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1

Ocena morfologii powierzchni spękań rozdzielczych w piaskowcach metodą profilometrii laserowej

Rembiś Marek, Oczkowski Łukasz

Przegląd Geologiczny

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2025

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Vol. 73, nr 1

81--89

EN

This paper attempts to determine the relationship between the lithology, the type of mechanism of disintegration of sandstone samples and the morphology of the resulting separation surfaces, which has a significant impact on the magnitude of displacements occurring within the rock mass. Six lithologically different sandstones from the Carpathians, Sudetes and Holy Cross Mountains were analysed. The first element of the research was petrographic studies. The next tests consisted of carrying out strength tests, including tests of rock resistance to uniaxial compression strength and flexural strength under concentrated force. Then, a total of 12 surfaces obtained were examined using a laser profilometer. Laser profiling data was correlated with petrographic and strength test data. They showed that the strength value is influenced by the type of rock itself and that the morphology of the separation surfaces differs depending on the type of disintegration. Surfaces obtained by uniaxial compression testing are rougher than those obtained by bending forces. Moreover, the study revealed a fairly clear relationship between sandstone textures and roughness parameters of surfaces, regardless of the disintegration test. The highest roughness values are found on the surfaces of sandstones from Radków, Tumlin and Bieganów. On the other hand, there is no correlation between waviness values and rock textures. Therefore, waviness parameter is a poor tool for describing the morphology of the separation surfaces in sandstones.

2

Thermal Effects on the Structural and Mechanical Microstructure Parameters of Siliceous Sandstone from Kielce Upland

Pachnicz Michał

Civil and Environmental Engineering Reports

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2025

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Vol. 35, no. 1

250--271

EN

This study explores the thermal evolution of the microstructure and mechanical properties of Jurassic sandstone from the Kielce Upland, subjected to temperatures between 20°C and 1000°C. Combining microcomputed tomography (micro-CT) and nanoindentation techniques, it analyzes how geometric changes affect mechanical parameters. Key features like porosity, pore size distribution, and solid matrix thickness were assessed alongside indentation modulus (MIT) and hardness (HIT). The results reveal a strong correlation between microstructural changes and mechanical responses. At 200°C, microstructural compaction and thermal tightening lead to temporary strengthening. Above 600°C, increased porosity, microcrack formation, and rock matrix degradation cause significant reductions in mechanical properties. Reconstructed grayscale values are identified as reliable estimators for mechanical property changes, particularly for indentation modulus, when baseline parameters are available.

3

Experimental study on triaxial compression mechanical properties of grouting reinforcement of broken surrounding rock

Yang Peng, Pang Dongdong

Archives of Mining Sciences

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2025

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Vol. 70, no. 2

273--291

EN

Grouting is a widely used method of reinforcement for stabilising fractured surrounding rock. To investigate the triaxial compression behaviour of surrounding rock after grouting reinforcement, laboratory-prepared grouted specimens were subjected to triaxial compression tests using an RMT-150B testing system. The analysis focused on the effects of confining stress, particle size, and water-to-cement ratio on the stress-strain behaviour. The internal friction angle and cohesion were determined based on the Mohr-Coulomb criterion. The variations in strain at peak stress and the elastic modulus were clarified, and the failure modes of the grouted specimens were examined. Additionally, Kendall’s correlation analysis was employed to evaluate the relationship between confining stress and other parameters. The results indicate that increasing confining stress significantly enhances the load-bearing capacity of the surrounding rock. The optimal rock particle gradation was observed when the particle size ranged between 5-10 mm, yielding the highest compressive capacity. Conversely, increasing the water-to-cement ratio reduced the strength of the specimens. Among the analysed factors, confining stress exhibited the strongest correlation with peak stress.

4

Considering the effects of local impact disturbance on deep sandstone: exploring strength weakening mechanism

Zhao Jihe, Jin Jiaxu, Li Yanfeng, Wu Pengfei, Wang Haibo, Shi Yingshuang

Archives of Mining Sciences

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2025

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Vol. 70, no. 1

63--83

EN

The stability of rock mass is an important safety issue in the process of deep mining, and the dynamic disturbance caused by excavation and blasting is an important factor affecting the stability of rock mass. To deeply understand the mechanical characteristics and damage mechanisms of deep sandstone after local impact disturbance by high prestresses, a self-developed rock disturbance system was used to carry out disturbance followed by a uniaxial compression test (UCT) on the rock samples. The whole process of UCT was monitored utilising acoustic emission (AE) technology, and the particle size and fractal dimension of debris after sandstone failure were analysed to explore its strength-weakening mechanism. The experimental study elucidated the influence mechanism of the coupled action of disturbance frequency f and impact area s on the strength weakening effect of sandstone, i.e., high prestressing force is the prerequisite and dominant factor of rock strength weakening, while the perturbation f and the s accelerate the induced rock damage. The fractal dimension D can be used to quantitatively evaluate the fragmentation characteristics of sandstone disturbed by local impact (between 1.68 and 2.14), and it shows a good linear increasing trend with the increase of local impact disturbance.

5

Reservoir Characterization of the Pre-Cenomainian Sandstone: Central Sinai, Egypt

El Sayed Abdel Moktader A., El Sayed Nahla A.

Inżynieria Mineralna

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2024

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Vol. 1, no. 1

97--104

EN

Fifty-one sandstone core samples obtained from wadi Saal area. They are belonging to the Pre-Cenomanian age. These samples were subjected to various laboratory measurements such as: density, porosity, permeability, electrical resistivity, grain size analysis and ultrasonic wave velocity. The parameters describing reservoir properties are outlined. Packing index, reservoir quality index, flow zone indicator and pore throat radius (R35 and R36) were calculated. The obtained interrelationships among these parameters allowing to improve petrophysical knowledge about the Pre-Cenomanian reservoir information. The obtained rock physics models could be employed with some precautions to the subsurface existences of the Pre-Cenomanian sandstone reservoirs especially in the surrounding areas.

6

Characteristics of sandstone unloading creep and modelling for safe tunnel construction under high perimeter pressure and high pore water pressure condition

Song Li, Tang Fujun, Kong Dehui

Archives of Civil Engineering

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2024

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Vol. 70, nr 3

499--512

EN

Research on the properties of sandstone in the tunnel environment has been conducted due to the building industry’s rapid development, which is gradually involving underground water. Sandstone used in tunnel construction is susceptible to high perimeter and water pressures as a result of the abundance of sand and gravel close to groundwater, which might result in mishaps resembling collapses. The modified Burgers Model for the Malm dataset is the foundation of this study, which aims to reduce the internal crack extension caused by sandstone’s unloading creep. First, the study increased the material’s Poisson’s ratio in accordance with the Mohr-Coulomb strength criterion and builds a triaxial loading model on its foundation. Next, it analyzed the extension of the fracture surface of sandstone while taking high peripheral pressure and high hydraulic pressure into account. Finally, it discretized the unloading creep of sandstone using the improved Burgers model. On the basis of the model put forward in the study, experimental validation was then done on the Malm dataset. The sandstone would reach the final rupture area without any protection measures in just 10 days, but the model suggested in the study can delay this time to 200 days, while the effects of the other three models would delay this time by 75, 60, and 41 days, respectively. The model’s breadth was indicated by the linear fit value of 0.9827 for 36 experiments. The experimental findings demonstrated that the model suggested in the study can successfully lower the rate of sandstone unloading creep and increase worker safety.

7

Water saturation effects on the fracturing mechanism of sandstone excavating by TBM disc cutters

Lin Qibin, Zhang Shenchen, Liu He, Shao Zuliang

Archives of Civil and Mechanical Engineering

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2024

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Vol. 24, no. 3

art. no. e154, 2024

EN

Water content is an important factor affecting the rock-breaking efficiency of tunnel boring machine (TBM) disc cutters. However, limited efforts have been made to study the fracturing mechanism of sandstone excavation by TBM disc cutters under varying water content conditions. To investigate the breakage behavior of water-soaked sandstone by TBM disc cutters, five sets of penetration tests on sandstone specimens with different water content levels were performed. The tests were conducted using a modified RYL-600 computer-controlled rock shear rheometer. An acoustic emission (AE) monitoring system was utilized throughout the entire process to track the AE activity of the specimens. The force–depth curves of the penetration process at various water content levels were investigated. The effects of water content on AE characteristics, rock fracture properties, and specific energy were analyzed. The results indicate that AE activity can be divided into three stages: quiet period, slow rise period, and active period. With increasing water content, peak penetration force, consumed energy, and specific energy decrease gradually, while chip volume increases. Water promotes mutual penetration of surface and internal cracks of the specimen, resulting in the formation of larger chip volumes. These findings provide theoretical guidance for designing and improving TBM cutter head parameters in water-rich soft rock formations.

8

Dynamic compressive behavior of impact‑damaged and water‑soaked sandstone with different length‑to‑diameter ratios

Luo Kun, Wang Yuanmin, Luo Song, Li Xiaoshuang, Peng Kang

Archives of Civil and Mechanical Engineering

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2024

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Vol. 24, no. 1

art. no. e21, 2024

EN

In backfill mining, surrounding rock damaged by impact loading (e.g. blasting) is immersed in backfill water after backfilling, and the instability of the impact-damaged and water-soaked (IDWS) surrounding rock can occur under blasting loads. To study the dynamic mechanical properties and the size effect of rock under such working conditions, triaxial dynamic compression tests were conducted on four groups (four length-to-diameter ratios) of first impact-damaged and then water-soaked sandstone specimens using an improved split Hopkinson pressure bar device. The test results show that, at a similar strain rate (approximately 10 s −1 ), the peak strength and elastic modulus of IDWS specimens are lower than those of the intact specimens, whereas the peak strain is higher than that of the intact specimens. Both the peak strength and peak strain of the IDWS specimens increase with strain rate, exhibiting a strong strain rate dependency. The peak strength, peak strain, and elastic modulus all display a size effect. This size effect varies over different strain rate ranges. When the strain rate is approximately 10 s −1 , the peak strength decreases as the length-to-diameter ratio increases. In contrast, at a strain rate of approximately 30 s −1 , the peak strength increases with an increase in the length-to-diameter ratio. There is a linear relationship between the incident energy and absorbed energy of the intact and IDWS specimens. Under the same incident energy, the IDWS specimens show higher absorbed energy than the intact specimens. This relationship is independent of the length-to-diameter ratio of rock specimens.

9

Modele zmian ściśliwości przestrzeni porowej mioceńskich skał zbiornikowych z rejonu zapadliska przedkarpackiego

Nowak Krzysztof

Nafta-Gaz

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2023

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R. 79, nr 10

640--650

PL

Ściśliwość porowa skał jest jednym z istotnych parametrów wykorzystywanych w trakcie badań złóż węglowodorów. Nieprawidłowe oszacowanie tego czynnika, a co za tym idzie – porowatości pierwotnej w warunkach in situ, prowadzi do błędów w szacowaniu zasobów złóż węglowodorów. Dotychczasowe próby opisania zależności pomiędzy porowatością mierzoną w ramach rutynowych badań petrofizycznych a ściśliwością porową doprowadziły do powstania szeregu modeli umożliwiających oszacowanie współczynnika ściśliwości porowej. Niestety, w trakcie prac zaczęto zauważać, że wyniki otrzymane na podstawie modeli nie mogą zastąpić badań laboratoryjnych, a jedynie służyć jako narzędzie pomocnicze. Dodatkowo wykazano, że uzyskane rezultaty różnią się w zależności od litologii, miejsca pochodzenia próbek i ciśnień, w jakich były badane. Doprowadziło to do powstawania coraz większej liczby modeli o różnym przeznaczeniu. W artykule użyto kilku najpopularniejszych modeli służących do oceny współczynnika ściśliwości piaskowców, które próbowano dopasować do uzyskanych wyników eksperymentalnych. Obiektem badań było 20 próbek piaskowców i heterolitów z rejonu zapadliska przedkarpackiego o porowatości od kilku do dwudziestu kilku procent. Przebadano je pod kątem właściwości petrofizycznych takich jak porowatość i przepuszczalność, a także dokonano analizy petrograficznej. Następnie przeprowadzono badanie ściśliwości porowej i wykonano analizę zależności pomiędzy ściśliwością a porowatością. Po uzyskaniu wyników eksperymentalnych porównano je z wynikami otrzymanymi na podstawie modeli literaturowych. W wyniku analizy statystycznej wytypowano najlepszy z modeli, który następnie został zmodyfikowany z wykorzystaniem języka R i środowiska Posit w celu jak najlepszego dopasowania do danych laboratoryjnych. Pozwoliło to na opracowanie modelu, który w porównaniu z dostępnymi modelami pozwala z dużo większą dokładnością przewidzieć współczynnik ściśliwości porowej piaskowców i heterolitów z zapadliska przedkarpackiego.

EN

The pore compressibility of rocks is a crucial parameters used in studying hydrocarbon deposits. Inaccurate calculations of this parameter, along with the initial porosity of reservoir rocks under geostatic pressure conditions, can result in errors when estimating the capacity and potential scale of hydrocarbon accumulation. Owing to the challenges associated with conducting these measurements and their time-consuming nature, for more than fifty years, several authors have endeavoured to describe the relationship between the initial porosity measured from the obtained cores in surface conditions and the pore compressibility. These efforts led to the development of many models that allow for the calculation of the pore compressibility coefficient using the initial porosity as a basis. Unfortunately, during the course of these studies, it became evident that the results derived from models cannot substitute laboratory tests but only serve as an auxiliary tool. In addition, the results vary depending on the lithology, and the pressures applied during testing. This has led to the creation of an increasing number of models for various purposes. In the following article, multiple well-known sandstone models were used and compared with laboratory test findings. Finally, a new model was formulated, tailored to the examined rock samples. The study focused on 20 samples of sandstones and heteroliths sourced from the Carpathian Foredeep with a porosity spectrum ranging from a few to twenty percent. The samples were tested to assess their petrophysical characteristics, including porosity and permeability alongside a petrographic analysis. Then, pore compressibility tests were conducted, and an examination of the correlation between compressibility and porosity was carried out. After obtaining the experimental data, a comparatice analysis was performed, contrasting the obtained results with those derived from existing literature models. As a result of a statistical analysis, the best model was identified and subsequently adjusted using the R language and the Posit environment to optimize its alignment with the laboratory data. This resulted in the creation of a model that, in contrast to existing models, allows for significantly enhanced accuracy in predicting the pore compressibility coefficient for selected sandstones and heteroliths originating from the Carpathian Foredeep.

10

Predicting Young’s modulus of Indian coal measure rock using multiple regression and artificial neutral network

Chakraborty Sayantan, Bisai Rohan, Roy Rohit, Palaniappan Sathish Kumar, Pal Samir Kumar, Rao Karanam Uma Maheshwar

Journal of Sustainable Mining

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2023

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Vol. 22, iss. 1

41--54

EN

Accurate information on Young’s modulus (E) is required for simulating rock deformation in mines; on the other hand, it is very cumbersome to obtain in the laboratory and collecting drilled cores in sufficient amounts, especially in the case of soft rocks, is quite impossible. Empirical equations were deducted for - from easily determinable rock properties, and the final model was selected through different statistical strength parameter tests. The generalization of the equation was verified through the normal distribution tests of residues of the equation. R2 came to be 0.609 and was validated using an artificial neural network with an improved value of 0.73.

11

Shear strength characteristics of weathered jointed Kenny Hill interbedded formation for cylindrical specimen under direct shear test

Abbas Hasan Ali, Mohamed Zainab, Taher Muntadher J., Kudus Sakhiah Abdul, Salman Manaf Raid, Ghaltan Hasanain Muhammad

International Journal of Applied Mechanics and Engineering

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2023

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Vol. 28, no. 2

1--12

EN

The sliding failures commonly occur in interbedded formations along the weakness plane of the bedding plane a sedimentary rock or the joint interface. Therefore, studying the shear strength characteristics at the bedding plane or interface is crucial for evaluating the expected failure plane. In this study, the shear strength characteristics of planar jointed Kenny Hill shale, sandstone, and shale-sandstone specimens were investigated using the direct shear box method. The results reveal that the friction angle values for the planar sandstone, shale-sandstone, and shale are 31.28°, 21.1°, and 19.34°, respectively. These findings, combined with the shear stress-strain behavior, suggest that the interface (shale-sandstone) is primarily influenced by the shale characteristics rather than the sandstone characteristics. Hence, it is important to consider failure along the interface when analyzing critical conditions, particularly in slope failure scenarios.

12

Morphometric analysis of pebbles in verification of transport processes and interpretation of palaeoenvironment: A case study from the Ogwashi Formation (Oligocene), Niger Delta Basin, Nigeria

Ogbe Ovie B., Osokpor Jerry, Emelue Chukwunomso V., Ocheli Azuka

Geologos

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2023

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Vol. 29, No. 1

21--31

EN

The present paper discusses a palaeoenvironmental interpretation of the Oligocene Ogwashi Formation (Niger Delta Basin, Nigeria) through morphometric analysis of pebbles, a research method essentially depending on the quantitative evaluation of pebble size and shape which change during transport processes in a range of depositional environments. The relationship of bivariate and ternary-diagram plots of independent functions was determined from freshly exposed sandstone sections in quarries at Ibusa, near Asaba, Nigeria. The grain size of pebbles ranges from fine (11.00 mm) to very coarse (41.33 mm), with a mean size of 21.05 mm (coarse pebbles). A bivariate plot of the flatness index vs maximum projection sphericity index shows 37% of the pebbles to fall within a beach (marine) environment, and 33% within a fluvial environment; the remaining 30% are uncertain. The maximum projection sphericity index vs oblate-prolate index bivariate plot indicates that 47% of pebbles fall within a marine environment and 22% within a fluvial environment, while the remaining 31% are uncertain. The sphericity-form ternary diagram plot shows that the pebbles primarily comprise bladed, platy, very bladed and very platy of near-equal proportions with minor elongate and very elongate stones, which suggests that the pebbles are diverse in origin. The sphericity-form bivariate plot indicates that the pebbles are largely of disc and blade shapes with a minor number of spherical and rod shapes. The near-equal proportion of pebbles in different segments of the bivariate and ternary diagram plots, and the wide distribution of the pebble grain sizes and shapes suggest the Ogwashi Formation is composed of redeposited sediments that likely were transported and deposited in a mix of marine and fluvial settings with possible transitional environments. In other words, the pebbles can be interpreted as marine-influenced fluvial sediments in marginal-marine settings.

13

Theoretical analysis and verification of the influence of bubble, pore throat and water film on pore water seepage characteristics‑taking sandstone as the research object

Fan Shengyuan, Song Zhanping, Li Xu, Tian Xiaoxu, Liu Lianbaichao, Li Kanglin

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 4

art. e225, 1--21

EN

Bubble, pore throat and water film will significantly affect the seepage characteristics of pore water. Based on the theory of porous media and mass and momentum conservation of pore water, this research investigates the blocking effects of bubble, pore throat and water film on the seepage water. According to the bubble force balance relationship, there exists a threshold ΔP at the pore throat. It is discovered through theoretical analysis that the small bubble cannot obstruct the pore throat, while the large bubble could pass through the pore throat after deforming and rupturing as the water pressure is greater than ΔP. In contrast, the bubble cannot pass through the pore throat and will block the water seepage. Meanwhile, the energy will be consumed in the aforementioned process, which will cause a drop in the pressure and seepage velocity of pore water along the seepage path, resulting in the non-uniform seepage characteristics of pore water. Combined with theoretical analysis, considering the factors of water injection pressure and pore size, the seepage and distribution characteristics of pore water are evaluated from macro- and micro-levels through sandstone water injection tests and numerical simulation analysis. Two experimental findings are very consistent, both reflect the non-uniform seepage characteristics of pore water and validate the rationality and precision of the theoretical analysis about the throat threshold ΔP. The findings of this study have certain theoretical reference significance for the theoretical research and practical engineering application about pore water seepage.

14

Mechanical and fracture characteristics of single tunnel under the induced effect of a key joint

Wang Fei, Zhang Peng, Li Kaihui, Wang Cong, Cui Pengfei

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 3

art. no. e206, 2023

EN

The existence of joint at key position will change the stress distribution law around the tunnel, thereby changing the strength and stability of the tunnel. Therefore, a series of uniaxial compression tests were performed on the single-holed samples containing a joint to explore the effect of key joint parameters, including joint inclination (0°, 30°, 45°, 60°, and 90°) and length (20, 30, 40, and 50 mm), on the mechanical and fracture characteristics of the tunnel. Meantime, the DIC equipment and box dimension method were used to analyze the surface strain field of the sample and quantitatively characterize the surface crack of the failed sample, respectively. The experimental results show the uniaxial compressive strength of samples reaches the maximum and minimum values at joint inclination angles of 0° and 60°, respectively, and the strength of samples is negatively correlated with the joint length. Interestingly, the existence of some key joints can help to improve the strength of the single-holed sample. The strain bands and cracks mainly develop around the joint and the tunnel, which is well explained by the stress distribution results calculated by COMSOL software. The numerical results show that with the increase of joint inclination, the tensile stress at the upper endpoint of circular hole is increasing, and the compressive stress at left and right endpoints of the hole slightly increases. Analyzing the relative positional relationship between the coalescence path and the tunnel, the failure modes of the sample with different joint inclinations are classified into three types: center-symmetric failure (0° and 90°), through-joint failure (30° and 45°) and axisymmetric failure (60°). Additionally, the box fractal dimension of the surface crack of failed sample at the peak stress is closely related to the failure mode of the sample, and the box fractal dimension of samples with the same failure mode is positively correlated with their peak stress.

15

Detrital heavy minerals as guides to provenance of Albian arenites of southern extra-Carpathian Poland

Kotowski Jakub, Olszewska-Nejbert Danuta, Nejbert Krzysztof

Acta Geologica Polonica

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2023

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Vol. 73, no. 4

801--832

EN

The potential of heavy minerals as a provenance tracer in Albian arenites of extra-Carpathian Poland was assessed. Studies in this area have focused on various methods based on heavy mineral chemistry that provide an effective tool for reconstructing the provenance of quartz-rich sediments. The previously suggested division of the study area into two domains with different source areas: the western domain – the Miechów area, and the eastern domain – the Lublin area, was based on geochronological (monazite and muscovite dating) and rutile mineral chemical studies. The mineral chemistry of newly examined heavy minerals supports the previously suggested division. The mineral chemistry of detrital tourmaline suggests medium-grade metamorphic rocks as the main source in both domains. Detrital garnet in the western domain shows affiliation to the Góry Sowie Massif, while garnet in the eastern domain was most probably sourced from southern/central Norway. The western domain was most probably fed from rocks of the Bohemian Massif. The main source area for the eastern domain was most probably located in the Baltic Shield. The distinct division of the study area into two domains was caused by the palaeogeography of the region in the Albian and the action of longshore currents in south-eastward and eastward directions.

16

Piaskowiec w architekturze Poznania : formy jego deterioracji na przykładzie elewacji budynku Collegium Iuridicum

Szczepaniak Małgorzata

Przegląd Geologiczny

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2022

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Vol. 70, nr 2

126--134

EN

The article presents various forms of deterioration in sandstone panels of the Collegium Iuridicum building in Poznań. The facade of this building is exposed to various urban and rural pollutants, which have a very significant influence on the weathering of the stone. The climatic conditions in which the test building is located and structure of the stone are also an important factors of the weathering. They can significantly accelerate the stone destruction processes. Based on the ICOMOS guidelines, deterioration forms were described and classified in macro and micro scales. For this purpose, optical, cathodoluminescence and scanning microscopy with EDS analyser were used. As a result of the research, secondary mineralization and the presence of numerous elements in the black crusts were identified. They are directly related to polluted air and the combustion of solid fuels. The identified elements include: Na, Mg, Al, Ca, P, K, S, Hg, Pb, Fe, Ti, Sc, Ni, Br, Mo, Zn, Mn, gypsum, calcite, fly ash particle.

17

Analiza współczynnika ściśliwości piaskowców o zróżnicowanych parametrach petrofizycznych w zmiennych warunkach ciśnień porowych i nadkładu

Nowak Krzysztof

Nafta-Gaz

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2022

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R. 78, nr 7

503--512

PL

Współczynnik ściśliwości przestrzeni porowej skał ma duże znaczenie dla szacowania objętości złóż węglowodorów. Próbki przechowywane w magazynach rdzeni ulegają relaksacji (spowodowanej zmianami ciśnienia i temperatury), co prowadzi do zawyżania mierzonej wielkości współczynnika porowatości w porównaniu z rzeczywistymi warunkami złożowymi. Brak uwzględnienia tego typu zmian w szacowaniu objętości złóż węglowodorów może doprowadzić do niewłaściwych wniosków dotyczących wartości złoża. Celem publikacji jest przedstawienie wpływu ciśnień na współczynnik ściśliwości, a także znaczenia tego współczynnika w badaniach nad porowatością. Ze względu na dotychczasowy brak eksperymentalnych badań współczynnika ściśliwości w Polsce celem pracy było również wskazanie możliwych dalszych kierunków badań pozwalających na lepsze poznanie tego zagadnienia. W niniejszym artykule przedstawiono wyniki badań współczynnika ściśliwości dla próbek 14 piaskowców o dobrych parametrach petrofizycznych w różnych ciśnieniach porowych i nadkładu. Analizowane próbki reprezentują piaskowce karpackie (10 próbek) oraz piaskowce dolnej jury Niżu Polskiego (4 próbki). Dla wszystkich próbek oznaczono parametry petrofizyczne, które zostały następnie użyte do sprawdzenia, czy istnieją zależności między nimi a ściśliwością. Badania zmian przestrzeni porowej przeprowadzono na aparacie przystosowanym do pomiarów ściśliwości porowej poprzez zadawanie odpowiednich ciśnień nadkładu i ciśnienia porowego. Pomiary wykonywano dla ciśnienia porowego wynoszącego 300 psi, 1000 psi i 2000 psi przy maksymalnym ciśnieniu nadkładu 7000 psi, a jako medium wypełniającego przestrzeń porową użyto 5-procentowego roztworu NaCl. W wyniku przeprowadzonych badań uzyskano szereg danych dotyczących zmian ściśliwości przestrzeni porowej oraz wyliczono współczynnik ściśliwości Cpc. Wyniki pokazują, że porowatość przeanalizowanych próbek pod wpływem ciśnienia nadkładu zmniejsza się od jednego do kilku procent, a z opracowanych modeli zmian porowatości przy różnych ciśnieniach porowych wynika, że im mniejsza różnica między ciśnieniem nadkładu a porowym, tym mniejsza zmiana porowatości. W artykule wykazano też zależność pomiędzy porowatością a współczynnikiem ściśliwości oraz wskazano kierunek dalszych prac nad tymi zagadnieniami.

EN

The pore volume compressibility is important for estimating the volume of hydrocarbon fields. Samples stored in the core warehouses relax (due to pressure and temperature changes), which leads to overstating the measured value of the porosity factor in comparison to the actual deposit conditions. Failure to take into account such changes in the estimation of the volume of hydrocarbon fields may lead to incorrect conclusions regarding the value of the field. The aim of the publication is to present the influence of pressures on the pore volume compressibility as well as its importance in research on porosity. Due to the lack of experimental studies of the pore volume compressibility in Poland so far, the aim of the work was also to indicate possible further directions of research allowing for a better understanding of this issue. The paper presents the results of the pore volume compressibility tests for samples of 14 sandstones with good petrophysical parameters under different pore and overburden pressures. The analyzed samples represent Carpathian sandstones and Lower Jurassic sandstones of the Polish Lowland. Petrophysical parameters were determined for all samples and then used to check the relationship between them and compressibility. The research on changes in the pore space was carried out using the apparatus adapted to the pore compressibility measurements by assigning appropriate overburden and pore pressure. Measurements were made at pore pressures of 300, 1000 and 2000 psi with a maximum overburden pressure of 7000 psi, and a 5% NaCl solution was used as the pore-filling medium. As a result of the research, a number of data on changes in the compressibility of the pore space was obtained and the compressibility factor Cpc was calculated. The results show that the porosity of the analyzed samples under the influence of the overburden pressure decreases from one to several percent. The developed models of porosity changes at different pore pressures show that the smaller the difference between the overburden pressure and the pore pressure, the smaller the change in porosity. The article shows the relationship between porosity and compressibility of the pore space and indicates the direction of further work on these issues.

18

Experimental study on fatigue mechanical properties of sandstone after dry and wet cycle

Jin-Song Zhang, Yu Lu, Heng-Liang Zhang, Yu-Di Yang, Yi-Shun Bu

Archives of Civil Engineering

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2022

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Vol. 68, nr 4

377--387

EN

At present, many studies have been carried out on the fatigue mechanical properties of conventional rocks, but there are few studies on the mechanical properties of rocks after water rock interaction. The aim is to better study the fatigue mechanical characteristics of sandstone after dry wet cycle and the research object we take was sandstone samples after a certain number of drying and wetting cycles. The WAW-2000 electro-hydraulic servo pressure system was used to carry out uniaxial fatigue cyclic loading and unloading tests with different amplitudes and different upper limit stresses. The test found that: when the sample is damaged under fatigue load, the stress-strain curve shows a sharp downward trend and a sudden instability failure occurred in the sample. With the increase of the upper limit stress and amplitude, the life of the sample decreases gradually which also conforms to the change of power function. Then the relationship between fatigue life and stress is obtained. The fatigue stress-strain curve is characterized by sparse-dense-sparse. With the increase of cycle time, the axial strain of the sample shows an inverted “S” shape. The strain change can be divided into three stages: initial stage, constant velocity stage and acceleration stage.

19

Shear rupture behaviors of intact and granulated Wombeyan marble with the flat-jointed model

Li Kaihui, Han Dongha, Fan Xiang, Yang Yi, Wang Fei

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e51, 2022

EN

Many large hydropower projects have been constructed in the highly interlocked and non-persistently jointed rock mass (e.g., the columnar jointed basalt). Regarding the granulated Wombeyan marble as an analog of such rock mass, a series of direct shear test simulations under constant normal loading (CNL) and constant normal stiffness (CNS) boundary conditions were performed to better understand its shear rupture behavior using the flat-jointed model based on the discrete element method. The results show that the shear process under the CNS condition can be divided into four stages: linear-elastic stage, yielding stage, shear wear stage and shear sliding stage. The strain-strengthening in the shear wear stage is evident due to the feedback normal stress provided by the cap induced by shear dilation. As the initial applied normal stress increases, the peak shear strength point of specimens under CNL approaches the yield point of specimens under CNS. Additionally, the shear rupture process under CNS is strain controlled in granulated specimens but stress controlled in intact specimens. Correspondingly, the shear rupture zone creation in granulated specimens is not but that in intact specimens is dependent on the initial applied normal stress. Finally, it is demonstrated that the CNS condition can improve the stability of rock slopes or underground excavations embedded in such rock mass and its improvement effect increases with the normal stiffness.

20

Changes of physical properties of thermal damaged sandstone with time lapse

Wang Zuoquan, Zhang Weiqiang, Shi Zhoujian, Zhang Shaoteng

Acta Geophysica

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2022

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Vol. 70, no 3

1193--1202

EN

Understanding the change of physical properties of thermal damaged rock with time lapse in high temperature engineering plays an important role in the prediction of engineering life and the prevention of engineering disasters. In order to study the effect of time lapse on the physical properties of heat damaged sandstone, the sandstone was heated to the target temperature and cooled, and its resistivity, Leeb hardness, volume and mass were measured. The values of these parameters should be measured again after placing the thermally damaged sandstone for 3, 6 and 9 months. The results show that, after being placed for 3 months, the quality of heat damaged sandstone increased at all test temperatures. At 200 °C, 400 °C, 600 °C and 900 °C, the resistivity of heat damaged sandstone decreases, and there is no obvious change in Leeb hardness and volume. At 800 °C, the resistivity of thermally damaged sandstone increases, the Leeb hardness decreases and the volume increases. After being placed for 6 months, the resistivity, Leeb hardness and volume of thermally damaged sandstone did not change at all test temperatures, but the mass of thermally damaged sandstone increased at 800 °C and 900 °C. After being placed for 9 months, the resistivity, Leeb hardness, volume and mass have no obvious change at all test temperatures.