Landslips
Why landslips cause train delays
Landslips can block railway lines, damage infrastructure and cause significant disruption, particularly after long periods of heavy rain.
Find out what causes railway landslips, why they can take time to repair and how we monitor and strengthen slopes to keep passengers and trains safe.
Railway landslips: key facts
- Landslips happen when soil, rocks or earth move onto or towards the railway.
- Prolonged heavy rain can saturate the ground and make slopes unstable.
- Debris can block tracks and prevent trains from running safely.
- A slope may remain unstable after the first landslip.
- We use monitoring equipment including motion sensors and CCTV at known risk areas.
- Repairs can include improving drainage, installing steel rods or soil nails, or changing the angle of the slope.
What is a landslip?
A landslip (also known as a landslide) on the railway is generally defined as when soil, rocks and earth fall onto and either wholly or partially block the track. Landslips can occur anywhere, moving slowly or quickly. When they impact railways, roads, and other infrastructure, they can cause a lot of disruption.
What causes landslips?
Landslips commonly occur when the ground becomes saturated with water after long periods of heavy rain. As the earth becomes heavier, the water forces apart grains of soil so that they no longer lock together. This results in a landslip as the structure becomes loose and unstable.
Why heavy rain increases the risk of landslips
Long periods of heavy rain can saturate the soil around the railway. As the ground absorbs more water, it becomes heavier and the grains of soil may no longer hold together as firmly.
This can weaken slopes, cuttings and embankments. Even after the rain stops, saturated ground can continue to move, so the risk may remain after the weather appears to have improved.
What we do when there’s a landslip
When landslips happen, unfortunately so do delays. A train can’t swerve to avoid debris on the line in the same way a car can avoid a small obstruction on the road. So when there‘s debris on the tracks after a landslip, we will often need to re-route services.
Before trains can run on the line again after a landslip, we’ll remove any debris and check that the infrastructure is safe and working.
There are ongoing concerns, even after an initial landslip. Once a landslip has started to move, the slope is permanently weakened. It means it’s much more likely that there will be further landslips. Some of the slopes – or cuttings, as they’re also known – on either side of our tracks need to be strengthened by improving drainage or adding stronger materials to the slope itself, such as steel rods or soil nails. This work to stabilise the earth can take time.
How we’re reducing delays caused by landslips
- It’s important that we identify the sites prone to landslips to ensure that we keep passengers and our engineers safe. We use helicopters equipped with laser imaging, detection and ranging to do this.
- Where we know sites are at risk of landslip, we use motion sensors and CCTV to detect soil and rock movement. These sensors send an alarm to the signaller, who will stop the train if alerted and wait until the area has been inspected by engineers.
- We can also stabilise the slope by putting in drainage or using steel rods or soil nails.
- If these options are not sufficient, we will then re-profile the slope to reduce its angle, making it less prone to a landslip.
- When we get flood warnings from the Environment Agency and Flood Forecasting Centre, we send people and equipment to the at-risk areas so we’re in a position to act quickly.
Earthworks and managing vegetation
To keep our earthworks safe, we often need to manage vegetation.
Sometimes vegetation may help the stability of an earthwork slope. But in many cases, it has a detrimental effect.
This can include:
- roots dislodging blocks from the slope
- trees causing shrinkage of clay slopes, leading to settlement of the track
- vegetation preventing access to the slope for inspection or maintenance.
The decision to remove vegetation from an earthwork slope will generally seek to balance the vegetation effect on the earthwork with the impact on other parts of the railway and the environment.