Abstract

Review of the meeting of the Engineering Group held at Burlington House on 9 November 1982.

Dr Hawkins, Chairman of the Engineering Group, welcomed everyone to the meeting, which began with a review of the value of geophysical surveys in ground engineering. The presentation entitled ‘Engineering geophysics—an overview’ by Dr B. W. Darracott of Wimpey Laboratories took the form of a narrated slide show of various case histories undertaken by the speaker. The usefulness of seismic refraction surveys was discussed, particularly for rock head determination, foundation design and the selection of quarry face advance direction. The analysis of shear waves was shown to aid in the better determination of the rock type and its properties. Cross-hole shooting between boreholes also enables shear waves to be measured accurately and leads to the determination of the Shear modulus and Young's modulus of the rock mass between the boreholes. This latter method may also be useful where ground surface shooting methods would not be possible due to unfavourable conditions. Over-water seismic surveys were also covered by the speaker, showing how continuous profile reflection work could be carried out on river estuaries and off-shore.

Electrical resistivity surveys were shown to be particularly useful for resolving rock layering problems and for helping with many aspects of field work involving water supply. Dr Darracott illustrated a case history where a semi-confined aquifer at depth had given rise to a slip plane in the upper near surface layers.

Magnetic methods were shown to be potentially useful in

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