Influence of Fines Content on Liquefaction from a Critical State Framework: the Christchurch Earthquake Case Study

In earthquake engineering practice, the liquefaction potential of soils is commonly evaluated through simplified procedures. These approaches are suitable for sands with very low to no fines content, which have been traditionally thought to be the only liquefiable materials. However, field observations and experimental research have extensively demonstrated that low plasticity silty sands can also be highly liquefiable. Thus, this paper investigates the effect of nonplastic fines contents on the liquefaction potential of soils, taking the 2010–2011 Canterbury Earthquake Sequence as a case study. The validity of standard simplified procedures for high fines content soils is critically evaluated and compared with a finite element model based on a full solid–fluid coupled formulation. The model includes a state parameter-based constitutive law within the generalised plasticity theory, which allows the fines content to be taken into account explicitly. The standard simplified procedures are shown to be less effective in the evaluation of liquefaction potential in soils with high fines content but are still indispensable tools for evaluating the performance of soils over large urban areas. As the main conclusion, it is recommended that empirical models are complemented with an advanced numerical analysis in those cases where silty sands with high fines content are identified, as its outcomes can more realistically represent the soil behaviour during a seismic event

Numerical simulation of observed liquefaction phenomena from the 2011 Christchurch (New Zealand) event

Soil liquefaction at the ground often cause damages to various infrastructure assets. Its consequences have been widely made evident by the performance of the Telecommunication Network Services during the 2010-2011 Canterbury Earthquake Sequence (CES) which stroke the Canterbury region in New Zealand. Despite the relevance of loss of functionality of the telecommunication system, especially during the post-event recovery phase, studies in the literature on the network performance about damages due to liquefaction are still limited. Exploring an unprecedented database of in-situ geotechnical inspections collected after the CES, this research first compares alternative empirical liquefaction-triggering models available in the literature with observation maps. Then, a soil column profile is evaluated adopting a constitutive model based on generalised plasticity (‘modified Pastor-Zienkiewicz’) through a Finite Element based home-developed code. The obtained results from the numerical models are finally crosschecked with the empirical analyses, the existing liquefaction investigation maps and field observations collected in the aftermath of the CES

Why Are Outcomes Different for Registry Patients Enrolled Prospectively and Retrospectively? Insights from the Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF).

Background: Retrospective and prospective observational studies are designed to reflect real-world evidence on clinical practice, but can yield conflicting results. The GARFIELD-AF Registry includes both methods of enrolment and allows analysis of differences in patient characteristics and outcomes that may result. Methods and Results: Patients with atrial fibrillation (AF) and ≥1 risk factor for stroke at diagnosis of AF were recruited either retrospectively (n = 5069) or prospectively (n = 5501) from 19 countries and then followed prospectively. The retrospectively enrolled cohort comprised patients with established AF (for a least 6, and up to 24 months before enrolment), who were identified retrospectively (and baseline and partial follow-up data were collected from the emedical records) and then followed prospectively between 0-18 months (such that the total time of follow-up was 24 months; data collection Dec-2009 and Oct-2010). In the prospectively enrolled cohort, patients with newly diagnosed AF (≤6 weeks after diagnosis) were recruited between Mar-2010 and Oct-2011 and were followed for 24 months after enrolment. Differences between the cohorts were observed in clinical characteristics, including type of AF, stroke prevention strategies, and event rates. More patients in the retrospectively identified cohort received vitamin K antagonists (62.1% vs. 53.2%) and fewer received non-vitamin K oral anticoagulants (1.8% vs . 4.2%). All-cause mortality rates per 100 person-years during the prospective follow-up (starting the first study visit up to 1 year) were significantly lower in the retrospective than prospectively identified cohort (3.04 [95% CI 2.51 to 3.67] vs . 4.05 [95% CI 3.53 to 4.63]; p = 0.016). Conclusions: Interpretations of data from registries that aim to evaluate the characteristics and outcomes of patients with AF must take account of differences in registry design and the impact of recall bias and survivorship bias that is incurred with retrospective enrolment. Clinical Trial Registration: - URL: http://www.clinicaltrials.gov . Unique identifier for GARFIELD-AF (NCT01090362)

A more fine-grained measure towards animal welfare: a study with regards to gender differences in Spanish students

The environmental issue is nowadays taking more importance in the environmental awareness all around the world, and in this field, animal consideration is more and more spread. A highlighted part in globalisation is the animal welfare awareness. This article presents a study comparing attitudes towards animals among secondary and university students in reference to gender. It was carried out on 1394 Spanish participants from 11 to 26 years. The instrument used in the study is the reviewed version of the Animal Welfare Attitude Scale which was renamed as “Animal Welfare Attitude-Revised Scale” (AWA-R Scale), with a Cronbach a reliability value of 0.85. It is subdivided into four components namely C1: animal abuse for pleasure or due to ignorance; C2: leisure with animals; C3: farm animals; and C4: animal abandonment. These components have been deeply detailed by a confirmatory factor analysis (CFA), which highly contributes to define the position of participants for the different dimensions of animal welfare. It is concluded that significant differences exist between males’ and females’ attitudes in all components of the AWA-R Scale. It is also suggested that two social characteristics—people’s attitudes towards animals and towards environmental protection—are, at the very least, coexistent and may indeed be interdependent. These differences between gender in matters of socialisation could thus be reflected in environmental attitudes, and also in others related to them, i.e. animal welfare attitudes

XIII International Conference on Computational Plasticity. Fundamentals and Applications -COMPLAS XIII

ABSTRACT Landslides can cause major economic damage and a large number of casualties as it is possible to see from past events occurred all over the world. Being able to predict these kind of hazards would then suppose the achievement of great benefits. Here a model that combines a depth integrated description of the soil-pore fluid mixture together with a set of 1D models dealing with pore pressure evolution within the soil mass is presented. In this way, pore pressure changes caused by vertical consolidation, changes of total stresses resulting from height variations and changes of basal surface permeability can be taken into account with more precision. The mathematical model is based on the Biot-Zienkiewicz equations, from where a depth averaged model is derived. Concerning the material behaviour, the approach used is the one suggested by the Perzyna viscoplasticity, which has been extensively used in the past to model solid behaviour prior to failure. Three different yield criterion are considered in the framework of Perzyna's model: a Von Mises, a Mohr Coulomb and a Cam Clay yield criterion. The obtained results lead to a good agreement with the results achieved using classical rheological models. Then, a simple shear rheological model is derived, providing the basal friction needed in depth integrated models. The Smoothed Particle Hydrodynamics (SPH) has been the numerical technique chosen to spatially discretised the depth integrated equations of the mathematical model. The SPH technique has been enriched by adding a 1D finite differences grid associated at each SPH node in order to improve the description of pore water profiles in the avalanching soil. The purpose of this work is to apply the SPH depth integrated numerical model, together with the sub-model that predicts the evolution of the pore water pressure inside the landslide, to simulate the propagation phase of the Aberfan flowslide occurred in 1966. REFERENCES [1] M. Pastor, M

Risk profiles and one-year outcomes of patients with newly diagnosed atrial fibrillation in India: Insights from the GARFIELD-AF Registry.

BACKGROUND: The Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF) is an ongoing prospective noninterventional registry, which is providing important information on the baseline characteristics, treatment patterns, and 1-year outcomes in patients with newly diagnosed non-valvular atrial fibrillation (NVAF). This report describes data from Indian patients recruited in this registry. METHODS AND RESULTS: A total of 52,014 patients with newly diagnosed AF were enrolled globally; of these, 1388 patients were recruited from 26 sites within India (2012-2016). In India, the mean age was 65.8 years at diagnosis of NVAF. Hypertension was the most prevalent risk factor for AF, present in 68.5% of patients from India and in 76.3% of patients globally (P < 0.001). Diabetes and coronary artery disease (CAD) were prevalent in 36.2% and 28.1% of patients as compared with global prevalence of 22.2% and 21.6%, respectively (P < 0.001 for both). Antiplatelet therapy was the most common antithrombotic treatment in India. With increasing stroke risk, however, patients were more likely to receive oral anticoagulant therapy [mainly vitamin K antagonist (VKA)], but average international normalized ratio (INR) was lower among Indian patients [median INR value 1.6 (interquartile range {IQR}: 1.3-2.3) versus 2.3 (IQR 1.8-2.8) (P < 0.001)]. Compared with other countries, patients from India had markedly higher rates of all-cause mortality [7.68 per 100 person-years (95% confidence interval 6.32-9.35) vs 4.34 (4.16-4.53), P < 0.0001], while rates of stroke/systemic embolism and major bleeding were lower after 1 year of follow-up. CONCLUSION: Compared to previously published registries from India, the GARFIELD-AF registry describes clinical profiles and outcomes in Indian patients with AF of a different etiology. The registry data show that compared to the rest of the world, Indian AF patients are younger in age and have more diabetes and CAD. Patients with a higher stroke risk are more likely to receive anticoagulation therapy with VKA but are underdosed compared with the global average in the GARFIELD-AF. CLINICAL TRIAL REGISTRATION-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01090362

A State Parameter Based Generalized Plasticity Model for Unsaturated Soils

This paper presents an extension of the Generalized Plasticity model proposed by Pastor - Zienkiewicz in 1986. The extension is based on (i) incorporating a state dependant parameter to model the mechanical behaviour of sand under a wide range of relative densities and confining pressures (ii) the definition of the effective stress of Schrefler (1984) modified to obtain unique CSL for different suction and (iii) the work conjugated variable proposed by Houlsby (1997). Several examples are presented for saturated and unsaturated soils

A reference state curve to define the state of soils over a wide range of pressures and densities

Granular materials exhibit a behaviour that is strongly dependent on density, effective confining pressure and grain characteristics. The complexity is such that, in the past, for a given sand, loose and dense specimens, or specimens subjected to very low or very high confining pressures were considered as different materials and were modelled as such, using different constitutive parameters. The introduction of the state parameter improved both understanding of the behaviour and modelling of granular materials. Several alternative definitions have been proposed for the state parameter but they suffer from some limitations, especially when sand is very loose, has fines, or is subjected to high confining pressures. The purpose of this paper is to describe those deficiencies and to introduce a new state index based on a novel reference state curve. The proposed reference state curve is then applied to understanding and predicting some important aspects of soil behaviour such as: (a) stress ratios at the peak point of undrained effective stress paths and (b) the ‘reverse behaviour’ of sandy soils that show an unusual behaviour in undrained shearing under high effective confining pressure. </jats:p