Large Collapse Research Articles

Prediction Method of Three‐Dimensional Crack Propagation Path Based on Deep Learning Application

In engineering, most structural components suffer from local damage in service or fabrication. Under different loading conditions, such local damage will further expand to large cracks and structural collapse. For ensuring longevity and reliability, the study of brittle crack growth is important. In structural damage prediction, various methodologies are commonly used and have demonstrated success in the past. Most traditional simulation methods, however, have the problems of large calculation quantities and long calculation times. At the same time, the mutual influence of crack opening stress and crack image on crack widening is rarely considered in existing works based on the deep learning framework. Herein, a deep learning model is developed to predict the spread of fracture of brittle materials under stress to improve the aforementioned problems. By developing a nonlinear relationship between crack stress and damage effects, this approach predicts crack growth, thus avoiding the loss of required information on crack growth behavior. The model emphasizes repeatability and extensibility, which is verified using extended finite element method (XFEM) Abaqus software through multiple sets of material crack data generated. This model's potential applications are material design and evaluation of residual life.

Pressure-induced octahedral tilting distortion and structural phase transition in columbite structured NiNb2O6

High-pressure behavior of the technologically important compound NiNb2O6 adopting a columbite-type orthorhombic structure at ambient pressure and temperature conditions was investigated using synchrotron x-ray powder diffraction, Raman spectroscopic measurements, and first-principles calculations. The x-ray diffraction data indicate the occurrence of irreversible pressure-induced structural phase transition in the studied compound beyond 9 GPa. The high-pressure phase is found to be monoclinic with space group P2/m. The large volume collapse (∼4.4%) at the transition indicates the nature of the transition to be of the first order. There is a change in oxygen anion coordination number around Nb from 6 to 8; however, the coordination number around Ni remains 6. The experimental pressure–volume data when fitted to the Birch−Murnaghan equation of states yield the value of ambient pressure bulk modulus (B0) as 178.7 (17) GPa for the orthorhombic phase and 244 (6) for the high-pressure monoclinic phase. The changes in Raman spectra indicate the distortion of NbO6 octahedra resulting in structural phase transitions. The logarithmic variation of unit cell volume (V) with optical lattice mode frequency (ν) helped us to calculate their respective Grüneisen parameters (γ) and it also supports the instability of the orthorhombic columbite structure of NiNb2O6 beyond 9 GPa, originated due to strong octahedral deformation of NbO6 octahedra. The variation of structural, electronic, and optical properties with pressure has also been discussed through first-principles calculations based on density functional theory using the revised Perdew–Burke–Ernzerh of generalized gradient approximation. The theoretical bandgap collapses and the distortion of NbO6 octahedra through the O chains with pressure are emphasized from the density of states data.

Conditions of inertial-viscous transition and related jetting in large cavity collapse

Viscosity and surface tension of fluids regulates the collapse dynamics of a large cavity where collapse is initially inertial with the minimum radius ${r}_{m}\ensuremath{\sim}({t}_{0}\ensuremath{-}t{)}^{1/2}$, where ${t}_{0}\ensuremath{-}t$ is the time remaining for collapse. In low-viscosity fluids, an inertial-capillary transition occurs (exponent changes from 1/2 to 2/3), while it is inertial-viscous (exponent changes from 1/2 to 1) in viscous fluids at a late stage of collapse. The inertial-viscous transition occurs when the local capillary number is greater than 1 and the local Ohnesorge number is greater than 0.1.

Pressure-Induced Phase Transition in Mn(Ta,Nb)2O6: An Experimental Investigation and First-Principle Study.

The high-pressure and high-temperature behaviors of manganotantalite Mn(Ta,Nb)2O6 have been investigated by single-crystal X-ray diffraction and Raman spectroscopy combined with diamond anvil cell technique, as well as first-principle calculations. A pressure-induced reversible phase transition of manganotantalite occurs at 9.5 GPa and room temperature, accompanied by a large volume collapse (∼7.0%) and drastic color change from brownish-yellow to red. The space groups of low-pressure (LP) and high-pressure (HP) phases are the same (Pbcn), but the coordination numbers of Mn increase from six to eight and Ta increase from six to seven, respectively. The band gap becomes narrow from 2.37 to 1.59 eV. We determined the P-T phase diagram of manganotantalite with a positive Clapeyron slope of dP/dT = 0.0073 GPa/K. The P-V data were fitted to a second-order Birch-Murnaghan equation of state with B0 = 149(4) GPa for the LP phase and B0 = 188(3) GPa for the HP phase. The isothermal Grüneisen parameters were determined to be 0.23∼2.03 of the LP phase and 0.59∼0.86 of the HP phase for Raman modes. High-pressure behaviors of Mn(Ta,Nb)2O6 indicate that this kind of material is a potential effective pressure sensor to monitor pressure change or warn pressure abnormality.

All-Nitrogen Cages and Molecular Crystals: Topological Rules, Stability, and Pyrolysis Paths

We combined ab initio molecular dynamics with the intrinsic reaction coordinate in order to investigate the mechanisms of stability and pyrolysis of N4 ÷ N120 fullerene-like nitrogen cages. The stability of the cages was evaluated in terms of the activation barriers and the activation Gibbs energies of their thermal-induced breaking. We found that binding energies, bond lengths, and quantum-mechanical descriptors failed to predict the stability of the cages. However, we derived a simple topological rule that adjacent hexagons on the cage surface resulted in its instability. For this reason, the number of stable nitrogen cages is significantly restricted in comparison with their carbon counterparts. As a rule, smaller clusters are more stable, whereas the earlier proposed large cages collapse at room temperature. The most stable all-nitrogen cages are the N4 and N6 clusters, which can form the van der Waals crystals with densities of 1.23 and 1.36 g/cm3, respectively. The examination of their band structures and densities of electronic states shows that they are both insulators. Their power and sensitivity are not inferior to the modern advanced high-energy nanosystems.

Satellite radar observation of large surface collapses induced by the 2017 North Korea nuclear test

The artificial earthquake of mb 6.1 related to the North Korea’s sixth nuclear test occured at Mt. Mantap, North Korea on September 3, 2017. It was reported that a large and complex surface deformation was caused by the event. The surface deformation was composed of expansion of explosions, collapse, compaction and landslides. Since the precise vertical deformation measurement is very important to estimate the stability of the nuclear test facility, we retrieved a precise 3D surface deformation field and then decomposed the vertical deformation pattern from the 3D deformation. The measured maximum deformation was about − 491, − 343 and 166 cm with the measurement uncertainty of about 3.3, 4.1 and 2.7 cm in the east, north and up directions, respectively. The maximum horizontal deformation was approximately 515 cm. The horizontal deformation clearly showed a radial pattern because it was mainly caused by the explosions and landslides, while the vertical deformation displayed a rugged pattern because it was affected by the explosions, compaction and collapse. The collapse may seem to occur along the underground tunnels and at the test site’s epicenter as well. Moreover, the severe collapse was observed westside from the epicenter of the sixth nuclear test, and it has a depth of about 68.6 cm on the area of 0.3765 km2. On the basis of our results including the shapes, locations and volume changes of the large collapse, evidently a new vital piece of information was obtained so that it could be used to interprete the sixth nuclear test more accurately.

Editorial: Flank dynamics, sector collapses, lahars, and rockfalls: analysis, monitoring, and modelling of small to large scale volcanic slope instability

Slope dynamics in volcanic environments comprise a wide spectrum of phenomena, from large lateral collapse to shallow debris remobilization, which may represent a major threat for human communities and infrastructures. Many volcanos built up from the ocean floor and large portions of the volcano edifice are submerged. In these settings, only the edifice’s summit can be investigated by terrestrial remote sensing and in-situ approaches. Growth and destruction, including tectonics and gravitational phenomena, affect entire volcano flanks and are not limited to the physical boundary of the sea level but could comprise their subaqueous parts

Seismic Collapse Assessment of Composite Plate Shear Walls

Collapse evaluation of composite plate shear walls (C-PSWs) under seismic loading requires a reliable analytical model that can accurately capture deterioration in the strength and stiffness of the system. In this study, research was carried out to develop a macromodeling approach for C-PSWs. Nonlinear time history analyses of six multistory (7-, 10-, and 13-story) C-PSWs (traditional and innovative) located in Western Canada were performed. It was observed that a significant portion of the story shear was resisted by the boundary members, while the RC panel resisted less than 10% of the total story shear. To estimate the seismic response parameters (i.e., ductility-related and overstrength-related force modification factors) for designing C-PSWs, incremental dynamic analysis (IDA) was performed for all archetypes following a standard procedure. It was observed that all archetypes provided significant safety margin against collapse (large collapse margin ratio). In addition, a sensitivity study was conducted and the effects of postyielding parameters (ductility capacity and postcapping stiffness) adopted for the deterioration model for infill plate and postcracking parameters (shear strain corresponding to maximum shear stress, yielding shear strain, and residual stress) adopted for the deterioration model for RC panel on seismic collapse capacities of traditional C-PSWs were investigated. It was observed that postyielding parameters for the steel infill plate can affect the seismic response of C-PSWs. On the other hand, variation of postcracking parameters for the concrete panel had a minor effect on seismic collapse capacity of the C-PSW system.

Preliminary Results of an Experiment to Determine the Thickness of Snow Cover Using Ground Penetrating Radar and a Laser Rangefinder

The article discusses the combination of a ground penetrating radar (GPR) with a laser rangefinder to determine the snow cover thickness, an experiment is described in accordance with the proposed methodology and a comparative analysis of the data obtained is carried out. The purpose of the proposed development of the combined method is to improve the accuracy of snow cover depth determination. Many tasks require high spatial resolution both in the horizontal coordinate and in the depth of the snow cover, since local excess of its critical level can lead to irreversible consequences. Such a situation can arise, for example, when avalanches come down in mountainous areas or when roofs of a large area collapse when snow accumulates on them. The accuracy of the snow depth determination obtained in the experiment is ∼ 10 cm and the resolution along the horizontal coordinate is ∼ 5 cm. The predicted distance based on the equipment used is about 500 meters. The proposed method can be used for determining the amount of snow on roofs of buildings and structures, as well as in predicting the descent of avalanches, and in search for hidden objects under the snow in emergency situations.

Load reduction algorithm for power grid low-frequency optimization

Dynamic monitoring and effective control of system frequency is the key to ensure the normal operation of power system. In this paper, a hierarchical load shedding algorithm model is constructed, which can prevent the frequency from continuously decreasing when the system affects stability due to increased load, so as to avoid large area blackouts and system collapse. It is of great significance to the safe and stable operation of power system and the national economy. It has opened up a train of thought for studying the current system frequency control methods in smart grid.

Pressure-induced structural transition and metallization in MnSe2

The high-pressure behavior of manganese diselenide MnSe2 was investigated by synchrotron angle-dispersive X-ray diffraction (ADXRD) and infrared reflection spectroscopy equipped with a diamond-anvil cell. It was found that MnSe2 with a pyrite-type structure undergoes a transformation into a disordered intermediate phase at ~ 12.5 GPa, with a ground state composed of an arsenopyrite-type structure, as confirmed by laser-heating treatment. The pyrite to arsenopyrite phase transition was found to be coupled to a large collapse in the unit-cell volume (∆V ~ 19%) and an electronic transition from a high-spin to low-spin state for manganese cations (Mn2+). With a fixed value for the pressure derivation of the bulk modulus K' = 4, fitting of the pressure–volume data to a second-order Birch–Murnaghan equation of state yielded isothermal bulk modulus values of K0 = 56.1(9) GPa and K0 = 93.1(4) GPa for the pyrite-type and arsenopyrite-type phases, respectively. The measured infrared reflectivity (Rsd) for MnSe2 showed a drastic increase at pressures between 13 and 20 GPa, but became insensitive to pressure under further compression, implying a pressure-induced transition from an insulator to metallic state.

Study on the Manifold Cover Lagrangian Integral Point Method Based on Barycentric Interpolation

To achieve numerical simulation of large deformation evolution processes in underground engineering, the barycentric interpolation test function is established in this paper based on the manifold cover idea. A large-deformation numerical simulation method is proposed by the double discrete method with the fixed Euler background mesh and moving material points, with discontinuous damage processes implemented by continuous simulation. The material particles are also the integration points. This method is called the manifold cover Lagrangian integral point method based on barycentric interpolation. The method uses the Euler mesh as the background integral mesh and describes the deformation behavior of macroscopic objects through the motion of particles between meshes. Therefore, this method can avoid the problem of computation termination caused by the distortion of the mesh in the calculation process. In addition, this method can keep material particles moving without limits in the set region, which makes it suitable for simulating large deformation and collapse problems in geotechnical engineering. Taking a typical slope as an example, the results of a slope slip surface obtained using the manifold cover Lagrangian integral point method based on barycentric interpolation proposed in this paper were basically consistent with the theoretical analytical method. Hence, the correctness of the method was verified. The method was then applied for simulating the collapse process of the side slope, thereby confirming the feasibility of the method for computing large deformations.

Airblasts caused by large slope collapses

AbstractLarge slope collapses have been known to trigger extreme rushes of air loaded with projectiles (airblasts) capable of causing destruction and fatalities far beyond run-out of the rock mass. An appraisal of the likelihood of a destructive airblast should be a component of landslide risk assessments. Yet there is an absence of risk studies directly examining landslide-related airblasts. In this work we back-analyze an unreported airblast in the Sikkim Himalayas (India) and several other airblasts documented around the world. We explore the conditions a large slope collapse should meet to trigger a significant airblast, and we establish a semi-empirical relationship linking the potential energy in a collapse with airborne trajectory and the extent of the related airblast. The collapse of thousands or millions of cubic meters falling from a significant height results in a sudden release of energy (1011J to 1013J) and a high degree of comminution of rocks, causing a violent displacement of air. Average wind speeds of airblasts following impacts with airborne trajectory can be double the speed of rock avalanches. The size of the damage zone depends on the potential energy of the falling rock mass and can be amplified or reduced depending on how confined the valley is where the airblast occurs.

Characterization of the 2008 Phreatomagmatic Eruption of Okmok From ArcticDEM and InSAR: Deposition, Erosion, and Deformation

AbstractOkmok volcano, one of the most active volcanoes in the Aleutian Islands, erupted between 12 July and 19 August 2008 and produced a new tephra cone (Ahmanilix) up to 253 m high. A coeruptive deposit thickness map and the posteruptive elevation change rate map are generated for this phreatomagmatic eruption using the new, high‐resolution (2 m) digital elevation model (DEM) time series provided by ArcticDEM. The total dense rock equivalent (DRE) volume over the proximal deposit field classified from the elevation change map is estimated as 0.147 ± 0.001 km3 DRE (bulk volume of 0.453 ± 0.003 km3). Combined with the distal deposit volume derived from field measurements, the total DRE is 0.25 km3 (bulk volume of 0.76 km3). The estimated erosion rate is up to −15 ± 3 m/year along the flanks of Ahmanilix, and the redeposition rate is about 1 ± 0.3 m/year at the base and 6 ± 1 m/year within the center of Ahmanilix. The surface elevation change also reveals a large ground surface collapse that disrupted the old Cone D lava bench, with a total collapse area of 0.15 km2 and a volume of (7.1 ± 0.4) × 10−3 km3. We also produce a coeruptive deformation map from satellite interferometric synthetic aperture radar (InSAR) using topography from both ArcticDEM and the Shuttle Radar Topography Mission (SRTM) and compare the results. Finally, based on historical eruption volumes, the magma supply rate at Okmok is estimated as (1.77 ± 0.1) × 10−3 km3/year.

Economic impact of electricity supply interruptions in South Africa

In past studies on the costs of interruptions of electricity supply in South Africa, the concepts of sporadic and chronic interruptions were introduced. Cost was modelled using different parameters, and the measurement of customer interruption cost (CIC) was acquired through surveys. Rotational load shedding, as experienced during more than a decade in South Africa, shares many characteristics with chronic interruptions and large system collapse scenarios. Since CIC data are based on electricity customers' valuations of their impacts from electricity interruptions, and allow only for a bottom-up estimation of the economic cost of large electricity interruption events (without considering sectoral interdependencies), an alternative assessment of the cost using a suitable macroeconomic model that employs less subjective data allows for a validation of CIC-based results and a determination of a plausible range of estimates of the cost of large electricity interruptions. We test this proposition using a combination of a time-dependent probabilistic CIC model based on CIC survey data, and a dynamic inoperability input-output model (DIIM) that accounts for sectoral interdependencies, economic resilience and the temporal variation of electricity interruption impacts. The results lead to estimates of the costs of large interruptions of electricity supply in South Africa.

Vertical and Inclined Lime Injected Piles Under Footing Resting on Collapsing Soil

Gypseous soil, as one type of collapsible soils, is widely separated in Iraq. Gypsum concentrations of more 60% are not uncommon, and such soils are present in the western and northern parts of this country. Distresses in engineering facilities resulting from high collapse settlements are well known by the locals and as such causing much financial problems in government and private sectors. Soil improvement and replacement techniques are used as a result of tackle the large collapse of the soil. This laboratory research is directed in using lime piles to reduce the collapse potential of the gypseous soil. A comparison study is conducted between vertical lime piles and inclined lime piles. The inclination angle is chosen arbitrarily to be 30° to the vertical. A plain strain footing is used to simulate the separate foundation having length-to-width ratio (L/B) of 4. Three spacing patterns are used for each case of lime piles, namely B/3, B/2 and B. Test results reveal that inclined lime piles have much advantage over the vertical ones in reducing the collapse potential. Measured improvements in reducing settlement for inclined over vertical lime piles are 42% for spacing of B/3, 46% for spacing of B/2 and 27% for B. Unfortunately, the presence of lime piles has been found experimentally to increase the settlement in case, the collapsing soil is in dry condition compared to the untreated soil.

Pressure-Induced Metallization and Structural Phase Transition in the Quasi-One-Dimensional TlFeSe2**Supported by the National Key R&D Program of China (2018YFA0305700), the National Natural Science Foundation of China (11904391, 11834016, 11874400, 11888101, 11921004), the Beijing Natural Science Foundation (Z190008), the Strategic Priority Research Program and the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (XDB25000000, QYZDBSSW- SLH013), and

We report a comprehensive high-pressure study on the monoclinic TlFeSe2 single crystal, which is an antiferromagnetic insulator with quasi-one-dimensional crystal structure at ambient pressure. It is found that TlFeSe2 undergoes a pressure-induced structural transformation from the monoclinic phase to an orthorhombic structure above Pc ≈ 13 GPa, accompanied with a large volume collapse of ΔV/V0 = 8.3%. In the low-pressure monoclinic phase, the insulating state is easily metallized at pressures above 2 GPa; while possible superconductivity with K is found to emerge above 30 GPa in the high-pressure phase. Such a great tunability of TlFeSe2 under pressure indicates that the ternary AFeSe2 system (A = Tl, K, Cs, Rb) should be taken as an important platform for explorations of interesting phenomena such as insulator-metal transition, dimensionality crossover, and superconductivity.

The Great Recession and a Missing Generation of Exporters

While the large collapse in aggregate international trade volumes during the Great Recession has been widely studied in the literature, the recovery is much less well understood. Indeed, by 2014 U.S. foreign sales were still below their historical post-recession level. In this note, we summarize the results of Lincoln, McCallum, and Siemer (2019), which considers how much of a role a "missing generation of exporters" played in explaining the relatively slow growth of foreign sales after the financial crisis.

Six‐Axis Ground Motion Measurements of Caldera Collapse at Kīlauea Volcano, Hawai'i—More Data, More Puzzles?

AbstractNear‐field recordings of large earthquakes and volcano‐induced events using traditional seismological instrumentation often suffer from unaccounted effects of local tilt and saturation of signals. Recent hardware advances have led to the development of the blueSeis‐3A, a very broadband, highly sensitive rotational motion sensor. We installed this sensor in close proximity to permanently deployed classical instrumentation (i.e., translational seismometer, accelerometer, and tiltmeter) at the Hawaiian Volcano Observatory (USGS). There, we were able to record three ~Mw 5 earthquakes associated with large collapse events during the later phase of the 2018 Kīlauea summit eruption. Located less than 2 km from the origins of these sources, the combined six‐axis translational and rotational measurements revealed clear static rotations around all three coordinate axes. With these six component recordings, we have been able to reconstruct the complete time history of ground motion of a fixed point during an earthquake for the first time.

Assessing Seismic Collapse Safety and Retrofitting Low-Ductility RC Frame Structures on the Basis of the Acceptable Collapse Safety Margin in China

The relationship between the average annual collapse probability and collapse safety margin of structures is identified to evaluate structural collapse performance quantitatively. A method is then proposed to determine the acceptable collapse margin ratio (CMR) with a certain annual collapse probability. Two methods, namely adopting steel braces and enlarging column cross sections, are used to retrofit a four-story, low-ductility reinforced concrete (RC) frame structure. On the basis of the acceptable CMR, the seismic collapse resistance of the structure is assessed before and after strengthening. Furthermore, a four-story RC frame structure, which is designed in conformity to the minimum design criteria of the building code, is constructed. The incremental dynamic analysis method is used in consideration of collapse uncertainties. Results show that when the acceptable annual collapse probability is equal to 1.24 × 10−4, which is calculated using the collapse probability at maximum considered earthquake (5%, as proposed in CECS 392), the collapse safety margin of the four structures does not satisfy the seismic collapse resistance requirements with large collapse uncertainty. The structures that are retrofitted and designed in conformity to the code can satisfy the collapse safety margin requirements when the acceptable annual collapse probability is increased to 2 × 10−4. The comparison of the two retrofitting schemes used to improve the seismic collapse resistance of the structure indicates that the steel brace-retrofitting method is better than increasing the column section. This work is an important reference for the reinforcement of the seismic resistance of structures and for corresponding research on collapse resistance.