This is a T-junction in south London, and frost has done its work heaving up the surface in an area already weakened by previous road repairs. The aggregate stone beneath the surface is exposed and is scattering across the road. This sort of adverse frost action can take place place in two main ways. The first is frost heave, where ice forms below ground level and pushes the surface upwards. The second involves weakening of the substrate due to saturation of the under-surface as the ice melts. Concepts | Danger | Failure | Construction Industry | Industry