Soil challenges in the airport of the future (Mexico)

The airport of the future
Last year it was announced the construction of the Mexico city new international airport. Not only it will be one of the world's largest airports but it will also be the world's most sustainable airport and the first airport to be LEDD Platinun certified. As a matter of fact, it was called the "airport of the future" and "an inspiration for future airports".

The design of the airport was inspired by Mexican architecture and symbolism and was created to evoke a feeling of flight. The airport will honour the Mexican flag's coat of arms, which is a reference to Tenochtitlan, the pre-Columbian city on which the capital is built.

Image 1. Mexico City new international airport
Source: MexDF

The design and construction of this airport present special and unique challenges. The site for the new airport is located on the bed of the former Lake Texcoco. During the rainy season large sections of this area are inundated for several months and the soft soil conditions combined with ground water extraction result in large settlements. It is reported that some parts have already sunk some 5 meters since 1960. In order to deal with such challenges several engineering and technological innovations were required. In the present article we will discuss a little about the soil challenges (other features will be discussed in further articles).

Soil challenge
Mexico city and surrounding areas are located in what used to be a shallow lake (Texcoco lake). Thus, there is unstable soil with high water content and little capacity and the area is literally sinking. This poses extraordinary challenges for the design of structures. In the case of Mexico city new airport, this soil unstability posed two main problems: runways and terminals.

Runways
Six runways are planed for the new airport, each will be about 4 km long concrete topped embankments. In order to overcome sinking problems, each runway will be over a pile based deep foundation combined with polystyrene and other light materials.

Terminals
The initial design was composed of two terminals connected by a railway. However, a railway was not a good alternative because in such unstable soil conditions tracks will bend or move. Thus, engineers decided to modify the initial idea by one spectacular six million square feet terminal (560 000 sqm). This will be the second biggest airport terminal in the world (Hong Kong terminal one 570 000 sqm). Besides, in order to ensure a very light building engineers decided that the whole terminal would be enclosed within a continuous, lightweight grid shell that embraces the inner layers of the building and seamlessly acts as both its walls and roof. Combining both skin and structure in a single system, the shell stretches from the fixed boarding bridges to the top of the roof. For better understanding, it as a series of interlocking shell structures that resist their loads through in-plane forces - rather than bending - and are, as a consequence, extremely lightweight. Moreover, such kind of structure does not require false work or scaffolding, it can be erected much faster and more economically with fewer materials and less energy than ordinary buildings.

Image 2. Inside of terminal


References and further reading
Airport of the future in Mexico.
Mexico City's new airport: an inspiration for future airports
NACO wins a multi-million euro tender to design the airside infrastructure for Mexico City's new airport