Mining mules at work in Metro construction

That's how we were, that's how we are now: From mining mules to tunnel boring machines, more than a century growing under your feet

The first Metro line, 4 kilometres long and with 8 stations, began to be built in the summer of 1917. More than a century later, our network now has 295 kilometres and 302 stations and is still growing. How did it do it then and how does it do it now? We tell you all about it!

For several decades, mining systems were used to dig the ground in Madrid, specifically the so-called Belgian method, which remained in use in Madrid until 1969, when the traditional Madrid method began to be used.

Underground construction work in 1918

The mining mules

To implement this Belgian method, workers had very special helpers who rode forklifts down into the tunnel: pack mules. It is hard to believe today, but as recently as the 1960s, earth extraction was not mechanised, and it was the mules who dragged the wagons with the rubble.

An article from January 1967 recalls 14 of these mules, illustrated with a photo of "Torda" embellished for the occasion with collars and leashes. The story goes that the Animal Protection Societies were concerned about their work situation, until the City Council showed them that "they are not treated cruelly, that they have the most suitable places for their leisure time and that they work about six hours a day, like any other workers in developed countries". Interesting, isn't it?

Emergence of the traditional Madrid method

With the advent of concrete, the Belgian method became obsolete. Until then, the lining of the tunnel vaults was made of solid brick and the shoring or propping was done with wood, but when this new material began to be used, wood had to be replaced by more resistant metal profiles.

Underground extension work in 1950

This gave rise to what is now known as the "traditional Madrid method", which has been so successful that it has been used for many years. In fact, of the 116 kilometres of the Metro network in 1996, 80 had been built using this method, and it has continued to be used as recently as the construction of Metrosur, inaugurated in 2003, and the extension of line 2 to La Elipa in 2007. There have even been cases, such as the Islas Filipinas station on line 7, where two sections of tunnel have been completed at the same time, one bored with a tunnel boring machine and the other using the traditional Madrid method.

Underground extension work in the 90s

The arrival of tunnel boring machines

Until 1995, the Belgian method coexisted with two other methods: spear shoring machines and the first tunnel boring machines, known as "open face" because they did not have any protection at the excavation head.

From that date onwards, these tunnel boring machines were replaced by closed front or EPB (Earth Pressure Shields), although, like the previous ones, they were not alone either, because both the traditional Madrid method and the execution by means of screens have continued to be used, the latter mainly in the stations.

Tunnelling machine at a Metro construction site

From galleries to modern stations

Not only has the way the Metro is built evolved, but so has the design of the stations, with increasing emphasis on accessibility. This way, the old galleries that characterised the first Metro stations have gradually given way to wide halls that minimise the distances travelled by passengers.

And this commitment to accessibility has also been transferred to the older network, which, thanks to the different modernisation plans, has been incorporating improvements in this sense. The result is that 70% of stations are currently accessible and the current plan will enable this percentage to increase to 82%.