Site investigation and in situ tests

[Extract] Unlike other civil engineering materials, soils and rocks have significant variability associated with them. Their engineering properties can vary dramatically within a few meters in an area of proposed construction. A thorough and comprehensive site investigation (aka site exploration or site characterization) is therefore a prerequisite for design of all civil engineering structures and is one of the most important steps in a foundation design. Site investigation refers to the appraisal of the surface and subsurface conditions at a proposed construction site. Information on surface conditions is necessary for planning construction techniques. Information on subsurface conditions at a site is used to plan, design, and construct the foundations of structures and other underground works. A typical site investigation includes preliminary studies such as a desk study and site reconnaissance, geophysical surveys, drilling boreholes, in situ testing, sampling and laboratory testing of samples, and groundwater observations and measurements. Desk study involves collection of as much existing information as possible about the site through geological maps, aerial and satellite photographs, soil survey reports, site investigation reports of nearby sites, etc. Site reconnaissance consists of a walk-over survey to visually assess the local conditions such as site access, adjacent properties and structures, topography, drainage, etc