Modelling of wetting tests for a natural pyroclastic soil

Mariagiovanna Moscariello,Sabatino Cuomo,Manuel Pastor,Vito Foresta,Diego Manzanal,P Delage,S Ghabezloo,Y.-J Cui,J.-M Pereira,A.-M Tang

doi:10.1051/e3sconf/20160917007

Mariagiovanna Moscariello, Sabatino Cuomo + Show 8 more

Open Access

https://doi.org/10.1051/e3sconf/20160917007

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Abstract

The so-called wetting-induced collapse is one of the most common problems associated with unsaturated soils. This paper applies the Modified Pastor-Zienkiewicz model (MPZ) to analyse the wetting behaviour of undisturbed specimens of an unsaturated air-fall volcanic (pyroclastic) soil originated from the explosive activity of the Somma-Vesuvius volcano (Southern Italy). Both standard oedometric tests, suction-controlled oedometeric tests and suction-controlled isotropic tests are considered. The results of the constitutive modelling show a satisfactory capability of the MPZ to simulate the variations of soil void ratio upon wetting, with negligible differences among the measured and the computed values.

Highlights

The Water Retention Curve (WRC), which relates the degree of saturation (Sr) to the matric suction, is available from previous experiments performed through both Volume-Extractor and Suction-Controlled-Oedometer, (Fig. 1) on specimens sampled at Sarno site and characterized by different void ratios [13]
The paper dealt with the constitutive modelling of the mechanical behaviour of an unsaturated air-fall volcanic soil, originated by the explosive eruptions of the Vesuvius volcano in southern Italy
The capability of the constitutive model is evaluated with reference to the soil volumetric strain and the variation of void ratio

Summary

Material

The paper deals with an unsaturated air-fall volcanic (pyroclastic) soil of Southern Italy, originated from the explosive activity of the Somma-Vesuvius volcano [12]. The Water Retention Curve (WRC), which relates the degree of saturation (Sr) to the matric suction, is available from previous experiments performed through both Volume-Extractor and Suction-Controlled-Oedometer, (Fig. 1) on specimens sampled at Sarno site and characterized by different void ratios [13]. The magnitude of soil collapse was strongly influenced by the initial void ratio, the stress level at the beginning of the wetting stage and the type of test performed, which influence in turn the stress path followed. This complex mechanical behaviour requires specific constitutive models to be quantitatively reproduced. Three vertical net effective stresses were selected (100, 300 and 500 kPa), and the principal details of the tests are reported in Tab. 1

Theoretical framework

Constitutive modelling

Validation and model performances

Conclusions