Sudden Release Of Energy Research Articles

A fast-filament eruption observed in the Hα spectral line

Context. Solar filament eruptions usually appear to occur in association with the sudden explosive release of magnetic energy accumulated in long-lived arched magnetic structures. The released energy occasionally drives fast-filament eruptions that can be the source regions of coronal mass ejections. A quantitative analysis of high-speed filament eruptions is thus essential to help elucidate the formation and early acceleration of coronal mass ejections. Aims. The goal of this paper is to investigate the dynamic processes of a fast-filament eruption by using unprecedented high-resolution full-disk Hα imaging spectroscopy observations. Methods. The whole process of the eruption was captured in a wide spectral window of the Hα line (±9.0 Å), which allowed for the detection of highly Doppler-shifted plasma. By applying the “cloud model” and obtaining two-dimensional optical thickness spectra, we derived the Doppler velocity; the true eruption profiles (height, velocity, and acceleration); and the trajectory of the filament eruption in 3D space. Results. The Doppler velocity maps show that the filament was predominantly blueshifted. During the main and final process of the eruption, strongly blueshifted materials manifest, traveling with velocities exceeding 250 km s−1. The spectral analysis further revealed that the erupting filament is made of multiple components, some of which were Doppler-shifted approximately to −300 km s−1. We found that the filament eruption attains a maximum true velocity and acceleration of about 600 km s−1 and 2.5 km s−2, respectively, and its propagation direction deviates from the radial direction. On the other hand, downflows manifested as redshifted plasma close to the footpoints of the erupting filament move with velocities of 45–125 km s−1. We interpret these redshifted signatures as draining material and therefore as mass loss of the filament, which has implications for the dynamic and the acceleration process of the eruption. Furthermore, we have estimated the total mass of the Hα filament, resulting in ∼5.4 × 1015 g.

Causal Attention Deep-learning Model for Solar Flare Forecasting

Solar flares originate from the sudden release of energy stored in the magnetic field of the active region on the Sun, but the trigger for flares is still uncertain. Currently, deep-learning-based solar flare prediction models have achieved good results and are widely recognized. However, these models focus more on data correlation rather than causality. An ideal flare prediction model should probe into the causes/triggers of solar flares, and diagnose the precursors of flares rather than just correlation analysis. To extract more informative precursors of flares from magnetograms, while suppressing the interference of confounding factors, a causal attention module is introduced to disentangle causal and confounder features from the input features. To address the problem of imbalanced positive and negative samples in the data set, an adaptive data set split mechanism is proposed. It divides the data set into several balanced subsets of positive and negative samples, and dynamically adjusts the subsets according to the model’s prediction results during the training process. The experimental results demonstrate that our proposed model achieves 4.08%, 8.38%, and 2.19% higher accuracy, true skill score, and area under the receiver operating characteristic curve than the baseline model. Additionally, the class-specific heatmaps by using the gradient-weighted class activation mapping method reveal that our proposed model generally focuses on the polarity inverse line of active regions, well in line with theoretical study.

An explanation for the slow-rise phase of solar eruptions

ABSTRACT Solar eruptions are sudden release of the magnetic free energy accumulated within a quasi-static evolutionary process of the corona. Interestingly, many solar eruptions are preceded by a short-term slow-rise phase, during which the pre-eruption structure rises at a speed significantly larger than that of the quasi-static evolution. Here we suggest an explanation for the slow-rise phase based on a recent high-accuracy magnetohydrodynamic simulation for initiation of solar eruption. The simulation shows that by continuously shearing a bipolar magnetic arcade, an internal current sheet forms gradually, and an eruption begins once magnetic reconnection is triggered at the current sheet. We find in the simulation that the overlying field presents a slow-rise phase before the reconnection sets in. In addition, the rising speed is significantly larger than that of the core field during this phase. This slow rise is a manifestation of the growing expansion of the arcade in the process of approaching a fully open field state, which is inherent to the formation of a current sheet before the eruption. We also show three flare events with slow-rise phases that are highly consistent with these key characteristics in the simulation: an expansion of the overlying coronal loops with speeds much larger than the quasi-static evolution speed, and for those events with filament eruption, the slow rise of filament is much smaller than that of the overlying loops. In this type of events, the eruption might be initiated through the mechanism as shown in the simulation, and the expansion of overlying coronal loops is a better indicator of the slow-rise phase.

Strengthening and embrittlement effect of cryogenic temperature on fiber reinforced geopolymer composite

Understanding the cryogenic behaviour of geopolymer composite (GPC) is essential to implement them in real structural elements at cryogenic temperatures. The paper presents a comprehensive investigation on the compressive strength, flexural behaviours, and energy absorption capability of both plain GPC and fiber-reinforced geopolymer composite (FRGPC) containing different fiber types and contents subjected to in-situ −170 °C. The results demonstrate that the compressive strength of plain GPC and FRGPC increases by 104.9 %–213.6 %, and the flexural strength increases by 73.4 %–212.5 %, exhibiting a significant cryogenic strengthening effect. Moreover, compared to flexural strength, compressive strength of GPCs displays a higher sensitivity to the cryogenic strengthening effect. The failure mode of FRGPCs changed from ductile failure to ductile-brittle failure at −170 °C, which is due to the decreased ductility induced by the cryogenic embrittlement effect. Additionally, cryogenic exposure has a greater impact on reducing the ductility of FRGPCs containing PP fibers than those with steel fibers. However, the negative effects of cryogenic embrittlement effect on ductility can be mitigated by incorporating steel fibers and increasing fiber content. The further analysis reveals that strengthening and embrittlement effect are associated with the increased cumulative energy and the sudden release of local energy, respectively. These findings contribute to the understanding of GPC performance at cryogenic temperature, which can guide the development of more resilient and durable GPC for cryogenic applications.

Comparative Seismic Analysis of Regular and Irregular Multistorey Structures with and without Bracings and Shear wall

Abstract Seismic effect is one of the main factors which has to be considered during the design of structure. Earthquake is one of the supreme hazards for living and assets on earth. It is a natural phenomenon, occurring with uncertainties as a result of sudden release of energy within earth crust in the form of seismic waves. As the earthquake forces affects the stability of the building and about 60% of region in our country is under the influence of seismic forces, the buildings are provided with alternatives to withstand the horizontal forces and to increase the strength, stability and stiffness. Present paper investigates the performance of different structures provided with seismic resisting components. In this paper Shear walls and bracings are incorporated to make the structure moment resisting frame. A comparative seismic analysis of high-rise structures with and without shear walls and bracings is included in this discussion which is done using ETABS 2019 software by Response Spectrum Analysis. The parameters considered for analysis are natural frequency, natural time period, base shear, story stiffness, story displacement and story drift. in constructing both.

Impact of the 2008 MW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_W$$\\end{document} 7.9 Great Wenchuan earthquake on South China microplate motion

Tectonic plate motions drive the earthquake cycle, as they result in the slow accrual and sudden release of energy along plate boundaries. Steadiness of plate motions over the earthquake cycle is a central tenet of the plate tectonics theory and has long been a main pillar in models of earthquake genesis, or of plate-margins seismic potential inferred from slip-deficit estimates. The advent of geodesy in the geosciences and the availability of multi-year-long series of position measurements permit tracking the motions of tectonic plates from before to after the time of significant seismic events that occur along their margins. Here, we present evidence that large earthquakes are capable of modifying the motions of entire microplates. We use high precision Global Navigation Satellite System (GNSS) position time-series covering the periods 2001–2004 and 2014–2017 to demonstrate that, contrary to the tenet above, the South China microplate motion changed after the 2008 MW\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_W$$\\end{document} 7.9 Great Wenchuan earthquake. The GNSS data and associated uncertainties indicate a plate motion slowdown of up to 20% that is beyond the possible impact of data noise and is thus tectonically meaningful. We use quantitative models of torque balance to show that generating this kinematic change requires a force upon the South China microplate compatible with that imparted by the Great Wenchuan earthquake of 2008. The existence of a kinematic signal linked to the earthquake cycle that impacts an entire microplate might offer an additional, novel perspective to assessing the hazards of earthquake-prone tectonic regions.

Coal burst mechanism in large-scale panel under extra-thick key strata

Extra-thick key strata (ETKS) are a key factor causing coal bursts. In this study, field monitoring, physical and numerical modelling, and theoretical analysis were comprehensively adopted to investigate the effect of ETKS on the static and dynamic stress and its impact on coal bursts. Firstly, the coal bursts and the stability of ETKS were investigated. The roof strata structure and the mining-induced stress in a large scale panel under ETKS were analyzed. Then, the coal burst mechanism under ETKS is discussed. The results show that when the panel reaches the 4th and 5th longwall faces, the inferior ETKS and the main ETKS break, respectively, and large-scale cantilever-articulated structures involving the ETKS are formed. This moment, the overburden load is transferred downwards massively, and the coal seam becomes overstressed and accumulates massive elastic energy. Meanwhile, the collaborative collapse of multiple strata in the large cantilever-articulated structures causes the sudden release of elastic energy and high-energy seismicity, which exerts strong dynamic disturbances on the overstressed coal mass and leads to coal burst. Finally, strategies for coal burst control under ETKS including deep-hole pre-splitting blasting and panel size optimization are proposed and validated.

Seismic Risk Assessment of Existing Buildings of HSTU Campus in Dinajpur

Bangladesh is at high risk of earthquakes due to its geographic location. Earthquakes can cause widespread damage to buildings and infrastructure, as well as significant loss of life, due to the sudden release of energy in the form of seismic waves. Therefore, identifying and assessing the vulnerability of existing buildings is crucial for earthquake risk reduction. Hajee Mohammad Danesh Science and Technology University (HSTU) is situated just 13 kilometers from Dinajpur, which falls under zone II, a medium-risk zone according to the Bangladesh National Building Code (BNBC, 1993). This study aims to evaluate the seismic vulnerability of HSTU's existing buildings. A widely used seismic assessment technique, the Turkish two-level assessment procedure, was employed in this study to identify seismically vulnerable buildings. A total of 79 buildings were surveyed at level I, considering vulnerability parameters such as soft storey, heavy overhanging, pounding effect, topographic effect, short column, shape of building, number of storeys, apparent quality of building, and soil type. Based on these parameters, performance scores were assigned to each building, and they were classified into damage categories of safe, moderate, and unsafe at level I. Digital photographs of each building from at least two directions were taken for easy identification. All 79 buildings on the HSTU campus were found to be safe after the level I survey. Level II assessment was conducted on only one building to validate the level I findings, and it was classified as a low-risk structure. A significant outcome of this study is the identification of damage categories and the potential to reduce seismic risk at HSTU by creating a comprehensive building inventory.

Dimensionless Parameters for Waveform Characterization of Acoustic Emission Signals: Application to Sedimentation and Soil Compression Experiments

Acoustic Emission (AE) is a non-destructive evaluation method that uses transient elastic waves produced by the sudden release of mechanical energy in a material or structure. This method generates multiple AE events during testing; therefore, it is important to develop parameters that capture the characteristics of each event (AE hit). The paper introduces new dimensionless parameters to characterize the waveform of AE signals: Earliness, Transitoriness, and Early Transitoriness. The study shows that these parameters provide an accurate description of AE waveforms, in some respects, better than traditional parameters, which makes them suitable for filtering with simple rules or in combination with machine-learning techniques. Two examples of the application of AE hit filtering from sedimentation and soil compression experiments are provided. In the sedimentation test analysis, the proposed parameters were used with K-means clustering to filter AE hits from outside the zone of interest and to calculate the rate of sedimentation. In the compression test of a sand sample under oedometric conditions, a simple filtering rule was applied to discriminate AE hits from unwanted sources and obtain a clear AE energy cumulative curve. In both cases, the dimensionless parameters have shown the capacity to discriminate between different AE sources and paths and the possibility of filtering hits from unwanted sources.

Gaussian mixture model in clustering acoustic emission signals for characterizing osteoarthritic knees

High-frequency acoustic waves produced by the sudden release of energy within a material caused by mechanical loading, deformation, corrosion, or other forms of damage are detected by Acoustic Emission (AE). It is a non-destructive testing technique utilized to monitor the structural health of materials and components and to detect and locate defects or damage that could lead to failure. Researchers in the biomedical field have lately focused on AE due to its potential for early detection, tracking, and managing various health issues, such as identifying and evaluating joint disorders, tissue damage, etc. However, due to the variance in AE signals produced from complex structures like knee joints, a general statistical method frequently finds it difficult to differentiate between distinct types of AE signals from different kinds of damage. In such instances, machine learning (ML) and deep learning (DL) can be beneficial for differentiating these signals. In this study, the application of Gaussian mixture model (GMM) clustering with principal component analysis (PCA) for dimension reduction was proposed to detect knee osteoarthritis (OA) from AE data. Four groups of participants, Group A (age 20–39), Group B (age 40–59), and Group C (age 60+), along with diagnosed OA as Group D, were included in this study. Avoiding overlapping AE signal parameters from different groups of participants is a significant challenge. GMM was applied to identify and eliminate the coinciding data points to address this issue. Moreover, the impact of this approach on clustering was also investigated in this research, and by utilizing GMM and PCA, compact clustering of the AE data potentially ensured the efficiency and effectiveness of early diagnosis of OA using the AE Technique (AET).

IMPACT OF HIGH RADIO FREQUENCY SATELLITE OSCILLATIONS ON INITIATING EARTHQUAKES

Advanced satellite technology is worse than all the disasters on Earth due to the lack of dynamic security. The study of earthquakes is the most innovative research of all man-made disasters - no doubt, but there are new horizons of wonder for the thoughtful. Earthquakes are increasing unexpectedly in different countries of the world. People of most countries are worried about sudden earthquakes, but no one is able to reveal the main secret of these earthquakes. Many are blaming nature for this earthquake. Through this survey the exact origin of the matter has been presented to the whole world with proper evidence. Research shows that climate criminals are misusing advanced satellite technology to cause these earthquakes. According to research, misuse of advanced satellite technology causes artificial earthquakes at specific GPS locations on Earth, resulting in severe damage to humans, animals, plants and other objects. The intensity of these earthquakes is so intense that everyone is surprised. Studies have shown that the misuse of satellite technology has caused massive damage in man-made technological earthquake at a particular tectonic plate and other disasters. Due to these sudden earthquake, human suffering increases, standing institutions are demolished, road communication systems are ruptured, crop lands and residential areas are destroyed, individuals lose their lives. The study revealed that artificial earthquakes are caused by sudden radio-waves and strong oscillations of variable magnitude anywhere on earth. The study also showed the climate criminals use various fake messages and wireless tracking to influence policy-makers, the public and the media, as can be doubted in this study, All citizens and administrations should be aware and vigilant to prevent the rise of earthquake terror. The research shows that using advanced satellite technology, earthquakes can be created in time on any tectonic plate on the Earth. Moreover, the question remains that when technology was not invented, but earthquakes occurred - which were natural. Humans now generate artificial oscillations at specific GPS locations through earthquake simulation coding by multiplying the magnetosphere of previous natural earthquakes. The study shows that the EMMAST (Earthquake Mitigation and Management through Advanced Satellite Technology) model will make disaster mitigation systems safer and more efficient, saving millions of lives. The study on earthquakes is unique with world- class scientific research, which will open many research gateways for future generations.

Comparing Gardner-Knopoff, Gruenthal, and Uhrhammer Earthquake Declustering Methods in Aceh, Indonesia

The sudden release of energy from inside the earth, which generates seismic waves, causes earthquakes on the earth’s surface. Foreshock, mainshock, and aftershock are terms commonly used in this subject. These phrases refer to the three stages of an earthquake event—before the main event, the primary event, and after the main event. The earthquake data catalogue, however, typically does not distinguish between mainshock data and foreshocks/aftershocks. For seismic-related studies, justifying the mainshock is very crucial. There are several methods for separating the mainshock of earthquake data from the foreshocks/aftershocks. This study employs three declustering techniques, including Gardner-Knopoff (1974), Gruenthal, and Uhrhammer (1986). The present study collected and analyzed 3543 earthquake events from 1971 to 2021 for Aceh region. In order to determine which method provides the highest a-value and b-value outcomes for Aceh’s seismicity conditions, this study compares the aforementioned three approaches. The Uhrhammer method (1986) has an a-value of 5.82, a b-value of 1.05, 1893 main shock events, 305 clusters, and 3.3 percent of the total seismic moment generated at that location are the findings from this study. According to the Gruenthal method, the results had an a-value of 4.53, a b-value of 0.823, 776 mainshock events, 304 clusters, and released 1.3 percent of the total seismic moment at that location. a-value of 5.1, b-value of 0.929, 1097 main shock events, 319 clusters, and a release of 1.08 percent of the total seismic moment at that location were the results of the Gardner-Knopoff method (1974). For seismic hazard evaluation with the highest level of risk, the Uhrhammer (1986) technique is appropriate. The Gruenthal approach is suggested for more conservative cases.

The Characteristics of Acoustic Emissions Due to Gas Leaks in Circular Cylinders: A Theoretical and Experimental Investigation

An acoustic emission (AE) is caused by the sudden release of energy by a material as a result of material degradation related to deformations, cracks, or faults within a solid. The same situation also occurs in leaks caused by turbulence in the fluid around the leak. In this study, analytical modeling for an AE due to leakage through a circular pinhole in a gas storage cylinder was performed. The displacement fields responsible for AEs, excited by the concentrated force (CF) associated with the turbulent flow though the pinhole, were derived by solving the Navier–Lamé equation. The CF as an excitation source was formulated in terms of a fluctuating Reynolds stress (FRS) and spatial Green’s function. In particular, a series of experiments were conducted under different operating conditions to explore the characteristics of the AE signals due to leak in a gas cylinder. Finally, the simulation and experimental results were compared to verify the accuracy of the simulation results.

Earthquake impact on the stress magnitude at the area of shear zones

Both tectonic activity and geological environment such as faulting and shearing in the rock mass influences the in-situ stress condition in the rock mass. The large-scale earthquakes cause both accumulation and sudden release of strain energy resulting the changes on the magnitude and direction of the in-situ stresses. This is the case in the Himalayan region, where the tectonic movement is active and periodic dynamic earthquakes are common. This manuscript assesses the influence of local shear faults on the in-situ stress condition along the pressure tunnel of Upper Tamakoshi Hydroelectric Project in Nepal. For this a 3D numerical modeling is carried out to assess potential changes in the magnitude of in-situ stresses, in particular the magnitude of minimum principal stress, due to dynamic loading (earthquake).

Earthquake Disaster Risk Analysis for Mitigation Efforts in Seram and Buru Islands, Maluku

Earthquakes occur due to the sudden release of energy from within the earth causing seismic waves. Earthquake activity with a magnitude ³ 3.5 SR is grouped over 21 years from 2000-2020 to determine the level of seismicity in Seram Island, Buru Island, and surrounding areas. The area of seismic activity is clustered over three blocks. The purpose of this research is to determine the seismicity level and mitigation model in each block in the research area. The results showed that seismic activity in the study area with shallow earthquakes was mostly in Block II as many as 1195 times (40.4%) and Block III as many as 1135 times (38.4%). This block is estimated to have the potential for a tsunami to occur. Mitigation efforts to reduce the risk of earthquakes are by implementing a resilient-elastic building system and the location of settlements from the coastline > 100 m with a topography of at least 25 meters

Energy Storage and Release of Class I and Class II Rocks

As underground excavations become deeper, violent rock failures associated with the sudden release of elastic energy become more prevalent, threatening the safety of workers and construction equipment. It is important to figure out the energy-related failure mechanisms of rocks. However, the energy evolution across the complete deformation of different types of rocks and the effect of high confinement on energy storage and release are not well understood in the literature. In this study, a series of cyclic triaxial compression tests were conducted for Class I and Class II rocks to investigate the confinement-dependent characteristics of energy evolution. The results showed that three types of energy evolution were identified as the rock behavior changed from brittle to ductile. The energy storage limit was linearly enhanced by confinement. The nonlinear increase in dissipated energy at peak stress with increasing confinement was suggested to indicate the start of the brittle–ductile transition. The post-peak fracturing process was characterized using the ratio of the local withdrawn elastic energy and fracture energy, and a novel energy-based index was proposed to quantify the failure intensity of the rock. This paper presents a complete investigation of the energy conversion characteristics of the rock, which may shed light on the failure mechanisms of violent rock failures in underground projects.

The F-CHROMA grid of 1D RADYN flare models

Context. Solar flares are the result of the sudden release of magnetic energy in the corona. Much of this energy goes into accelerating charged particles to high velocity. These particles travel along the magnetic field and the energy is dissipated when the density gets high enough, primarily in the solar chromosphere. Modelling this region is difficult because the radiation energy balance is dominated by strong, optically thick spectral lines. Aims. Our aim is to provide the community with realistic simulations of a flaring loop with an emphasis on the detailed treatment of the chromospheric energy balance. This will enable a detailed comparison of existing and upcoming observations with synthetic observables from the simulations, thereby elucidating the complex interactions in a flaring chromosphere. Methods. We used the 1D radiation hydrodynamics code RADYN to perform simulations of the effect of a beam of electrons injected at the apex of a solar coronal loop. A grid of models was produced, varying the total energy input, the steepness, and low-energy cutoff of the beam energy spectrum. Results. The full simulation results for a grid of models are made available online. Some general properties of the simulations are discussed.

A Statistical Search for a Uniform Trigger Threshold in Solar Flares from Individual Active Regions

Solar flares result from the sudden release of energy deposited by subphotospheric motions into the magnetic field of the corona. The deposited energy accumulates secularly between events. One may interpret the observed event statistics as resulting from a state-dependent Poisson process in which the instantaneous flare rate is a function of the stress in the system and a flare becomes certain as the stress approaches a threshold set by the microphysics of the flare trigger. If the system is driven fast, and if the threshold is static and uniform globally, a cross-correlation is predicted between the size of a flare and the forward waiting time to the next flare. This cross-correlation is broadly absent from the Geostationary Operational Environmental Satellite (GOES) soft X-ray flare database. One also predicts higher cross-correlations in active regions where the shapes of the waiting time and size distributions match. Again, there is no evidence for such an association in the GOES data. The data imply at least one of the following: (i) the threshold at which a flare is triggered varies in time; (ii) the rate at which energy is driven into active regions varies in time; (iii) historical flare catalogs are incomplete; or (iv) the description of solar flares as resulting from a buildup and release of energy, once a threshold is reached, is incomplete.

Correlational relationships of intestinal wall parameters after barotraum

Explosions are physical phenomena that lead to a sudden release of energy; they can be chemical, nuclear or mechanical. This process results in an almost instantaneous increase in pressure above atmospheric pressure. Damage to the abdominal organs after the action of explosion factors (shock blast wave, striking elements of the explosive device, secondary shells, chemical and thermal factors) is a fairly common clinical situation. The small and large intestines are the most vulnerable to the impact of a shock blast among the abdominal organs. The aim of the study was a study of the distant consequences of the influence of barotrauma on the morphometric parameters of the intestines of white rats and their correlations. The studies were performed on 20 white outbred sexually mature rats weighing 180-200 g. The wall of the small intestine was stained with hematoxylin and eosin according to the generally accepted method. The thickness of the entire intestinal wall, mucous, muscular and serous membranes, the length and width of the villi, the depth and width of the crypts were determined. Statistical processing of morphometry results was performed using the Statistica 10.0 program. Analysis of histopathological changes in the wall of the small intestine by light microscopy on the seventh day after the impact of the shock air wave on the anterior abdominal wall showed a significant thickening of the mucous membrane, submucosa, muscle membrane compared with the control group of animals. Thickening of the intestinal wall layers occurred due to intercellular edema and edema of stromal elements. At the time of the study, an inflammatory reaction with predominantly neutrophilic infiltration was present in all mucosal, submucosal, and muscular membranes. From the vascular bed in the vessels of the mucous and submucosal membranes, circulatory disorders occurred in the form of plethora and stasis in the vessels of various diameters and affiliations. Thickening of the layers of the intestinal wall occurred due to intercellular edema, swelling of stromal elements. The analysis of the morphometric parameters of the wall of the small intestine showed that in experimental rats after barotrauma simulation, quantitative changes occur at both the cellular and tissue levels, which correlate with the observation period. The muscular shell is subject to more pronounced changes under the action of a shock wave, which is confirmed by morphometric studies and correlation analysis. When conducting a correlation analysis, it was established that all indicators had strong positive relationships with each other, except for the parameter of the thickness of the muscle layer. Changes in the average thickness of the mesenteric layer had a moderate relationship with all parameters except crypt width and mucosal thickness.

Synergies between Heat- and Stress-Induced Spalling Theory Applied to Rock and Concrete in Tunnel Applications

Fire-induced and stress-driven catastrophic failures in rock and concrete are commonly known as spalling (or rockburst in its severe form) that have jeopardised the safety of personnel, seriously damaged rock structures, and shut down operations for months or even permanently in certain circumstances. Particularly in Australia, spalling and rockburst in deep excavations results in a heavy toll on mine safety and have become a constraint to the economic viability of several Australian deep mines since the early 1950s. The prevailing industry approach is to treat such unwanted failures and associated microseismic events as a result of insufficient energy absorption by the spalling-prone rock/concrete at the post-peak stage. However, this approach does not allow efficient handling of heat- or stress-induced failures as it requires an in-depth understanding of their mechanics. Prediction of these events based on the available failure criteria does not help either due to the numerous criteria involved and the difficulty in determining their parameters at the excavation scale. A proper understanding of the fracture growth in such failures is needed to understand the behaviour of rock or concrete structures resulting in a sudden release of energy at deep excavations. This paper investigates the similarities and differences between heat-induced concrete spalling and stress-driven rockburst and further examines the effect(s) of material, geometrical, geological properties, and the applied deviatoric stresses on these failure modes.