During a site investigation, information is collected, evaluated, and reported in order to provide sufficient information for building. Site investigations often reveal sufficient subsurface data to design and construct stable foundations that are safe from detrimental movements or collapse. During a site investigation, data is collected and evaluated, and the results are reported. Ground characteristics must be well understood to design an economical, long-lasting, and safe structure with a low maintenance cost. The primary scope of site investigation is:
- Soil profile
- Groundwater condition
Site investigation ought to be organized to obtain all possible information to understand the subsurface condition and probably foundation behavior thoroughly.
Stages of site investigation
A site investigation process comprises four stages:
- Desk study and site reconnaissance. The initial step in site investigation is to find as much historical and geological information as possible. Maps may be used to choose sites because they provide accurate grid references in ordinance survey maps. Old maps are employed to find historical data such as mine workings, filled ponds, old pits, landslide zones, and so on. Geological maps, aerial photography, and past investigation records are all used for this phase. The surface condition, site layout, climate, and hazard water levels are all taken into account on site visits. Prior to the feasibility study, a desk study indicates that the site is viable. If the desk study shows that the site is feasible, the preliminary investigation will be conducted.
- Preliminary ground investigation. Prior to undertaking any groundwork, this phase seeks to determine the geological structures, soil profiles, and groundwater levels by drilling a few boreholes. The analysis should identify any ground structures that may require further investigation: for example
- The extent of disturbed strata,
- The location and extent of natural cavities and mine workings.
- Fractures and river crossings or alluvial areas that may have buried soft material or pet, their liability to cause subsidence, surface movements, or instability
- During this phase, soil suitability for fill work, groundwater conditions, and flooding risk should be assessed.
- Detailed ground investigation. Prior to laboratory testing, a thorough ground investigation is required to determine the scope of the test, the number and depth of boreholes, and the type of lab testing to be performed. Soil exploration is the stage where soil exploration takes place. Soil exploration involves three phases:
- Boring in situ-testing
- Laboratory testing
Most structures require one boring at each corner and one in the middle to get started. Additional test borings may be necessary, depending on the consistency of the subsoil. To assess the firmness of soil layers, test borings should traverse through unsuitable foundation materials.
- Monitoring. This process is very crucial to the success of any project, whether the expectations of the proceeding investigations have been realized or not. Field observation can help diagnose problems during construction and consequently solve the problem. During the monitoring stage, the measurement to be made are settlement, inclination, displacement, deformation, and pore water pressure.
Supplementary investigation and construction control
The best way to ensure the site is suitable for construction is to double-check by performing additional investigations such as:
- Climatic factors include flooding, seasonal swelling, shrinkage, permafrost, and soil erosion.
- The quality and availability of local construction materials, such as concrete aggregates, building stones, and water.
- To construct a maritime or river structure, it is necessary to know the normal spring and neap tide ranges, the extreme high and low tidal ranges, the seasonal river levels and discharges, the tidal and river current speeds, and other hydrographic and meteorological parameters.
- Analyses of soil and rock samples relevant to the foundation design or construction.
- Analyses of soil, fill materials, and groundwater to determine possible harmful effects on foundation structures.
- Analyses of contaminated soils, fill materials, and emissions to determine health hazards.
All site investigations necessitate field investigations; the geotechnical contractor should obtain data on the kind of structures that will be erected and their functions. In addition, critical aspects of the structure when it is constructed are required. For instance, what construction methods will be utilised, and how long the project will take. The site investigation process includes a geotechnical and geoenvironmental assessment of the ground conditions and an in-depth look at the project’s engineering and environmental concerns. Without adequate site investigation, a construction project is likely to hit several brick walls. Therefore, using professionals for these processes is crucial to achieving the best results..