Abstract
An innovative specimen reconstitution technique for sandy and silty soils that simulates underwater deposition is presented and evaluated. The technique is an upgraded version for triaxial testing of the well-established slurry deposition method. This novel setup integrates the reconstitution mould and the mixing tube into a single unit to avoid transferring the sample from the mixing tube to the mould. This subtle, but critical, modification enables reconstitution of very loose specimens as sample transfer disturbance, which can be significant, is eliminated. The quality of specimens prepared by the new reconstitution method was assessed by experiments on a clean sand from the UK (Ham River sand) and a silty sand from Norway (Øysand). The method, as any slurry-based procedure, is capable of producing homogeneous specimens with high initial degree of saturation, even in the absence of back pressure. The procedure is shown to be suitable for sands with or without fines. Moreover, the new method is able to achieve a wide range of initial void ratios, from very loose to very dense, without imposing any particle crushing in the latter case.
Highlights
Sampling of sands is a major challenge for geotechnical analyses that rely on the use of high-quality undisturbed samples to model soil behaviour
A critical requirement for any reconstitution method is its ability to simulate in situ soil fabric as closely as possible so that the behaviour inferred from reconstituted specimens is representative of the sand in situ
In the slurry deposition method described by Carraro and Prezzi [6], the sample is pluviated through a column of water or slurry inside a mixing tube with diameter slightly smaller than the reconstitution mould
Summary
Sampling of sands is a major challenge for geotechnical analyses that rely on the use of high-quality undisturbed samples to model soil behaviour. In the slurry deposition method described by Carraro and Prezzi [6], the sample is pluviated through a column of water or slurry (the latter being necessary for sands with fines) inside a mixing tube with diameter slightly smaller than the reconstitution mould. The new method presented and evaluated has the same advantages of the original slurry deposition method It yields saturated, homogeneous, uniform specimens with fabric and mechanical behaviour similar to sands deposited underwater in the field. The new method has a key improvement: the reconstitution mould is included as an integral part of the mixing apparatus, which avoids transferring the sample from the mixing tube to the mould This prevents lateral migration of soil particles and undesired sample densification of very loose sands. Details of the new procedure and quality assessment techniques applied are described below
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