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Session 2: Pressuremeter Testing in Soils |
Department of Civil Engineering, The University of Newcastle upon Tyne, NE1 7RU, UK
The self-boring pressuremeter can be used to determine in situ consolidation characteristics of clays (Clarke et al. 1979). The test procedure includes undrained loading from which total horizontal stress, shear modulus and strength can be determined. Excess pore pressures are generated during loading. These decay during the holding portion of the test when the membrane is held at about 10% cavity strain. The rate of decay is used together with a theoretical prediction of consolidation around a cavity to determine the horizontal coefficient of consolidation. The main disadvantage of this is the difficulty with measuring the pore water pressure. As the excess pore pressures dissipate the total applied pressure within the membrane is reduced. The total pressure can be monitored more accurately than the pore pressure and, hence, holding tests based on total pressure decay would be a preferred field technique. This paper discusses work carried out at the SERC Bothkennar soft clay site where undrained SBP and holding tests were carried out down to a depth of 19.6 m. The tests have been interpreted using total pressure observations. The tests have also been interpreted using a finite element package which includes the Cam Clay model and coupled consolidation. This interpretation allows a comparison to be made between the use of pore and total pressure decay in the analysis and recommendations for an alternative test procedure are made.
