Module 1 : Site Exploration and Geotechnical Investigation
Lecture 1 : Introduction [ Section 1.1 : Planning For Subsurface Exploration ]
   
1.1 Planning For Subsurface Exploration
  The planning of the site exploration program involves location and depth of borings, test pits or other methods to be used, and methods of sampling and tests to be carried out. The purpose of the exploration program is to determine, within practical limits, the stratification and engineering properties of the soils underlying the site. The principal properties of interest will be the strength, deformation, and hydraulic characteristics. The program should be planned so that the maximum amount of information can be obtained at minimum cost. In the earlier stages of an investigation, the information available is often inadequate to allow a firm and detailed plan to be made. The investigation is therefore performed in the following phases:
1.
 Fact finding and geological survey
Reconnaissance
        1.  Preliminary exploration
        2. Detailed exploration
        3. Special exploration
1. Fact finding and geological survey
 

Assemble all information on dimensions, column spacing, type and use of structure, basement requirements, and any special architectural considerations of the proposed building. Foundation regulations in the local building code should be consulted for any special requirements. For bridges the soil engineer should have access to type and span lengths as well as pier loadings. This information will indicate any settlement limitations, and can be used to estimate foundation loads.

2. Reconnaissance
 

This may be in the form of a field trip to the site which can reveal information on the type and behavior of adjacent sites and structures such as cracks, noticeable sags, and possibly sticking doors and windows. The type of local existing structure may influence, to a considerable extent, the exploration program and the best foundation type for the proposed adjacent structure. Since nearby existing structures must be maintained, excavations or vibrations will have to be carefully controlled. Erosion in existing cuts (or ditches) may also be observed. For highways, run off patterns , as well as soil stratification to the depth of the erosion cut , may be observed. Rock outcrops may give an indication of the presence or the depth of bedrock.

 
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