Environmental Engineering Reference
In-Depth Information
footings, or articulated or flexible design to allow compensation for some differential
movements of structures.
Case 2
Large distortions are anticipated or small distortions cannot be tolerated, when pillar sup-
port is questionable, collapse has not occurred, and the mine is at relatively shallow
depths. Solutions may include:
Relocate project to a trouble-free area.
●
Provide mine roof support with construction of piers in the mine or installation of
grout columns, or completely grout all mine openings from the surface within the
confines of a grout curtain installed around the site periphery.
●
Install drilled piers from the surface to beneath the mine floor.
●
10.4 Solution of Rock
10.4.1
General
Significance
Ground subsidence
and
collapse
in soluble rock masses can result from nature's activities, at
times aided by humans, or from human-induced fluid or solid extraction. Calcareous
rocks, such as limestone, dolomite, gypsum, halite, and anhydrite, are subject to solution
by water, which causes the formation of cavities of many shapes and sizes. Under certain
conditions, the ground surface over these cavities subsides or even collapses, in the latter
case forming sinkholes (see
Section 6.2.3).
The Hazard
Geographic distribution
is widespread, and there are many examples in the literature of
damage to structures and even deaths caused by ground collapse over soluble rocks.
Examples are the destruction of homes in central Florida (Sowers, 1975)
(Figure 10.15);
the
sudden settlement of a seven-story garage in Knoxville, Tennessee (ENR, 1978); and a
foundation and structural failure in an Akron, Ohio, department store that resulted in 1
dead and 10 injured (ENR, 1969). Collapses resulting in substantial damage and in some
cases deaths have also been reported for locations near Johannesburg and Paris (see
Section 10.4.3)
.
Subsidence and sinkholes associated with the removal of halite have been
reported for areas around Detroit MI; Windsor, Ontario; and Hutchinson, Kansas.
Collapse incidence is much less than that for slope failures, but nevertheless the recog-
nition of its potential is important, especially since the potential may be increasing in a
given area. Collapse does occur as a natural phenomenon, but the incidence increases sub-
stantially in any given area with an increase in groundwater withdrawal.
10.4.2
Solution Phenomenon and Development
Characteristics of Limestone Formations
General
Limestone, the most common rock experiencing cavity development, is widely
distributed throughout the world, and is exposed in large areas of the United States,
