Ground movement
| Ground movement | |
| Type | Cause of damage |
|---|---|
| Includes | Subsidence, heave, settlement, washout |
| Affects | Buried pipes and building foundations |
| Foundations standard | BS 8004 |
| Relationship to leaks | Both a cause and a consequence |
Ground movement is displacement of the soil supporting a structure or a buried pipe. It covers downward movement, whether by subsidence or by settlement, upward movement by heave, and loss of support where material is washed out. Foundations and their design in relation to ground conditions are addressed by BS 8004.[1] In leak work ground movement matters in both directions: it can cause a pipe to fail, and a leaking pipe can cause it.
Ground movement as a cause of leaks[edit]
A buried pipe is supported along its length by the material around it. Where that support changes unevenly, load concentrates. Clay soils shrink in dry conditions and swell when rewetted, which imposes cyclical movement on anything buried in them; nearby trees accelerate the drying. Poorly compacted backfill settles after installation, and a stone left against a pipe becomes a point load that plastic pipe will slowly deform around.
The result is failure at joints and at points of restraint, such as where a pipe enters a building through a wall and is fixed on one side but free to move on the other.
Leaks as a cause of ground movement[edit]
The reverse is common enough to be the first thing to rule out. Water escaping from a buried pipe can wash fines out of the surrounding soil, creating a void that removes support from whatever sits above it: a path, a driveway or, if the escape is close enough, a foundation. On sands and gravels this can act quickly.
Where subsidence damage is being investigated, a leaking drain or supply pipe in the vicinity is a standard line of enquiry, and locating and stopping the escape precedes any assessment of the structural movement, since the movement will continue while the cause is running.
Detection considerations[edit]
Ground penetrating radar can show voids and disturbed ground as well as the pipe route,[2] though a void is an indication rather than a diagnosis. Where washout is suspected the practical sequence is to establish whether there is a live escape, locate it, and only then assess the ground, because a survey carried out while a leak is running measures a moving situation.
See also
References
- ^BS 8004: Code of practice for foundations. BSI. Retrieved 2026-09-05
- ^PAS 128: Specification for underground utility detection, verification and location. BSI. Retrieved 2026-09-05