116 research outputs found
Mining Safety and Sustainability I
Safety and sustainability are becoming ever bigger challenges for the mining industry with the increasing depth of mining. It is of great significance to reduce the disaster risk of mining accidents, enhance the safety of mining operations, and improve the efficiency and sustainability of development of mineral resource. This book provides a platform to present new research and recent advances in the safety and sustainability of mining. More specifically, Mining Safety and Sustainability presents recent theoretical and experimental studies with a focus on safety mining, green mining, intelligent mining and mines, sustainable development, risk management of mines, ecological restoration of mines, mining methods and technologies, and damage monitoring and prediction. It will be further helpful to provide theoretical support and technical support for guiding the normative, green, safe, and sustainable development of the mining industry
Interpretation of fracture mechanisms in ductile and brittle materials by the Acoustic Emission Technique
Nowadays, the measure of the damage phenomena inside a structure is a complex problem that requires the use of innovative Structural Health Monitoring (SHM) and non-destructive investigation methodologies. The non-destructive method based on the Acoustic Emission (AE) technique has proved highly effective, especially to predict fracture behavior that take place inside a material subjected to mechanical loading.
Objective of the research is to use the Acoustic Emission monitoring to evaluate the fracture propagation process during tensile tests, three-point bending (TPB) tests and compression tests. The most representative AE parameters have been measured by sensors in order to obtain detailed information on the wave propagation velocity, signals localization as well as on the dominant fracture mode. As a matter of fact, the waves frequency and the Rise Angle are used to discriminate the prevailing cracking mode from pure opening or sliding. Moreover, the cumulated number of AE events and their amplitude are used to compute the signal energy. For the three-point bending tests on concrete beams, the energy dissipated to create the fracture surfaces and the energy emitted and detected by the AE sensors have been compared on the basis of their cumulative value at the end of the test and their rate during the process loading, in order to investigate on their correlation.
A numerical simulation of the mechanical response of the TPB tests has been also performed on the basis of the cohesive crack model. This approach has permitted to obtain a step-by-step evaluation of the crack propagation and a more detailed analysis of the mechanical energy dissipation rate during the loading test.
In addition, a dedicated in-situ monitoring at the San Pietro - PratoNuovo gypsum quarry located in Murisengo (AL) - Italy, is started and it is still in progress, developing the application aspects of the AE technique, which has been widely studied from a theoretical and experimental point of view by some Authors in the safeguard of civil and historical buildings.
Preliminary laboratory compression tests on gypsum specimens with different slenderness (λ=0.5, λ=1, λ=2) were conducted to assess the validity and efficiency of the system in view to a permanent installation for in-situ monitoring.
Currently the quarry is subjected to a multiparameter monitoring, by the AE technique and the detection of the environmental neutron field fluctuations, in order to assess the structural stability and, at the same time, to evaluate the seismic risk of the surrounding area
Civil and Environmental Engineering for the Sustainable Development Goals
This open access volume collects emerging issues in Environmental and Civil Engineering, originating from outstanding doctoral dissertations discussed at Politecnico di Milano in 2021. The advanced innovative insights provided are presented with reference to the relevant sustainable development goals (SDGs), hoping that scientists, technicians and decision makers will find them as a valid support to face future sustainability challenges. Indeed, the fast evolution of our society often falls short in properly taking into consideration its relationship with the environment, which is not only the primary source of any resource and the sink of all the wastes we generate throughout our activities, but also the cause of most of the loading and constraints applied to structures and infrastructures. The lack of a proper consideration of the relationship between the needs of both the society and the environment may lead to strong disequilibria, generating a large amount of threats for a robust, resilient and continuous development. In this perspective, the SDGs set by the United Nations represent the criteria to revise our development model, towards the ability to conjugate different needs to build a safe relation between anthropic activities and the environment. Civil and Environmental Engineering plays a relevant role in providing methods, approaches, risk and impact assessments, as well as technologies, to fulfil the SDGs. Research in these fields may in fact provide technical knowledge and tools to support decision makers and technicians in: (i) planning mitigation and adaptation actions to climate change, extreme weather, earthquakes, drought, flooding and other natural disasters; (ii) designing efficient and sustainable strategies for resources exploitation, minimizing the impact and the unequal distributions; (iii) increasing the safety of structures and infrastructures under exceptional loadings and against the deterioration due to their lifecycle; (iv) adopting a holistic risk management approach and appropriate technologies to reduce pollution and environment deterioration, which increase vulnerability; (v) providing a safe drinking water and sanitation system to protect human health
Fracture characterisation and performance evaluation of corroded RC members by AE-based data analysis
Steel reinforcement corrosion has been regarded as one of the major causes of
reinforced concrete (RC) structures failing prematurely, posing a serious structural
durability problem worldwide. Detailed assessment of corrosion-induced damage and
its effects on RC structures is critical for sustaining structural reliability and safety. This
study develops and examines the feasibility of acoustic emission (AE) monitoring and
data analysis methodologies to characterise corrosion-induced damage in RC
members, followed by an evaluation of the effect of corrosion on load behaviour.
Experimental investigations were conducted on a series of specimens of different
configurations, namely concrete cubes with steel bars for pull-out tests and RC beams
of different dimensions to be subjected to static and cyclic loading regimes. Focusing
on developing evaluation methods based on AE monitoring and data analysis, a
summary of work completed, and the associated findings are given as follows.
Characterisation of the concrete cracking using parametric and waveform analysis
was conducted to investigate the effect of corrosion on steel-concrete bond behaviour
in the pull-out tests of concrete cubes. It was found that a small amount of corrosion
(approximately 6%) could slightly increase the bond strength as a result of the rust
expansion and reactionary confinement of concrete. Corrosion was also found to be
able to mitigate the damage caused by cyclic loading. AE signal analysis indicates that
the concrete cracking mode during the steel-concrete de-bonding process has
changed as a result of steel corrosion.
Characterisation of load behaviour and failure mode of corroded RC beams was
conducted by flexural load tests aided by AE monitoring and digital image correlation
(DIC). The DIC strain mapping results and AE signal features revealed that corrosion
has an influence on the concrete cracking mechanism of the beam specimens.
Corrosion has also altered the failure mode of a shear-critical beam specimen series
to flexure owing to the change of steel-concrete bond behaviour.
Numerical simulation of AE wave front propagation in RC media and tomographic
evaluation of internal damage was implemented on one group of RC beam specimens
tested in this study. The numerical model of the specimens was discretised using
finite-difference grid meshing, and the different acoustic properties of steel and
concrete were defined. On this basis, simulation of AE wave front propagation
considering concrete cover cracking and steel rust layer formation was carried out
using the fast-marching method. The effect of corrosion-induced damage on the AE
rays was studied by examining non-linear ray tracing in the simulation. A tomographic
reconstruction approach that solved by the quasi-Newton method provided a potential
way to quantitatively evaluate the internal damage of RC beams using AE monitoring
data.
A novel method was developed for assessing the corrosion level in RC beams using
a data-driven approach. Normalization of AE data was applied using principal
component analysis to minimise variations in AE signal features caused by differences
in the geometrical and material properties of RC beams as well as in the AE monitoring
instrumentation setup. The machine learning models, including k-nearest neighbours
(KNN) and support vector machines (SVM), were trained using the normalised AE
features. The trained KNN models were found effective at predicting the corrosion
level in RC beams using the secondary AE signals as input, which could be acquired
from the cyclic loading of beams.
Key words: Steel Corrosion, Concrete cracking, Steel-Concrete Bond, Reinforced
Concrete Beam, Load Behaviour, Acoustic Emission, Digital Image Correlation,
Tomographic Reconstruction, Data-driven
Acoustic and Elastic Waves: Recent Trends in Science and Engineering
The present Special Issue intends to explore new directions in the field of acoustics and ultrasonics. The interest includes, but is not limited to, the use of acoustic technology for condition monitoring of materials and structures. Topics of interest (among others): • Acoustic emission in materials and structures (without material limitation) • Innovative cases of ultrasonic inspection • Wave dispersion and waveguides • Monitoring of innovative materials • Seismic waves • Vibrations, damping and noise control • Combination of mechanical wave techniques with other types for structural health monitoring purposes. Experimental and numerical studies are welcome
Proceedings of the 8th International Conference on Civil Engineering
This open access book is a collection of accepted papers from the 8th International Conference on Civil Engineering (ICCE2021). Researchers and engineers have discussed and presented around three major topics, i.e., construction and structural mechanics, building materials, and transportation and traffic. The content provide new ideas and practical experiences for both scientists and professionals
Evolution, Monitoring and Predicting Models of Rockburst: Precursor Information for Rock Failure
Load/unload response ratio predicting of rockburst; Three-dimensional reconstruction of fissured rock; Nonlinear dynamics evolution pattern of rock cracks; Bayesian model for predicting rockburs
Proceedings of the 8th International Conference on Civil Engineering
This open access book is a collection of accepted papers from the 8th International Conference on Civil Engineering (ICCE2021). Researchers and engineers have discussed and presented around three major topics, i.e., construction and structural mechanics, building materials, and transportation and traffic. The content provide new ideas and practical experiences for both scientists and professionals
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