Marco Rosone

Microstructure Characteristics of Unsaturated Compacted Scaly Clay

Microstructure characteristics of unsaturated compacted scaly clay are investigated by MIP tests on freeze dried samples and observation of SEM photomicrographs. Effects of scale microstructure and increasing compaction stresses, and microstructure changes induced by loading and unloading paths and clay saturation are analysed.

Volumetric Behaviour of Lime Treated High Plasticity Clay Subjected to Suction Controlled Drying and Wetting Cycles

The paper presents some experimental results collected on samples recovered from an experimental embankment obtained by compacting a lime-treated clay. Samples were collected soon after the in situ compaction and they were cured in controlled environmental conditions for at least 18 months. Mercury intrusion porosimetry tests (MIP) were carried out on freeze-dried specimens to characterize the microstructure of the material. In order to assess the durability of the improved material, laboratory tests focused on the effects of cyclic variations of the degree of saturation on the water retention properties and the volumetric behaviour of the stabilized clay. Collected results show that the lime-treated clay undergoes an almost irreversible volumetric behaviour; this irreversible contraction is associated to severe drying processes .

Shear Strength of a Compacted Scaly Clay from Suction-Controlled Triaxial Tests

The paper presents the results of an experimental research aimed at investigating the shear strength characteristics of an unsaturated compacted scaly clay. Shear strength was investigated by suction-controlled triaxial compression tests on dynamically compacted samples. Collected results point out that suction effects on stiffness and shear strength can be very different for suction values applied lower or greater than air entry value (AEV), corresponding to the material void ratio.

The Residual Shear Strength of the Shaly and Sandy Facies of the Opalinus Clay

The paper presents a comprehensive laboratory campaign carried out with the aim to asses the residual strength of the Opalinus Clay. Ring shear tests with vertical effective stress up to 1 MPa were performed on remoulded samples of two different facies of the Opalinus Clay. Test results show that the «Shaly» facies is characterized by a low range of variation of residual strength while the strength of the «Sandy» facies is very sensitive to the variation of grain size distribution. Microstructural analyses (SEM) suggest that the difference in the observed mechanical behavior of the two facies can be related to different particles arrangements along the shear surfaces.

The Permeable Concrete: A Low Energy Consumption Solution for Deep Draining Trenches

The reduction of pore water pressures is one of the very effective measures to improve the stability conditions of marginally stable water-bearing slopes or to stabilise landslides. For this purpose the trench drains have been used long since. Like filling material of deep trenches the permeable concrete can be effectively employed. It presents relatively high hydraulic conductivity, filtering capacity in order to prevent the internal erosion of the soil in which the trench drain is installed, enough residual hydraulic conductivity after possible clogging, sufficient shear strength after a short curing time to avoid the instabilisation of adjacent previously built panels or piles. Results of a laboratory experimental research on the mix-design, hydraulic conductivity and strength of pervious concrete are reported in the paper, proving that proper mix-design can be devised meeting the above requirements. Permeable concrete is a very poor material and a low energy consumption solution for slope stabilisation.

Microstructure and shear strength evolution of a lime-treated clay for use in road construction

ABSTRACT The results of a comprehensive experimental programme are presented for assessing the long-term microstructural modifications and evaluating the effects of microstructural rearrangement on the stress–strain behaviour of a lime-treated high-plasticity clay for road embankments. The stress–strain behaviour at different lime content and curing time was investigated by means of direct shear tests; microstructural analyses were carried out combining Scanning Electron Microscope observations and Mercury Intrusion Porosimetry tests. The results show that the stress–strain behaviour of treated clay is strongly dilatant with a high peak of strength, which increases with time and lime content. Furthermore, a hyperbolic function may be used for predicting the increase in strength at the end of the stabilisation process. Microstructural analysis shows that the treatment induces a redistribution of the porosity between macro- and micropores and an increase in matric suction, associated to a low reduction of water content and to aggregates shrinkage. This behaviour is affected by lime content and curing time since it results from the formation of the pozzolanic compounds on the surface of clay aggregates that induces both a bonding between hardened clay aggregates and an increase of their interlocking degree, with a consequent increase in the shear strength.