 All civil engineering projects like dams, reservoirs etc. constructed on earth crust and constructed by material obtained from the crust.  So it is essential that are engineer should have fullest geological idea about the foundation on which project is executed and from which it is made such knowledge has an important bearing on the design, stability and cost.  Geological condition at foundation are an important factor in the design structure.

 Detailed geological investigation have therefore to be carried out to find out the geological condition at the foundation before the design of structure is taken hand.  Numerous cases are on record in which neglect of geological conditions has given rise to all sort of difficulties and has led to unavoidable delays and increases in cost of project  Proper geological investigation have therefore to be carried out before starting work on a project.  In most of engineering project geological investigation are aimed to finding out the nature and structure of rock at the work site, Ground.water condition,geomorphology of the area etc.

 Surface investigation  Subsurface investigation  Surface Investigation :-  Surface investigation can be done in two stages :-  Preliminary Survey  Detailed survey

 Preliminary geological investigation are made to find out the nature and structure of rock at work site and its surrounding with v iew to select best-suited site project.  Preliminary investigation consist of mapping the entire area and if this has not been done earlier and there by interpreting the occurrence and distribution various types of rock, Stratification folding rock of the work site can be had from previous geological literature but all information required for engineering project are not always available and so geological survey are essential.

 This survey consist of mapping and examination of the rock,nothing their structural features and determination of physical properties of representative rock specimen,suitability of topography and leak zone etc.  On basis of this work a geological report is prepared describing the distribution, nature and structure of all rocks in the area and discussing the their engineering behavior.  The results of the surface survey are also depiciated on a large scale geological map of the area,the scale being at least 1cm = 100m or even more depending on the detail required to be shown.

 In addition to the distribution of the various rock types the map shows in details the deposition and nature of natural divisional planes in the rock as joints, fractures, faults, bedding planes etc. and the broad structural features such as folds, dips etc.  Geological section constructed from these map provides a clear picture of programs the underground structure and the of subsurface explorations by excavation and drilling is prepared on the bases of these section.

 Can be made by two ways :-  Indirect subsurface exploration  Direct penetration of the material i.e Boring.  Indirect subsurface exploration by making certain physical measurement from the surface without direct penetration and then interpreting those date for ascertaining the required subsurface information.  Direct penetration of material can be made by method of excavation by core drilling both have their advantages and limitation.  Exploratory Excavation :- Excavation will usually be found to be economical up to depth about 10 meter and maximum possible use should be made of excavation up to this depth. Test pit,Trenches,Adit, drifts, exploratory tunnel,pilot cut, shaft etc.are dug and they provide very accurate information as rock and their structure exactly as they occurred in nature, can be directly observed in excavation

 Core drilling :-  Core drilling is a process of drilling by which specimen of rock from different depth can be brought to the surface in tact in the form of solid cylinder. A) Diamond drilling :- can not be used for hole larger than 100mm.in diameter B) calyx or shoot drilling :- larger holes calyx drilling has to be used

 To ensure that drilling is not misinterpreted and also the valuable data should not loose.  The location of drill hole and their depth should be decided taking the account of local geological structure and the nature of information required.  The core should be numbered in sequence and their depth noted.  The core should be placed in core log and its report should be made indicating necessary information such as project location No. Time required for drilling,Drilling mud should also be observed,drill water loss indicate leak Zone  Core –log and Litho-log