Environmental Engineering Reference
In-Depth Information
Postconstruction Phase
Instrumentation (stage 5) is good practice for heavy foundation loading or other condi-
tions in which settlements are anticipated for retaining structures in critical locations, and
for slopes, dams, and tunnels. The purpose is to provide an early warning system for
potentially troublesome conditions, and to provide data to advance the state of the art and
reduce the degree of conservatism in future projects.
1.3.4
Study Planning
The basic considerations in study planning are the lateral and vertical extent to which the
proposed construction or development will significantly influence the geologic environ-
ment (or be influenced by the environment).
Lateral Extent of Influence
The lateral extent of influence of the proposed construction can vary from the immediate
area of the project to many meters beyond if dewatering of excavations is anticipated, to
an entire valley or region where deep mineral extraction is planned, to several hundred
kilometers where area seismicity is of concern.
Vertical Depth
For structures on or near the surface, the vertical influence is a function of several vari-
ables. These can include: (1) the size and loading of the structure that imposes changes on
the natural stress conditions to some significant depth; (2) unfavorable geologic conditions
that require explorations to depths adequate to define suitable support for deep founda-
tions; and (3) excavations that require explorations to some distance below their maximum
depth to determine groundwater, rock, and soil conditions, both within and below the
excavation zone. Deep excavations for tunnels or mines and the deep extraction of fluids
require a knowledge of geologic conditions between the point of excavation or extraction
and the surface, and at times between even deeper points and the surface.
