Cave-in

This article is about a geologic phenomenon. For the rock band, see Cave In.

Illustration of mine collapse aftermath, from 1878

A cave-in is a collapse of a geologic formation, mine or structure which may occur during mining, tunneling, or steep-walled excavation such as trenching. Geologic structures prone to spontaneous cave-ins include alvar, tsingy and other limestone formations, but can also include lava tubes and a variety of other subsurface rock formations. Glacier caves and other ice formations are very prone to collapse from exposure to warm temperatures or running water.

In mining, the term roof fall ^[1] is used to refer to many types of collapses, ranging from the fall of a single flake of shale to collapses that form sink holes that reach to the surface. However, roof falls in mining are not all accidental. In longwall mining and retreat mining, miners systematically remove all support from under large areas of the mine roof, allowing it to settle just beyond the work area. The goal in such mining methods is not to prevent roof fall and the ensuing surface subsidence, but rather to control it.

Causes

Cave-ins are commonly caused by leakage from old pipelines, which weakens rock and soil near the leak. ^[2] For this reason, poor drainage and heavy rain or snowfall are also risk factors for cave collapse. Cave-ins can also be caused by weathering, such as repeated freezing and thawing or tree roots growing through the roof of a cave. ^{[2] : 7} In mining, many cave-ins are caused by poorly constructed roof support, such as excessively wide bolt spacing and insufficient support around a joint, especially in caves with a relatively thin roof. ^[3] In larger falls, insufficiently supported joints and weathering are the two most common causes of cave-ins. ^{[3] : 24}

Prevention

The most common measures taken to prevent cave-ins in excavation include keeping heavy equipment away from trench edges, inspecting trenches, and training workers on shoring. ^[4]

Geological formations

• Alvar structures such as on the Stora Alvaret, Öland, Sweden
• Karst limestone such as in the Madagascar dry deciduous forests

References

1. "Glossary of Mining Terms". Kentucky Coal Education. Archived from the original on 5 October 2014. Retrieved 19 May 2015.
2. Canakci, Hanafi. "Collapse of caves at shallow depth in Gaziantep city center, Turkey: A case study" (PDF). ResearchGate: 5-6.
3. van der Merwe, J.N.; van Vuuren, J. J. "Causes of Falls of Roof in South African Collieries". p. 19.
4. Thwala, Wellington Didi; Mustapha, Zakari. "Management of Health and Safety Risk Associated with Excavation Cave-in" (PDF).