Subsurface 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.

Estimation of rock core indices for development of underground infrastructure using non-invasive geophysical methods

Rock mass characterization offers the basis of the stability criterion for the planning and advancement of civil engineering projects. Rock core index (RCI) is one of the key geotechnical parameters adopted in rock mechanics and rock engineering. RCI provides risk assessment regarding the success criteria of engineering design. Consequently, an accurate estimate of such parameters is a challenging task in the context of credibility, budget, and time. However, the traditional estimation of geomechanical parameters needs lots of drilling tests at some selected points. The point-scale data often cause more ambiguity and less authenticity in engineering design. Besides, the conventional approaches are invasive, uneconomical, and laborious and cannot investigate the complete project site. We offer an indirect technique for the estimate of RCI using empirical relationships between drilling and geophysical data, which addresses the drawbacks of the conventional methods. Geophysical techniques offer the subsurface volumetric data and are faster, more affordable, and easier to use. In this study, we employ a non-invasive CSAMT (controlled-source audio-frequency magnetotellurics) method for the first time to quickly assess 2D and 3D RCI models. The suggested approach assesses the intricate geological subsurface at a depth of 1 km in order to produce a more precise and complete image of the quality of the rock mass across a wide area. These findings are crucial for improving our understanding of the intricate geological conditions, estimating the likelihood of failure early on, and supporting the safe, stable, and cost-effective construction of deep underground engineering structures. In regions where there is a deficiency of mechanical drilling data, our approach decreases the gaps between an appropriate geotechnical model and insufficient data, yields more objective indices, and serves as a guide for more correct engineering structure design.

Experimental testing on the performance of solar dryer equipped with evacuated tube collector, rock bed heat storage and reflectors

Agricultural products can be dried in an open sun; but such drying method has poor quality of the product causes to grow bacteria and microorganisms and long drying time. In order to alleviate those draw backs of open sun drying, direct solar dryers were developed; but this type of dryer reduces the product quality due to direct exposure of solar radiation. Then, an indirect solar dryer became more important and efficient method. However, the most solar dryers were developed with less efficient flat plate solar collectors. A few solar dryers were developed using efficient solar collector called evacuated tube solar collector (ETC) but they have low overall performance. The goal of this research is to create a dependable solar dryer system for drying agricultural products. It was a solar dryer system with an independent rock bed thermal storage unit and an evacuated tube collector having reflectors. In this case, a rock bed has been a well-insulated with thermal insulation and its top surface is covered by a transparent double-glass. This system is intended to dry potato slice that weigh of 7.5 kg sample having a wet base initial moisture level of 80.1 %, until it reaches the ideal moisture content of 7–13 %. The solar dryer has been developed from drying chamber having size of (length x breadth x height) of 85 cm×61 cm x 62 cm, evacuated tube collector area of 1.3 m2, and rock bed volume of 0.137 m3 (with a solar absorber area of 0.52 m2 and a depth of 0.26 m). The solar dryer system was built and tested with loading slices at various air flow rates and open sun. Here, at a 0.016 m3/s air flow rate as compared to lower and higher air flow rates, more moisture reduction (9.3 % within eight hours and 0.664 kg/h), higher efficiency of the solar collector (62.02 %), more heat production from the system (20.79 MJ, of which 4837.8 kJ was recovered from the rock bed), and higher dryer efficiency (23.87 %) were attained. Compared to open-sun drying, 20 % less time was needed for drying. In addition, the study examined the significance of the reflectors and the rock bed. In comparison to the situation of utilizing ETC alone and 30 % of the drying period in relation to the open sun, the introduction of a reflector on the collector increased the average net heat obtained from the collector by 5.1 %. In another instance, the slice's moisture content was lowered to 12.37 % in under eight hours using ETC alone, while the dryer's efficiency was 29.82 %. However, the drying rate rise by 3.7 % in comparison to the dryer equipped with ETC alone because of the enhanced heat output in the dryer, which used ETC with a rock bed's help.

Borehole‐Based Interval Kriging for 3D Lithofacies Modeling

AbstractDeveloping a three‐dimensional (3D) lithofacies model from boreholes is critical for providing a coherent understanding of complex subsurface geology, which is essential for groundwater studies. This study aims to introduce a new geostatistical method—interval kriging—to efficiently conduct 3D borehole‐based lithological modeling with sand/non‐sand binary indicators. Interval kriging is a best linear unbiased estimator for irregular interval supports. Interval kriging considers 3D anisotropies between two orthogonal components—a horizontal plane and a vertical axis. A new 3D interval semivariogram is developed. To cope with the nonconvexity of estimation variance, the minimization of estimation variance is regulated with an additional regularization term. The minimization problem is solved by a global‐local genetic algorithm embedded with quadratic programming and Brent's method to obtain kriging weights and kriging length. Four numerical and real‐world case studies demonstrate that interval kriging is more computationally efficient than 3D kriging because the covariance matrix is largely reduced without sacrificing borehole data. Moreover, interval kriging produces more realistic geologic characteristics than 2.5D kriging, while conditional to spatial borehole data. Compared to the multiple‐point statistics (MPS) algorithm—SNESIM, interval kriging can reproduce the geological architecture and spatial connectivity of channel‐type features, meanwhile producing tabular‐type features with better connectivity. Because the regularization term constrains kriged value toward 0 or 1, interval kriging produces more certainty in sand/non‐sand classification than 2.5D kriging, 3D kriging, and SNESIM. In conclusion, interval kriging is an effective and efficient 3D geostatistical algorithm that can capture the 3D structural complexity while significantly reducing computational time.

Geological survey techniques and carbon storage: Optimizing renewable energy site selection and carbon sequestration

Geological survey techniques play a crucial role in optimizing site selection for renewable energy projects and identifying suitable locations for carbon storage to mitigate climate change. This abstract provides an overview of how geological survey techniques can be used to achieve these objectives. Renewable energy development, particularly solar and wind power, requires careful site selection to maximize energy generation efficiency and minimize environmental impacts. Geological surveys are instrumental in assessing factors such as subsurface geology, topography, soil composition, and hydrological conditions. These surveys help identify suitable locations with optimal wind or solar resources and geologic conditions for infrastructure development. Additionally, geological surveys are essential for identifying suitable sites for carbon storage, a critical component of carbon capture and storage (CCS) technologies aimed at reducing greenhouse gas emissions. Geological formations, such as deep saline aquifers, depleted oil and gas reservoirs, and unmineable coal seams, can serve as storage reservoirs for captured carbon dioxide (CO2). Geological surveys help characterize these formations to assess their suitability for long-term CO2 storage, considering factors such as porosity, permeability, and sealing integrity. Optimizing site selection for renewable energy projects and carbon storage requires a comprehensive understanding of subsurface geology and environmental conditions. Advanced geological survey techniques, such as seismic imaging, remote sensing, and geophysical surveys, are essential for acquiring detailed subsurface data. These techniques enable scientists and engineers to assess site suitability, evaluate risks, and design effective mitigation measures. In conclusion, geological survey techniques are invaluable tools for optimizing site selection for renewable energy projects and identifying suitable locations for carbon storage. By leveraging these techniques, stakeholders can make informed decisions that promote sustainable energy development and mitigate the impacts of climate change.

Mineral Recource Prospecting and Evaluation of Dry Stream Sediments of Wadi Umm Gheig – Umm Naggat Area, Eastern Desert, Egypt

The area of Wadi Umm Gheig-Umm Naggat is located at the central part of the Eastern desert, Egypt, 50km south to El-Quseir city at the Red Sea coast. The area is dominated by metavolcanics, Older Granites, Dokhan Volcanics, intrusive cumulate gabbro and Younger Granites. This works focuses on heavy minerals distributed in dry stream sediments of Wadi Umm Gheig and Gabal Umm Nagat. The study has followed up the traditional methods for sample collection from the stream sediments and the plane study for investigation and prospecting, as well as evaluation of heavy mineral deposits. The studied bed rocks are represented mainly by monzogranite, alkali feldspar granite, syenogranite and alkali granite. The investigated heavy minerals dominating the stream sediments are given by magnetite, ilmenite, rutile, leucoxene, zircon, fluorite and apatite which are arranged in decreasing order as percentages of abundances. Few trace minerals are detected in some samples like thorite and monazite, and xenotime as well. The evaluation of heavy minerals concentration reveals higher concentration of magnetite, ilmenite and zircon at the western sector, while fluorite show random distributions within the stream sediments area.

An Improved Method for Estimating Earthquake-Induced Permanent Displacement of Bedding Rock Slopes

An Improved Method for Estimating Earthquake-Induced Permanent Displacement of Bedding Rock Slopes

High‐density offshore seismic exploration with an optical fibre towed streamer based on distributed acoustic sensing: Concept and application

AbstractSeismic technique is widely used to image the subsurface geology for oil and gas exploration. The image quality depends on the spatial sampling density. However, it is challenging and expensive to acquire high‐density seismic data, particularly in the marine environment. Distributed acoustic sensing data are increasingly used in data acquisition because of their low cost and dense spatial sampling. Here, we present a novel type of high‐density towed streamer based on distributed acoustic sensing technology and report the results of a sea trial. This sea trial was conducted in a gas hydrate province as the major driver to develop this technique is to better characterize gas hydrate deposits. Throughout the experiment, several high‐quality datasets were obtained, and parameters like source energies and filler materials were examined. The trace interval of distributed acoustic sensing streamer data reaches 1 m, which is a significant improvement over the usual 3.125 or 6.25 m in the conventional towed streamer. A detailed analysis was carried out from three different perspectives: amplitude, noise and frequency. One of the datasets was further processed following a routine workflow to obtain the final image. Though direct comparison with the image obtained by a conventional towed streamer along a coincident line is not available, the comparison with the previous image from a nearby line shows the improvement in resolution. The final image is of good quality and the presence of gas hydrate could be inferred. The sea trial results demonstrate the feasibility of the use of a distributed acoustic sensing optical fibre streamer in acquiring high‐density seismic data in the marine environment.

Inferring arsenic anomalies indirectly using airborne hyperspectral imaging – Implication for gold prospecting along the Rise and Shine Shear Zone in New Zealand

Well-exposed mineral deposits are scarce at a global level and presently potential mineral-rich sites are underlying vegetation cover and topsoil, which are suboptimal for direct remote sensing based exploration techniques. This study aims to implement an indirect approach to arsenic (As) distribution mapping using the surface manifestations of the subsurface geology and link it to the known gold mineralisation in the study area. Rise and Shine Shear Zone (RSSZ) in New Zealand is broadly a part of the Otago schist hosting lower to upper green-schist facies rocks manifesting mesothermal gold mineralisation. The area has several surficial geological imprints separating mineralised and non-mineralised zones, but these are dominated by topographic ruggedness, soil moisture and vegetation (mainly grass/tussock) spectra in the hyperspectral data. Initially, a band selection using Recursive Feature Elimination (RFE) was executed. The bands generated were tallied with the field and geological understanding of the area. The resultant 85 bands were then further put through Orthogonal Total Variation Component Analysis (OTVCA) to concise the information in 10 bands. OTVCA output was then classified using Random Forest classifier to map three levels of As concentration (<20 ppm, between 20 and 100 ppm and >100 ppm). The potentially high As concentration zones are likely to be related to the gold mineralisation. The geology of the area correlates with soil exposure which is captured by the classification in some parts, this increases the accuracy but also makes the classification analysis challenging.

Influence of geological uncertainty on longitudinal deformation of tunnel based on improved coupled Markov chain

The complex geological condition encountered during excavation is the key challenge for tunneling projects. Therefore, tunnel design and construction require a comprehensive understanding of the subsurface geology. This study aims to reveal the effect of geological uncertainty on tunnel longitudinal deformation based on a reconstruction geological model using the improved coupled Markov chain method. The improved coupled Markov chain method makes the predicted results more suitable for the possible stratigraphic distribution by optimizing the transition probability matrix, and breaks through the limitations of non-coaxial predicted cell updating in traditional methods. A mapping method was proposed to establish a matching relationship between the irregular grids of the geological model and the numerical tunnel model. Then, a long tunnel in Shenzhen was selected as a case study to demonstrate the effectiveness of the proposed framework. The correlation coefficient was used to verify the relationship between tunnel deformation and the surrounding stratum with different tunnel cover depths. The geological uncertainty of various strata was quantitatively measured based on the proposed geological uncertainty index. The three-dimensional strata surrounding the tunnel were reconstructed based on exceedance probabilities for adverse geological conditions. Quantitative analysis was conducted on the tunnel vertical convergence during the excavation process.

ANALYSIS OF GEOPETROLEUM DATA FROM THE NGA-1, KNY-1 AND BYU-1 EXPLORATION WELLS IN THE NGANZI BLOCK, ONSHORE D.R. CONGO COASTAL BASIN

In the Nganzi Block, onshore DR Congo, three wells have been drilled in plays that demonstrate an inverted stratigraphic relationship between the Middle Bucomazi source rock beds and the older Lucula Sandstone reservoirs. Despite having an average porosity of 18% and a relative permeability of 110 Millidarcy, the Lucula Sandstone reservoirs have little hydrocarbon saturation in the three exploration wells; Kinganga Myanga-1 (KNY-1), Nganga-1 (NGA-1), and Byangu-1 (BYU-1). An understanding of the relationship between the inverted stratigraphic relationship and the hydrocarbon charge will lead to greater confidence in migration, charge and trap of this play.

Performance study of low temperature air heated rock bed thermal energy storage system

AbstractOne of the primary types of sensible heat storage systems in drying applications is the packed rock bed. However, to create large‐scale heat storage systems for industrial use, one must comprehend the hydrodynamic and effectiveness of the heat transport mechanism inside the bed. In this study, the thermal storage unit uses river rock as heat storage materials with equivalent particle diameters of 36 mm in bed 1 and 56 mm in bed 2. The rocks were stacked in a truncated cone‐shaped concrete wall section with an average diameter and depth of 1.1 m and 1.3 m, respectively and a volume of 2.32 m3. During the charging phase, two airflow configurations were used, one from the top with an air mass flow rate of 0.753 and 0.332 kg/m2‐s and the other from the bottom with an air mass flow rate of 0.955 kg/m2‐s. During the discharging phase, the entire flow configuration is from the bottom section. It was observed that the mass flow rate and particle equivalent diameter had an important effect on the thermal performance and behaviour of the rock bed during charging and discharging operations. Maximum efficiency was achieved with an airflow configuration provided from the bottom when charging at 0.955 kg/m2.s. Consequently, a sizable quantity of heat or energy (60 MJ) was retained. It was also observed that the relationship between air mass flow rate and particle size was significant, with smaller particles retaining more energy. When comparing bed 1 with bed 2 at this air mass flow rate, bed 1 stored 2.1 times more energy than bed 2. A wind tunnel experiment was used to measure the pressure drop in the packed rock bed. The pressure drop in the bed increases with an increase in particle Reynolds number and decreases with an increase in particle size. Rock bed heat transfer coefficient and Nusselt number were calculated using the correlation that has already been established in the literature smaller particles showed higher heat transfer coefficients and lower Nusselt numbers. This is due to the increase in particle‐to‐particle interaction and larger particle surface areas. For a given Reynolds number, the Nusselt number increases with the size of the rock particle.

Early exploration modelling of natural hydrogen systems through the use of existing open source data

Natural hydrogen’s viability as a sustainable energy source will be enhanced through comprehensive geological modelling. This paper integrates existing open-source data to delve into the geological aspects of natural hydrogen exploration and proposes possible workflows. Geological and geophysical modelling entails characterising subsurface formations conducive to natural hydrogen generation and trapping. Utilising geological surveys, field observation, geophysical seismic and gravity data, alongside existing well logs, this analysis looks to identify regions with favourable geological conditions for the generation, migration and structures for accumulation of natural hydrogen. Furthermore, understanding the subsurface geology aids in the development of safe and efficient extraction techniques. By incorporating geological modelling into the evaluation of natural hydrogen, this paper provides a comprehensive overview of its potential as a sustainable energy solution. Leveraging existing open-source data alongside geological insights ensures a robust foundation for decision-making in exploration, production, storage, and utilisation strategies. This integrated approach empowers stakeholders to make informed choices in shaping a greener, more sustainable energy landscape.

Combined onshore and offshore wide-scale seismic data acquisition and imaging for carbon capture and storage exploration in Havnsø, Denmark

Strong global actions for climate change include carbon capture and storage (CCS) as a feasible solution to reach carbon neutrality and raise opportunities for detailed subsurface investigations. An acquisition set-up designed for onshore-offshore zones was maximized for wide-scale high-resolution structural imaging and implemented to cover a domal structure of interest for CCS utilization close to the town of Havnsø (Denmark). The challenges of the combined acquisition and processing of land and marine multisensor data along a 42 km seismic profile are analyzed, the suggested solutions are applied, and the limitations are discussed. On the onshore side, a nodal array and a seismic landstreamer system were simultaneously used, whereas along the transition zone, a marine seismic streamer and ocean-bottom seismometers were added to record the seismic response generated by two seismic vibrator sources. The adopted sensing domains (velocity, acceleration, and pressure) were studied, and different processing steps were evaluated to enable their processing and subsequent data set merging. Results suggest, as the best approach, a separate prestack processing of the different data sets and the computation of new geometries and new surface-consistent residual static correction after their merging. The data acquired in the transition zone illuminate, for the first time, the subsurface geology of the region, delineating an expected domal closure. The final seismic section shows high continuity of the reflections with good resolution along the entire profile, identifying the main reservoir structure and the surrounding areas, which are important to ensure reservoir integrity and safe exploitation over longer time scales. Shallow and deep reflections are consistent with the stratigraphic column from a well log near the profile. The presented study shows a comprehensive workflow for processing such a multisensor data set in onshore and transition zone settings.

Imaging along-strike variability in fault structure; insights from seismic modelling of the Maghlaq Fault, Malta

Seismic modelling studies of outcrop analogues have proven a powerful method to provide a link between geology as observed at outcrop, and the interpretation of subsurface geology from seismic data. Seismic imaging of fault zones is inherently challenging, as they may be associated with steep dips, narrow zones of heterogeneously deformed rocks, and complex geometries at the limit of seismic resolution. We here investigate how along-strike variations in fault geometry and structural style are imaged in reflection seismic images, based on seismic modelling of well-exposed outcrops of the Maghlaq Fault hosted in the Miocene-Oligocene carbonate rocks in Malta. Using two-dimensional seismic modelling, selected structural cross-sections have been modelled, focusing on variations in fault- and hangingwall bed geometries, and dominant seismic signal frequency. The seismic models show great variability in resolution and, thus, level of resolved geologic detail. The modelled seismic images show that, for all signal frequencies, the fault itself is not imaged, but is manifested by terminations of footwall reflections as well as fault-related strain in the form of drag folding of hangingwall beds, in addition to fault-proximal seismic imaging artefacts. Rotated and ‘drag-folded’ hangingwall beds along the fault produces a high-amplitude fault parallel reflection bundle in the immediate hangingwall of the fault. The illumination issues that dominate in low dominant frequency seismic models are less prevalent in the higher-resolution, higher dominant frequency models. The results of this outcrop-to-seismic study offer insight to the relationship between faults and seismic images, which may improve our ability to accurately interpret faults in the subsurface form reflection seismic data.

LESSONS LEARNT FROM SOIL IMPROVEMENT CASE STUDIES

In Saudi Arabia two methods of soil improvement have been customarily employed. They are soil improvement by means of stone columns, and soil improvement by means of controlled modulus columns, that is CMC. Each of these methods have their own challenges to offer. Experience has shown that the sub-surface geology of the coastal areas of Saudi Arabia are marked with deep layers of poor soil termed locally as sabkha soil. Test results have determined that sabkha soil is known to have low shear strength, high soil compressibility, and high concentration of chlorides and sulphates which are corrosive to concrete, steel, and other construction materials. Design of foundations over a sabkha deposit remains a challenge and requires soil improvement. The CMC installation utilizes reverse flight augers, which displaces the soil laterally. However, it offers a huge challenge of post-operation trimming and cutting of CMCs. for stone columns, soil is removed during the drilling operation creating environmental issue. It also offers challenges as the huge impact during its operation are likely to damage the underground utilities. The environmental issues thus created can pose yet other challenge. This research paper is a case study that collates the experiences of soil improvement methods employed on a project in Saudi Arabia – vis-à-vis their advantages and the challenges encountered.

LESSONS LEARNT FROM SOIL IMPROVEMENT CASE STUDIES

In Saudi Arabia two methods of soil improvement have been customarily employed. They are soil improvement by means of stone columns, and soil improvement by means of controlled modulus columns, that is CMC. Each of these methods have their own challenges to offer. Experience has shown that the sub-surface geology of the coastal areas of Saudi Arabia are marked with deep layers of poor soil termed locally as sabkha soil. Test results have determined that sabkha soil is known to have low shear strength, high soil compressibility, and high concentration of chlorides and sulphates which are corrosive to concrete, steel, and other construction materials. Design of foundations over a sabkha deposit remains a challenge and requires soil improvement. The CMC installation utilizes reverse flight augers, which displaces the soil laterally. However, it offers a huge challenge of post-operation trimming and cutting of CMCs. for stone columns, soil is removed during the drilling operation creating environmental issue. It also offers challenges as the huge impact during its operation are likely to damage the underground utilities. The environmental issues thus created can pose yet other challenge. This research paper is a case study that collates the experiences of soil improvement methods employed on a project in Saudi Arabia – vis-à-vis their advantages and the challenges encountered.

Experimental Study on Anisotropic Mechanical Characteristics of Shale under Triaxial Loading

Shale is composed of a rock matrix and bedding planes with a layered structure, resulting in significant anisotropy in its mechanical properties. In order to study the anisotropic mechanical properties of shale, the shale samples were prepared in different orientations with respect to the bedding planes, and the composition and microstructure of shale were first analyzed by X-ray diffractometer (XRD) and scanning electron microscope (SEM), and then the uniaxial and triaxial compression experiment on shale samples with five different bedding angles (the angle between the loading direction and the normal direction of the bedding planes, 0°, 30°, 45°, 60°, and 90°) were conducted under five confining pressures (0, 10, 20, 30, and 40 MPa), respectively; meanwhile, the acoustic emission (AE) test was carried out in the uniaxial test. The results indicate that the mechanical properties and parameters of shale have obvious anisotropy, and the AE characteristics of shale samples with different bedding angles are significantly different during uniaxial loading. Furthermore, the compressive strength and elastic modulus of the shale samples first decrease and then increase with the increase in the bedding angle under different confining pressures. Moreover, according to the anisotropic grade of compressive strength, the shale has moderate anisotropy. In addition, the failure mode of the shale samples is also anisotropic, and varies with the bedding angle and confining pressure.

Slope instability mechanism with differential rock mass structure along a fault: a mine landslide from Southwest China

Mine slope stability and mining sustainability are related to the local geological structures, which could change the rock mass structure in deep mining. After 20 years mining in a mudstone mine, western China, the slope structure transforms from anti-dipping structure into a bedding structure by a recently discovered fault (F1), further inducing the two landslides (Landslide #I and Landslide #II). Landslide investigation suggested the residual deposits in Landslide #I first slid over 100 m and overburdened the rear of Landslide #II. The bedding rock with weak interlayers at footwall is separated from the anti-dipping rock at the hanging wall by F1. After excavation, a weak interlayer was exposed and softened by rainfall, resulting in the slip of footwall rock mass and further inducing large scale toppling deformation. The fragmented rock mass sliding along a weak interlayer triggers consequent deformation of adjacent slope, reducing safety reserve of the open mine. The discrete element analysis reveals that the bedding rock mass of footwall slid once the weak interlayer was exposed by mining. And retrogressive deformation transmitted to the hanging wall and induced bending and toppling deformation of anti-dipping rock mass. Mine feasibility assessment should recognize the potential deep geological structures as important in the future.

Impact of flow direction on the isothermal pressure drop through a packed bed of crushed rock – A DEM-CFD approach

Pressure drop plays a crucial role in the design of a packed bed of crushed rock, necessitating a deep understanding of flow behaviour for precise determination of pumping power. This study employs ellipsoidal particles to represent crushed rock, matching the volume and aspect ratio of the sampled rocks. A discrete element model was employed to generate packed beds of ellipsoidal particles, while computational fluid dynamics simulated the flow through the voids in different directions. The model's findings were validated against experimental results from both ellipsoidal particles and crushed rocks. While the ellipsoids effectively capture general flow trends, they underestimate pressure drop through crushed rocks by 5% horizontally and overestimate it by 20% vertically. Consequently, the study proposed a correlation to predict pressure drop in a packed bed using the porous media approach, expressing inertial resistance as a tensor to capture flow direction effects.