Site investigations

Site investigations taken at an early, feasibility stage of a project will seldom be adequate for construction. More site tests will be necessary for individual foundations, etc. British Standard BS 5930: 1999, Code of practice for site investigations, acts as a general guide for further site tests, but this needs to be supplemented  by information contained in other publications as suggested at the end of this chapter. The resident engineer will be expected to have an understanding of the major principles and techniques of soil mechanics so that he can direct work intelligently. But for specifying tests and interpreting their results, an experienced geotechnical engineer is essential, otherwise misleading assumptions can be made which later lead to serious trouble on a job.
There is an art as well as a science in deciding what additional site investigations should take place when construction is started. Advice from a geotechnical engineer or engineering geologist should always be sought, but when choosing where to site extra boreholes or trial pits hunch and suspicion can play a part. A hunch should not be dismissed as unscientific; it can arise from studying the known facts and an apprehension that more needs to be known about some aspect of a situation than is currently known at the time. An experienced engineer will always worry more about what he does not know about below-ground conditions, than what he does know. Thus investigating some suspicion there might be a possible unconformity in conditions below ground can sometimes prove more revealing than gridding an area with boreholes at regular intervals but not always!

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