SITE CHARACTERIZATION & INSTRUMENTATION MODULE 1

Module 1: Introduction to Site Characterization:

Topics:
 Introduction
 The Importance of Site Investigation
 Purposes of a Site Investigation
 Objectives
 Need for Site Characterization
 Advantages of Site Investigation

Keywords:Soil investigation, site characterization, objectives, advantages, applications

1.1 Introduction:
Adequate knowledge of ground conditions is very important for analyses, design and
construction of projects. Project delays, failures and cost over-run are the result of
inadequate and inappropriate soil investigations.
Hence, soil investigation must be part of the design process.
Site characterization is the process of collection of information, appraisal of data,
assessment and representation through maps without which the hazards in the ground
beneath the site cannot be known.
Modern site investigation differs from its forbears principally because of the need to
quantify soil behaviour.
Site investigation is considered to be an integral part of construction.
For most construction projects, the variability of the ground and groundwater
conditions is a major risk, which if not properly addressed can endanger the physical
stability of the construction, either during construction or during the use of the
building.
In principle, all sites must be investigated if construction is to be safe and economical.
In practice, the way in which they are investigated can vary widely and the costs and
time necessary will be significantly different.
During site characterization, information about the site necessary to develop a site
conceptual model capable of supporting selection and implementation of remedial
actions is gathered.
Typical site characterization activities include evaluations of the historical uses of
property, site reconnaissance and collection and analysis of environmental samples.
Site investigation will often be carried out by specialists in the field of soil mechanics.
A geotechnical investigation will include surface exploration and subsurface
exploration of a site. Sometimes, geophysical methods are used to obtain data about
the sites. Subsurface exploration usually involves soil sampling and laboratory tests of
the soil samples retrieved.
Geo-technical site characterization is usually done through in-situ tests (standard
penetration and cone penetration tests), laboratory tests (plasticity, particle size
analysis etc.).

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SITE CHARACTERIZATION & INSTRUMENTATION MODULE 1

Surface exploration can include geologic mapping, geophysical methods and

photogrammetry, or it can be as simple as a geotechnical professional walking around
on the site to observe physical conditions.
To obtain information about the soil conditions below the surface, some form of
subsurface exploration is required.

1.2 The Importance of Site Investigation:

1) To study the general suitability of the site for an engineering project.
2) To enable a safe, practical and economic design to be prepared.
3) To determine the possible difficulties that may be encountered by a specific
construction method for any particular civil project.
4) To study the suitability of construction material (soil or rock).
5) To prevent the delay of any construction project due to problematic ground
conditions.

1.3 Purposes of a Site Investigation:

A site investigation program is necessary to provide information for design and
construction and for environmental assessment. The purposes of a soil investigation
are:
1. To evaluate the general suitability of the site for the proposed project.
2. To enable an adequate and economical design to be made.
3. To obtain physical and mechanical properties of soils for design and construction.
4. To obtain groundwater conditions.
5. To disclose and make provision for difficulties that may arise during construction due
to ground and other local conditions.
6. To determine suitability of materials for construction.

1.4 Objectives of Site Characterization:

Site characterization is done with the following objectives:
o Determination of the soil properties.
o Development of map for the region.

1.5 Site characterization should provide the following information:

The objectives of site investigation have been defined by the various Codes of
Practice (BS CP 2001:1950, 1957; BS 5930:1981). They can be summarized as
providing data for the following.

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SITE CHARACTERIZATION & INSTRUMENTATION MODULE 1

1.5.1 Site selection:

The construction of certain major projects such as earth dams is dependent on the
availability of a suitable site. Clearly, if the plan is to build them on the cheapest,
most readily available land, geotechnical problems due to the high permeability of the
sub-soil or slope instability may make the final cost of the construction prohibitive.
Since the safety of lives has to be taken care of, it is important to consider the
geotechnical merits or demerits of various sites before the site is chosen for a project
of such magnitude.
1.5.2Foundation and earthworks design:
Generally, factors such as the availability of land at the right price, in a good location
from the point of view of the eventual user, and with the planning consent for its
proposed use are of over-riding importance. For medium-sized engineering works,
such as motorways and multi-storey structures, the geotechnical problems must be
solved once the site is available, in order to allow a safe and economical design to be
prepared.
1.5.3Temporary works design:
The actual process of construction may often impose greater stress on the ground than
the final structure. While excavating for foundations, steep side slopes may be used
and the in-flow of groundwater may cause severe problems and even collapse. These
temporary difficulties, which may in extreme circumstances prevent the completion of
a construction project, will not usually affect the design of the finished works. They
must however be the object of serious investigation.
1.5.4The effects of the proposed project on its environment:
The construction of an excavation may cause structural distress to neighbouring
structures for a variety of reasons such as loss of ground and lowering of the
groundwater table. This will result in prompt legal action. On a wider scale, the
extraction of water from the ground for drinking may cause pollution of the aquifer in
coastal regions due to saline intrusion, and the construction of a major earth dam and
lake may not only destroy agricultural land and game, but may introduce new diseases
into large populations. These effects must be the subject of investigation.
1.5.5Investigation of existing construction:
The observation and recording of the conditions leading to failure of soils or
structures are of primary importance to the advance of soil mechanics, but the
investigation of existing works can also be particularly valuable for obtaining data for
use in proposed works on similar soil conditions. The rate of settlement, the necessity
for special types of structural solution, and the bulk strength of the sub-soil may all be
obtained with more certainty from back-analysis of the records of existing works than
from small scale laboratory tests.
1.5.6 The design of remedial works:
If structures are seen to have failed or to be about to fail, then remedial measures must
be designed. Site investigation methods must be used to obtain parameters for design.
1.5.7Safety checks:
Major civil engineering works such as earth dams, have been constructed over a
sufficiently long period for the precise construction method and the present stability

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of early examples to be in doubt. Site investigations are used to provide data to allow
their continued use.

1.6 Need for site characterization:

1) As the soil and rock deposition is irregular, they are notoriously variable and often
have the properties which are undesirable for the proposed structure which jeopardize
the structure if not understood and mitigated.
2) Site characterization helps in determining the nature of the site and its behaviour
which influences the project.
3) The main purpose of site characterization is to reduce the economy.
4) It plays a very important role in the assessment and determination of the
environmental effects.
5) Site characterization provides information regarding the geology, hydrology,
hydrogeology, climatic conditions, radioactivity, etc., of the site.

1.7 Advantages of Site Characterizations:

1) Determines the nature of the site and its influence on the project.
2) It reduces the economy.
3) It enables an adequate and economical design to be made.
4) It provides information regarding the geology, hydrology, hydrogeology, climatic
conditions, radioactivity, etc., of the site.
5) It determines the ground water conditions.

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