Dynamic Disintegration Research Articles

On typical inhomogeneities controlling dynamic disintegration of concrete structures

For the disintegration of aged concrete structures in densely populated urban areas, use of safer and more controllable electric discharge impulses (EDI) may be time-wise and space-wise efficient. Surrounded by other structures, very careful treatments of dynamic fracture in these aged structures are required, but the mechanical details of three-dimensional fracture development subjected to dynamic impact by EDI have not been fully understood yet. Here, we consider some typical structural inhomogeneities that may affect or be utilized for controlled dynamic fracture in such concrete structures. By performing field fracture experiments and tracing dynamic disturbances with finite difference simulations, we find the controlling effects of free surfaces, empty dummy holes and reinforcing steel bars. Not only the “connecting/sandwich effect” of outer free surfaces and empty dummy holes but also the newly identified “virtual interface effect” of reinforcing steel bars to guide dynamic EDI-induced waves can be used in real disintegration work to crush and remove only desired parts of concrete structures that need renovation.

Precisely controlled dynamic disintegration of steel-concrete composite structures

Precisely controlled dynamic disintegration of steel-concrete composite structures

Precise dynamic disintegration of concrete structures by controlling wave motion

By applying more safely usable electric discharge impulses and based on the theory of wave and fracture dynamics, we try to establish more effectively controllable techniques for precise partial disintegration of concrete structures. The models experimentally examined in the field and numerically studied in the laboratory include (un)reinforced concrete blocks, realistically large concrete slabs and steel-concrete composite structures. In order to guide three-dimensional wave interaction and ensuing dynamic fracture development in the models exactly as desired, we make use of free surfaces and pre-existing planes of weakness such as interfaces between concrete, reinforcing steel bars, steel girders and headed stud shear connectors. We also introduce, in addition to blast holes containing energy sources and emitting waves, empty dummy holes and slits in the models, and find that the development of fracture network and the final structural disintegration pattern depend sensitively on the geometrical settings of the above inhomogeneities. Our ultimate goal is to crush and remove only concrete material while other parts of structures like headed stud shear connectors and steel girders remain undeformed for later renovation work, even in densely populated urban areas.

Evidences of an unknown debris avalanche event (

Azufral volcano is an active composite volcano located in SW Colombia, whose edifice is mostly formed by pyroclastic deposits and lava flows. Recent road works in the region, NE of the volcano, revealed unknown deposits, one of them related to a debris avalanche event. This deposit, herein named San Roque debris avalanche deposit, outcrops along a 13 km section in the Túquerres - Samaniego road. Using this long exposure, the deposit was studied through sedimentological, grain size, microtextural and mineralogical analyses. The deposit is massive, varicolored, poorly sorted, with a predominance of gravel and sand-sized clasts; it contains angular megaclasts some of them with jigsaw cracks, and exhibits injections, faults, and horsts-and-graben structures. Surface microtextures in some clasts evidence collisions and shearing interactions among them, while mineralogy evidences the collapsed material involved in the avalanche. Based on stratigraphic relationships, the collapse occurred between 0.58 Ma and ~18 ka. The San Roque debris avalanche deposit covers an area of 56.01 km2, has an estimated volume of 0.51 km3, an approximated runout of 11 km, and an apparent friction coefficient H/L of 0.109; these parameters are indicative of a large and very mobile flow. Its main transport mechanism responded to a dynamic disintegration of the larger clasts and a subsequent interaction by contact or collision (inertial-granular flow model), although some zones moved in a cushioned way remaining coherent over long distances (multi-shear model).

The Great Inequality and the Dynamical Disintegration of the Outer Solar System

Abstract Using an ensemble of N-body simulations, this paper considers the fate of the outer gas giants (Jupiter, Saturn, Uranus, and Neptune) after the Sun leaves the main sequence and completes its stellar evolution. Due to solar mass loss—which is expected to remove roughly half of the star’s mass—the orbits of the giant planets expand. This adiabatic process maintains the orbital period ratios, but the mutual interactions between planets and the width of mean-motion resonances (MMR) increase, leading to the capture of Jupiter and Saturn into a stable 5:2 resonant configuration. The expanded orbits, coupled with the large-amplitude librations of the critical MMR angle, make the system more susceptible to perturbations from stellar flyby interactions. Accordingly, within about 30 Gyr, stellar encounters perturb the planets onto the chaotic subdomain of the 5:2 resonance, triggering a large-scale instability, which culminates in the ejections of all but one planet over the subsequent ∼10 Gyr. After an additional ∼50 Gyr, a close stellar encounter (with a perihelion distance less than ∼200 au) liberates the final planet. Through this sequence of events, the characteristic timescale over which the solar system will be completely dissolved is roughly 100 Gyr. Our analysis thus indicates that the expected dynamical lifetime of the solar system is much longer than the current age of the universe, but is significantly shorter than previous estimates.

Dynamic disintegration processes accompanying transport of an earthquake-induced landslide

Aiming to understand the dynamic disintegration and transport behavior of an earthquake-induced landslide, a dynamic discrete element method has been employed to analyze the Wangjiayan landslide triggered by the 2008 Ms 8.0 Wenchuan earthquake. Absorbing boundary condition is used for the seismic wave transmission and reflection at the slope base. The numerical results show that under seismic loading, internal rock damage initiates, propagates, and coalesces progressively along the weak solid structure and subsequently leads to fragmentation and pulverization of the slope mass. This can be quantitatively interpreted with the continuously rapid increase of the damage ratio and sudden decline of growth ratio of the number of fragments after the peak seismic shaking. During emplacement evolution, fragmented deformation patterns within the translating joint-defined granular assemblies are affected by the locally high dilatancy with a simultaneous occurrence of highly energetic collisions related to the action of shearing, and this can be quantified by the enhancement of particle kinematic activities (high vibrational and rotational granular temperatures) and intense fluctuations of location-dependent global dispersive stress. In this process, slope destabilized and transports downward in a rapid pulsing motion as friction bonds are locally and continually overcome by the seismic- and gravity-induced shear forces. The joint-determined fragment network before movement initiation and the final fragmented depositions after the rapidly sheared transport have been systematically investigated by fragment statistics (fragment size distribution, fragment mass distribution, and fractal dimension) and morphometric characters (fragment shape isotropy) to offer new insights into the disintegration characteristics of the earthquake-induced catastrophic mass movements.

Diagnosing the Stellar Population and Tidal Structure of the Blanco 1 Star Cluster

Abstract We present the stellar population, using Gaia DR2 parallax, kinematics, and photometry, of the young (∼100 Myr), nearby (∼230 pc) open cluster, Blanco 1. A total of 644 member candidates are identified via the unsupervised machine learning method StarGO to find the clustering in the five-dimensional position and proper motion parameter (X, Y, Z, , μ δ ) space. Within the tidal radius of 10.0 ± 0.3 pc, there are 488 member candidates, 3 times more than those outside. A leading tail and a trailing tail, each of 50–60 pc in the Galactic plane, are found for the first time for this cluster, with stars further from the cluster center streaming away faster, manifest stellar stripping. Blanco 1 has a total detected mass of 285 ± 32 M ⊙ with a mass function consistent with a slope of α = 1.35 ± 0.2 in the sense of , in the mass range of 0.25–2.51 M ⊙, where N is the number of members and m is stellar mass. A minimum spanning tree (ΛMSR) analysis shows the cluster to be moderately mass segregated among the most massive members (≳1.4 M ⊙), suggesting an early stage of dynamical disintegration.

On (p1,\u2026,pk)-spherical distributions

The class of (p1,…,pk)-spherical probability laws and a method of simulating random vectors following such distributions are introduced using a new stochastic vector representation. A dynamic geometric disintegration method and a corresponding geometric measure representation are used for generalizing the classical χ2-, t- and F-distributions. Comparing the principles of specialization and marginalization gives rise to an alternative method of dependence modeling.

ИЗУЧЕНИЕ ДИНАМИЧЕСКОГО ПРОЦЕССА ИСТИРАНИЯ ГОРНЫХ ПОРОД В ТЕРОЧНОЙ МЕЛЬНИЦЕ С РАБОЧИМ ОРГАНОМ, УПРАВЛЯЕМЫМ ГИРОСКОПОМ

ИЗУЧЕНИЕ ДИНАМИЧЕСКОГО ПРОЦЕССА ИСТИРАНИЯ ГОРНЫХ ПОРОД В ТЕРОЧНОЙ МЕЛЬНИЦЕ С РАБОЧИМ ОРГАНОМ, УПРАВЛЯЕМЫМ ГИРОСКОПОМ

Controlled disintegration of reinforced concrete blocks based on wave and fracture dynamics

In this contribution, field experiments of dynamic fracture by electric discharge impulses (EDI) are performed and fracture development in rectangular concrete blocks with reinforcing steels bars is analyzed also numerically in the three-dimensional context. It is found that the development of fracture network depends very sensitively on the geometrical settings (e.g. positions of empty dummy holes prepared for controlling crack propagation directions) in the blocks, and cracks extending from blast holes may tend to arrest on the (pre-)existing planes of weakness (e.g. interfaces between concrete material and reinforcing steel bars). This characteristic can be used to actualize more efficient and precise disintegration of a given structure, for instance, removal of reinforced concrete (RC) lining segments from the surroundings in an underground space. Optimal positions of blast and empty dummy holes for predictable and controlled dynamic destruction may be determined for each specific structure by the established simulation technique, which is effective for both conventional and modern dynamic disintegration methodologies, namely, fragmentation by blasting using explosives as well as by EDI.

The extreme mobility of debris avalanches: A new model of transport mechanism

AbstractLarge rockslide‐debris avalanches, resulting from flank collapses that shape volcanoes and mountains on Earth and other object of the solar system, are rapid and dangerous gravity‐driven granular flows that travel abnormal distances. During the last 50 years, numerous physical models have been put forward to explain their extreme mobility. The principal models are based on fluidization, lubrication, or dynamic disintegration. However, these processes remain poorly constrained. To identify precisely the transport mechanisms during debris avalanches, we examined morphometric (fractal dimension and circularity), grain size, and exoscopic characteristics of the various types of particles (clasts and matrix) from volcanic debris avalanche deposits of La Réunion Island (Indian Ocean). From these data we demonstrate for the first time that syn‐transport dynamic disintegration continuously operates with the increasing runout distance from the source down to a grinding limit of 500 µm. Below this limit, the particle size reduction exclusively results from their attrition by frictional interactions. Consequently, the exceptional mobility of debris avalanches may be explained by the combined effect of elastic energy release during the dynamic disintegration of the larger clasts and frictional reduction within the matrix due to interactions between the finer particles.

The formation and breakup of molten oxide jets

Experimental investigations on the capillary breakup of jets of molten oxides (slags) at high temperatures in an inert atmosphere are presented in this paper. The (in)stability of ligaments, threads, or jets of metallurgical slags is of importance in many heat and mass transfer processes related to high-temperature metal production, and aftertreatment of slags as currently investigated in the dry slag granulation process. In order to quantify the dynamic disintegration process of slag jets into droplets, a three-zone high-temperature furnace with maximum temperatures of 1750°C and optical access was built. In the present study, a molten synthetic calcia/alumina slag at 1600°C was used to form jets of 1mm in diameter at different flow rates. The various phenomena of jet formation, appearance of instability waves, jet disintegration and droplet detachment were captured using a high-speed camera. The jet length distribution was calculated and compared with predictions. A Fast Fourier Transform of the temporal development of the jet length was also performed. The jet length showed good agreement with empirical correlations if the instability wave velocity is used in the definition for Reynolds and Weber number. The size distribution of the formed droplets was investigated and compared to theoretical predictions. For higher flow rates, the main peak agrees very well with theoretical equations. For low flow rates near to transition to the dripping regime, short jets formed in a highly repetitive manner. The drop size distribution was found to be very narrow with a mean diameter according to Tate's law taking into account a Harkins and Brown correction factor.

Focal Mechanisms of Mine-Induced Seismic Events an Explanation of Geomechanical Processes in the Area of Longwall 6, Seam 510 In Hard Coal Mine “Bobrek-Centrum” / Mechanizm Ognisk Indukowanych Wstrząsów Górniczych Wyjaśnieniem Procesów Geomechanicznych W Rejonie Ściany 6, Pokład 510 W Kopalni „Bobrek-Centrum”

Abstract Exploitation in a coal mine “Bobrek-Centrum” of the longwall 6 in seam 510 has led to the occurrence of very high seismic activity. From January 2011 to June 2012 took place almost 3500 tremors with the energy of 102-104 J and 95 tremors of energy more than to 105 J. In an attempt to identify the character of that seismicity, calculations of focal mechanism parameters were carried out, and according to them local stress field was determined. Three periods of exploitation of longwall 6 were distinguished which vary in type of focal mechanism. Tremors, which occurred in exploitation periods I and III were characterized by normal slip mechanism, occurred due to domination of vertical principal stresses σ1, horizontal intermediate stresses σ2 and minimal ones σ3. Such stress arrangement characterizes local state of rock mass behaviour as a result of cracking and collapse of sandstone, tremor-generating strata during advancing exploitation. In exploitation period II, of non-shearing mechanism of foci occurred. That was the period of change of longwall run from the NE-SW direction to E-W direction, that is the period of so called “slanting” of exploitation front. It can be presumed that this type of tremor mechanism could have occurred due to a sudden coal bed load by superimposed roof strata, which may have led to extreme load conditions and to a dynamic disintegration of seam part. It was confirmed by geomechanical calculations, which indicated that in the region of rockburst existence on 19.07.2011, layers which were located above and under seam 510 in area of longwall no. 6 were strongly deformed locally causing compression of certain parts of seam.

Meteoric lithification of catastrophic rockslide deposits: Diagenesis and significance

Deposits of catastrophic rockslides composed of lithologies rich in carbonate minerals may undergo precipitation of cements that can be used to proxy-date the rockslide event and/or subsequent geomorphic changes of the rockslide mass. In the Alps, localized to widespread lithification of post-Glacial rockslide deposits is observed in lithologies ranging from limestones and dolostones to metacarbonates to calcphyllites. Lithification of rockslide deposits to breccias may be localized to meteoric ‘runoff-shadows’ below larger boulders, or may comprise a layer of breccia or may affect a rockslide mass down its base. In addition, precipitation of cements and small stalactites may take place in megapores on boulder undersides. Cements found in rockslide deposits comprise skalenohedral calcite, prismatic calcite, blocky calcite, calcitic micrite and micropeloidal calcitic cement and, rarely, botryoidal aragonite. Initial cement formation probably is driven by meteoric dissolution–re-precipitation of (mini-) micritic abrasive rock powder generated by dynamic disintegration during the rockslide event. Preliminary 234 U/ 230 Th ages of rockslide cements support a concept that cementation starts immediately or early after a rockslide event. In rockslide deposits of calcphyllite with accessory pyrite, oxidation of pyrite probably also propels the process of carbonate dissolution–re-precipitation. Limestone-precipitating springs emerging from rockslide masses, and well-cemented talus slopes and fluvial conglomerates percolated by rockslide-derived groundwaters, indicate that rockslide deposits remain diagenetically active long after emplacement.

Heterogeneity of Polyelectrolyte Diffusion in Polyelectrolyte−Protein Coacervates: A 1H Pulsed Field Gradient NMR Study

Proton pulsed field gradient (PFG) NMR was used to study the diffusion of poly(diallyldimethylammonium chloride) (PDADMAC) in coacervates formed from this polycation and the protein bovine serum albumin (BSA). Application of high (up to 30 T/m) magnetic field gradients in PFG NMR measurements allowed probing the diffusion of PDADMAC on a length scale of displacements as small as 100 nm in coacervates formed at different pH's and ionic strengths, i.e., conditions of varying protein-polycation interaction energy. Studies were carried out for a broad range of diffusion times and corresponding values of the mean square displacements. Several ensembles of PDADMAC polycations with different diffusivities were observed in the measured range of diffusion times. The existence of these ensembles and the pattern of their changes with increasing diffusion time support the hypothesis about the microscopic heterogeneity of PDADMAC-BSA coacervates and also provide evidence for the dynamic disintegration and reformation of dense domains.

Coolant film flow over the edge of a nozzle in a rarefied gas

The flow of a thin liquid film over the nozzle wall under the action of tangential friction and pressure gradient is considered. For the slow flow of the film with constant thermal physical properties, analytical dependences of the film thickness and temperature at the interface on the coordinate along the nozzle edge are derived. The flow of the film over the variable-curvature nozzle edge when the gas expands into vacuum is considered. At the initial section of the curvilinear edge, the film thickness increases in inverse proportion to the root of the friction stress at the interface. Near the end point of the nozzle, the film thickens drastically because of a decrease in the friction and, consequently, the curvature of the interface diminishes. As a result, the deceleration of the liquid by the Laplace pressure gradient drops, which causes an additional sharp growth of the thickness of the film with the possibility of its dynamic and thermal disintegration and, eventually, contamination of the spacecraft surface.

A slab-on-slab model for the Flims rockslide (Swiss Alps)

The Flims rockslide is the largest landslide in the Alps, with an estimated volume of 12 km3. It resulted from a prehistoric high-speed movement of a large limestone mass. Several main factors influenced the mobility of the Flims rockslide: (i) the steep slopes of the Rhine River valley that blocked the spreading of the rock debris out of the limits of Rabiusa and Carreratobel tributary valleys; (ii) the resisting forces taking place at the base of the rockslide by friction and substratum obstacles; and (iii) the rock mass evolving to a granular state, as observed in the deposits, in which coherence of the original rock massif has been preserved. We expect that most of the energy was consumed by impacting on the opposite slope, forcing the rock mass to stop. Lateral parts and some portions of debris, which entered valleys of the right tributaries of the Rhine River, created tongues by rock avalanche motion, indicating transport velocity. These rock masses eroded the valley fill to create a large mixed mass at the toe of the rockslide deposits. Thus, the Flims rock slope movement can be classified as a rockslide to its middle section and as rock avalanches at its lateral margins. A slab-on-slab model is proposed to characterize transformation of the rock mass during transport, with different stages of motion. Beginning as a rockslide, a delaminating process took place to produce a multislab shearing motion. Shearing and fracturing create dilatancy of the sliding rock debris, with spreading constrained by topographic effects. Dynamic disintegration processes explain the production of fine particles and are at the origin of the granular state of the deposits. Lateral sections of the debris mass continued to flow in the absence of topographic constraints.Key words: rockslide, rock avalanche, Flims, disintegration, topographic control.

Dynamic disintegration processes accompanying transport of the Holocene Flims sturzstrom (Swiss Alps)

A sturzstrom is a large-scale landslide that evolves during transport into a rapid granular flow (rock avalanche) by a dynamic disintegration process. Numerous theoretical hypotheses have been proposed to explain the excessive mobility of these catastrophic mass movements, but the role of disintegration processes remains poorly understood. Exceptional outcrop conditions at the giant (12 km 3) Flims sturzstrom (Swiss Alps) permit the analysis of disintegration processes that result from shearing during transport. In confined zones of the rock mass, shearing is concentrated along preferred surfaces (originating as bedding planes), which evolve into shear band layers. Differential velocities of slabs separated by these shear layers induce oblique fractures in the slabs by accommodation. Contacts between grains are maintained in the shear layers. In unconfined zones near the top and the lateral margins, shearing generates dilatancy. The rock mass is affected by anisotropic dispersion without mixing, and disintegrated material is preferentially produced to the top due to inflation. The rock slide then evolves to a granular flow. The consequence of these processes is the formation of two distinct depositional facies in the sturzstrom. The structured facies exhibits a stratified aspect close to the base, reflecting confined slab-on-slab shearing motion. Towards the top and distally, it evolves into a chaotic facies with some isolated pockets of the structured facies. Reduction of confining forces on the moving sturzstrom allows transformation of the structured facies into the chaotic facies. This characteristic transition, observable in many sturzstrom deposits, seems to be necessary for the rock avalanche process to occur, and offers insights into the long-runout characteristics of these catastrophic mass movements.

Multifragmentation of gold nuclei by light relativistic ions: Thermal breakup versus dynamical disintegration

The multiple emission of intermediate-mass fragments (IMF) is studied for collisions of p, 4He, and 12C on Au with the 4π FASA setup. The mean multiplicities of IMF saturate at a value of around 2 for incident energies above 6 GeV. An attempt at describing the observed IMF multiplicities in the two-stage scenario, a fast cascade followed by a statistical multifragmentation, fails. Agreement with the measured IMF multiplicities is obtained by introducing an intermediate expansion phase and modifying empirically the excitation energies and masses of remnants. The angular distributions and energy spectra from p-induced collisions are in agreement with the scenario of “thermal” multifragmentation of a hot and expanded target spectator. In the case of 12C + Au(22.4 GeV) and 4He (14.6 GeV) + Au collisions, deviations from a pure thermal breakup are seen in the fragment energy spectra, which are harder than those both from model calculations and from the measured ones for p-induced collisions. This difference is attributed to a collective flow with the expansion velocity at the surface of about 0.1c (for 12C + Au collisions).

Dynamic disintegration and expansion of a liquid volume

Dynamic disintegration and expansion of a liquid volume