first phase of the first line of Almaty metro were completed. The works continued in 2003. When there was a significant economic development of the state and the expansion of civil engineering. Almaty is located in the south eastern part of Kazakhstan. There is harsh Fig. 1 Almaty location continental climate with cold winters and hot summers. The city lies on the slopes of Altai Mountains at an altitude of 600-900m. Almaty is located in earthquake prone area with significant seismic activity of 9 degrees (Merkalli scale). Geological environment for the building is very unsuitable, and it consists of glacier layers of unbound materials, granite and granodiorite. Particles of dust and clay, mixed with rock material as well as the compression achieved by long-standing natural consolidation make it conditionally stable. 1st International Congress on Tunnels andUunderground Structures in South-East Europe „USING UNDERGROUND SPACE“ April 7-9, 2011, Dubrovnik, Croatia 1.1 Participants in the construction Investor of metro system is the administration of Almaty (City Government) that participates in the financing with 15%, while the remaining 85% is co-financed from the budget of the Republic. The designer is company "Metroprojekt" from Almaty with significant involvement of design organizations from Tashkent, Moscow and St Petersburg. In 2005, Austrian company "Beton und Monierbau" completes the new, NATM based design of "Zibek Zoli" metro station. The General Contractor is "Almatimetrokorilis". It is a state-owned company established to build a metro in Almaty. Company, "Energoprojekt Civil Engineering" from Belgrade, Serbia has carried out construction works on two underground metro stations: "Almaty" and "Abay", as the only foreign construction company on this project As there were no accurate designs, the contract was Design&Build type. Serbian consulting company, "DuoDEC" from Belgrade provided design service, for "Energoprojekt ". 1.2 The metro lines in Almaty According to general plan of Almaty, there are planned three lines as follows: The first line, to be built in two phases: • The first phase makes the underground part of 8.5 km length • The second phase consists of continuation of the line, of 12 km length, where the tunnels are built using a TBM, while building of metro station is provided in an open excavation. The second line of 10 km length connects the first line with the airport. Due to poor underwater terrain it will be the third line closes the transport ring around the City centre and at two points it crosses the first line. For this line has not been adopted the position Fig. 2 Almaty metro lines (underground or above-ground) yet, as well as the type of structure, provided to work in an open excavation. It should be noted that the terrain is mostly sloppy. Harsh continental climate and significant vegetation, the most probably affected the above-ground position of this line. Traffic flows, population density as well as location of important buildings have caused different position of metro lines and different type of structure 1.3 Types of structures for metro stations at the first phase of the first metro line The first phase of the first line is built as a deep-lying line in the very city centre, 8.5 km in length. It consists of two parallel tunnel tubes with a diameter of 5.5 m each and wheelbase of 21m. They were performed by mechanized shield (TBM) with four construction starting points from stations Raimbek and Alatau, which were performed as Cut and Cover structures. At the first phase of the first line, were built seven metro stations (two as C&C and five underground deeply placed stations), and there were applied three types of structures. 1st International Congress on Tunnels andUunderground Structures in South-East Europe „USING UNDERGROUND SPACE“ April 7-9, 2011, Dubrovnik, Croatia TYPE 1 Metro station Raimbek is arched box construction built in open excavation under the protection of RC piles. Metro station. Alatau was constructed as cut and cover structure, with temporary protection of slopes and secured by a steel mesh and shotcrete TYPE 2 Metro stations "Zibek Zoli" and "Almaty" are underground metro stations comprising vestibule, sloping tunnel and platform structure at the level of platforms. It consists of three independent tunnel tubes that were subsequently fused with transverse passes to form joint platform construction. This is, so called, "Three tubes" structure. TYPE 3 Metro stations: Abaya, Bajkonor and Tulpar are underground metro stations, where construction at the platform level, consists of three RC vaults with common RC walls (columns), called "Column-type" structure. Fig. 3 Station types 2. Almaly metro station 2.1 Description The bottom of the station is 37 meters below the ground level extremely bad geotechnical conditions 9th zone of seismically activity. The station consists of the main platform, approach corridor and technical premises the main platform consists of the 3 tubes, 2 side tubes 115 m long each and the middle tube 104 m long which serves for the passenger approach. During the construction tunnel tubes are separate and independent but upon the completion of construction they are being connected with cross corridors on each 10 meters. The approach corridor is the extension of the middle tunnel tube, it is 45 m long and leads to Fig. 4 Station Almaly - cross section the sloping side tunnel with escalator. The technical premises follow the approach corridor with the total length of 45 m. Cross sections of the approach corridor and technical premises are the same but different from the cross sections of the station tunnels. Each tunnel was build independently, using NATM, which consists from the following steps: • embedding of steel pipes Ø114/6 mm which make so called "pipe roof" excavation, • shotcrete lining made of shotcrete reinforced with welded wire mesh and steel arches, • waterproofing and inner lining made of reinforced concrete 1st International Congress on Tunnels andUunderground Structures in South-East Europe „USING UNDERGROUND SPACE“ April 7-9, 2011, Dubrovnik, Croatia 2.2 Almaly metro station -facts • total structure works value 21. mil. $ • total area of station platform is 1950 m 2 • the bottom of the station is 37 meters below the ground level • extremely bad geotechnical conditions • 9th zone of seismicall activity • the station consists of the main platform, approach corridor and technical premises • the main platform consists of the 3 tubes, 2 side tubes 115 m long each and the middle tube 104 m long which serves for the passenger approach. During the construction tunnel tubes are separate and independent but upon the completion of construction they are being connected with cross corridors on each 10 meters. • the approach corridor is the extension of the middle tunnel tube, it is 45 m long and leads to the sloping side tunnel with escalator. • the technical premises follow the approach corridor with the total length of 45 m. Cross sections of the approach corridor and technical premises are the same but different from the cross sections of the station tunnels Fig. 5 Station Almaly - layout and longitudinal section • each tunnel was build independently, using NATM, which consists from the following steps: embedding of steel pipes Ø114/6 mm which make so called "pipe roof" excavation shotcrete lining reinforced with welded wire mesh and steel arches waterproofing inner lining made of reinforced concrete • excavated 37188 m 3 of soil • embedded: 6850 m 3 of shotcrete 12840 m 3 of concrete 1604 t reinforcement steel bars 14428 m 2 of waterproofing • shotcrete lining 08-1.2 m/ day • inner lining 2.0 m/ day 1st International Congress on Tunnels andUunderground Structures in South-East Europe „USING UNDERGROUND SPACE“ April 7-9, 2011, Dubrovnik, Croatia 2.3 Construction method of Almaly metro station Construction at the platform level is located at 37m below the ground surface and consists of a station area, access corridor and technical premises. The station area consists of three independent tunnel tubes, the two side tubs where the trains pass through, long 115m each, and a middle tube for passenger access, 104m of length.