Search Results (1,087)

Caves have long fascinated humanity, serving as shelters, canvases for artistic expression and now significant attractions in the realm of tourism. Among these remarkable geological formations, the Maltravieso cave in Extremadura, Spain, stands out for its rich archaeological and paleontological heritage, particularly its collection of Paleolithic rock art. Despite its cultural significance, there is a notable dearth of studies addressing the stability of the cave from an engineering perspective. This article presents a pioneering study aimed at assessing the stability of the Maltravieso cave through a multidisciplinary approach: using empirical geomechanical classifications such as the Q Index, Rock Mass Rating (RMR) and the recently formulated Cave Geomechanical Index (CGI), alongside other techniques like Structure from Motion (SfM), 2D numerical modeling and 3D wedge analysis. This research aims to fill the gap in our opinion of cave stability assessment. By combining field data collection with sophisticated analysis methods, this study seeks to provide valuable insights into the geomechanical properties of the Maltravieso cave and validate a simple yet effective methodology for evaluating the stability of natural caves. This work not only contributes to the body of knowledge regarding cave geomechanics but also underscores the importance of preserving these invaluable cultural and geological treasures for future generations. Full article

Because of the international significance of Dobšiná Ice Cave (Slovakia), it is important to have proper data about the state, movement, or decrease of the ice in which various information about past environments can be preserved. Thus, the goal of the study is to find out which of the 3D scanners used here is the most suitable for long-term monitoring of ice changes. A comparison of the 3D point clouds acquired from laser scanners Leica C10 and Leica RTC360 and the mobile scanners GeoSLAM Zeb Horizon and the iPhone 14 Pro to reference clouds from photogrammetry or tacheometry is provided, and also the process of data acquisition and registration is described. To catch the differences in point clouds according to different types of ice, cross-sections of the vertical and layered ice wall, horizontal ice surface, and artificial ice tunnel are analysed. Some remarkable but also unwanted properties of 3D scanners have been concluded, and the best compromise for 3D scanning of this ice cave has been chosen. According to the diversity of ice types and different layers occurring in Dobšiná Ice Cave, results could be partially helpful in choosing a suitable measurement technology for ice in other caves worldwide. Full article

So as to efficiently address the distortion of surrounding rock in tunnels constructed utilizing ADECO-RS, it is crucial to define suitable parameters for advanced support systems. This study took the 8 # tunnel in the F3 portion of the E60 Expressway in Georgia as an engineering case. Initially, the original support scheme underwent systematic monitoring and analysis in the field. Subsequently, the FLAC3D 6.0 software was employed to examine the influence of the advanced pipe roof and tunnel face fiberglass bolts on the steady state of the surrounding rock. Optimization of the support parameters was also proposed. Further, the sensitivity of different parameters to the distortion of the rock surrounding the tunnel was analyzed and ranked via an orthogonal experiment. Ultimately, the effectiveness of the optimization scheme was evaluated by numerical methods and field observations. The findings of the research indicate the following: (1) The monitoring results of the original support parameters show that the irrational design of the support parameters can bring about deformation non-convergence in the tunnel’s surrounding rock. Support parameters must be optimized. (2) The spacing of the pipe roof is positively correlated with the distortion of the surrounding rock. In contrast, the length and the grouting strength are negatively correlated with the distortion of the surrounding rock. The reinforcement density, length, and lap length of glass fiber bolts exhibit an inverse relationship with the distortion of the surrounding rock. (3) The efficacy of pipe shed grouting in mitigating subsidence and deformation of the vault is superior, followed by the spacing of the supports. In contrast, the length of the supports demonstrates comparatively lesser effectiveness. Under optimal parameters, the vault subsidence was reduced by 23.2%, 10.2%, and 2.0%, respectively. The most significant factor controlling the extrusion deformation of the tunnel face is bolt lap length, followed by reinforcement density and then reinforcement length. Extrusion displacement was reduced by 52.5%, 40.3%, and 9.3%, respectively, under the optimal parameters. (4) In comparison to the primordial support system, the optimized support scheme reduces the subsidence of the vault by about one time and the convergence deformation around the cave by about two times. The research findings offer guidance for analogous engineering support design and parameter optimization. Full article

The present study contributes to the morphogenesis of the Miresii Cave, located in Cheia Mare of Dâmbovița in the area of the Bran—Dragoslavele Corridor, an important tourist axis in Romania. The main aim of the research is the proposal to the Scientific Council of Piatra Craiului National Park to bring to the attention of the national decision-making commissions that the cave be declared a natural monument. The inventory of this speleological geomorphosite suggested its inclusion in a thematic geotouristic circuit integrated into national and EU-protected natural areas. The novelty of the present research lies in the fact that the cave has never been studied before, being difficult to access. This cave, spatially found in the strict protection zone of the national park, is not included in its management plan. When being integrated into other nature protection areas, it is necessary to exclude any form of recreational tourism so that the cave can be exploited as a geotouristic resource strictly for research and educational purposes. The morphogenetic analysis of the cave, based on the information synthesized from geomorphological and geological literature, allowed us to decipher the morphological individualization of Miresii Cave in the local and regional geocronomorphological context, in accordance with the chronological separation of the karstification phenomenon manifested first in phreatic and later in vadose karst. The diversified typology of speleothems has been rendered according to the geomorphologic generating processes. The identification of the Rhinolophus ferrumequinum chiropteran colony and observations of its biotope highlighted the ecological significance of the cave. The inventory of the individuals of the colony led to the conclusion that the cave harbors one of the first two largest bat communities of this species in the national park and the adjacent depressional corridor. The present study may allow the documentation of the photographs and description of the geomorphosite integrated into the proposed thematic circuit to be included on billboards and in promotional brochures. Thus, it could also be useful for the decision-making authorities of Rucar and Podu Dâmboviței villages, which are interested in making decisions related to the promotion of geotourism, especially due to the existence of numerous geological and geomorphological tourist resources in the administrative territories. Full article

An in-depth understanding of gas (oxygen and methane) seepage characteristics in coal mine goafs is essential for the safe production of mines and for advancing sustainable development practices within the mining industry. However, the gas distribution and its flow processes still remain ambiguous. In this article, we developed a three-dimensional porous media mining goaf mathematical model (considering the heterogeneity) to analyze the methane and oxygen flow features. Firstly, based on the variation laws of the “three zones”—the free caving zone, fracture zone, and subsidence zone—porosity changes in the vertical direction were set. A three-dimensional physical model of a fully mechanized caving mining area with a “U”-shaped ventilation system was established as the basis, and a COMSOL Multiphysics multi-field coupled model was built. Secondly, based on the established model, the characteristics of porosity distribution, mixed gas pressure changes, and the volume fraction of oxygen in the goaf were analyzed. The results show that as the distance from the working face increases, the compaction intensity in the mined-out area gradually rises, resulting in a decreasing porosity trend. The porosity distribution characteristics significantly impact the mechanical behavior and gas flow. The gas pressure inside the mined-out area is much higher than the surroundings, decreasing with depth. The upper and middle parts have the highest-pressure concentrations, requiring focused assessment and targeted monitoring measures based on the pressure characteristics of different regions. The oxygen concentration gradually decreases with depth due to poor ventilation, leading to potential explosive gas mixtures, necessitating ventilation system optimization, enhanced monitoring, and emergency preparedness. The gas exhibits vertical stratification, with higher concentrations in the upper and deep regions. Targeted drainage and ventilation methods can effectively control the gas concentration and ensure production safety. Full article

This paper presents an innovative numerical approach to simulating the progressive caving of rock mass in the overburden and floor during longwall mining. A modified caving algorithm is incorporated into FLAC3D 9.0, augmented with the IMASS constitutive model, to accurately replicate the fracturing response of various strata. This study aimed to analyze the longwall caving performance, overburden fracturing response, and shield support characteristics to optimize the mining process and enhance safety. The numerical analysis revealed a progressive stress release at the longwall face, attributed to damage in the form of spalling, which was accompanied by a high level of displacement. The fracture process zone above the shield canopy was not significant, indicating the effective performance of the shield in controlling the roof. However, the floor heave highlights the need for the implementation of effective risk and safety measures. Goaf is predicted to form with a longwall advance rate of 25.0–30.0 m, resulting from progressive macroscopic fracturing caused by the development of cracks initiated by bedding plane and rock mass failures. Above the caved zone, an active fracture zone is observed to evolve due to the continuous longwall mining and caving process. Full article

Cave microbiota knowledge has greatly expanded in the past decades, driven by the development of molecular techniques, which allow an in-depth characterization of diversity and its metabolic potential. This review focuses on the contribution of DNA sequencing technologies to depict the cave microbiome for the three domains of life (Bacteria, Archaea, and Microeukaryotes), assessing their advantages and limits. Cultural methods do not provide a representative view of cave microbial diversity but do offer, subsequently, the possibility to genomically characterize the strains isolated from caves. Next-generation DNA sequencing permits an exhaustive description of microbial biodiversity in caves, using metabarcoding (for taxonomic assessment) or metagenomics (for taxonomic and functional assessments). It proved useful to compare caves, different rooms, or substrata (water, soil, bedrock, etc.) within a cave, or the effect of cave disturbance in Lascaux and elsewhere. The integration of next-generation DNA sequencing with cultivation techniques, physico-chemical characterization, and other complementary approaches is important to understand the global functioning of caves and to provide key information to guide cave conservation strategies. Full article

In mines where the natural caving method is used, the frequent occurrence of underground debris flows and the complex mine environments make it difficult to prevent and control underground debris flows. The source is one of the critical conditions for the formation of debris flows, and studying the impact of source material gradation on underground debris-flow disasters can effectively help prevent and control these occurrences. This paper describes a multiscale study of underground debris flows using physical model experiments and the discrete-element method (PFC^3D) to understand the impact of the source material gradation on the disaster mechanism of underground debris flows from macroscopic and microscopic perspectives. Macroscopically, an increase in content of medium and large particles in the gradation will enhance the instantaneous destructive force. Large particles can more easily cause disasters than medium and fine particles with the same content, but the disaster-causing ability is minimized when the contents of medium and large particles exceed 50% and 60%, respectively. With increasing fine particle content, the long-distance disaster-causing ability and duration is increased. On the microscopic level, the source-level pairs affect the initial flow mode, concentration area of the force chain, average velocity, average runout distance, and change in energy of the underground debris flow. Among them, the proportion of large particles in the gradation significantly affects the change in kinetic energy, change in dissipative energy, time to reach the peak kinetic energy, and time of coincidence of dissipative energy and gravitational potential energy. The process of underground debris flow can be divided into a “sudden stage”, a “continuous impact stage”, and a “convergence and accumulation stage”. This work reveals the close relationship between source material gradation and the disaster mechanism of underground debris flows and highlights the necessity of considering the source material gradation in the prevention and control of underground debris flows. It can provide an important basic theory for the study of environmental and urban sustainable development. Full article

With the increase of mining height at the working face, the influence range of roof fractures in the goaf increases, the advanced supporting pressure on the coal wall increases, ground pressure becomes more intense, and roof support becomes more difficult. Based on the analysis of ground pressure behavior in the first mining and caving stage, the normal mining stage, and the final mining breakthrough stage of the fully-mechanized mining face near 12,404, the relationship between conveyor current and coal speed is studied and compared. Based on the intelligent control system of the fully-mechanized mining face with a super-high mining height of 12,404 and the structure of the football team, the “playing football” roof control mode of the fully-mechanized mining face with super-high mining height under the background of 5G+ big data is put forward. The conclusions are as follows: In 12,404, the ground pressure was first mined. During normal mining, when the roof with a buried depth of more than 200 m is broken, the speed of the coal machine is kept within 12 m/min, and the full guard defends and controls the roof, pulling the lead frame through the area with severe ground pressure. When the roof is good, it is necessary to speed up the coal cutting and get rid of the pressure. When it is less than 200 m, it will overcome the local weighting, and show an offensive trend to speed up and increase production. In the final mining breakthrough stage, the speed of the coal machine should be controlled within 8 m/min, with attention to defense, guarding against roof leakage, and reducing waste rock. Full article

Surface subsidence resulting from block caving mining causes considerable environmental and economic harm in mining areas, highlighting the critical need for accurate predictions of surface subsidence. Given the unique features of the block caving technique and the resemblance between the released ore pillars and the mining processes, this paper developed a lightweight model to forecast surface settlement utilizing the probability integration approach to address the issue of predicting surface settlement in metallic mines. This study focuses on the Pulang Copper Mine, situated in the northeast of Shangri-La County within the Yunnan Province, as a case example. This mine employs the block caving method, which results in substantial surface subsidence. A visual mining simulation program is designed to combine the ore mining plan with the prediction model, manage the ore output of each mining point in batches, treat the ore pillars released in the planning cycle as strip work, and simulate and calculate the surface area above the ore pillars settlement value. The calculated values of surface subsidence induced by ore drawing are then interpreted as the downward displacement of the surface subsidence beneath the strip workings. Furthermore, to verify the reliability of the model, three-dimensional laser point cloud data of the Pulang Copper Mine in recent years were collected, and the differences between the predicted surface and the measured surface were calculated and analyzed. Full article

On 19 September 2021, a strombolian volcanic eruption began on the island of La Palma in the Canary Islands. This event resulted in the destruction of 73 km of roads, urban infrastructure, numerous houses, and agricultural crops, affecting approximately 7200 people and causing losses exceeding 1.2 billion euros. Around 12 km² were covered by aa and pahoehoe lava flows, which reached thicknesses of over 70 m. Following the end of the eruption, thermal, geological, and geotechnical site investigations were carried out for the reconstruction and territorial and urban planning, with the main objectives focused on opening roads through hot lava, constructing new urban settlements in areas covered by lava flows, and facilitating the agricultural recovery. The primary challenges to reconstruction included the very slow cooling rate of the lava, resulting in persistent high temperatures, exceeding 500 °C, its highly heterogeneous geotechnical properties with numerous cavities and lava caves, and the presence of toxic gases. Site investigations included geotechnical boreholes, seismic geophysics and ground-penetration radar, and temperature measurements of lava flows using drones and thermocouple devices inside boreholes. To estimate the cooling rates of the lava flows, two physical cooling models were developed based on thermal behavior and geological–geotechnical data. The results indicated that lava cooling durations in some areas exceed practical waiting times for commencing reconstruction. This led to the development of geological engineering solutions that permit road construction and urban and agricultural reconstruction to begin sooner than estimated by the cooling models. On the other hand, potential hazards arising from the eruption process have also been taken into account. Stability analyses of the 200 m high volcanic cone formed during the eruption indicate the possibility of failure in the event of heavy rain and consequently lahar hazards. The results of the investigations carried out and their applications to post-disaster reconstruction may be useful for other volcanic regions, contributing to minimizing risk to infrastructure and urban settlements. Full article

An improved meshfree method that considers cracking, contact behaviour and fluid–solid interaction (FSI) was developed and employed to shed light on the progressive failure of the water-resistant stratum and inrush process in a karst tunnel construction. Hydraulic fracturing tests considering different scenarios and inrush events of the field-scale Jigongling karst tunnel in three scenarios verify the feasibility of the improved meshfree method. The results indicate that the brittle fracture characteristics of the rock mass are captured accurately without grid re-meshing by improving the kernel function of the meshfree method. The complex contact behaviour of rock along the fracture surface during inrush is correctly captured through the introduction of Newton’s law-based block contact algorithms. FSI processing during inrush is accurately modelled by an improved two-phase adaptive adjacent method considering the discontinuous particles without coupling other solvers and additional artificial boundaries, which improves computational efficiency. Furthermore, the improved meshfree method simultaneously captures the fast inrush and rock failure in the Jigongling karst tunnel under varying thicknesses and strengths of water-resistant rocks and sizes of karst caves. As the thickness and strength of water-resistant rock increase, the possibility of an inrush disaster in the tunnel decreases, and a drop in the water level and an increase in the maximum flow velocity have significant delayed effects during the local inrush stage. Full article

In the context of mines, roof-caving incidents constitute the most common and expensive accidents. To enhance the management and prevention of roof-caving accidents, it is imperative to investigate the factors that contribute to such incidents and comprehend the intricate causal relationships among them. This study aims to classify the causes of these accidents into three categories: basic factors, controllable factors, and sudden factors, based on the mechanism of roof caving. The categorization is primarily determined by two indicators: intervisibility and variability. Furthermore, the study delves into analyzing the mutual influence relationships among these factors and proposes the BCX theory (Basic-Controllable-Sudden causing theory) for roof caving. Subsequently, based on this theory, an index system called BCX is established for roof caving, and the DEMATEL method is employed to analyze the factors within this index system. To attain more accurate results, this study utilizes interval trapezoidal type-2 fuzzy number scale optimization and Tsallis relative entropy to address the limitations of the DEMATEL method. By comparing the outcomes of the traditional and optimal DEMATEL methods, it is observed that the optimal method exhibits superior applicability in the BCX index system of roof caving, with results that align closely with the actual scenario. Therefore, the optimal DEMATEL method’s analysis of centrality, importance, and chain relationships between the factors within the BCX index system will offer valuable guidance for preventing roof-caving accidents in mining operations. Full article

Virtual studies involving pedestrians have gained relevance due to the advantage of not exposing them to actual risk, and simulation setups have benefitted from rapid technical advancements, becoming increasingly complex and immersive. However, it remains unclear whether complex setups affecting participants’ freedom of movement impact their decision-making. This research evaluated the effects of a more realistic approach to studying pedestrian crossing behavior by comparing a perception-action task requiring participants to walk effectively along a semi-virtual crosswalk with a similar experiment using static crossing conditions. Using a CAVE system, two real-world streets were modeled in two different virtual scenarios, varying vehicle speed patterns and distance from the crosswalk. Visual stimuli were presented to two groups of 30 participants, with auditory stimuli adapted accordingly. The impact of various factors on participants’ crossing decisions was evaluated by examining the percentage of crossings, crossing start time, and time-to-passage. Overall, the experimental approach did not significantly affect participants’ crossing decisions. Full article

In recent years, the simplified computation of position and velocity changes in nonlinear systems using Lie groups and Lie algebra has been widely used in the study of robot localization systems. The unscented Kalman filter (UKF) can effectively deal with nonlinear systems through the unscented transformation, and in order to more accurately describe the robot localization system, the UKF method based on Lie groups has been studied successively. The computational complexity of the UKF on Lie groups is high, and in order to simplify its computation, the Lie groups are applied to the manifold, which efficiently handles the state and uncertainty and ensures that the system maintains the geometric constraints and computational simplicity during the updating process. In this paper, a multi-sensor fusion localization method based on an unscented Kalman filter on manifolds (UKF-M) is investigated. Firstly, a system model and a multi-sensor model are established based on an Autonomous Underwater Vehicle (AUV), and a corresponding UKF-M is designed for the system. Secondly, the multi-sensor fusion method is designed, and the fusion method is applied to the UKF-M. Finally, the proposed method is validated using an underwater cave dataset. The experiments demonstrate that the proposed method is suitable for underwater environments and can significantly correct the cumulative error in the trajectory estimation to achieve accurate underwater localization. Full article