For designing and constructing a stable engineering structure we should know the character of rock and soil in which it will be built. In-Situ investigation is the gathering of information about the site. The geological condition of the site which forms the rocks and soils and the nature of material which are present on the site which is used for the construction are taken in to account. Constructing a road, tunnel, dams, bridges or any other engineering structures from selected construction material, strength of the structures and requirements of the load and its displacement may be predicted.
In ground investigation two things should be consider, Firstly the character of rock or soil mass and secondly geological environment. The quality of rock and soil is obtained by the observation and some physical test; like how hard or soft rock material is present, by crushing with machines and also studying its composition. Presence of fluid can be obtained by saturation test and if present so its pressure can be calculating by measuring from instruments like hydrometer. It is useful before commencing further exploration.
There is no fixed approach to ground investigation but code of practice or methods exists. Program of In-situ investigation should be flexible as it enables the investigation to be amended when unexpected features of importance come in to explanation. The main components of In-Situ Investigation is Desk Study, Field Reconnaissance, Field Investigation, Sampling and reporting. However these components may be over-lapped depending upon the circumstances.There is also a lot of use of geological advice for getting the best use of geological condition. In ground investigation the geologist uses theory of probability to aid them besides the knowledge of materials and its genesis.
The Cost of Site investigation is about .5% to 1% of the cost of project but it is not necessary. The purpose should be completed and that is to know the stability of the site for the design and construction. Moreover;
Is there any fluid present which will affect the construction of a structure?
Obtain information about the quality and quantity of a material.
Ground Investigation should not be ignored for saving money as it could be dangerous in future.
Remember one thing that the Money can be saved in design and construction once engineers know the exact conditions of ground.