Great advances have been made in electronics and computing since the last edition of BS5930 was published.This and the development ofmore accurate shallow land surveying techniques mean geophysical methods are more appropriate for site investigations.
These developments are reflected in the new code's geophysical surveying section, which is more extensive than before.As well as detailing the wide range of techniques available, it includes quick reference tables providing a check (and grading) of their suitability to particular geotechnical and geological problems.
Geophysics can offer time and cost savings, the code says, but only if the appropriate techniques are used and surveys are fully integrated into investigations.'The application of geophysical techniques to the solution of engineering problems has sometimes been disappointing, either because a method was used that lacked the precision required in a particular site investigation or because a method was specified that was inappropriate to the problem under consideration, 'the code says.
Expert advice needs to be taken as early as possible, preferably before site works begin, to assess which method should be used.If there is any doubt, it says, then trial surveys should be carried out.This should reduce the chances of surveys not producing the information expected by the engineer.
Some common pitfalls are also given.
These include: specifications written by engineers with little or no specialised understanding of geology and geophysics; choosing inappropriate techniques - and extreme cases when 'any attempt by the geophysicist to suggest alternative approaches has led to penalisation by rejection'; and rigid tenders using an inappropriate bill of quantities to measure field work.