Discussion: Engineering properties and performance of clay fills

DR A.D.M. PENMAN, Building Research Station A dam retaining 90 m depth of water has to sup port a horizontal thrust of more than 4000 t/m length of dam. It was to be expected, therefore, that a dam would be pushed downstream by a measurable amount when the reservoir was first filled.

The horizontal plate gauge,1 which has given extensive information about the movements of dis crete points within the fill of embankment dams, has made it possible to measure the movements of several points on the downstream face of the clay cores of two dams during reservoir impound ing. The positions of the gauges on the major section of the two dams are shown in Fig.l, in which C indicates clay core, R indicates the rockfill shoulders and P the positions of stable reference pillars to which core movements could be related with an accuracy of ± 2 mm. Measure ments were made several times as the reservoirs filled; the horizontal movements are given in Table 1. Dam A was 70 m high and measurements were made where the top and third from the top gauges went into the downstream face of the core. Dam B was 90 m high and measurements were made on the downstream face of the core at the crest and at each of the three horizontal plate gauges.