“Compaction variables” (i.e. compaction technique, energy, molding water content) have a key role on the mechanic and hydraulic behaviour of compacted fine grained soils. An extensive project has been developed at the University of Napoli (Italy) in order to have a deep insight on this topic. In this paper the results of a experimental investigation, carried out to analyse the influence of the compaction technique on the pre-failure behaviour of a clayey silt, will be reported. The soil tested is a medium plasticity inorganic silt used to construct an experimental embankment on Po river. Soil specimens have been prepared at different molding water contents. For each water content soil specimens have been compacted at the same dry density by dynamic (Proctor standard) and kneading (Harvard) compaction methods. The compaction curve obtained by the Proctor standard technique (ASTM D698-91) has been used as reference energy curve. All the compacted specimens have been saturated at constant volume and then tested: monotonic cyclic and dynamic torsional shear tests have been carried out using a RCTS apparatus, always following the same stress history. Results have been analysed in terms of shear stiffness, damping ratio and their variation with confining stress and strain level. The experimental data obtained show that, for the Proctor compaction technique, specimens compacted at optimum water content show higher shear moduli than those compacted on both dry and wet side of optimum. The opposite behaviour has been observed in the case of the specimens compacted by the Harvard method. It seems that different moisture contents lead to different structures while different compaction techniques induce different anisotropy.

Influence of compaction variables on the small strain behaviour of a clayey silt

D'ONOFRIO, ANNA;
2003

Abstract

“Compaction variables” (i.e. compaction technique, energy, molding water content) have a key role on the mechanic and hydraulic behaviour of compacted fine grained soils. An extensive project has been developed at the University of Napoli (Italy) in order to have a deep insight on this topic. In this paper the results of a experimental investigation, carried out to analyse the influence of the compaction technique on the pre-failure behaviour of a clayey silt, will be reported. The soil tested is a medium plasticity inorganic silt used to construct an experimental embankment on Po river. Soil specimens have been prepared at different molding water contents. For each water content soil specimens have been compacted at the same dry density by dynamic (Proctor standard) and kneading (Harvard) compaction methods. The compaction curve obtained by the Proctor standard technique (ASTM D698-91) has been used as reference energy curve. All the compacted specimens have been saturated at constant volume and then tested: monotonic cyclic and dynamic torsional shear tests have been carried out using a RCTS apparatus, always following the same stress history. Results have been analysed in terms of shear stiffness, damping ratio and their variation with confining stress and strain level. The experimental data obtained show that, for the Proctor compaction technique, specimens compacted at optimum water content show higher shear moduli than those compacted on both dry and wet side of optimum. The opposite behaviour has been observed in the case of the specimens compacted by the Harvard method. It seems that different moisture contents lead to different structures while different compaction techniques induce different anisotropy.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11588/184143
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