By W G H Hodges, Portsmouth Polytechnic
This paper was first published in the April 1976 issue of GE
At two sites in Hampshire, in situ tests have been conducted in Grade II and Grade V chalk - the former in a road cutting on the Whitchurch By-Pass in 1974 and the latter in the grounds of the Waterworks Pumping Station at Otterbourne in 1970. This grading, which conforms to the classification system for chalk suggested by Ward, Burland and Gallois (1968) and correlated with dynamic soundings by Wakeling (1969), and which is reproduced in Table I below, was established by visual examination of the material on site. At both locations the groundwater table was well below ground level. Detailed results of the two investigations are given elsewhere.
The present reports describes the work carried out, and summarises the results. It puts forward tentative expressions for a preliminary estimate of the “immediate” and “consolidation” settlements of circular plates, up to about 1m in diameter, placed near ground level and loaded up to about 1 000kN/m’or these two sites. Insufficient data have been studied to present any kind of general rule and these expressions should therefore be treated with caution.
Apart from the dynamic soundings at Otterbourne all the work was supervised by members of the Geotechnical Division of the Civil Engineering Department of Portsmouth Polytechnic. Southern Soil Investigations and Frankipile conducted the dynamic and static soundings at Whitchurch.
Further similar work is intended at other sites and, in addition, the effect of rapid cyclic loading is to be investigated since this is thought to produce greatly increased settlements above a certain threshold stress value