A probabilistic approach for the evaluation of the stabilizing forces of fully grouted bolts

The essential task of the ground reinforcement techniques is to keep the rock as stable as possible. In particular passive rock bolt should resist the rock movements along its entire length and through the resulting reaction forces, to improve the load-bearing capacity of the rock. Among different calculation techniques, the calculations based on Block Reinforcement Procedure (BRP) was used in this paper, also adopting some simplified equations available in the scientific literature. However, parameters influencing the interaction are difficult to evaluate. Therefore, the problem of the reliable definition of the parameters that most influence the behavior of the bolts and the evaluation of the stabilizing forces of the potentially unstable block of rock remains. A new probabilistic approach is presented in this article, able to appropriately manage the uncertainties present on the fundamental parameters of the bolt-rock interaction and on the mechanical characteristics of the sliding surface of the block. Through the use of a Monte Carlo procedure, in fact, it was possible to obtain different samples of the safety factors of the rock block, one for each diameter of the steel bars used for its stabilization. Finally, the probabilistic management of the safety factor samples allowed the correct design of the steel bars, by evaluating the probability that the safety factor of the block with regard to potential slipping has a value lower than a pre-established limit. The probabilistic approach developed was applied to a real problem of stabilization of a potentially unstable rock block due to planar sliding, present on a municipal road in North Italy

A simplified mathematical approach for the evaluation of the stabilizing forces applied by a passive cemented bolt to a sliding rock block

Passive bolting is used to stabilise unstable rock blocks in surface and underground structures due to the various advantages it offers. Despite its use, the design phase still presents aspects of considerable complexity because the fact that the load of the bolt and therefore, its static action depends on its interaction with the block and the stable rock. In the present work, a mathematical model was developed which is capable of directly calculating the stabilisation forces as a function of the characteristic parameters of the bolt and of its interaction with the rock. This discussion is based on a simplified hypothesis of bolt behaviour, which provides negligible errors, and on the observation that the critical point is positioned at the intersection of the bolt with one of the lateral surfaces that separate it from the portion of stable rock. The formulation of the stabilisation forces obtained made it possible to evaluate the static contribution of each single bolt to the stability of the rock block, by varying the diameter of the steel bar and then designing the bolting operation to achieve acceptable stability conditions for the rock block. The application of stabilising equations to a real case, for which the results of load tests on bolt tests were available, allowed us to outline steps to be taken in the bolt design process

A fracture mechanics model to study indentation cutting

Many cutting processes, such as chopping, slicing, and carving, consist in 2 different stages: an initial stage of indentation, in which the cutting tool is pushed into the material under the action of an external force, and a second stage, where the target material undergoes a progressive separation. This second stage is characterised by the formation of a fracture surface followed by the cut propagation due to the increasing external force, until eventually a steady state might occur. The purpose of this paper is to analyse the cutting process by means of some concepts of fracture mechanics and discuss the occurrence of the steady state. A simple model is used to obtain an analytic expression of the stress intensity factor at the tip of the cut and investigate the evolution of the fracture process. It is found that the cut propagation depends on the wedge sharpness. The analytic results are compared with finite element analyses, where the effect of tip blunting due to plasticity is taken into account. The influence of the cutting tool geometry is also discussed

on the fracture processes of cutting

Abstract: The process of cutting is treated as a fracture mechanical process. For an elliptic rigid wedge pressed into an elastic material, fracture may occur as an autonomous process if the tip of the wedge is sufficiently blunt or is affected by the geometry of the wedge if the tip is sharp. The conditions leading to the former or the latter case is obtained as a relation between the wedge tip radius, the fracture toughness and the modulus of elasticity. These limits and the intermediate states are discussed. The implications of the drastic changes of the mechanical state of the near tip region when the wedge edge is sharp are also discussed

Psychometric properties of a Portuguese version of the Subjective Happiness Scale

The Subjective Happiness Scale (SHS) constitutes an instrument for assessing subjective happiness. This study aims to present the validation of the SHS in a Portuguese adult population. A large representative sample (1,017 participants), from five different age groups was considered. Configurational invariance of the unidimensional structure of the scale was tested through multi-group confirmatory factorial analysis, and reliability and criterion-validity were investigated. The results support the single factorial structure and reliability of the SHS. Furthermore, the SHS correlated positively with the Satisfaction with Life Scale, thus supporting its criterion validity. Therefore, the Portuguese version of the SHS is a valid instrument to use with an adult Portuguese Sample.info:eu-repo/semantics/publishedVersio

Entrepreneurial self-efficacy in Italy: an empirical study from a gender perspective

Entrepreneurial self-efficacy (ESE) is a key factor for the promotion of entrepreneurship. Literature emphasizes the need for and, indeed, recommends a gender perspective in the study of ESE. The aim of this study is twofold: To begin analyzing some of the psychometric properties of the McGee, Peterson, Mueller, and Sequeira (2009) ESE scale in the Italian context, and to explore the gender differences in the ESE levels in an Italian sample of entrepreneurs and non-entrepreneurs. Confirmatory factor analysis, multigroup confirmatory factor analysis and a 2 × 2 MANOVA were conducted. The results support the possible use of McGee et al.'s ESE scale in the Italian context. Furthermore, they reveal that the gender difference in the sample of non-entrepreneurs is greater than in the entrepreneur sample. The main practical implication is that women entrepreneurs should receive specific training both before and after creating a new venture.info:eu-repo/semantics/publishedVersio

Influence of Acute Resistance Training on Memory, Executive Function, and Mood

Click the PDF icon to download the abstract

A daily diary investigation on the job-related affective experiences fueled by work addiction

Background and aims: We studied the quality of the job-related emotional experiences associated with work addiction. We hypothesized that work addiction would fuel both a higher level of daily job-related negative affect and a lower level of daily job-related positive affect and that such affective experiences would mediate the relationship between work addiction and emotional exhaustion reported at the end of the working day. Additionally, in light of typical behaviors and cognitions associated with work addiction, we also hypothesized that work addiction would modify the relationships between day workload and same day emotional strain reactions (i.e., job-related negative affect and job-related positive affect). Methods: Participants were 213 workers (42.5% female), most of whom holding a high-profile job position, who were followed for 10 consecutive working days in the context of a daily diary study. Results: Multilevel analyses controlling for neuroticism revealed that work addiction was uniquely and positively related to daily job-related negative affect and that the latter mediated the relationship between work addiction and daily emotional exhaustion. On the other hand, work addiction was not negatively related to daily job-related positive affect; this relationship emerged only when removing neuroticism from the model. Additionally, work addiction strengthened the relationship between day workload and day job-related negative affect. Discussion: Results indicate that work addicted are characterized by the experience of a negatively connotated affect during work, and that this kind of affect may be a mechanism explaining the work addiction-burnout relationship

The good, the bad and the blend: The strategic role of the “middle leadership” in work-family/life dynamics during remote working

The ongoing epidemiological crisis has suddenly steered us towards a new futuristic work scenario in which most service sector employees work remotely, which could be a permanent reality for most service sector employees. This paper focuses on the strategic role that leadership could play in the radical change process that is taking place in work environments. Particular attention was paid to the role of ‘middle managers’ who perform an important function as a link between the strategic vision of top management and the workforce. In addition, special attention was paid to gender differences in work-life dynamics, which are particularly relevant in countries with traditional cultural identities. As this is a conceptual contribution, the most recent studies on this specific role of middle managers have been taken into account and embedded in the current scenario. Therefore, the main contribution in terms of originality was that the current review aimed to leverage such a legacy of knowledge and create a system of evidence-based practical implications for effectively supporting change in organizational culture through the identification of the most appropriate middle management leadership models for remote working that could prevent and/or limit any psychosocial risks (e.g., workaholism and technostress) and longer-term outcomes such as sustainable work-life interface

Evaluation of the safety factors of shotcrete linings during the creep stage

Sprayed concrete linings (SCLs) used in tunnels generally develop secondary deformations over time, even in the presence of constant stress levels within the lining. These deformations influence the loading process on the lining and therefore also the stress levels within the support structure. The behaviour of a SCL in a tunnel was investigated under different operating conditions in order to evaluate the effect of secondary deformations on the evolution of stability conditions (safety margins with respect to the possible concrete failure) over time, after completion of the tunnel construction. A parametric analysis was performed to study eight different types of tunnels, with variable geometry and rock quality, and eight different types of sprayed concrete. The 64 cases of the parametric analysis covered the vast range of variability of influential parameters and yielded useful information concerning the effects of secondary deformations over time on the static behaviour of the lining and on the safety factor with reference to the possible failure of the sprayed concrete