Rock Density Research Articles

Palaeoenvironmental and palaeoclimatic inferences based on X-ray computer tomography: a case study of alkaline lake deposits in Hungary

Widely distributed freshwater carbonate sediments, i.e., limestone, dolomitic limestone and dolomite, developed in inter-dune alkaline ponds of the Danube-Tisza Interfluve in the centre of the Carpathian Basin during the Holocene. The key parameters that determine the formation of any given type of carbonate mineral (calcite, dolomite) are temperature, evaporation rate, pH and ion concentrations, in addition to CO2 absorption by aquatic plants. CT analysis is capable of recording small-scale density variations attributable to compositional differences of sedimentary rocks. As the type and proportion of rock-forming minerals and other components is an artifact of past environmental and climatic conditions, CT values may act as potential palaeoenvironmental proxies. The present study compares variations in rock-forming components obtained for freshwater carbonates utilizing the CT method with already available geochemical and palaeoecological proxy data. Variations in molluscan ecology and isotope geochemistry, sedimentation times and CTbased rock density values all indicate the relevance of millennial-scale, climate-driven changes in carbonate formation. As previously observed, the emergence of colder conditions in the North Atlantic, which resulted in increased cyclonic activity and heavier rainfall in western Europe and the Danube watershed area between 10.3 and 9.3 kyr cal BP, resulted in the emergence of humid conditions favouring a rise in the groundwater table at our site and precipitation of calcite from pore waters as opposed to high-magnesium calcite. This is clearly reflected in a negative shift in CT density values in our dated rock samples.

RIMFAX Ground Penetrating Radar Reveals Dielectric Permittivity and Rock Density of Shallow Martian Subsurface

AbstractThe Mars 2020 Perseverance Rover is equipped with the RIMFAX ground penetrating radar instrument which has been continuously surveying the shallow subsurface during the rover's journey. Within the first 379 mission days, we identify hyperbolic patterns in the data, which are thought to be caused by objects such as buried boulders or cavities located in the upper 5 m of the subsurface. To obtain the first detailed estimates of radar wave propagation velocity, we match these scatterer‐generated patterns with theoretical traveltime hyperbolas, which take into account the refraction at the surface. We employ these estimates to derive the average dielectric permittivity and bulk rock density of the volume above the scatterer source. The parameters compare well with those obtained through orbital radar measurements and those measured by other instruments onboard the Perseverance Rover. Our findings are consistent with a subsurface dominated by solid rock and mafic material.

Coupled TMD modeling of cryogenic treatment of borehole in coal under confinement

Cryogenic fracturing using liquid nitrogen (LN2) is a waterless fracturing technology that is under extensive research nowadays given the high demand of environmental-friendly development of unconventional oil and gas resources. Excluding the exerted hydraulic pressure, the initiation and propagation of cryogenic fractures in rock materials largely depend on thermal stress generated by LN2 and the rock properties. So far, there are quite a few experimental studies elaborating on the cryogenic fracturing process of coal rocks; however, modeling studies on the topic are still very preliminary with no damage quantification. This study first set up a coupled thermo-mechanical (TM) modeling procedure by solving the heat conduction and rock mechanics equations in a serial manner and incorporating the maximum principal stress failure criterion. Then the numerical stability of this modeling procedure was examined through time step and grid resolution tests, and the model accuracy was corroborated by analytical solutions. Furthermore, the damage criterion was quantitatively validated against our experimental observations. Using this thermo-mechanical damage (TMD) modeling procedure, a systematic examination of the effects of key factors on cryogenic circulation treatment of coal rock borehole was carried out using realistic parameters. Trends and patterns of the cryogenic damage upon key factors, including realistic temperature boundary with the Leidenfrost effect, Young's modulus, thermal expansion coefficient, Poisson's ratio, specific heat capacity, density, thermal conductivity, in-situ stresses, and initial temperature of the coal rocks have been revealed and discussed. The modeling results herein are of great significance to understand the mechanisms of cryogenic fracturing of coal rocks, and this TMD modeling procedure could be further expanded to evaluate and optimize cryogenic treatment process of coal seams in field pilot tests.

Evaluating translocation success of wild eastern hellbenders (Cryptobranchus alleganiensis alleganiensis) in Blue Ridge Ecoregion streams using pre- and post-translocation home range sizes and movement metrics.

Translocations of freshwater species have become a widespread conservation strategy to mitigate the impacts of habitat fragmentation, yet they are not often rigorously monitored using animal movement data to determine their success. We demonstrate the value of monitoring pre- and post-translocation movements and home-range sizes of a fully-aquatic, benthic stream salamander, the eastern hellbender (Cryptobranchus a. alleganiensis) to determine translocation success. We studied the home range sizes, movements, and habitat use of individuals (n = 27) in two self-sustaining populations (S1 & S2) for one year, and then subsequently collected similar data from a subset of these individuals (n = 17) that were translocated into two nearby streams (T1 & T2) with dam-isolated, declining populations in the Blue Ridge Ecoregion of Tennessee. We collected 1,571 location data points (869 pre-translocation and 715 post-translocation) from four study sites, and evaluated effects of mass, sex, and pre-translocation home range size/sedentariness, as well as habitat covariates on home range size and movements. Hellbender home range sizes increased from pre-translocation estimates at both sites, but response depended primarily on physical characteristics of release sites. Home range and fine-scale movement metrics indicated that hellbenders translocated from S1 to T1 settled in more quickly, had greater site fidelity, and smaller home ranges than hellbenders translocated from S2 to T2. Hellbender movements were influenced by cover rock size and density rather than individual characteristics. Study-long survival rates of translocated hellbenders increased from S1 to T1 (80% to 100%) and decreased from S2 to T2 (76% to 33%). Monitoring pre- and post-translocation movements was a valuable method for evaluating short-term translocation success in a freshwater environment. For future hellbender translocations, managers should prioritize selecting suitable release sites with contiguous boulder-dense areas (1-2 per m2), adequate prey (crayfish) densities (>1/m2), and habitats with low risk of predation.

Effect of Sub- and Supercritical Water on the Transformation of High-Molecular-Mass Components of High-Carbon Rocks from Unconventional Formations (A Review)

State-of-the-art in the field of recovering high-molecular-mass hydrocarbon components of bituminous and shale rocks by intrastratum transformation into readily recoverable forms using sub- and supercritical water is analyzed. The phase composition of water and its properties in the critical state and the transformations of a number of substances in subcritical (SBW) and supercritical (SCW) water are discussed. The substances under consideration include model polycyclic and heteroatomic compounds containing nitrogen, sulfur, and oxygen, metal porphyrin complexes, asphaltenes, oil sands, and heavy oils and organic matter (OM) of kerogen-containing shale rocks. The preventing effect of hydrogen donors and catalysts for hydrogenation and oxidative cracking on the coking in the course of transformation of heavy hydrocarbons in SCW is compared. The catalytic effect of the mineral matrix of rocks in the course of generation of oil fractions from them is analyzed in detail. The published data concerning the possibility of using SBW and SCW for the transformation of high-molecular-mass components of high-carbon dense rocks from unconventional formations demonstrate high potential of hydrothermal and supercritical fluid technologies

Petrophysical Acoustic Characterization of Weathered Granite: A Case Study of Mesozoic Granites in the Coastal Area of Fujian Province, China

In recent years, with the exploration and development of granite buried-hill oil and gas reservoirs, petrophysics research has played an important role in the study of reservoir characteristics and fluid identification. Through analysis of the relationship between the fluid-bearing petrophysical parameters and the reservoir, the seismic response changes caused by reservoir fluid changes can be determined. Mesozoic granites in the coastal area of Fujian Province in eastern China were investigated as the research object of this project. The mineral composition, density, porosity, P-wave velocity, and S-wave velocity of the granite were measured and analyzed by X-ray diffraction, rock density, rock porosity, and rock acoustics methods. Therefore, the granite’s petrophysical properties, fluid response characteristics, and gas sensitivity parameters were analyzed. The result of the study shows that the granite is predominantly monzogranite. According to the type of reservoir space assemblage, the samples can be divided into two types: those containing fracture-dissolution pores and those containing only dissolution pores. All the samples were characterized by medium to high densities and low to extra-low porosity. There was a linear correlation between the P-wave velocity and S-wave velocity under gas and water-saturated conditions. Factors such as P-wave to S-wave velocity ratio, Poisson’s ratio, Lame coefficient, and other parameters of the samples were analyzed, and the threshold values that distinguished the water and gas-saturated states of the samples were measured and determined. In addition, there were negative correlations between the P- and S-wave velocities and porosity. The sensitivities of the petrophysical parameters to the gas capacity from high to low are Ip2 − 2.03 Is2, λ − 0.03 μ, λ, λ/μ, E − 2.03 μ, σ, K/μ, K, Ip, Vp/Vs, Vp, E, μ, Vs, and Is. For granite-buried hill reservoirs, the variation ranges of the parameters, such as the density, porosity, and P-wave velocity, of the fracture-dissolution pore granite samples were larger than those of the dissolution pore samples. The bulk parameters (Ip, Vp, K, λ) and combination parameters (Ip2 − 2.03 Is2, K/μ, λ− 0.03 μ, E − 2.03 μ, λ/μ) of the dissolution pore samples were more sensitive to the gas capacity. The results of this study provide a basis for the geophysical identification of granite-buried hill reservoirs.

«Қарқаралы» Мемлекеттік ұлттық табиғи паркінің топырақ түзілу факторлары және үдерістері

Мақалада «Қарқаралы» Мемлекеттік ұлттық табиғи паркінің (МҰТП) топырақ түзілу факторлары және үдерістеріне талдау бойынша жүргізілген жұмыстар нәтижелері берілген. Мемлекеттік ұлттық табиғи паркінің топырақ жамылғысының зерттелген аймағында олардың негізгі екі фактордан — тік зональдылық және аймақтың геологиялық ерекшеліктеріне байланысты әсерінен дамитыны байқалды. Аудан топырағы гранит, диорит және метаморфтық тығыз жыныстардан құралған. Барлық ежелгі жыныстар қуаттылығы әр түрлі төрттік шөгінділерімен жабылған. Атқарылған жұмыстар бақылау нүктелеріне маршруттар және зерттеу бағдарламасын құрастырудан басталған. Осыдан соң бақылау нүктелерін зерделеу; топырақ кесінділерін жасау — топырақтың морфологиялық қасиетін сипаттау, горизонттар бойынша топырақ үлгілерін алу жұмыстары орындалды. Жүргізілген далалық жұмыстар орманды, таулы-орманды және далалық ландшафттарда өтті. Осы жерлердегі сынамалық нүктелердің топырақ кесінділері бойынша олардың түсі Манселл шкаласы бойынша айқындалды. Топырақтың ылғалдылығы мен гранулометриялық құрамы және хлорлы сутектегі қайнауы анықталды.

Formation Timing and Features of Stylolites and Controlling Factors for the Second-Period Stylolites in the Carboniferous KT-I Formation of NT Oilfield

The formation timing of stylolites, which is of great importance for analyzing the controls of stylolites, has nearly never been examined. In this paper, based on the data of cores, imaging logging, conventional logging, and mercury injection, the characteristics of stylolites formed in different stages of tectonic movement were investigated, and the controlling factors of oil-stained stylolites, formed in the second period of tectonic movement, were analyzed in particular. Furthermore, the influence of different controlling factors on the development of stylolites was compared, by using grey correlation analysis. The results show that there are three periods of stylolites in the study area, and all three periods developed both low-angle stylolites and high-angle stylolites. The prominent characteristics of both the low-angle and high-angle stylolites of the second period, are being oil-stained. The higher the structural location, the greater the buried depth, the lower the dolomite content, the higher the calcite content, the higher the clay content, the smaller the rock density, the greater the porosity, the smaller the rock grain size, the easier it is to develop both the low-angle stylolites and the high-angle stylolites. The influence of different controlling factors on the development of low-angle stylolites is given by depth, porosity, curvature, rock density, rock grain size, clay content, dolomite content, and calcite content, in this order. The importance of the influences on the development of high-angle stylolites proceeds as follows: curvature, calcite content, depth, rock particle size, clay content, rock density, dolomite content, and porosity. Tectonism is the most important influencing factor on the development of stylolites.

Efficiency assessment of the environmental variables in the Qanat systems based on major hydrological basins in Iran

Qanat system, as a great human heritage, contributes to the sustainable management of groundwater in the arid and semiarid regions of the world. The main aim of this paper was to efficiency assessment of the environmental variables in the construction of the Qanat system in Iran. Using the geographical information system (GIS) and statistical method of receiver operation characteristic (ROC), the efficiency of 20 environmental variables was assessed based on divisions of 30 major hydrological basins. Results revealed that most physical parameters and anthropogenic characteristics have significant effects on the construction of Qanat water lines with an AUC index > 0.6. The Pearson correlation test also confirmed the positive and significant relationships between the Qanat system and mentioned environmental parameters. From a geological viewpoint, the results highlighted the effective role of Quaternary aged alluvial sediments with very high permeability and low density of crust rocks in arid soils of arid and semiarid regions, such as playa fields in NamakTehran, Kavir, Lut, and Siahkuh basins. Regarding the spatial expansion of the Qanat system in Iran, the higher effects of some test variables, such as the climatic element of temperature, fault density, and drainage density, were rejected due to poor discrimination values of the AUC index < 0.6.

Experimental Study on the Size of Rock Fragments Ejected from Boreholes Drilled in Coal Mine Roadway Floors

Borehole drilling is required if floor heave in underground mines is to be controlled using bolts through the floor. How well the bolt is anchored depends, in part, on the borehole’s quality. A major factor that can reduce borehole quality is the difficulty of discharging rock fragments from a small-diameter borehole drilled at a downward angle. Therefore, a fuller understanding of the sizes of the rock fragments will aid attempts to achieve smooth fragment discharge. In this study, drilling experiments in the laboratory and SEM imaging were carried out to determine the size and shape of the fragments generated when drilling boreholes in three sedimentary rocks typically found in roadway floors. The results show that the size distribution of the rock fragments conformed to the three-parameter generalized extreme value distribution. The mean fragment size increased with rock density and the mean size of the fragments larger than 1.5 mm increased with the rock’s uniaxial compressive strength. The fractal dimension of the cracks in the fragments was lower for high-density rocks and the mean fragment size was larger for rocks whose cracks had a lower fractal dimension. When a drill rod drills through very dense or high-strength rock, the mean size of the fragments will increase and the discharge power should be increased to prevent fragment discharge blockages. This paper may provide a theoretical basis and a data reference for discharge power settings and discharge channel optimization.

Identification of Geological Structure Based on Gravity Method in Tangkuban Parahu Volcano, Bandung, Indonesia

Tangkuban Parahu Volcano, located in Cikahuripan, Lembang, West Bandung Regency, West Java, Indonesia, has a geothermal potential. However, this potential is accompanied by geohazard risks, one of which is a volcanic eruption that can interfere with the development of geothermal potential. On February 12, 2022, there was a gust of volcanic gas from Ratu Crater, indicating an increase in volcanic activity after an eruption in 2019. Based on the geological map of Tangkuban Parahu/Sunda Volcano Complex, it is estimated that there is a fault structure in a northwest-southeast direction, where if a volcanic eruption occurs, it will cause greater deformation because it cuts through Ratu Crater. Further studies with geophysical methods are needed to estimate the fault structure. The study of the subsurface geological structure of Tangkuban Parahu Volcano was carried out using the gravity method by studying variations in the gravitational field on the earth’s surface to determine differences in rock density. The Complete Bouguer Anomaly (CBA) value from the gravity method at Tangkuban Parahu Volcano shows 68 – 73 mGal, and residual anomaly values ranged from -0.95 to 0.67 mGal. The negative residual anomaly value between -0.95 to 0 mGal shows the weak zone due to volcanism in the crater. On the other hand, high residual anomaly values ranging from 0 to 0.67 mGal are interpreted as the influence of Lava 1 Tangkuban Parahu (Tl1). Analysis using First Horizontal Derivative (FHD) and Second Vertical Derivative (SVD) shows a fault structure trending Northwest – Southeast, which can be a way out of the accumulation of high-pressure water vapor due to volcanic activity.

A nuclear magnetic resonance proxy model for predicting movable fluid of rocks based on adaptive ensemble learning

The movable fluid percentage and movable fluid porosity of rocks are important parameters for evaluating the development potential of petroleum reservoirs, which are usually determined by expensive and time-consuming low-field nuclear magnetic resonance (NMR) experiments combined with centrifugation. In this study, an NMR proxy model based on adaptive ensemble learning was proposed to predict the rock movable fluid indexes efficiently and economically. We established adaptive ensemble learning via an opposite political optimizer (AEL-OPO), which adaptively combines 33 base learners through political optimization to increase the prediction accuracy of the NMR proxy model. To improve the generalization ability of the AEL-OPO, opposition-based learning was introduced to improve the global search speed and stability of the political optimizer. Accessible petrophysical parameters, such as rock density, porosity, permeability, average throat radius, and maximum throat radius, were used as a training set, a validation set, and a test set. The prediction results show that our new strategy outperforms the other 33 base learners, with R2 (coefficient of determination) values of 84.64% in movable fluid percentage and 74.09% in movable fluid porosity.

The structure of oil deposits of the Bashkirian stage within low-amplitude uplifts of the eastern side of the Melekess depression

The Bashkirian deposits of low-amplitude uplifts of the eastern side of the Melekess depression are currently considered as potentially oil-bearing objects. Despite the high level of regional OWC, which covers 2/3 of the the Bashkirian age section, industrial oil inflows were obtained on several structures. An analysis of the structure of oil-productive uplifts showed that up to two oil-bearing reservoir layers with a thickness of 2.0 to 8.0 m can be localized in them. Oil-bearing formations are confined to the roof of the sections of the Bashkirian stage. The upper layer abuts against dense clayed limestones of the Vereian horizon of the Moscovian stage, the lower layer is supported by the bottom waters of the modern OWC. Between them there is a dense bridge of dense carbonate rocks. The reservoir rocks are leached foraminiferal and algal-lumpy limestones, packstones and grainstones, formed at the stage of transgressive development of the epicontinental marine sedimentation basin of the Bashkirian age. Pseudobrecciated and microgranular mudstone formed at the stage of regression of the Bashkirian epicontinental paleobasin are dense cap rock. Reservoir rocks are characterized by porosity at the level of 10-15%, permeability - from 0.062 to 0.195 µm2 rocks.

The use of gravel crushing siftings sands for the production of cast emulsion-mineral mixtures «Slarri Sil»

In the article, the authors present the main use results of mineral materials from local open cast mines for the cast emulsion-mineral mixtures making «Slarri Sil» for the protective wearing course installation for asphalt concrete pavements. The production of cast emulsion-mineral mixtures «Slarri Sil» using sand sifting from crushing local gravel materials was carried out on regional category III highways (according to traffic intensity) of the Amur Federal Highway passing through the Amur Region. In accordance with the requirements for mineral materials for the production of cast emulsion-mineral mixtures «Slarri Sil», it was ruled to use the sandy fraction of the stone crushing sifting products of igneous rocks in accordance with National State Standard 8736 with the following properties quality indicators: strength grade greater than or equal to 1200, abrasion grade greater than or equal to I-1, frost resistance grade greater than or equal to F50. Due to the limited number of deposits with siftings for crushing dense rocks and the length of regional highways in the Amur Region, deposits use for the production of cast emulsion-mineral mixtures throughout the entire route make the construction of wear layers unprofitable. The research objective is the local sand and gravel mix of the Zeya and Bureya rivers for the production of Slurry Seal type cast emulsion-mineral mixtures. The authors present the results of determining the physical and mechanical parameters and grain compositions of sands from siftings of crushing sand and gravel mix and rock for protective wear layers of asphalt concrete pavements. The results of determining the adhesion of the binder with the mineral part of cast emulsion-mineral mixtures «Slarri Sil» on various sands of crushing siftings are presented. The results of testing sands from siftings of crushing gravel and siftings of igneous rocks for wet abrasion are shown. The results of experimental studies made it possible to substantiate the use of sand from gravel crushing siftings for the construction of a protective wear layer for asphalt concrete pavement made of cast emulsion-mineral mixtures type «Slarri Sil» on the roads of the Amur Region, including federal ones. The obtained results were used to prepare the standard of the organization company standard — closed stock corporation «Asfalt» — 001-2012 «Production of works on the installation of protective wear layers for asphalt concrete pavements from cast emulsion-mineral mixtures of the Slurry Seal type».

Estimation of in-situ rock strength from borehole geophysical logs in Australian coal mine sites

This study aims to improve the conventional empirical rock strength estimation method that is widely adopted in the Australian coal mining industry and provide more accurate rock uniaxial compression strength (UCS) predictions based on artificial neural network (ANN) models. 274 laboratory-measured UCS data (sample dimension: 60 mm (diameter) × 150 mm (height)) were collected from two longwall coal mines in Australia, along with the four geophysical logs (sonic, gamma, neutron, and porosity logs) and rock density of the tested core specimens. A two-layer ANN model was developed from these data based on the Levenberg–Marquardt algorithm as a base model. As compared to conventional sonic-UCS fitting equations, the mean percentage error, root mean squared error and maximum absolute error of the proposed ANN model were reduced from 34.27%, 15.23 MPa and 70.66 MPa to 20.67%, 11.02 MPa and 47.66 MPa, respectively. Further investigations were conducted by splitting the dataset based on rock lithology and mine locations, and separate ANN models were developed based on the divided subsets. Both lithology-specific and site-specific models exhibited improved estimation accuracy in comparison to the base model, indicating lithology and local geological conditions could considerably affect the estimation accuracy. Among the three types of models, the lithology-specific models yielded the most accurate predictions over the 274 data (MPE: 17.55%; RMSE: 8.84 MPa), followed by the site-specific models and the base model in descending order. Overall, all three models significantly outperformed the current empirical methods adopted in the studied mine sites. The outcomes of this study could provide more accurate UCS predictions for further geotechnical analysis in underground constructions, such as tunnel stability analysis and estimating in-situ stresses based on borehole breakout.

A Mineralogical Model for Thermal Transport Properties of Rocks: Verification for Low-Porosity, Crystalline Rocks at Ambient Conditions

AbstractThermal conductivity (K) describes the response of matter to temporal or spatial variations in temperature (T). To quantify the effect of varying mineralogy on heat transport of rocks, an accurate (±2%) contact-free heat transfer method was applied at ambient T to multiple sections from 33 different low porosity, continental, igneous and metamorphic rocks. Thermal diffusivity (Dheat) was measured using laser-flash analysis, which was previously used to construct our large mineralogical database and which mitigates spurious radiative transfer found in other techniques. These measurements constrain K, because K is the product of Dheat with the known (or calculable) properties of density and specific heat measured at constant pressure (P). Compositions, proportions, and orientations of minerals, plus rock density, average grain-size (L), and porosity were characterized for 61 sections from 29 silicate rocks plus 5 sections from 3 marbles. Our database was used to evaluate component summation (averaging) formulae that were recently developed by considering Fourier’s laws, and to quantify the dependence of K and/or Dheat on key rock descriptors. We found that: (1) phase proportions and compositions are the main cause of variations; (2) minor porosity and foliation have minor effects; and (3) within ~5%, isotropic rocks follow Dheat = ½{[Σ(fi/Di)]−1 + Σ(fiDi)} where fi is volumetric mineral fraction, analogous to the Voigt-Reuss-Hill average for elastic moduli. Using this formula predictively depends on the accuracy of fi and Di. Quartzo-feldspathic rocks can be described by a new formula that uses only quartz fraction and plagioclase composition. Combining our mineralogical model with a universal formula for Dheat(T) and a thermodynamic identity for K(P) accurately constrains conductive thermal transport for Earth’s low porosity, crystalline rock layers.

Estimating Flyrock Distance Induced Due to Mine Blasting by Extreme Learning Machine Coupled with an Equilibrium Optimizer

Blasting is essential for breaking hard rock in opencast mines and tunneling projects. It creates an adverse impact on flyrock. Thus, it is essential to forecast flyrock to minimize the environmental effects. The objective of this study is to forecast/estimate the amount of flyrock produced during blasting by applying three creative composite intelligent models: equilibrium optimizer-coupled extreme learning machine (EO-ELM), particle swarm optimization-based extreme learning machine (PSO-ELM), and particle swarm optimization-artificial neural network (PSO-ANN). To obtain a successful conclusion, we considered 114 blasting data parameters consisting of eight inputs (hole diameter, burden, stemming length, rock density, charge-per-meter, powder factor (PF), blastability index (BI), and weathering index), and one output parameter (flyrock distance). We then compared the results of different models using seven different performance indices. Every predictive model accomplished the results comparable with the measured values of flyrock. To show the effectiveness of the developed EO-ELM, the result from each model run 10-times is compared. The average result shows that the EO-ELM model in testing (R2 = 0.97, RMSE = 32.14, MAE = 19.78, MAPE = 20.37, NSE = 0.93, VAF = 93.97, A20 = 0.57) achieved a better performance as compared to the PSO-ANN model (R2 = 0.87, RMSE = 64.44, MAE = 36.02, MAPE = 29.96, NSE = 0.72, VAF = 74.72, A20 = 0.33) and PSO-ELM model (R2 = 0.88, RMSE = 48.55, MAE = 26.97, MAPE = 26.71, NSE = 0.84, VAF = 84.84, A20 = 0.51). Further, a non-parametric test is performed to assess the performance of these three models developed. It shows that the EO-ELM performed better in the prediction of flyrock compared to PSO-ELM and PSO-ANN. We did sensitivity analysis by introducing a new parameter, WI. Input parameters, PF and BI, showed the highest sensitivity with 0.98 each.

Identification of the relatively low permeability area in coal and gas outburst seams by seismic wave tomography technique: Field application and validation

Identifying relatively low permeability areas (RLPA) is significant for site selection and parameter design for implementing enhanced gas mining measures (e.g. hydraulic fracturing, hydraulic perforation, etc.) in coal and gas outburst seams. The P-wave velocity of coal is sensitive to the variation of porosity. This paper researched the P-wave velocity change of coal with respect to confining pressure and gas pressure, the mathematical relationship model between P-wave velocity with porosity and permeability, and the relative permeability identification index. The research found that the P-wave velocity response to gas pressure varies non-monotonically. When the gas pressure is <2 MPa, the confining pressure is the main control factor leading to P-wave velocity variation. The mathematical model of P-wave velocity versus porosity and permeability was derived based on the linear relationship between wave velocity and porosity in dense rocks and the Seidle permeability model for porous media. Then the wave velocity anomaly coefficient (An) is used as the identification index for the relative permeability of the coal seam. That is, when the anomaly coefficient of coal seam wave velocity An < -8%, the coal seam is a relatively high permeability area (RHPA); when −8% <An < 8%, the coal seam is relatively normal permeability area (RNPA); when An > 8%, the coal seam is (RLPA). Based on the identification indexes studied, two RHPA (H1 and H2) and two RLPA (L1 and L2) were identified in the field engineering application. Comparing the drainage parameters in different relative permeability areas, the gas drainage volume fraction and flow in the RLPA are 56% and 90% lower than RHPA, respectively, validating the accuracy of identifying RLPA in the coal seam.

A comprehensive study of some features from characteristics of enhanced ground‐penetrating radar wave images through convenient data processing within carbonate rock, west of Assiut, Egypt

AbstractThe Eocene limestone plateau, west of Assiut, is characterized by different sedimentary structural features such as fractures, karst, cavities and marble. All conventional methods failed to detect these features due to their inhomogeneities. In this study, a ground‐penetrating radar survey was applied to an area including an old quarry of marble lying at the eastern part of the limestone plateau. The field survey was carried out using a 200‐MHz antenna following the profiling and areal mapping techniques. The acquired ground‐penetrating radar wave images were processed and interpreted using the available software program to enhance the different reflection characteristics from the subsurface anomalous materials. A series of the three‐dimensional model cross section with variable depths were constructed to identify and characterize different georadar facies changes vertically and laterally. The obtained results were adjusted and compared with the excavated features of the quarry; therefore, ground‐penetrating radar anomalies and reflections were calibrated. In the present study, the ground‐penetrating radar survey succeeded in differentiating between dense limestone rocks, onyx marble and microstructural features resulting from recent tectonism. Moreover, the investigation of ground‐penetrating radar reflection waves is useful in differentiating between low‐ and high‐quality limestone and onyx marble. This study identifies the various features of the limestone plateau lying below the ground surface, west of Assiut, that are to be taken into account by planners when establishing new urban centres on the plateau in the future.

Comparison of Earthquake and Moisture Effects on Rockfall-Runouts Using 3D Models and Orthorectified Aerial Photos

Rockfall hazard gains popularity nowadays among researchers in different scientific fields, decision-makers and urban planners. The assessment of rockfall hazard requires detection, mapping and estimating the maximum travel distance that rock boulders may reach, commonly known as “rockfall runout”. This latter can change significantly under the effects of different triggering factors such as soil conditions, chemical, physical and geological rock properties. However, comparing and analyzing these different effects represents, to the best of our knowledge, one of the newest scientific challenges that need to be addressed. This paper presents a complete methodologic approach aiming to assess the rockfall hazard through runout estimation in three different conditions: (i) gravity, (ii) earthquakes, and (iii) the presence of moisture along the slope. The “Mtein” Village and its surrounding areas in the Mount Lebanon region were chosen as the study area because there have been numerous historic rockfalls and various-sized rocks, such as cobbles and boulders, scattered throughout the area. Thus, three-dimensional simulations were conducted using the Rockyfor3D software and aerial photos for the year 1999 to assess the rockfall runout, the energy curves, and the number of deposited rocks. The results reveal that earthquakes have the highest triggering effect on rockfall and that moisture has a damping effect on RFs by decreasing the kinetic energy. The study shows the importance of taking into consideration the influence of triggering factors as well as rock density on rockfall runout and hazard.