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Protocols for Site Investigation
Transcript of Protocols for Site Investigation
Implementation of Site Investigation
Planning Ground Investigations
Ground investigation is carried out to avoid as many difficulties as possible when undergoing construction. Inadequate planning of ground investigation and interpretation of the results of the ground investigation from boreholes, drilling and trial pits can have an additional cost over-runs on construction project. Thus conducting planning ahead for a ground investigation is important.
Site walk over survey
An examination of the site, based on defined classes of information, which complements the desk study and typically provides valuable information on matters such as:
*Surface Water & Ground Water
* Local Knowledge
*Access & Services
The key points in checking the effectiveness of a site investigation are as follows:
1. Avoid excessive disturbance
2. Check for water
3. Check depths
4. Look for faulty equipment
5. Examine driller’s records regularly
What is a Site Investigation?
The process by which geological, geotechnical and other information which may affect the construction or performance of a civil engineer or building project is acquired.
Why is it necessary?
* Simply put, it is used to determine the site’s suitability for building and the nature and the preliminary work that will be needed.
Objectives of Site Investigations.
* Site investigations aim to determine all the information relevant to the site such as meteorological, hydrological and environmental information.
* The objectives have been defined by various codes of practice and can be summarized as providing for the following:
1. Site selection
2. Foundation and Electrical design
3. Temporary work design
4. The Effects of the proposed project on its environment
5. Investigation of existing construction
6. The Design of remedial works
7. Safety checks
• A desk study is the collation and review of information already available about a site, and is carried out at an early stage of site appraisal to inform and guide the reminder of the site investigation
Preliminary subsurface exploration.
Planning trial pitting, boring and drilling
• To establish the general nature of the strata below a site;
• To establish the vertical or lateral variability of soil conditions;
• To verify the interpretation of geophysical surveys;
• To obtain samples for laboratory testing;
• To allow in situ tests to be carried out; and
• To install instruments such as piezometers, or extensometers.
Sampling, laboratory testing and in situ testing requirements
The sampling routine should be aimed at:
1. Providing sufficient samples to classify the soil into broad soil groups, on the basis of particle size and compressibility;
2. Assessing the variability of the soil;
3. Providing soil specimens of suitable quality for strength and compressibility testing; and
4. Providing specimens of soil and groundwater for chemical testing.
When conducting a site investigation...
* Inevitable uncertainties are always present therefore at the very start of designing, the advice of a geotechnical engineer should be taken into consideration so that the most effective method is used in approaching a solution.
Dealing with inevitable uncertainties
1. Desk study and geotechnical advice.
2. Standard ground investigation.
3. Limited investigation.
4. The observation method.
The following steps are carried out by the contractor or the geotechnical engineer when conducting or implementing a site investigation:
. Preliminary desk study.
. Site walk-over survey.
. Preliminary subsurface exploration.
. Soil classification by description and simple testing
. Laboratory testing
. Evaluation of data.
. Geotechnical design.
. Field trials
. Liaison by geotechnical engineer with site staff or engineer during project construction.
Role of Engineering Geology in Site Investigations
Engineering Geology is the application of the geologic sciences to engineering practice for the purpose of assuring that the geologic factors affecting the location, design, construction, operation and maintenance of engineering works are recognized and adequately provided for.
Engineering geologic practice is also closely related to the practice of geological engineering, geotechnical engineering, soils engineering, environmental geology and economic geology. If there is a difference in the content of the disciplines described, it mainly lies in the training or experience of the practitioner.
Geophysical methods may be used for:
1. Geological investigation, for example in determining the thickness of soft, superficial deposits, and the depth to rock, and in establishing weathering profiles, usually to provide cross-sections;
2. Resource assessment, for example the location of aquifers, the delineation of saline intrusion, the exploration of the extent of sand and gravel deposits, and rock for aggregate;
3. Detecting critical buried features, such as voids (mineshafts, natural cavities, adits, pipelines) and buried artefacts (old foundations, wrecks at sea, etc.); and
4. Determining engineering parameters, such as dynamic elastic moduli, and soil corrosivity.
In procuring the services of geotechnical specialists, whether consultants, contractors, or specialist sub-contractors, it is recommended that, other things being equal, those who offer a certified quality management system, or an accredited laboratory or field testing service should be favoured.
Safety should be of major concern during the fieldwork and laboratory testing phases of ground investigation. Potential hazards include:
1. Incapacity as a result of prolonged exposure to bad working conditions
2. Injury or death as a result of misuse of plant and equipment
3. Poisoning, as a result of inhaling or ingesting toxic gases or substances
4. Damage to health, or death, as a result of contact with animal carcases or sewage
VIDEO 1 - Trial Pit to determine Soil Conditions
VIDEO 2- Wash Boring Method