Collapse Of Blocks Research Articles

Bedding effect on progressive crack propagation in layered sandstone grotto roof

Roof failure significantly threatens the safety and stability of grottoes. For the layered roof of sandstone grottoes, the failure process is closely related to bedding effects of crack propagation. Taking the Yuanjue Cave as an example, the progressive failure process of the layered roof was summarized. The mechanisms of crack propagation in the roof were analyzed theoretically, and bedding effects together with influencing factors of crack propagation were explored. Results showed that the instability process of the layered roof in sandstone grottoes can be summarized into four stages: tensile fracture of the roof, vertical expansion of cracks, horizontal deflection of cracks, and instability collapse of blocks. The development and propagation of cracks constituted the intrinsic cause of the instability of layered roofs. A fracture mechanics model for crack propagation in layered roofs was established considering the bedding effect, and the criteria for vertical expansion of cracks in grotto roofs was derived. Moreover, the fracture criterion of crack competition was modified in combination with the bedding effect, revealing that an increase in interlaminar cohesion inhibited the crack deflection mode. The crack deflection mode in grotto roofs was jointly determined by the stress at the crack-tip (σfxx and σfyy), the strength of the rock layers and bedding plane (σ't, μ and c). To control the crack propagation in roofs, the engineering reinforcement of grotto roofs can be achieved by weakening bedding effects and indirectly reducing the roof span. This study is of great significance for revealing the progressive failure process and optimizing the reinforcement scheme of layered roofs in grottoes.

Гнездовые группировки орлов на ключевой орнитологической территории «Чинк Донызтау» в 2022 году

Гнездовые группировки орлов на ключевой орнитологической территории «Чинк Донызтау» в 2022 году

In Situ SERS Sensing by a Laser-Induced Aggregation of Silver Nanoparticles Templated on a Thermoresponsive Polymer.

A stimuli-responsive (pH- and thermoresponsive) micelle-forming diblock copolymer, poly(1,2-butadiene)290-block-poly(N,N-dimethylaminoethyl methacrylate)240 (PB-b-PDMAEMA), was used as a polymer template for the in situ synthesis of silver nanoparticles (AgNPs) through Ag+ complexation with PDMAEMA blocks, followed by the reduction of the bound Ag+ with sodium borohydride. A successful synthesis of the AgNPs on a PB-b-PDMAEMA micellar template was confirmed by means of UV–Vis spectroscopy and transmission electron microscopy, wherein the shape and size of the AgNPs were determined. A phase transition of the polymer matrix in the AgNPs/PB-b-PDMAEMA metallopolymer hybrids, which results from a collapse and aggregation of PDMAEMA blocks, was manifested by changes in the transmittance of their aqueous solutions as a function of temperature. A SERS reporting probe, 4-mercaptophenylboronic acid (4-MPBA), was used to demonstrate a laser-induced enhancement of the SERS signal observed under constant laser irradiation. The local heating of the AgNPs/PB-b-PDMAEMA sample in the laser spot is thought to be responsible for the triggered SERS effect, which is caused by the approaching of AgNPs and the generation of “hot spots” under a thermo-induced collapse and the aggregation of the PDMAEMA blocks of the polymer matrix. The triggered SERS effect depends on the time of a laser exposure and on the concentration of 4-MPBA. Possible mechanisms of the laser-induced heating for the AgNPs/PB-b-PDMAEMA metallopolymer hybrids are discussed.

Graben type calderas: The Bolaños case, Sierra Madre Occidental, Mexico

Graben calderas are volcano-tectonic structures that use the faults of a graben as main vents from which magma is massively erupted from a shallow magma chamber during collapse of intra-graben blocks. These eruptions are generally silicic and explosive and form large volume ignimbrite sheets without a previous Plinian major depressurization event. Graben calderas can be associated to tectonic settings ranging from pure extension to strike-slip transtension, including complete grabens, half-grabens or pull-apart grabens. The Sierra Madre Occidental (SMO) in western Mexico includes several of these graben type calderas with the corresponding large volume ignimbrite sheets that result from fissure type eruptions along the graben's border and interior faults. The Bolaños graben constitutes one of the best examples of these tectonically controlled collapse calderas and is the second largest caldera of the world after Toba caldera. It is a 90 × 25 km rectangular caldera and the vent of the 25.37 ± 0.36 Ma silicic Alacrán ignimbrite, with a minimum Dense Rock Equivalent volume of 2650 km3 (3800 km3 rock volume). Post-collapse silicic domes were emplaced just after the Alacrán ignimbrite from 25.02 ± 0.33 Ma to 23.94 ± 0.33 Ma, with a total minimum lava volume of 171 km3. Both ignimbrite and domes account for at least 2800 km3 rhyolitic magma output from Bolaños graben caldera, without considering the distal deposits, and in particular the co-ignimbrite ash-cloud deposit. We describe the characteristics of the Bolaños graben caldera focusing on its major products, the Alacrán ignimbrite and the post-collapse dome volcanism, providing the geological frame of the Bolaños graben area documented with 40Ar-39Ar ages. We finally propose a conceptual model to explain the dynamics of the Bolaños graben that can be applied to other similar volcano-tectonic depressions of the Sierra Madre Occidental and elsewhere in the world with similar geological settings.

Comprehensive safety evaluation method of surrounding rock during underground cavern construction

The deformation instability of surrounding rock and the collapse of rock blocks are two common failure modes observed during the construction of underground caverns. Therefore, a comprehensive safety evaluation method (CSEM) of surrounding rock for application during underground cavern construction is presented in this paper. The method can be used to evaluate the deformation stability of surrounding rock and predict the collapse of rock blocks, rapidly. First, a deformation stability prediction and evaluation method (DSPEM) for rock mass is established. It combines the safety evaluation method based on a deformation statistical analysis and an inverse deformation prediction method using measured deformation data of surrounding rock. This approach possesses the unique characteristics of complementary and mutual verification. In addition, a comprehensive early-warning index system (CWIS) for assessing the deformation stability of surrounding rock is presented. It consists of three types of warning indicators and three levels of warning values. The early-warning values can be adjusted reasonably by the prediction correction method according to the measured displacements. For the collapse of rock blocks controlled by structural surfaces, a rapid prediction method of rock block collapse (RPMBC) based on the block theory is then presented. Finally, combining the DSPEM, RPMBC, and CWIS, the CSEM of surrounding rock for assessing the safety of cavern construction is established. It can provide technical support for decision making on the safety of surrounding rock during the construction of underground caverns.

SINKHOLE DEVELOPMENT MODEL. PART 2. INVESTIGATION OF THE STRUCTURE OF SINKHOLES IN NATURE

The main methods of sinkhole research in nature were: the morphometric method, excavations of sinkholes, cone penetration test (CPT) and drilling in the sinkhole zones, the study of the kinematic and dynamic characteristics of the sinkholes and accompanying effects. The study of morphological features of the sinkhole parameters has allowed to establish, that almost everywhere the appearance of the sinkholes corresponds to the elementary geometric shapes: arched — cylindrical — conical — cupped — saucer-shaped. In the case where the covering deposits are represented by clayey soils, most of the karst sinkholes have an arched or cylindrical shape and conical and cupped forms are typical for sandy soils. Excavations of karst sinkholes have established the arch character of the collapse of soils in the intermediate cavity in the development of a sinkhole on the earth's surface. The CPT of the sinkhole zones revealed specific features of the soil decompaction in the sinkhole, which testify to the collapse of the soils into the intermediate cavity. Drilling operations in the conditions of carbonate and sulphate karst have established that the intermediate cavities develop over the karst cavities. In 2015, the authors were lucky to observe the sequence of the sinkhole development on the earth's surface and to distinguish three stages of the sinkhole formation. The results of karst sinkholes investigations in nature conditions and laboratory modeling of the mechanism of their formation are in good agreement and clearly indicate that the destruction of the cover soils over the karst cavities in the collapse of their roofs begins with the formation of a primary intermediate cavity the surface of which is described by an arch of natural equilibrium. Further, there is a successive collapse of the arch of this primary intermediate cavity and the formation of an intermediate cavity at a lower depth. Thus, the intermediate cavity "moves" to the earth's surface. In the initial stage of formation of a sinkhole on the earth's surface, concentric cracks appear and a small saucer-shaped lowering, the formation of an arch sinkhole occurs in the main stage, in the final stage there is a collapse and displacement of blocks of soil with formation of a depression of a steady state.

The development of cave passage in Donomulyo, Malang-Indonesia

The cave passages formed in Donomulyo sub–district are formed in epigenic and hypogenic conditions in coastal areas. The dominant factors form the morphological condition of the cave passage that is the existence of structural factors, underground water flow, and tectonism that affect the condition of the passage. Structural factors form the existence of linement that affect the cave passage. Underground water flow forms a passage due to the change of vadose, epipreatic, and phreatic conditions. The existence of tectonism leads to the removal of limestone into several levels of cave passage development, in addition, there is the collapse of blocks, plates, talus, and sheets. The development of the cave passage level is also related to surface physiographic, which is connected to 5 levels with marine terrace, including 244–325 masl (level 1), 182–244 masl (level 2), 111–181 masl (level 3), 30–110 masl (level 4), and 0–29 masl (level 5). The development of fifth level shows that the level limit is located in the Sengik Cave, the fourth level is located in the Jebrot Cave, and the second level is located in the Banyu Cave, these three caves are the output of the underground rivers.

The geomechanical state of the mine «mnogovershinnoe» lower levels monitoring

In the low level mining of the Mnogovrshonniy mine, there was a harmful rock stress manifestation in the form of displacement and collapse of rock blocks, which adversely affected the safety of mining operations and reduced the mining efficiency. There was an urgent need to conduct special studies of the geomechanical execution process at the mine. In the process of research the basic physical and mechanical rock characteristics were determined, the initial natural ground stress, manmade stress in mines and pillars was measured, the stability degree of underground cavities was determined. Based on the current geological and surveying documentation analysis and visual observations, the areas of mine workings that are dangerous because of the rock stress and displacement manifestations were established. For the identified areas, projects to set the observation stations to monitor the parameters of the geomechanical state of excavations that affect the safety of mining operations have been developed. The most optimal methods and observing techniques for specific conditions of the mine were chosen. Based on the developed projects, a complex of observation stations on the low mine level was set. Several series of observations were made. The research helped to identify the factors that had the most influence on the mine stability. The assessment of the underground cavities stability degree was carried out, measures to ensure the safety of mining operations were proposed, and the directions for the further research on the creation and improvement of the rock stress observation stations system at the mine were proposed.

Coastal cliffs, rock-slope failures and Late Quaternary transgressions of the Black Sea along southern Crimea

Rock-slope failures represent a significant hazard along global coastlines, but their chronology remains poorly documented. Here, we focus on the geomorphology and chronology of giant rockslides affecting the Crimean Mountains along the Black Sea coast. Geomorphic evidence suggests that high (>100 m) limestone cliffs flanking the southern slopes of the Crimean Mountains are scarps of rockslides nested within larger deep-seated gravitational slope deformations (DSGSDs). Such pervasive slope failures originated due to lateral spreading of intensively faulted Late Jurassic carbonate blocks moving atop weak/plastic Late Triassic flysch and tuff layers. By introducing a dating strategy relying on the combination of the uranium-thorium dating (U-Th) of exposed calcareous speleothems covering the landslide scarps with the 36Cl exposure dating of rock walls, we are able to approximate the time interval between the origin of incipient crevices and the final collapse of limestone blocks that exposed the cliff faces. For the three representative large-scale rockslides between the towns of Foros and Yalta, the initiation of the DSGSDs as evidenced by the widening of crevices and the onset of speleothem accumulation was >300 ka BP, but the recent cliff morphology along the coast is the result of Late Pleistocene/Holocene failures spanning ∼20–0.5 ka BP. The exposures of rockslide scarps occurred mostly at ∼20–15, ∼8, ∼5–4 and ∼2–0.5 ka, which substantially coincide with the last major Black Sea transgressions and/or more humid Holocene intervals. Our study suggests that before ultimate fast and/or catastrophic slope failures, the relaxation of rock massifs correlative with karstification, cracks opening, and incipient sliding lasted on the order of 104–105 years. Rapid Late Glacial/Holocene transgressions of the Black Sea likely represented the last impulse for the collapse of limestone blocks and the origin of giant rockslides, simultaneously affecting the majority of the SW coast of the Crimean Peninsula.

Karst landforms revealed at various scales using LiDAR and UAV in semi-arid Brazil: Consideration on karstification processes and methodological constraints

This paper analyzes different types of karst landforms and their relationships with fracture systems, sedimentary bedding, and fluvial processes. We mapped karst features in the Cretaceous carbonates of the Jandaíra Formation in the Potiguar Basin, Brazil. We used high-resolution digital elevation models acquired using LiDAR and aerial orthophotographs acquired using an unmanned aerial vehicle (UAV). We grouped and described karst evolution according to scale and degree of karstification. These degrees of karst evolution are coeval. Fractures are opened by dissolution, forming vertical fluid conduits, whereas coeval dissolution occurs along horizontal layers. This conduit system acts as pathways for water flow. The enlargement of conduits contributes to the collapse of blocks in sinkholes and expansion of caves during an intermediate degree of karstification. Propagation of dissolution can cause the coalescence of sinkholes and the capture of small streams. Fluvial processes dominate karst dissolution at an advanced degree of karstification. Comparisons with previously published ground-penetrating radar (GPR), borehole and seismic surveys in sedimentary basins indicate that these structures can be partially preserved during burial.

Current denudation rates in dolostone karst from central Spain: Implications for the formation of unroofed caves

Rock tablets of known weight were buried in the soil of a karst region in Central Spain to evaluate the carbonate weathering during a period of a year. The experiment was conducted at two different soil depths: 5–10 and 50–55cm from the surface. The parental rock used in the experiment is composed of dolomite and magnesite with variable proportion of accessory minerals and minor elements. Soil mineral and chemical composition as well as its texture was also characterized. Meteorological conditions at the site together with temperature and CO2 in both soil levels were monitored. Sets of tablets were retrieved after 6 and 12months of the start of the experiment to account for seasonal weathering. Different lithologies do not exhibit significant differences in weathering, although a large inter-sample variability is attributed to variable size and distribution of the porosity. Results show an enhanced weathering during the wet and cold season that accounts for 78±1% of the total annual weathering. Rock tablets examined under scanning electron microscopy prior and after exposure to natural environment show that most of the material lost occurred along cracks, edges or large pores. Although dissolution is a common process, most of the weathering is due to crystal detachment. Rock tablets at the depth of 5–10cm were weathered 68±1% more than those set at 50–55cm from the surface. Higher soil moisture and concentration of CO2 were found deeper in the soil, which likely enhanced the dissolution of carbonate. However, physical weathering dominated weight loss of rock tablets at both soil depths; especially at the 5–10cm level where soil thermal and moisture cycles were more frequent and greater. Denudation rate calculated from the 12months set provides values of 2.48±1.07μm/yr and 1.75±0.66μm/yr at the depths of 5–10 and 50–55cm, respectively. Since the conditions at the average contact between soil and bedrock are similar to those at the 50–55cm depth, we consider that this is a more reliable denudation rate for the studied location during the studied period. The calculated weathering rate suggests that denudation has a limited contribution to the thinning of bedrock over caves at this site. Therefore, we consider that the formation of unroofed caves in this region most likely results from the thinning of bedrock cover over caves due to collapse of blocks from their ceilings.

Paleozoic Exotic Blocks of the Crimean Mountains: Stratigraphy and Origin

Based on numerous geological data obtained by the authors for several decades, the stratification of Permian and Carboniferous ancient and exotic blocks of Crimean Mountains is performed. The sequence of geological events that cause their origin is revealed. Carnian-Norian, Rhaetian-Hettangian and Early-Pliensbachian phases of collapse, sliding and burial of Paleozoic blocks are specified. Final stage (block re-deposition) is confined to the Toarcian and Aalenian ages. The data obtained allow re-interpreting the origin of ancient exotic blocks of the Crimea.

Temperature-induced fluorescence enhancement of GFP chromophore containing copolymers for detection of Bacillus thermophilus

Green fluorescent protein (GFP) chromophore based copolymers with temperature-induced emission enhancement properties were successfully prepared and applied for biodetection. First, diblock copolymers (PEG-b-PNIPAM-c) with different poly(N-isopropylacrylamide) (PNIPAM) chain lengths were synthesized by atom transfer radical polymerization (ATRP) employing a poly(ethylene glycol) (PEG) macroinitiator and then modified with a GFP chromophore at one chain end through a click reaction. Owing to the different PNIPAM chain lengths, the block copolymers exhibited thermoresponsive phase transitions with adjustable lower critical solution temperature (LCST). Above the LCST, the fluorescence intensity of PEG-b-PNIPAM-c was enhanced dramatically, which could be attributed to the chromophore's conformational restriction by the collapse of PNIPAM blocks. Moreover, the emission intensity of PEG-b-PNIPAM-c increased with the PNIPAM chain length. Correspondingly, the temperature-dependent fluorescence enhancement properties of PEG-b-PNIPAM-c were successfully applied in the highly sensitive detection of Bacillus thermophilus with a 102 cfu per mL detection limit.

Observation of rapid drainage system development by thermal erosion of ice wedges on Bylot Island, Canadian Arctic Archipelago

AbstractRapid development of a new drainage system was observed on Bylot Island. A 750‐m long gully system was eroded in four years. The process was initiated by the formation of sinkholes eroded in ice wedges by runoff flowing into open frost cracks. The sinkholes evolved into underground tunnels cut in the ice‐wedge network and the ice‐rich permafrost. Widening of tunnels was followed by subsidence and collapse of their roofs and the development of open gullies. The drainage generally developed as the shortest line along the regional slope with some deviations caused by collapse of blocks of soil which temporarily obstructed the water flow. Retrogressive scarps exposed to flowing water retreated at maximum rates of up to 5 m/day for a total of 15 to 50 m during the summer. Scarps exposed to atmospheric heat and solar radiation retreated between 2.5 and 40 m over four summers with a mean of 15.5 m. Such slopes had nearly stabilised after four years with a retreat rate of only a few centimetres per year in the last year of observation. Copyright © 2007 John Wiley & Sons, Ltd.

CONCEPT OF RISK ASSESSMENT FOR ESTONIAN OIL SHALE MINES

The paper deals with the risk assessment problems in Estonian oil shale mines, where the roomand-pillar mining with blasting is used. This study addresses risks associated with the collapse of mining blocks, including environmental problems. Some of the various factors, which are relevant to Estonian oil shale mines, are determined. For risk estimation the event tree is used. Investigation showed that the likelihood and the consequences of the risk are not acceptable. Risk mitigation process reduces the likelihood. The used concept of risk assessment method is applicable for Estonian oil shale mines. It may be used for different purposes and levels. The results of the risk assessment are of particular interest for practical purposes.

Local Collapse in Soft Rock Bank Cavities

This paper examines an interesting problem of soil engineering: the collapse of blocks from the ceiling of cavities in soft rock banks. The Mohr-Coulomb yield state with the associated flow rule is assumed for the soil. The kinematic theorem of limit analysis based on the choice of paraboloidal collapse surface supplies the total dissipation function; the equilibrium equations and a solving procedure based on Kuhn-Tucker conditions yield a closed form for the solution. This solution is applied to common soils in southern Italy and it agrees with the real situation in cavities known to the writers. Several examples are listed reporting the dimensions and the weight of the collapsing block depending on the variability of mechanical properties of different soils. Finally a method for the design of the reinforcement of the cavities roof based on the proposed calculation is reported.

Failure in Mohr–Coulomb soil cavities

In many cavities, resulting from both natural excavation and anthropic action, the phenomenon of the collapse of blocks from the cavity roof presents a serious safety hazard. In a previous publication the authors proposed a method to calculate the shape and dimensions of the collapsing block by means of the upper bound theorem of the plasticity theory. The soft rock material was modelled by means of the Mohr–Coulomb yield criterion, and the associated flow rule was considered for strain plastic velocity. The linear yield criterion was suitably regularized by means of a circle in the tensile zone. The boundary of the collapsing block is described by a paraboloid surface. An optimization procedure formulated in standard Kuhn–Tucker form and an analytical solution were obtained. The above-mentioned algorithm has been successfully applied to common soils of southern Italy. To validate the theoretical formulation, several numerical tests are performed. These tests show an optimal agreement with the closed-form solution. Therefore the proposed modelling may be used as an efficient guideline for the cavity-strengthening design.Key words: roof stability, regularized Mohr–Coulomb material, limit analysis, failure mechanics.

Experimental modeling of extensional fault systems by use of plaster

Plane-strain extension experiments with plaster as the deforming medium produce faults and related structures that closely resemble natural examples. The faults with the largest displacement are normally developed at about 25% overall extension (β = 1.25). Major faults develop as composite structures, and although the main movement may be accommodated by a relatively simple slip surface, the fault zones commonly develop internal, lense-shaped geometries. Small, synthetic faults dipping more steeply than the main zone are typical components of the fault zones, particularly on the hanging wall side. Fault displacements develop over 2 orders of magnitude, and the distribution of fault displacements closely follows a power-law relationship similar to data from seismic and field mapping. The main, through-cutting faults accommodate about 60–70% of the total deformation, while smaller, visible faults typically account for ca 10–20%. Only 20–30% extension is due to faults and ductile deformation that occur below the resolution of the models, which roughly corresponds to seismic resolution when scaled up to natural size. The internal fault-block formation may include zones of normal faults accommodating significant internal shear deformation associated with collapse of fault blocks. Collapse has been recorded in the upper part of footwalls, resulting in a flattening of the upper part of the main faults. Although internal block deformation by simple shear or other deformations can be shown to play a significant role in the deformation, a component of rigid-block rotation is demonstrated, for example by the rotation of steep normal faults into orientations where they appear as reverse faults.

L'abri B des Eissartènes (Le Val, Var). Occupation et gravures post-glaciaires du site.

Shelter B is situated in the cliff of Eissartènes, under a slightly overhanging rock so that it is not very deep. The collapse of blocks that were above it has allowed a stratified accumulation of sediments, thus slightly enlarging the usable surface area of the place. The archaeological context shows the site to have been used several times from Late Bronze II until the first beginning of the Roman Empire. Studies on the material, the sediments and the bones allow to define the nature of the occupations and the periods of abandonment : camp site and secondary burying place in the late Bronze Age, pastoral activities and crafts in a temporary camp (shepherds, hunters) at the very end of the Bronze Age and early in the Iron Age, organised pastoral activities in an enclosed and covered space (goats ans sheep) in the Ist c. B.C. The ultimate sheepfold will be destroyed by the sudden caving in a stratum of rock, killing thirteen animals. It appears that a little later (around the change of era) the sheiter was decorated with schematic linear engravings.

Raman study of the formation of transition alumina single crystal from protonic ?/?? aluminas

Transition aluminas are usually obtained by thermal treatment of aluminium hydroxides between 450 and 1000 ° C. X-ray diffraction [1] but also IR spectroscopy [2] have been used to characterize the various phases (7, 0, &, x . . . ) occurring before crystallization in corundum (e-alumina). However, samples prepared this way are in the form of small crystallites and, aluminium oxides being poor scatterers, the use of Raman scattering was not successful. In previous work [3, 4], we have shown by X-ray diffraction and electron paramagnetic resonance how a protonic /3 (or /3") alumina single crystal can be transformed by heating into an e-alumina oriented polycrystal through the formation of a transition alumina single crystal. To our knowledge, this is the unique method to prepare easily large single crystals (a few tens of mm 2) of transition aluminas. These crystals are suitable for special studies, such as those of surface properties. The structure of/?-alumina consists in spinel blocks separated by a loosely packed plane where conducting iotas diffuse rapidly. The bridging between spinel blocks is made by two tetrahedra sharing the same oxygen ion. The difference between/3 and/?" phases resides in the nature of the conducting plane: only in the /3 phase is there a mirror plane from a crystallographic point of view. A protonic/?-alumina single crystal with composition equal to 1.25M20 • 11A1203 (M + = NH4 + or H+(H20),) is transformed above 400°C into a stoichiometric/?-alumina single crystal (composition close to (I-I30)20 • 1 IA1203). This transformation takes place from the reaction of interstitial oxygens ensuring the charge compensation mechanism, with the protons liberated by the desolvation of protonic ions [5-7]. Further heating above 800°C involves the diffusion of the remaining protons in the spinel blocks where they are trapped, Stacking faults are created by the collapse of some loosely packed conducting planes in between the spinel blocks. The samples remain in the form of single crystals; the /3-alumina unit cell is multiplied by three or even six along the a direction of the hexagonal plane (Fig. 1), whereas complex superstructures and diffusions are observed along the c direction [7]. Finally a topotactic growth of e-alumina crystallites is observed above 1100 ° C [4, 7, 8]. Similar transformations are observed for ion-rich /?and fl"-alumina single crystals with composition close to Allo.33Mgo.66017M1.66 (M = NH2, H+(H20)~). However, due to the new charge compensation mechanism (Mg2+/A13+ ion substitution) the stoichiometric form is not obtained and stacking faults occur at lower temperature with a drastic collapse of spinel blocks, above 320 and 400°C for ion-rich/3 and/3" phase, respectively [9]. A transition alumina phase with spinel-like structure is formed. Above 670°C syntactic nucleation of nonstoichiometric spinel occurs [9, 10]. Finally, separation into e-alumina and MgAI204 spinel is observed above 1000°C [10]. This quasi-continuous evolution of relatively well-ordered spinel-like structures into disordered ones provides a good opportunity to state the vibrational fingerprinting evolution of spinel-like materials. However, such structures are found for many solid-state reactions in ceramics (e.g. mullite