DBR metro line 4 – metro station called "Kelenföldi railway station" (general design)

 
   
DBR (South-Buda – Rákospalota) metro line 4 – metro station called "Kelenföldi railway station" (general design)
Year of design:   2007 - 2009
Client(s):   Hídépítő Zrt.
Contractor(s):   Hídépítő Zrt.
Structure:   Cut-and-cover structure built by means of the milanese method, supporting 28 tracks of MÁV as if it would be a railway bridge carried out with monolitic reinforced concrete roof-slab; mined tunnel for reversing the trains is connected to the cut-&-cover structure.
   


Related material

Kelenfold M4 Metro Station

    Kelenföld Underground Station is the startup station of Budapest Underground Line 4. As the south-western gate of Budapest, after its completion it will create a connection between the underground and the railway, serving as an intermodal junction. The civil engineered structure being built is the first different level underground – railway junction structure in Hungary.

    Site

    Kelenföld Station of Budapest Underground Line 4 is situated under the 28 pairs of rails of Kelenföld Railway Station, in east – west direction, perpendicularly to the north – south direction rails of the railway station. Besides serving as an underground – railway junction, the station is to connect Kelenföld and Őrmező as a pedestrian underpass. The underground station is continuing in a train reversing structure on the Őrmező side, connected to which a bus station and a deep garage providing P+R facility are to be built.

    On the Etele tér side the structure under the railway station is connected to the previously constructed TBM launching shaft (see graph 1: Air photo of "Kelenföld Underground Station" under construction).

    The pedestrian underpass and station shaft under the railway station is 260 m long; 340 m together with the adjoining train reversing structure, from which a 90 m long NATM tunnel starts, so the entire designed civil engineering section is 430 m long. With these data, Kelenföld Station will be the longest station in DBR Underground Line 4.


    Antecedents

    Authorization and tender structural plans of the underground station were completed, according to architectural conceptions of PALATIUM Studio, by Főmterv Zrt. The tender announced according to these plans and FIDIC "yellow" book was won by Hídépítő Zrt. in 2007. Assigned by the winner contractor, the construction reference drawings were completed by SPECIÁLTERV Kft. Designing is comprised of load bearing structures to be constructed and complete construction reference drawings of the railway station transformation necessary for building these load bearing structures.

    General description

    The shaft of Kelenföld Underground Station in its section under the rails is to be constructed with two 1.00 m thick diaphragm walls lowered as deep as 22 – 23 m, with 21.60 m distance between the axes. After cutting out the top level of the diaphragm walls, head-beams are to be constructed. The "roof slab" on top of the beams is to be constructed with reinforced pinned-hinged support, as a ballast track railway bridge. The structure is to be built with "Milanese Method", that is, after completing the first slab, the surface – the railway lanes in this case – is restored, and construction and soil removal continues under the slab. After stiffening of the slab, insulation, drainage, bedplate and rails are constructed on the surface, while soil removal begins underneath, between the diaphragm walls. (Graph 2: Soil removal from under the railway bridges)

    Soil removal between the diaphragm walls is carried out in one phase, going as deep as the bottom level of the base slab, which is about 18 m under the surface. In this temporary construction status, in order to avoid exposing diaphragm walls to water pressure, occasional waters to be found in the cohesive, watertight soil were "let in" by temporarily piercing the panels. After reaching the bottom level, blind concrete is to be made, which, together with the inner surface of the diaphragm walls, will be provided with sprayed membrane waterproofing.

    The base slab joins the diaphragm wall with moment bearing connection. The force conducting connection will be carried out by applying "lentons". The shucks prepared in advance in the diaphragm wall reinforcement and protected with temporary plastic caps will be found on the diaphragm wall surface already stripped, and the force conducting steel reinforcement will be joined into these (graph 3: One phase soil removal as deep as the level of the base slab and the connection of the diaphragm wall and the base slab by applying lentons).

    After concreting the base slab, reinforcing and concreting of the inner walls take place. A significant proportion of these walls are visible surfaces, for the fine implementation of which the application of special surface louvers, special concreting technology and strict technological discipline are necessary (graph 4: Visible concrete surface).

    In the greatest part of the station section under the rails, a slab with slanting supports will be constructed, according to the "visions" of the architectural designers (graph 5: Slab section with slanting supports).

    Connection between the upper pedestrian underpass level and the platforms between the rails will be provided with elevators stairways and escalators. Parallel with the underground shaft construction, the platform roofs will also be transformed. Owing to minimalization of the construction program durations, tail pieces harmonizing with the forms of the existing platform roofs will be applied. The shaft construction crosses the entire station service system besides the rails; therefore, appropriate substitution in different construction phases had to be made for the entire overhead cable network, signals and security equipment. Construction crossing the station is carried out in five main construction phases. In the first step, building started with closing the first eight railway tracks on the Őrmező side, and then came the "inner" construction phases, when diaphragm wall and reinforced concrete structure construction had to be organized on the "island" bordered by the operating railway lanes. Concrete is supplied through the existing pedestrian underpass, restricting the passenger area, applying concreting tubes.

    The train reversing structure joining in on the Őrmező side consists of two structural units: an 80 m long reinforced concrete structure built between diaphragm walls and a 90 m long "NATM" tunnel. The reinforced concrete structure, similarly to the section under the railway, is constructed with "Milan Method", however, in this case, not the roof slab but an intermediate slab directly above the inner section of the underground fulfils support functions. The NATM tunnel (one built with New Austrian Tunneling Method) receives underground vehicles of the station, temporarily functioning as a terminal, in one cross-section. In further perspectives, the underground line can be extended through this tunnel in the direction of Budaörs (graph 6: Tunnel cross-section).

    Diaphragm walls

    In the area concerned by the underground construction, middle Oligocene Kiscell clay can be found under made ground. Sizing the permanent static state of the diaphragm walls was carried out considering surface loads, at-rest soil pressure and water pressure considered on the whole surface of the side walls, while when carrying out sizing of temporary state, groundwater was only taken into account in the upper "weathered medium and fat clay" and "less weathered medium and fat clay" layers. Considering the deeper "intact medium and fat clay" as watertight, water pressure during construction was not taken into account in this layer. To make sure that this condition be valid, steel conducting tubes were installed in the watertight layer behind the 100 cm thick diaphragm wall, so as to eliminate incidental water pressure (2 tubes were installed for each reinforcement cages).

    Watertight diaphragm walls are built with 60 and 100 cm nominal thickness, while the guide beams on both sides are constructed with a cross-section of 20x100 cm. The 60 cm thick diaphragm walls border the adjoining platform stairways, while the 100 cm thick diaphragm walls border the structure of the subway. Watertight joints of the panels were carried out considering the HBM cutting technology of the contractor and in accordance with the CWS sectioning structure.

    Roof slab as railway bridge

    The roof slab of the underground station is a monolith reinforced concrete slab which also functions as a railway bridge. Considering its structural system, it bears the weight of the bedplate and burden of the railway as a two-legged support. The thickness of the monolith reinforced concrete slabs louvered on the ground varies between 1.45 and 1.60 m; the upper surfaces incline towards their supports by 1.5%, so, the thickness of the slabs at their outer ridges is 1.43 m.

    AAuthorization drawings were made with reinforced concrete slab bridges with girders. Economic comparisons analyzed the application of monolith and pre-manufactured tensed joint structures using "traditional" joints, and "new" half-"I" joints.

    Construction between the rails brought up severe technological inconveniences. The overhead cables operating on both sides made it extremely difficult to crane in great size elements, therefore, excluding the application of pre-manufactured beams and joints, monolith reinforced concrete slabs were made.

    The steel reinforcement of the slab bridges with a 21.60 m span is 40 mm diameter concrete steel arranged in two lines. Steel rods of this size can still be manhandled (graph 7: steel reinforcement of a monolith reinforced concrete slab bridge, visible concrete louver).

    The slab of the subway is articulated, according to the constructional phases, with operation gaps and dilatation joints bridged by watertight insulation. The dilatation joints created 8 pieces of separately moving reinforced concrete slabs, the equivalents of 8 railway structures lying side by side. The slab bridges lead across 2 – 5 pairs of rails each (graph 8: Cross-section of reinforced concrete slab bridges).

    On the platform edge of the slab bridges, brackets are made with "visible concrete" surface. The inner voids of these provide ventilation. Glass slabs between the slab bridges will provide natural daylight in the subway.

    The eighth slab bridge is U-shaped horizontally, opening up in the middle. The gap at its middle part provides connection of the subway with the new "A1" platform (graph 9: Construction of the U-shaped slab bridge 8 connecting to platform 3).

    Inner reinforced concrete structures

    Between the diaphragm walls and under the roof slab, inner reinforced concrete structures are made. These are: the base slab, the platform level, and a slab signed "P+1" at pedestrian underpass level and machinery areas (graph 10: General cross-section).

    • Base slab

    Longitudinally the base slab follows the longitudinal inclination of the underground rails (with 0.25% inclination); in cross direction its thickness varies between 1.40 and 2.70 m. Its bottom level, at the 4.80 m long section above the diaphragm walls, lowers 1.30 m above the axis of the shaft. At the recesses its thickness lessens to 1.20 m, while it is 2.20 m thick by the diaphragm walls. Its bottom level at the section next to the diaphragm walls lowers 1.85 m.

    • Subway level

    The subway level above the passenger traffic section of the platform level is parallel with the longitudinal inclination of the underground rails: it is an reinforced concrete slab ribbed underneath, with a 0.25% inclination. Its thickness is 40 cm, supported with a 1.80 m high rib at every 7.0 m, which are joined into a 1.80x0.80 m longitudinal rib. A slanting slab leads out of the longitudinal ribs, joining into the inner wall. This slab is horizontal above the operation areas; it is 40 cm thick and supported by walls on the Őrmező side and 40x40 cm pillars on the Kelenföld side.

    • Slab signed P+1

    P+1 level is only constructed at the operational areas, its thickness is 40 cm. It is supported by walls on the Őrmező side and 40x40 cm and 100x40 cm pillars on the Kelenföld side.

    • Platform level

    The platform level has an inclination of 0.25%, it is 30 cm thick on the Őrmező side; the monolith slab between the Őrmező side escalator and the platform is 25 cm; from the Kelenföld side escalator it is 40 cm thick.

    Temporary access ramp

    The removal and transportation of the approximately 120.000 m3 soil from 18 m under the surface could no practically be carried out with cranes and containers, as was the case with other stations. In the south-western corner of the shaft an access ramp was made, which joined in the service road of the railway station, and it made soil removal with "traditional" soil transporting vehicles possible. This ramp was constructed at the deeper parts in the side of the Őrmező hill with pile wall supporting, and with stabilized ground slope at shallower parts. There are gaps in the pile walls, so as to conduct infiltrating water. The diameter of the applied CFA piles is 80 cm; their length is adapted to the depth of the cutting. The applied reinforcement is in accordance with the actual strain. At parts where it is allowed by the depth of the cutting and size of the inner section, the pile walls facing each other are supported with steel stanchions. The stanchions were made from HEB 300 steel segments. The laminated beams recline on the reinforced concrete stanchion beams distributing the burdens of the beams. (graph 11: Temporary access ramp: voided drilled pile wall supported with steel stanchions).

    Train reversing structure

    The train reversing structure on Őrmező side is situated between two 1.05 m thick diaphragm walls lowered to a depth of 21.17 m, and the distance between their axes is 25.27 m. The entire length of the train reversing structure is 80.24 m. The diaphragm walls are lean on each other through a 140 cm thick slab right above the underground inner section. A diaphragm wall head-beam on top of the diaphragm walls helps them fully couple. At the bottom of the shaft a base slab is constructed between the diaphragm walls, which is joined to the diaphragm walls in a moment bearing way, with lentons.

    Owing to the length of the structure, the base slab and the intermediate supporting slab are divided into two dilatation sections. There are columns in the raster given between the diaphragm walls, which bear the burden of the supporting slab and the structures to be built on it, and they also transfer this burden to the base slab. (graph 12: Cross-section of the reinforced concrete structure of the train reversing structure).

    The planned structure is closed from underneath by the base slab, and it also protects it from groundwater break-in. The base slab is connected to the panels with lentons, in a moment bearing way.

    The NATM tunnel joining the cut and cover reinforced concrete shaft bears a cross-section enough for two underground vehicles. The distance between the rails is 4.75 m. The vertical distance between the rail level and the axis of the tunnel is 1.84 m.

    The entire excavation surface is 97,84 m2. Excavation is carried out with one side gallery and enlargement. The thickness of the closed circular lining is 0.30 m; the thickness of the temporary sidewall is also 0.30 m.
    The tunnel construction is controlled with a continuous monitoring system, which contains internal geodesic measurements, and those with inclinometer, extensometer and piezometer.



Graph 1: Air photo of "Kelenföld Underground Station" under construction

Graph 2: Soil removal from under the railway bridges

Graph 3: One phase soil removal as deep as the level of the base slab and the connection of the diaphragm wall and the base slab by applying lentons

Graph 4: visible concrete surface
 

Graph 5: Slab section with slanting supports

Graph 6: Tunnel cross-section

raph 7: steel reinforcement of a monolith reinforced concrete slab bridge, visible concrete louver

Graph 8: Cross-section of reinforced concrete slab bridges
 

Graph 9: Construction of the U-shaped slab bridge 8 connecting to platform 3

Graph 10: General cross-section

Graph 11: Temporary access ramp: voided drilled pile wall supported with steel stanchions

Graph 12: Cross-section of the reinforced concrete structure of the train reversing structure
 

Reinforced concrete inner structures

Reinforced concrete inner structures

Reinforced concrete inner structures

Reinforced concrete inner structures
 

Railway platform rooftops

Railway platform rooftops

Diaphragm wall

Diaphragm wall
 

construction of the railway tracks

Roofslab

Roofslab

Roofslab
 

Roofslab
 
 
 
 
   
 

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