Environmental Engineering Reference
In-Depth Information
1.3
Geotechnical Investigation: Objectives, Stages, Scope, and Planning
1.3.1
Basic Objectives
The basic objective of a geotechnical investigation is the characterization of the geologic
environment. Included are the determination of the following:
1
Lateral distribution and thickness of the soil and rock strata within the zone of
influence of the proposed construction or development.
2.
Groundwater conditions, considering the seasonal changes and the effects of
extraction due to construction or development.
3.
Physical and engineering properties of the soil and rock formations, and ground-
water quality.
4.
Hazardous conditions, including unstable slopes, active or potentially active
faults, regional seismicity, floodplains, ground subsidence, collapse, and heave
potential.
5.
Ground response to changing natural conditions and construction or develop-
ment brought about by surface loadings from structures, unloadings by surface or
subsurface excavations, or unloadings from the extraction of mineral resources.
6.
Suitability of the geologic materials for aggregate and for the construction of
pavements and embankments.
1.3.2
Stages of Investigation
Investigations are performed in a number of stages, each with a different objective, and
each requiring interpretation, analysis, and evaluation.
Stage 1: General geologic conditions are identified through the retrieval of exist-
ing data, the interpretation of remote-sensing imagery (landform analysis), and
field reconnaissance. Engineering geology maps are prepared.
●
Stage 2: Subsurface sections are prepared from exploration data obtained by test
borings and pits, geophysical methods, etc.
●
Stage 3: Samples of the soils and rocks are recovered for identification and labo-
ratory testing.
●
Stage 4: Measurements of engineering properties are made in the laboratory and
in situ
.
●
Stage 5: Instrumentation is installed to monitor ground and structural response
to changing field conditions.
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1.3.3
Phases of Investigation
Investigations can be divided into a number of phases based on their purpose, with vari-
ous investigation stages in each phase. In general, phases range from feasibility to prelim-
inary design, final design, construction, and postconstruction.
Feasibility
A feasibility phase is imperative when the investigator has no prior experience in the proj-
ect area, when the site is located in virgin or rural country, or for large important projects.
