Instrumented Piles Tested in 1969 in Fine Loose Sand at Holmen, Drammen: Revisited 2019

Abstract

The work presented here relates to the instrumented piles tested in 1969, by the Norwegian Geotechnical Institute (NGI) in loose sand at Holmen, Drammen. The material contained in the first publication, which is an Internal Report F.273.0 of NGI (Balasubramaniam et al., 1969), was mainly on the load tests only and contained the analyses of the vibrating wire gauges as based on the zero of the gauges after the pile driving, to make sure the best set of zero values were used. The publication of Gregersen et al. in 1969, includes pull out tests and also the effect of the residual stresses developed in the piles during pile driving. Further, the work of Gregersen et al. contains a detail section on the performance of the vibrating wire gauges and in particular the drifting of the zero of the gauges. The entire pile testing work and reporting in NGI internal report F.273.0 (Balasubramaniam et al., 1969) included a description of the instrumentation used and the results obtained from load and pull out tests on precast reinforced concrete piles. The piles, of circular cross section and available in standard lengths, can be joined together in the field by means of threaded connectors. The primary purpose of the instrumentation was to determine the distribution of axial load along the length of the pile and the point load and also to measure the distribution of lateral earth pressure acting on the periphery of the pile. To accomplish these goals, the piles were equipped at a number of levels with strain gauges embedded in the concrete, on the reinforcing steel, and earth pressure cells on the sides of the piles, together with hydraulic piezometers for measuring pore water pressure in the sand. The instrumentation system was based on...