Extension of Line 1. Section: Portazgo-Miguel Hernández

The work began in July 1.990 and to finish it in 36 months, it was decided to attack the underground work from three fronts, enough to meet the deadline without the impact on the surface affecting the living conditions of Vallecas. In the first section of the expansion, very close to where the Portazgo cul-de-sac ended, a shaft was opened that made it possible to attack the tunnel to the Buenos Aires station. In addition, near this and Miguel Hernández ramps were built to start the tunnels that were to converge at Alto del Arenal.

The terrain crossed is heterogeneous, being made up of consolidated sand and clay, with the presence of water, which forced in some areas to treat the terrain with specialized techniques to stabilize it.

At an average progress rate of 2 m per day on each of the three fronts, the first section to be completed was the one linking the Miguel Hernández and Alto del Arenal stations. But in this last stretch, the sandy ground and water made it necessary to inject binding products from the surface to bind and harden the ground. Thus it was possible to excavate without risk of landslides.

The other station, Buenos Aires, deeper and in more consistent terrain, is built in a mine, by a somewhat more complex method than the line tunnel.

Once the tunnel has arrived at the beginning of the station, three galleries are drilled along its total length, located two on each side, in what will be the future side walls, or "gables", and once in the center, to the height of the keystone of the vault. Once the lateral galleries in setback and in the shaft have been completed, the lower part of the lateral wall is excavated and concreted. Subsequently, and also starting at the back of the station, the vault is excavated from these same galleries, through successive 3,5 m wide transverse galleries that reach the keystone gallery. The vault is formed by concreting these "ribs", with their corresponding part of the side and keystone galleries, from the latter by gravity, using the land itself as a mould.

In this way, and in reverse, so that the concrete part does not interrupt the galleries, the entire vault and the side walls are buried. Under his protection, the emptying of the station and the concreting of the floor are carried out without danger.

While work was being done on the stations, the three sections of tunnel that were to join them were advancing.

As the most important characteristics of the different superstructure works, the following can be highlighted:

For the first time it is installed on a new line, concreted track, supported on reinforced concrete pads covered, on its lower and lateral faces, with a Corkelast-type elastometer, with a Pandrol-type rail fastening. This solution makes it possible to significantly reduce conservation and maintenance costs, as well as reduce vibrations and noise.

The 16 escalators installed make it possible to bridge the existing unevenness, having reduced the depth as much as possible to improve accessibility to the stations. Lifts have been installed for the first time in the network to allow and facilitate the use of the metro for people with reduced mobility (PRM).

The installation of ventilation driven under platforms in the stations and extraction in the tunnel, guarantees the permanent renewal of the air within the area in which the transport service is carried out. 11 ventilation shafts have been installed with a total air supply and extraction flow of 420.000 m³/ H.

The distribution of energy from the Buenos Aires substation is carried out from said substation to the transformers of the stations that transform the 15.000 volts of power to 380-220 volts, all of this in alternating current and that supplies energy to the equipment of the stations. , lighting, escalator motors, elevators, checkpoints, fans, etc.

From this substation, the necessary energy is also supplied for the traction of the trains in direct current of 600 volts, through the power cables or feeders, made of aluminum, to the contact wire, of cogre, from which it takes directly the train current through the pantograph wipers. As a novelty in this line extension, the Delta system has been adopted for the suspension of the contact wire, by means of a false support, made of insulated synthetic cable, which reduces maintenance costs during operation.

Automatic fire detection systems have been installed in the stations, both on escalators and in technical rooms, as well as a dry column that reaches from the surface to the platforms.

The signaling system consists of the necessary devices for the protection and safety of train traffic (ATP), similar to that of the rest of the lines, as well as automatic steering (ATO) and signaling remote control, linked to the control of centralized traffic (CTC). It incorporates two newly implemented subsystems in the Madrid Metro network, both of great technical innovation in the field of railway signaling applications. The first of these is made up of jointless track circuits (JTC) and its objective is the automatic detection of the state of occupation of each section of track by the trains that circulate on it, showing with total security, if a train occupies a certain predefined sector of the road. It differs from traditional track circuits in the elimination of existing joints, which improves maintenance and potential interference.

The other subsystem is "Westrace", a microprocessor-based railway signaling system that configures an electronic interlock. This system has been installed in the garages of Miguel Hernández.