Modelling unsaturated soil behaviour during normal consolidation and at critical state

An analysis of results from published laboratory tests on Jossigny silt and Barcelona clayey silt is presented to confirm the existence of a unique capillary bonding function linking the quotient between unsaturated and saturated void ratio, at the same mean average skeleton stress, to a single capillary bonding scalar variable. The analysis confirms that the same capillary bonding function applies to both normally consolidated and critical stress states. The above two experimental sets with the addition of further published data for Speswhite Kaolin are also used to study the relationship between unsaturated critical shear strength, mean average skeleton stress and capillary bonding variable. The results of such analysis are assessed in the light of a similar modelling framework proposed in the literature

Effect of in Situ and Laboratory Compaction on the Retention Behaviour of a Clayey Soil

International audience; A clayey soil has been tested in the laboratory in order to investigate the influence of the compaction procedure on the soil retention behaviour. In common engineering practice, data available for modelling are those of the soil compacted in the laboratory and soil behaviour during the earth structures lifecycle is predicted on that basis. This practice, however, seems to overlook the fact that construction procedures in the field might differ significantly from the compaction techniques used in the laboratory and this may induce considerable differences in material texture and therefore in the soil behaviour. The investigation shown in the present work aims to provide further insight into this aspect and to help endorsing or refuting the validity of such practice

post seismic relaxation and earthquake triggering in the southern adriatic region

SUMMARY An attempt at quantifying post-seismic relaxation triggered by decoupling earthquakes along the eastern thrusting border of the Adriatic plate (southern Dinarides) is carried out by finite element modelling, with a model constituted by an elastic lithosphere riding on a viscous asthenosphere. In particular, it is investigated the possibility that the above phenomenon is responsible for the fact that in the last two centuries most major earthquakes in the southern Dinarides (MS > 6) have been followed, within a few years, by intense, mainly tensional, earthquakes in southern Italy, i.e. the zone lying on the opposite margin of the Adriatic plate. This analysis has been applied to the last example of the supposed seismic interrelation, i.e. the triggering 1979 April 15 Montenegro event (MS= 6.7) and the presumably induced 1980 November 23 Irpinia earthquake in the southern Apennines (MS= 6.9). Results indicate that the strain induced in the southern Apennines by the triggering event has significant amplitude, since it largely exceeds the effect of earth tides, and the principal stress axes are consistent with those of southern Apenninic earthquakes. The order of magnitude of the time delay between the Montenegro and Irpinia events (1.6 yr) could be explained by assuming that earthquake triggering is most probable when the highest values of the induced strain rate reach the southern Apennines. In particular, this interpretation predicts the observed time delay when a model diffusivity of 400 m2 s−1 is assumed. The constraints that this diffusivity value may pose on the structural and rheological features of the crust–upper-mantle system in the study area are discussed. It is shown that the effects of the Montenegro event on the present velocity field are comparable to, though systematically lower than, the velocities suggested by geodetic observations in the Italian region. This suggests that geodynamic interpretations of geodetic data given without taking into account possible transient effects on the kinematic pattern, as those related to post-seismic relaxation, may be incorrect. Experiments carried out by tentatively simulating the presence of subducted lithosphere along the western margin of the Adriatic plate as a lateral variation of diffusivity, have shown that this structural feature may emphasize E–W tensional strains in the southern Apennines

Calibration of elasto-plastic models for unsaturated soils under isotropic stresses

This paper presents a new method for selecting parameter values in elasto-plastic models for unsaturated soils under isotropic stress states. The proposed method is an improvement over more traditional calibration approaches as it explicitly takes into account experimental yielding behavior when defining the unsaturated normal compression surface. This is achieved by “enriching” measured yield stresses with corresponding values of specific volume (estimated from the observed elastic and virgin responses), which generates experimental points that can be interpolated together with virgin compression data. The proposed methodology is general and independent of the chosen mathematical forms of normal compression surface, elastic law and constitutive variables. The validity of the method is demonstrated by calibrating a reference model from a set of constant suction isotropic compression tests. Both improved and traditional calibration approaches are employed to select model parameter values which are then used to predict yield curves in the mean net stress–suction plane. Because of the incorporation of yielding data in the interpolation of the normal compression surface, the improved calibration method produces a more accurate prediction of yield stresses at different suctions compared with the standard method. Due to its generality and limited subjectivity, the proposed method provides an unbiased tool to compare strengths and weaknesses of different constitutive models

L’informativa sui rischi nelle banche italiane quotate al FTSE All Share. Analisi empirica della disclosure nel triennio 2006-2008

Since the 2005 the relevance of the disclosure on company’s risks as well as the systems for risk management has increased and this is probably due to the major importance assigned to such information by the International accounting standards (particularly IFRS 7 and IAS 32) and the EU directive 51/2001. In this paper are presented the results of an empirical analysis carried out on the annual reports of Italian banks listed to the segment “FTSE All Share” of the Milan Stock Exchange. The main objectives of the research are: - Evaluate the propensity of the banks to report voluntary the information about their risks; - Analyze the attributes (qualitative vs. quantitative, past oriented vs. forward-looking orientation, etc.) of the risk disclosure; - Assess if some relations exist between the quantity of the risk disclosure and other key risk indicators such as the TIER 1 ratio and the Beta. The findings of our analysis reveal that the risk disclosure concerns almost entirely the mandatory information that the company must produce according to Italian law (particularly the “Circolare 262/2005” of Bank of Italy) whilst the voluntary disclosure is significant less extended than the mandatory one. The normative requirements influence the content of the external reporting so as the major part of the information regard those elements (type of risks, actions of risk management, units involved in the risk management processes, etc) that the company must produce to comply with the aforementioned Law. The analysis of data shows that a significant relation exists between the quantity of the risk disclosure that concerns credit risk, market risk and operational risk and the level of company’s risk. This means that those banks with a high level of inherent risk (measured by the Tier 1 ratio) and a high level of systematic risk (measured by the Beta) disclosure more information on risks. This mean that risk reporting could be seen by the financial statement’s prepares as a mean for reducing the perception of the bank’s risk profile that the stakeholders could have if they use other risk indicators as the Tier 1 ratio or the Beta

Effect of in Situ and Laboratory Compaction on the Retention Behaviour of a Clayey Soil

International audienceA clayey soil has been tested in the laboratory in order to investigate the influence of the compaction procedure on the soil retention behaviour. In common engineering practice, data available for modelling are those of the soil compacted in the laboratory and soil behaviour during the earth structures lifecycle is predicted on that basis. This practice, however, seems to overlook the fact that construction procedures in the field might differ significantly from the compaction techniques used in the laboratory and this may induce considerable differences in material texture and therefore in the soil behaviour. The investigation shown in the present work aims to provide further insight into this aspect and to help endorsing or refuting the validity of such practice

Microstructure Analysis of Laboratory and In-Situ Compacted Silts

International audienc

Benchmarking selection of parameter values for the Barcelona basic model

Seven teams took part in a benchmarldng exercise on selection of parameter values for the Barcelona Basic Model (BBM) from experimental data on an unsaturated soil. All teams were provided with experimental results from 9 tests performed on a compacted soil in order to determine values for the ten BBM soil constants and an initial value for the hardening parameter. The coordinating team then performed simulations (at stress point level) with the 7 different sets of parameter values, in order to explore the implications of the differences in parameter values and hence to investigate the robustness of existing BBM parameter value selection procedures. The major challenge was found to be selection of values for the constants lambda(0), r, beta, N(0) and p(c) and an initial value for the hardening parameter (p) over bar (0)(0), with the various teams proposing significantly different values for some of these key parameters. A key lesson emerging from the exercise is the importance of choosing a method for selecting values for the parameters beta and p(c) which places the main emphasis on attempting to optimise the match to the experimental spacing of normal compression lines at different values of suction. (C) 2015 Elsevier B.V. All rights reserved.Peer Reviewe

Benchmarking selection of parameter values for the Barcelona basic model

Seven teams took part in a benchmarldng exercise on selection of parameter values for the Barcelona Basic Model (BBM) from experimental data on an unsaturated soil. All teams were provided with experimental results from 9 tests performed on a compacted soil in order to determine values for the ten BBM soil constants and an initial value for the hardening parameter. The coordinating team then performed simulations (at stress point level) with the 7 different sets of parameter values, in order to explore the implications of the differences in parameter values and hence to investigate the robustness of existing BBM parameter value selection procedures. The major challenge was found to be selection of values for the constants lambda(0), r, beta, N(0) and p(c) and an initial value for the hardening parameter (p) over bar (0)(0), with the various teams proposing significantly different values for some of these key parameters. A key lesson emerging from the exercise is the importance of choosing a method for selecting values for the parameters beta and p(c) which places the main emphasis on attempting to optimise the match to the experimental spacing of normal compression lines at different values of suction. (C) 2015 Elsevier B.V. All rights reserved.Peer Reviewe