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Context

• As Delhi records an unprecedented rainfall this season, it is also witnessing an increase in incidents of road cave-ins across the city.

What causes a portion of the road to cave in?

• The cave-ins or cavities that look like a hole in the ground are actually a product of the incessant rain.
• The continuous rain leads to overflowing of drains, which can cause leaks in the pipeline.
• When a pipeline leaks and water from the pipeline flows into the layers of earth around it, the earth starts to erode and with time, it gets washed away with the water in the pipeline.
• Eventually, the portion of the road over it collapses because of the erosion.
• How long this takes, would depend on the size of the pipelines and the leak.

Fixing the road after a cave-in

• Once such an incident takes place, the first step is to find the leakage.
• The water flow needs to be shut first and this might take some time.
• As soon as the flow is shut and the location of the leak is established, work on the pipeline starts.
• After the work is complete, officials then fill the cavity with the required material.
• In smaller cavities, they fill the cavity with gravel while larger ones are filled with sand since it can be compacted easily.

https://indianexpress.com/article/explained/explained-road-cave-ins-and-why-they-common-delhi-this-year-7532846/

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