P31 Contract 4 Mining Beneath
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CONTRACT 4 Contract 4 Sections V & VI Contractor: Mining Beneath Fuenlabrada to Getafe Suburbs Contract 4 covers sections V and VI of Metrosur, and was awarded to Necso Entrecanales Cubertias in April, 2000. This contract is 6.517 km-long, roughly 5.2 km of which are in Fuenlabrada, and 1.3 km in Getafe. It includes four complete stations, one of which con- nects to the suburban railway system, together with a fifth station position, prepared for future use. It also includes 12 vertical shafts, of which four are for ventilation, two for pumping, one for ventilation and pumping, and five for emergency exits. The contract was awarded at a value of Pta 25,103,910,736 with a duration of 30 months from the date of the survey on 24th May, 2000, so the work should be completed by 24th November, 2002. Tunnel Alignment The alignment starts at the exit of Fuenlabrada 2 station, which services the In the Getafe municipality, the line Concreting alternate sections of King Juan Carlos University. It intersects the crosses beneath the M50 ring road to false tunnel roof. M-506 main road, and runs along Calle Getafe 1 station, which is located in Sector Francia to Fuenlabrada 3 station. It curves 3. This part of the line continues through right, and changes to a left curve to reach Sector 3, and finishes in Avenida de Arcas the existing Fuenlabrada station on the de Agua, at the entrance to Getafe 2 suburban railway system. Here, Fuenlabrada station. 4 metro station and the corresponding The tunnel runs at considerable depth of interchange with line C-5 will be located. 20 – 25 m under the developed areas, The alignment continues through old where the buildings are up to four storeys Fuenlabrada district, north of the previous high. town hall, and follows Calle Miguel de Unamuno. Fuenlabrada 5 station is located Geology and Geotechnics where this street joins Avenida de Venezuela. The line then runs along the latter avenue, The catchment area, which occupies most crosses Avenida de la Hispanidad, and then of the province, is know as the Cuenca de heads across open country towards Getafe. Madrid, and forms part of the Tagus river On its way, it crosses the Culebro gully, basin. It is filled with layers of Tertiary which has been diverted as part of the sediments of significant thickness, whose works. The future Fuenlabrada 6 station is character varies according to the position located on this stretch. in the catchment. Three types of facies can METROSUR 31 CONTRACT 4 be readily distinguished: the Madrid facies, consisting of arkosic sand of varying grain size and grey-brown or brown clay, locally identified with coarse sand and hardpan; the Intermedia facies, consisting of highly- plastic brown and green clay, or peñuelas, with intermittent layers of micaceous sand; and the Central facies, which is of a chemi- cal nature, consisting of chalk and chalky marl. This section is entirely located in areas of hardpan and sandy soils associated with the Madrid facies. One of the main charac- teristics of these materials is the structure. They cannot be classified as different strata, but appear as a group of lenticular deposits of differing lateral continuity which over- lap, and alternate with, sandy and clayey deposits. This makes it difficult to correlate their position at different points. On this section, the clayey soils pre- dominate over the sandy layers, although in some areas, the latter are present in con- siderable thickness. The main features of this section are, first, the hardpan or sedi- ments with high plasticity and properties similar to peñuela green clay, with an appearance of smooth areas, high plasticity and traces of sepiolite, especially at the end of the section. Secondly, important thick- nesses of poorly-compacted sandy soil corresponding to the feldspathic sandy inclines appear at higher levels. The initial 3.2 km, between the new Freight train crosses boxjack Quaternary alluvial deposits overlie the hospital and the by-pass, are located more section. Tertiary material in the bottom of valleys, than 20 m below the surface, under the accompanied by anthropic fill, usually of Fuenlabrada town centre. This will be exca- little thickness, in urban areas and their vated using an EPB TBM, the safest surroundings. method, with total support of the soil, The land affected by the project is including at the face. Settlement will be upper/lower Quaternary in nature, except minimised. This section contains three for the Quaternary soils, comprising stations, F3, F4 and F5, and four vertical anthropic fill, compacted fill and alluvial shafts. deposits, which have been identified locally The machine was introduced outside the on some sections of the alignment. urban area, close to the by-pass, using a The lithological features are as follows: ramp, and access is good. It is working Quaternary: compacted deposits; uncom- from west to east, and will be removed pacted anthropic fill; alluvial. Upper/lower near F2, in the area of the hospital. Quaternary: coarse sand; hardpan sands; The next following section, up to the sandy hardpan; hardpan; sepiolite; chalk. M50 ring road, runs through open land, and the tunnel is being excavated in open Contract Components cut. This section crosses the Culebro Schematic layout of Contract 4 gully, which has been diverted. It also tunnel, stations and shafts The contract can be divided into three includes the future F6 station, of which (V = ventilation, B = pumping, clearly different parts – in kilometre order. only the hall will be constructed. This E = emergency). S HA FT T (E B +B M L ) AU P N IT CH C OL G EB SH UL R A L O FT EY (V ) TBM FALSE TUNNEL TRADITIONAL MADRID METHOD METROSUR 33 CONTRACT 4 Lowering the cutterhead of the Herrenknecht TBM. him or her to relate to the otherwise dark, underground world, where his or her sense of direction tends to evaporate. The chosen finishes and lighting are also aimed at achieving this goal. The entrances consist of glass pavilions with stainless steel frames, which house the stairs and the escalators. These pavilions, and the corresponding lifts for the handi- capped, will receive special attention in the quest for a Metrosur corporate image, creating a reference point on the surface. Any solution will pursue transparency as a fundamental idea, to avoid the passenger reaching street level visionless. These are particularly significant elements in the urban landscape, so a search was made for a design which would have a low impact. F4 includes the interchange with the C-5 suburban railway. Here, a vestibule will be built under the tracks, with access to the platforms. Ground Treatment Construction of future station station will be completed when the area is The goal of the ground treatment is to pre- roof. developed. vent excessive settlement in sensitive areas, Lastly, from the M50 to the end of the mainly near buildings. This section of the contract, a distance of 1.4 km, the tunnel is project contains five micropile cut-off walls, being constructed using the traditional three grout curtains, and three operations Madrid method. This part contains the G1 to compensate for settlement. This is apart station and two shafts. from various fencing, pipe support work, The contract planning was based on the following outputs: Tunnel with tunnelling Section of EPB TBM. machine 350 m/mth Common Madrid tunnel (per face) 40 m/mth Open cut tunnel 100 m/month Cut-off walls (per team) 80 m2/day Tunnel section driving 1 mth Superstructure 700 m/mth Stations The design criteria for the stations are based on the organisation of space. The idea is to create a sense of order, where the user has a physical reference, which helps 34 METROSUR CONTRACT 4 special detection equipment and side slope stabilisation. Except for the side slope stabilisation, which is associated with the section in open cut, all of this work is located in the Fuenlabrada town area. The detection equipment will provide information on movement and on the water table, and other data which help to monitor the behaviour of the structures, and any possible deviation from the anticipated parameters. This equipment basically consists of lev- elling benchmarks on the surface, gauges on buildings, convergence marks in tun- nels, strain gauges on the tensile reinforce- ment of two sections at each station, ceramic pressure sensors where water is expected, and pressure cells in the roof and floor. These devices are fitted to all buildings affected by the construction, at all the stations, and to the tunnel cross-section at approximately 400 m-centres. Construction Methodology The cross-section of the driven tunnel is cir- cular, with an 8.43 m clear diameter and 9.07 m external diameter. There are seven liner segments of 0.32 m thickness and 1.50 m in length per ring. The tunnelling machine is called La Paloma, made by Herrenknecht. It can work in a closed environment, controlling the pressure at the face to prevent decom- Lining segments are produced off-site Standard TBM section for twin pression of the soil, and avoid settlement of by the carousel method, are steam-cured, track tunnel. buildings on the surface. and their quality is strictly controlled. The cutting wheel loosens the soil using For the open cut section, an excavation rotating teeth and discs, and mixes it with was first made from the TBM launch pit in foam to make it easier to handle. Soil is the opposite direction, towards Getafe. The removed from the pressure chamber via a open cut tunnel is constructed according worm screw, which discharges onto a belt.