Rock Cavities Research Articles

Estimating the influence of the technological interlayer lamination on stability of the goaf supporting elements

Within the Verkhnekamskoye salt deposit, productive sylvinite layers are mined using chambers supporting the overlying strata with pillars of various sizes, which stability is determined by mechanical properties of rocks, mining depths, a mining plan of layers, sizes of chambers, etc. The bearing capacity of the interchamber pillars is largely influenced by conditions of the roof and soil of the chambers and, especially, by the technological interlayer. The presence of thin clay interlayers reduces the rocks stability of the roof of underground structures and causes its intense lamination and caving of the interlayer rocks, thus, increases the height of the interchamber pillars and decreases their bearing capacity. The paper presents estimates of changing loads of the pillars during the lamination of the roof of the stoping of the lower productive layer, which is obtained by the multivariate mathematical modeling of the stress-strain state of the two-layer chamber block taking into account the main features of the geological structure and geometry of the mines. The calculations were carried out for the conditions of the plane strain state. The stress state of the chamber block was described by an ideal elastoplastic medium. The thin-layered medium was described using Goodman joint elements.

Estimation of earth surface deformations during pillar mining

Stoping of potash seams during pillar mining is accompanied by deformations in underworked rock mass and the destruction of roof rocks and floors of mine workings in the extraction pillars of longwall faces. This type of mining can also cause sudden caving of the roof and seam floor in an extraction pillar of a longwall face, thus posing a threat to miners, leading to unplanned stoppages of mining operations and reducing the efficiency of mining. In addition, during the advance of a longwall face, subsidence of the soil surface occurs. It is therefore important to study the deformation of the soil surface and find ways of predicting this during the underground mining of potash seams. To evaluate the stress-strain state of the rock mass during longwall mining, a geomechanical model of potash seam mining was constructed under conditions of slice mining. This model took into account the main structural features of the underworked mass, and the caving of the roof of an underworked seam with filling of the worked-out longwall face and the opening of clay contacts in the salt stratum during mining operations. The results of mathematical modelling showed that a localised area of plastic deformation is formed in the soil, which is associated with the formation of opening mode fractures. At the same time, caving of the roof rock and simultaneous filling of the worked-out space take place, preventing further development of the rock jointing zones. The properties of the rocks from the caved roof determine the nature of this mass deformation. By varying these properties, we were able to achieve acceptable agreement between the estimated subsidence and field observations of the displacement of the earth surface. A comparative analysis of the estimated and actual subsidence shows that in order to yield an accurate description of the mass deformation, softening of the caved rocks should not take place immediately to give the final values of the deformation properties, but should change over time.

Assessment of the extent of man-induced transformation of a subsoil block in upward mining using ore and host rock caving

Assessment of the extent of man-induced transformation of a subsoil block in upward mining using ore and host rock caving

Study of Tetrahydroxylated Anthraquinones-Potential Tool to Assess Degradation of Anthocyanins Rich Food.

Degradation of anthocyanins involves scission of the flavonoid skeleton yielding 2,4,6-trihydroxybenzaldehyde (phloroglucinaldehyde, PGA) and a phenolic acid. However, the process is not finished with the formation of PGA, as the consequent condensation of two PGA molecules providing colored hydroxylated anthraquinones was observed for the first time. This process was studied using a combination of preparative column chromatography, nuclear magnetic resonance, liquid chromatography/high resolution tandem mass spectrometry (LC/HRMS2), and quantum calculations using density functional theory. 1,3,5,7-tetrahydroxyanthraquinone (anthrachrysone) and its isomers were found to rise during heating (95 °C) in a buffered PGA model solution (phosphate buffer, pH 7). These compounds were detected in heated red wine after an increase of its pH value. The concentration of the identified anthrachrysone in the red wine reached 0.01 mg·L−1. Presence of those compounds could therefore indicate involvement of certain steps in the processing of plant materials rich in anthocyanins (e.g., utilization of a higher temperature and/or reduction of acidity) or long-term transformation of anthocyanins (potentially, for instance, in archaeological findings such as wine or fruit residues). Additionally, measurement of wine–soil suspensions proved an increase of their pH to the values suitable for anthocyanin cleavage (neutral to slightly alkaline; reached using soil from archaeologically well-known Bull Rock Cave). Although not found in artificially prepared samples (imitations) or authentic materials so far, according to our results the above mentioned conditions are suitable for the formation of tetrahydroxylated anthraquinone derivatives and their monitoring would be beneficial.

Stability Evaluation of Deformation (Denudation) of Yuanjue Rock Cave Roof Based on Multisource Monitoring

The grotto rock mass is a type of cave structure, formed under the complex forces of environment, geology, and human interventions. Many scholars have carried out a lot of work in the protection of cultural relics. However, the research on detection and monitoring methods based on the parametric evolution system remains incomplete. In recent years, with the intersection and integration of disciplines, IoT (IoT: Internet of Things) systems and sensor technologies have developed rapidly. Under this background, a new monitoring system suitable for the protection of cultural relics was independently developed and applied to the protection and research work of Yuanjue rock cave, and the system was corrected and improved in practice. In this paper, according to the complex force characteristics of the sandstone roof of the Yuanjue rock cave at Dazu Rock Carvings and the geological conditions. Initially, a detailed survey of the geological conditions of the Yuanjue rock cave area was conducted; furthermore, according to the unique structural and load characteristics of the outer and inner surfaces of the roof, the monitoring methods and principles of each main control factor were explored, while the layout of monitoring points was optimized; finally, based on the microsensing technology, intelligent high-precision sensing hardware was installed and debugged for each main control factor, while the network was formed to form a multisource monitoring IoT system for the roof stability of the circular sense hole. After nearly half a year of continuous monitoring, the deformation and denudation rules of the roof of Yuanjue Cave were revealed, and a new approach of evaluating roof stability was proposed. This research provided technical support and research ideas for monitoring the stability of similar cultural relics.

The biosignature of sparite permits the distinction between gravitational cement and endostromatolites

Following a brief summary of some fundamentals in carbonate sedimentology (sedimentary petrography) that highlights the significance of organic matter, some examples of biocrystals in carbonate grains/particles, such as bioclasts or ooids, are provided as an introductory chapter to a discussion on gravitational cements versus endostromatolites. The gravitational cements, either marine (fibrous) or continental (dog-tooth), are made of hyaline (i.e., translucent) sparitic crystals whereas endostromatolites are made of colored sparitic crystals and/or micrite. Gravitational cements forms in the vadose zone whereas endostromatolites grow in small rock cavities in the marine phreatic zone. As such the latter can grow centripetally in all directions (not only downward).

Treeline ecotones shape the distribution of avian species richness and functional diversity in south temperate mountains

Mountains produce distinct environmental gradients that may constrain or facilitate both the presence of avian species and/or specific combinations of functional traits. We addressed species richness and functional diversity to understand the relative importance of habitat structure and elevation in shaping avian diversity patterns in the south temperate Andes, Chile. During 2010–2018, we conducted 2202 point-counts in four mountain habitats (successional montane forest, old-growth montane forest, subalpine, and alpine) from 211 to 1,768 m in elevation and assembled trait data associated with resource use for each species to estimate species richness and functional diversity and turnover. We detected 74 species. Alpine specialists included 16 species (22%) occurring only above treeline with a mean elevational range of 298 m, while bird communities below treeline (78%) occupied a mean elevational range of 1,081 m. Treeline was an inflection line, above which species composition changed by 91% and there was a greater turnover in functional traits (2–3 times greater than communities below treeline). Alpine birds were almost exclusively migratory, inhabiting a restricted elevational range, and breeding in rock cavities. We conclude that elevation and habitat heterogeneity structure avian trait distributions and community composition, with a diverse ecotonal sub-alpine and a distinct alpine community.

Numerical Experimental Study on Ore Dilution in Sublevel Caving Mining

On the basis of physical ore-drawing test research, the irregular particle clusters are constructed by adopting particle element theory and PFC numerical simulation software. Meanwhile, the ore dilution mechanism in the process of stoping caving ore and rock bulk is investigated, especially, the permeability characteristics of small size particles. Main factors considered in the numerical test are particle density ratio, particle diameter ratio, vertical stress of overburden, and shape of large particle size. Results show that the irregular particle morphology could more accurately reflect the permeation characteristics of small size particle in caved ore rocks. The particle diameter ratio and large size particle morphology are significant factors that affect permeability characteristics of caved ore and rock. The infiltration rate and diameter ratio of small particles meet negative exponential function. Meanwhile, the closer the particle size is, the more difficult the infiltration is. In the actual ore-drawing process, the evenness of caving ore-rock bulk should be improved as much as possible, particularly near the ore-rock contact zone.

Why are Allogenic Watersheds not Protected (Again)?

<p><em>Allogenic recharge generally contributes to the formation of the main underground river system in a karst area. However, allogenic recharge have a higher susceptibility to contamination than autogenic recharge. This is because recharge from allogenic rivers enters the underground river system without undergoing filtration by soil or rock cavities. This paper discusses changes to ministerial regulations related to karst management that have led to the exclusion of allogenic river areas from the management of allogenic rivers, examines the urgency of managing allogenic rivers, and recommends future management of karst areas from the perspective of water resources management. The change in the Minister of Energy and Mineral Resources (ESDM) regulation regarding karst management has led to a simplification of the scope related to the main tasks and functions of the Ministry of ESDM. This should be followed by making changes to regulations that are higher than the ministerial level regulations so that the management objectives stated in the previous regulation can be covered and there is holistic management of the karst area.</em></p>

The Morro Vermelho hypogenic karst system (Brazil): Stratigraphy, fractures, and flow in a carbonate strike-slip fault zone with implications for carbonate reservoirs

The Morro Vermelho Cave (MVC) (Brazil) developed within the Morro Vermelho karst system, which affected Neoproterozoic limestones (Salitre Formation). The MVC experienced little interactions with meteoric processes and is an example of a hypogenic cave formed during strike-slip deformation. The Salitre carbonates in the MVC experienced distributed deformation along an elongated domain overlying a buried strike-slip fault. Gently dipping, semiductile shear zones formed with decimeter-scale (3.9 in.) dolomitic veins. In our model, Mg-rich fluids flowing along the Salitre aquifer caused at the same time extensive dolomitization of the body of rock (100-m [328-ft] scale) experiencing distributed deformation. With progressive displacement, the deep strike-slip fault propagated upward causing the development of an anticline pop-up, steepening sedimentary layers, and steep 1–10-m-long (3.3–33.8-ft) fractures, which served as pathways for upward fluid flow. These steep extensional fractures made it possible for fluids flowing in lower, quartzitic aquifers to enter the carbonate aquifer causing silica deposition in rock cavities and in fractures and fault planes. Following the main stage of speleogenesis, silica deposition took over again depositing on the cave walls a continuous silica crust, rarely observed in other settings worldwide. The interplay between regional bedding-parallel flow and focused circulation of fluids along steep faults and dipping layers, and the associated rock–fluid interactions are not unique to the contractional settings presented but can also occur in association with similar faults in rifted continental margins.

An Innovative Non-Pillar Coal-Mining Technology with Automatically Formed Entry: A Case Study

• Innovative approach of non-pillar coal mining is accompanied by the automatically formed entry. • The mutual cooperation of three key techniques achieves non-pillar coal mining engineering. • A field test verified the feasibility and effectiveness of the non-pillar coal mining technology. • The proposed non-pillar coal mining technology is supposed to popularize on a large scale. A non-pillar coal-mining technology with an automatically formed entry is proposed, which reduces the waste of coal resources and the underground entry drivage workload. Three key techniques in this technology cooperate to achieve automatic formation and retaining of the gob-side entry, and to realize non-pillar mining. Constant-resistance large deformation (CRLD) support ensures the stability of the entry roof; directional presplitting blasting (DPB) separates the entry roof and the gob roof; and a blocking-gangue support system (BGSS) integrates the caved rock material as an effective entry rib. An industrial test was conducted to verify the engineering effects of these key techniques. The field application results showed that the retained entry was under the pressure-relief zone due to the broken-expansion nature of the caved rock mass within the DPB height. After going through a provisional dynamic pressure-bearing zone, the retained entry entered the stability zone. The final stable entry meets the requirements of safety and production. The research results demonstrate the good engineering applicability of this technology. By taking the framework of the technology design principles into consideration and adjusting the measures according to different site conditions, it is expected that the proposed non-pillar coal-mining technology can be popularized on a large scale.

Analysis of the surface subsidence induced by sublevel caving based on GPS monitoring and numerical simulation

This paper describes a case study of the surface subsidence induced by sublevel caving without sill pillars in the Maogong Iron Mine, China. A comprehensive analysis based on GPS monitoring and numerical simulation is proposed and used to analyze the surface subsidence characteristics and damage range. GPS monitoring results showed that the vertical displacement reached 40.3 mm at the JC5 monitoring station and was accompanied by ground crack development. According to the in situ surface subsidence monitoring data and numerical calibration model results, the corresponding critical horizontal strain and angular distortion due to the surface subsidence were estimated as 1.5 × 10−3 and 2.0 × 10−3, respectively. The numerical results showed that the center of the surface subsidence was located in the hanging wall of the orebody, which changed to its far end with increasing mining depth. In the early surface subsidence stage, macro-tension cracks developed in the hanging wall rock mass, and the slabbed rock mass then collapsed into the cave through rotation and/or translation failure. With increasing mining depth, there will be unfilled goaf in the underground, and the rock mass will gradually collapse under high mining-induced stress concentration. Accumulation of caved rocks and the bulking effect result in slow surface subsidence. Notably, surface collapse will not occur suddenly in Maogong Iron Mine, and potential secondary hazards mainly small landslides in the hillside.

On the Stability of Underground Caves in Calcareous Rocks Due to Long-Term Weathering

This paper addresses the problem of the stability of structures on calcareous rocks due to long-term weathering processes. The case study consists of a building resting on a calcarenite rock formation where two abandoned man-made caves exist directly under the structure. The boundaries of the caves were exposed to a slightly acidic environment inducing time-dependent weathering. Analyses were performed following a semi-decoupled approach, where the weathering process, driven by a reactive transport mechanism, was first solved and its results were fed to the mechanical problem which hence accounted for the spatial and temporal evolution or rock damage. For the mechanical problem, a nonlocal constitutive model was employed for the objective simulation of localised deformations. Relevant outcomes are obtained regarding the evolution of the structure’s stability and about the importance of regularising the finite element solution in the presence of brittle materials.

ОЦЕНКА СОСТОЯНИЯ И МОНИТОРИНГ ПРОЦЕССА ВОРОНКООБРАЗОВАНИЯ ПРИ ПОДЗЕМНОЙ РАЗРАБОТКЕ СИСТЕМАМИ С БЛОЧНЫМ ОБРУШЕНИЕМ

Актуальность. Складирование отвальных пород в области обрушения подземных горных работ – один из рациональных методов отвалообразования, способствует экономии земельных ресурсов, уменьшению транспортного плеча доставки и др. Однако совмещение открытых и подземных горных работ – опасный производственный процесс, требующий специальных мер организации труда. Работа посвящена вопросам безопасности при отвалообразовании на земной поверхности в зоне обрушения действующих подземных рудников. Цель: разработка методов мониторинга и оценки состояния процесса воронкообразования для организации процессов по засыпке воронок обрушения и формированию отвала при работе в зоне обрушения. Методы: создание модели воронкообразования, связывающей объем воронки обрушения с объемом очистного пространства посредством коэффициента разрыхления обрушенного массива; разработка критерия оценки стадии воронкообразования. Критерием завершения роста воронок обрушения является увеличение воронки до максимально возможного объёма, зависящего от параметров очистной выработки. Определение коэффициента разрыхления in situ для условий первичных и вторичных воронок обрушения. Результаты. Разработана классификация этапов процесса воронкообразования. Установлена величина коэффициента разрыхления обрушенных пород в специфических условиях Соколовского месторождения при наличии мощного осадочного чехла, покрывающего комплекс скальных палеозойских пород. Коэффициент разрыхления обрушенного массива, определенный для условий первичных воронок обрушения, находится в рамках 1–1,4; зависит от соотношения осадочных и скальных пород в массиве над выработанным пространством. Для условий вторичного воронкообразования коэффициент разрыхления составляет около 1,0.

Cavity influence on fatigue performance of heavy haul railway Tunnel’s bottom structure

The smoothness of tunnel base directly affects the safety of train operation, and tunnel base diseases are usually difficult to detect and deal with due to the distinguishing features of heavy haul railway, the base diseases become one of the most harmful tunnel diseases. Therefore, with the increasing axle load and the basal deterioration of the existing heavy haul railway in China, studying the fatigue performance of the tunnel bottom structure is essential. A 3D train-tunnel-surrounding rock numerical model is established to obtain the dynamic response of the tunnel bottom structure under 30 t axle load trains. Then refer to the stress state and fatigue vulnerable position which are originated from the numerical simulation, a series bending fatigue tests are carried out to study the cavity influence on fatigue performance of heavy haul railway tunnel’s bottom structure in this paper. A non-linear cumulative damage model is proposed to quantify fatigue damage evolution characteristics of tunnel bottom structure with base cavity through the tests. The results suggest that, the base rock cavity remarkably reduces the fatigue life of the specimen and increases the development rate of damage; the existence of cavity not only deteriorates the bearing capacity of the structure, but also greatly improves the dynamic response and stress level of the bottom structure and base rock, which has multiple adverse effects on the fatigue performance of the tunnel bottom structure, and also accelerates the expansion of the cavity itself.

Planning and design of underground space construction during longwall mining in coal mines

ABSTRACT A large area of underground spaces form after the extraction of underground mineral resources, in which coal mining leads to billions of cubic meters of underground spaces every year. In China, there are 2,469 coal mines exist within 50 km (straight line distance) of the cities, and the annual volume of the goaf in the coal mines is 442 million m3. However, most of these spaces are filled caved rock fragmentation and can hardly be retained and used. To fill this research gap, an innovative scientific conception is proposed in this paper. High-water and quick-setting materials (HWQSMs) are used to build backfill bodies rapidly in mined-out spaces during longwall mining to retain a large amount of underground spaces. Three different methods of building cubic or cylindrical backfill bodies in the mining goaf are introduced. An integration craft and the potential backfilling materials for the construction of the underground space are described in detail. Technical and economical rationality of the proposed conception is evaluated. Further research prospects and the problems that need to be overcome to achieve this goal are discussed. The results shows that compressive strength reaches 10.5 MPa when the HWQSM specimen has a water to HWQSM ratio of 1.5 and the specimen sustains an obvious residual load-bearing capacity. Hence the backfill body will not fail instantaneously in the process of roof supporting. The average unitary underground space value is estimated to be 2,838.89 Yuan per m3, which has great economic value.

Sound production of the banded Sculpin, Cottus carolinae

The use of sound in social interactions has been documented in several species of sculpin and may be used to convey information concerning species identity, intent, or fitness. Sound production may be a particularly important mode of communication in sculpin due to their nocturnal behavior and construction of nests in rock cavities where the efficacy of visual cues may be diminished. In this study, we describe acoustic signals produced during conspecific behavioral interactions in Cottus carolinae, and compare signal characteristics to the only other known sounds producers in the genus Cottus including C. gobio, C. rhenanus, C. perifretum, C. bairdii, and C. paulus. Sounds were produced during nocturnal encounters between cavity residents and intruders, and consisted of pulsatile signals that were arranged into pulse trains with remarkably long pulse intervals of approximately 1 s, as well as tonal sounds in which the periodicity was increased to approximately 60 Hz. We found no relationship between fish standard length and pulse instantaneous frequency or total pulse train duration, but did find a positive correlation between fish standard length and pulse duration, as well as position of pulse interval within the pulse train. We found that C. carolinae pulse train structure differed significantly from that of other published sculpin species, and that C. carolinae produce tonal sounds; a characteristic unique within the genus Cottus.

Influence of Stresses and Displacements in Roof Rocks on Roof Fracture in Top Coal Caving

The process of roof caving at face during its advance is impossible to describe by static and kinematic solutions. It is necessary to take into account unsymmetry of deformation due to the dynamic component of the roof caving process. To that end, it is required to undertake experimental and theoretical studies into the unsymmetrical displacement distribution. It seems to be possible to obtain additional information on deformation and caving of roof rocks from the elastic solution. The main factors to ensure correct formulation of problems are the statics, kinematics and dynamics of rock mass deformation, and the proposed description of the inelasticity zone in the host rocks-mineable seam system.

Analysis of Internal Stress Distribution and Mechanics Characteristics of Pre-existing Cavity in Brittle Rock Under Triaxial Cyclic Loading

Abstract: In order to reveal the internal stress distribution and failure characteristics of pre-existing cylindrical cavity in granite under triaxial cyclic loading, bonded particle models containing cavity were established to investigate the variation of crack propagation, stress distribution, micro-cracks number, elastic modulus and poisson's ratio with the increase of cavity diameter. The results show that the cavity diameter has a significant effect on the tensile crack, compression-shear failure zone and compressive stress distribution. The peak strength decreases as the diameter of the cavity increases. However, the number of cracks increases and the plastic deformation increases more obviously. With the increase of the cyclic axial stress, the decreasing rate of the elastic modulus shows the rule of ‘first slow, fast later’, and the poisson's ratio increases. The distribution of local stress of σ1, σ2 and σ3 well explains the behavior of the cracking surrounding the circular cavity.

Reproductive Performance, Mate Fidelity and Nest Cavity Fidelity in Red-Billed Tropicbirds Phaethon aethereus mesonauta on St. Eustatius, Caribbean Netherlands

Mate choice and nest cavity selection are directly linked to reproductive performance in seabirds, and disruption of these can result in breeding failure. The Red-billed Tropicbird Phaethon aethereus mesonauta breeds on inaccessible and remote islands, nesting primarily in natural rock cavities. I examined the relationship between reproductive performance and mate and nest cavity fidelity on St. Eustatius from 2012 to 2016, corresponding to four successive breeding seasons. The majority of nest failures occurred during the incubation stage. Pairs that failed in their first breeding attempt and laid a replacement clutch were more likely to be faithful to their mate and nest cavity within and between seasons than pairs that bred successfully. Only two replacement clutches (3.8%) were laid after the loss of a chick in the first breeding attempt, whereas the remaining 50 replacement clutches (96.2%) were laid after the loss of an egg. The stage at which pairs split had no influence on mate or nest cavity retention the following season. There were no significant differences in the weight or morphological measurements of chicks from pairs that retained their nest mate and/or cavity and those that switched. The results of this study suggest that switching nest mate or nest cavity does not necessarily improve subsequent breeding success among Red-billed Tropicbirds on St. Eustatius.