The ground investigation, irrespective of the magnitude of the project, consists of four phases, which are discussed below.
1. Available Information
This is the first phase in which the collection of published geological and topographical information of the area, hydrological data, details of load regulations for construction activity, etc., are made.
2. Reconnaissance
At this stage a thorough study of the existing structures for the type of construction and defects such as cracks and settlement, availability of water, etc., for the building project are collected.
3. Preliminary Investigation
This is an important phase of the entire programme. As the sub-soils were formed under different geological environments, the first step towards a ground investigation is a thorough understanding of the geology of the site, which enables an efficient working out of the investigation programme. The second step is to obtain more details about the sub-soil strata (e.g., thickness of each stratum) from one or two exploratory drill holes. All further steps depend on the magnitude of the job and the character of the soil profile.
4. Detailed Investigation
Additional borings are planned from the data obtained from the preliminary borings. If the sub-soil is uniform in stratification, an orderly spacing may be planned. Often, additional borings are made to locate weak soil or rock zones, outcrops, etc., which may influence the design and construction of the project. Sufficient samples are procured to obtain relevant parameters for design and construction.
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