Choosing the appropriate geotechnical investigation method for a site requires several considerations to be made to ensure that sufficient data have been gathered for safe and efficient design and construction. The step-by-step procedure to help in making a decision is presented below:
1. Project Requirements
Scope of the work: Size, type, and purpose of structure, residential, commercial, or industrial.
Load Requirements: The applied loads and stresses that the structure is going to impart on the soil are determined.
Local Building Codes: Any statutory or regulatory requirement or guidelines that may exist for a geotechnical investigation.
2. Site Characteristics
Soil Type and Stratigraphy: The type of soil will dictate the choice of various tests. For example, sandy soils will need a different type of test compared to clayey soils.
Groundwater Conditions: The presence and depth of groundwater will modify the properties of soils and alter the selection of test methods.
Topography: The conditions of the site being flat, sloping, or hilly may impact the selection of investigation methods.
Site History: The site history as related to landfills and industrial sites can affect soil conditions.
3. Investigation Methods
Desk Study and Reconnaissance: Preliminary assessment by existing data, maps, and site reconnaissance to find out any probable problems.
Borehole Drilling: The detailed conditions of the subsurface are established. The method is suitable for deep investigation and sampling.
Standard Penetration Test: SPT is useful in measuring the resistance of penetration in soils and thus in general in soil characterization. Cone Penetration Test: There is continuous profiling for the properties of soils, which works effectively in soft soils. Trial Pits and Trenches: Especially used in shallow investigations and visual inspection of soil layers. Geophysical Methods: Non-invasive methods like seismic refraction, resistivity, and ground-penetrating radar, GPR, are employed in efficiently mapping subsurface conditions.
Laboratory Testing: Soil samples can be tested for a range of properties, including grain size, Atterberg limits, shear strength, and compressibility.
4. Budget and Time Constraints
Cost: The cost of a geotechnical investigation depends on the applied methods. Some of them are expensive, others not.
Time: The available time for the investigation. Some methods are faster than others.
5. Expertise and Availability of Equipment
Expertise of Consultants: The method adopted will be based in part on the experience capability of the geotechnical engineering firm or consultant.
Availability of Equipment: Ensure the availability and accessibility of necessary equipment for the selected methods.
6. Data Analysis and Integration
Data Integration: The data obtained from several methods of investigation need to be combined for a comprehensive understanding of the site conditions.
Risk Assessment: This is a process by which potential risks are assessed against the geotechnical data, and the investigation plan may be modified if necessary.
The Decision-Making Process
Initial Assessment: Desk study and site reconnaissance to obtain preliminary information.
Method Selection: The methods shall be selected based on project requirements, site characteristics, budget, time, and available expertise.
Investigation Execution: Execution of the selected geotechnical investigation method
Data Analysis: Analysis of the collected information towards design and construction decisions.
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