DEEP SOUNDING - ITS VALUE AS A GENERAL INVESTIGATION TECHNIQUE WITH PARTICULAR REFERENCE TO FRICTION RATIOS AND THEIR ACCURATE DETERMINATION

Deep sounding is a well-established method for assessing the settlement of embankments over saturated alluvial deposits. Two examples are given in which predictions are made about the final settlement under embankments currently being constructed. A useful development in deep sounding is the friction sleeve which enables a description of the subsoil to be made solely from the sounding readings. However it is shown that a high degree of accuracy is required in the measuring system if meaningful friction ratios are to be deduced and that this accuracy is probably not possible when conventional equipment is used in very soft, clayey alluvium. An improved electrical resistance, strain gauge, load-sensing apparatus is described which is cheap, can be used with any sounding machine and has the considerable advantage of recording automatically on a chart. This equipment has made it possible to compare South African correlations of friction ratio against material type with correlations obtained elsewhere. These are shown to be in agreement. It is suggested that relating the friction ratio to the plasticity index may be more useful than the conventional method of relating it to a percentage smaller than a given particle size, and a chart is drawn up on this basis. (A) /TRRL/