Compaction behaviour of clay

Abstract

This paper presents an experimental study of the compaction behaviour of non-active clay. One-dimensional static compaction tests were carried out at high and medium water content with matric suction monitoring using Trento high-capacity tensiometers. At lower water contents, a transistor psychrometer was used to measure post-compaction suction. Samples were compacted on the dry side of optimum to cover a wide range of compaction water contents and vertical stresses. Three water content regions were identified in the compaction plane depending on whether post-compaction suction increased, decreased or remained constant as the degree of saturation was increased at constant water content. Hydraulic paths of specimens subjected to loading-unloading cycles at constant water content have clearly shown that post-compaction suction may increase as the degree of saturation increases. This non-intuitive behaviour was demonstrated to be associated with the coupling between mechanical and water retention behaviour. To this end, a coupled mechanical water retention model was formulated. Irreversible one-dimensional mechanical paths were modelled by a boundary surface in the space average skeleton vertical stress, modified suction and void ratio. Irreversible hydraulic 'wetting' paths were modelled by a boundary surface in the space suction, degree of saturation, and void ratio. This study was completed by investigating the pore size distribution of compacted samples through MIP tests

The, K.M. A Study on the Relationship Between Matric Suction and the Void Ratio and Moisture Content of a Compacted Unsaturated Soil

“…After moving across the LOO, suction contours at the wet side of the LOO head toward the origin of the e -e w plane. This result is in accordance with the observation in Kodikara's [1] analysis using the data reported by Tarantino and De Col [8] and some others. It is noted here that the suction value at the dry side of the LOO is dependent on the values of suction (S r ) and moisture contents (e wr ) at the residual conditions (at point H in Fig.…”

“…At each value of moisture content six duplicated soil samples were compressed by a given vertical stress (100, 200, 300, 600, 1200 or 1800 kPa) at loading rates varying from 20 to 50 kPa/min (higher rate for larger value of compression) for the sample at the dry side of optimum. As highlighted by Tarantino and De Col [8] that at a loading rate of 5 kPa/min matric suction in soil sample did not exhibit discontinuities, in this study the loading rate was slowed down to 5 kPa per min when the state path close to the LOO (when S r > 80%). This treatment is necessary to make sure water can run out of soil samples during drained path and air pressure will not build up in samples.…”

“…3b that the measured moisture contents of the points at the dry side of the line of optimum (LOO) are identical and equal to the initial water content, meaning that water was maintained in the sample at those points; the compressibility coefficient is constant during loading. As highlighted by Tarantino and De Col [8], it can be assumed that the air phase is mainly continuous and is freely drained out of the samples, and the net stress is equal to the vertical stress. This trend was found in the other curves, as shown in Fig.…”

One-dimensional compression and swelling of compacted fly ash

“…Lambe and Whitman, 1969;Mitchell et al, 1965) the engineering properties of compacted cohesive soils were related to the compaction state, which was explained by the dispersed microstructure of soil compacted on the wet side and flocculated microstructure of the soil compacted on the dry side of the Proctor compaction curve. Mercury intrusion porosimetry tests for cohesive soils confirmed that the microstructure on the dry side of optimum water content was composed of aggregates with a welldefined distinction between the 'intra-aggregate pore population' and the 'inter-aggregate pore population' full of air, because water was located only in the aggregates (Delage et al, 1996;Tarantino and De Col, 2008). For material compacted on the wet side of the Proctor optimum water content, the initial bimodal pore size distribution depends heavily on the state of saturation during compaction (Delage et al, 1996).…”

Compacted soil behaviour: initial state, structure and constitutive modelling

“…14, which collates data reported by Romero et al (2011) on statically compacted Boom clay. Tarantino & de Col (2008) published MIP data on a few statically compacted samples of kaolin. The calculation of î m has also been based on the intrusion-extrusion diagram of MIP tests (Fig.…”