The first step in constructing the elevated guideway is building its foundation by installing piles. Piles are deep foundation structures that are built into the ground to support the load of the guideway. There are two types of piles on this project: drilled piles and driven piles.

The size and type of pile are based on multiple factors including geotechnical requirements, and site and ground conditions. The typical depth of piles on this project ranges from 10 metres up to 100 metres in areas with softer ground conditions.

Drilled piles

Drilled piles are constructed by drilling into the ground, then installing a temporary pile casing. Once the pile casing is placed, material is excavated to create a shaft. After rebar is installed, the pile casing is removed and the shaft is filled with concrete.

Driven piles

To construct driven piles, steel pile casings are hammered (“driven”) into the ground using specialized hammers. Soil and rock are excavated from within the pile casing, and the pile is filled with rebar and concrete. Driven piles are often used in areas with softer ground conditions.

Once the underground foundation is complete, construction starts above ground with the building of columns – the concrete pillars that support the guideway. Each column is built on top of a pile by first placing a rebar cage for reinforcement. Formwork is then added around the cage to create a mold, and concrete is poured in.

After the concrete sets, the formwork is removed, revealing the finished column. The Surrey Langley SkyTrain will have more than 480 of these guideway columns along the alignment! 

Concrete guideway segments are lifted between the columns using specialized lifting machines called launching gantries.

These guideway segments are manufactured at a precast concrete facility in Surrey and are transported to site using flat-bed trucks. The elevated guideway will have more than 4,400 concrete segments!

The concrete segments between the columns are joined together to create a section called a span. To connect the segments, a high-strength epoxy, which is a specialized construction glue, is applied to the edges of each segment. Steel cables, also known as tendons, are then threaded through the group of segments and pulled tightly to lock them together to form a span.

Once a span is complete, the launching gantry slides over to build the next section of the guideway. The launching gantry is equipped with rollers and hydraulic systems that help it move forward, using the next columns and the previously constructed span as supports.