White Sandstone Research Articles

A study on the optimal selection of similar materials for the physical simulation experiment based on rock mineral components

The physical model test can effectively solve the problems of great difficulty and the high cost of the field test. Similarity theory is an essential basis for model test design. Accurate and rapid selection, proportioning, and production of similar materials are of great significance in accurately simulating the project site's rock stratum geological situation. However, the existing preparation methods of similar materials have great blindness and a low success rate. Considering the critical influence of mineral composition on the physical and mechanical properties of rock, aiming at preparing rock sample materials in TBM tunneling simulation under high ground stress, this paper takes Sichuan white sandstone as the specific research object. We use mineral composition to guide similar materials' mix design and preparation. It is found that similar materials with the required geometric similarity ratio can be obtained by adjusting the water-cement ratio and cement content under the condition that the mineral composition is basically the same. The similar material sample of Sichuan white sandstone with a given geometric similarity ratio (a(a＞1.5)) can be designed with cement content (C) as C = 150a-1 and water cement ratio (Wrt) as Wrt = 0.072a + 0.108. We believe this method can also provide a reference for preparing similar materials for other rocks.

Research on Mechanical Behavior and Energy Evolution of Coal and Rocks with Different Thin Spray-On Liners Thickness under Uniaxial Compressive Loading

Compared with the traditional supporting materials such as the bolts, mesh, and concrete, thin spray-on liners (TSLs) have the advantages of improving impact energy bearing and absorption capacity of rocks. In this study, the uniaxial compressive mechanical response feature of white sandstone, yellow sandstone, and coal with different coating thickness of TSLs were investigated through laboratory tests and theoretical analysis. The hard segments and soft segments of TSLs induced microphase separation, and formed the physical cross-linking. The hard segment evenly dispersed in the soft segment, which improved the mechanical strength of the TSLs. The confining pressure was affected by the TSL-coated coal and rocks, which improved the mechanical strength of the rocks and coal under UCS loading. It was discovered that the uniaxial compressive strength (UCS) increases with an increase in the TSL coating thickness, and UCS increments of the coated white sandstone, yellow sandstone and coal were 4.6%, 25.51%, and 43.75%, respectively. The energy absorption capacities of the coated coal, and yellow and white sandstones gradually decreased with an increase in their TSLs coating thickness. Meanwhile, the energy-absorbing capacity of a coated rock reduced gradually as rock coating decreases. Furthermore, the energy-absorbing capacity of coal is greater than that of yellow sandstone or white sandstone. By increasing the coating thickness, the total and dissipative energies in the yellow sandstone, white sandstone, and coal specimens were gradually increased, and energy increment was significantly more in coal (2–3 times), while the elastic energy remained nearly unchanged.

Effect of Chemical Corrosion and Axial Compression on the Dynamic Strength Degradation Characteristics of White Sandstone under Cyclic Impact

Both chemical corrosion and axial compression impose critical influences on the internal microstructure of rock. Meanwhile, chemical corrosion can change a rock’s mineral composition, which in turn affects the physical and mechanical properties of the rock. To investigate the dynamic strength characteristics of white sandstone under the coupling effect of axial load and chemical corrosion, a dynamic and static combined loading test device was adopted for performing cyclic impact tests on white sandstone immersed in chemical solution. The results show that with the increasing number of cycles under the same load, the peak strength of the rock presented a trend of ‘strengthening first and then weakening’. The strength of rock resistance to impact failure reached its maximum when the solution of pH was 7 and axial pressure was 12.6 MPa. Under the same axial pressure, the effect of solution pH on the initial dynamic strength of white sandstone is a normal distribution. Acidic and alkaline environments are harmful to rocks during the initial impact, while neutral environments exert little effect and the pH of the solution influences the particle size of impact crushing particles. In addition, the chemical solution has a significant effect on the deterioration of rock strength during the process of initial impact, and the effect is inconspicuous in the later period.

Evaluation of white sandstone mechanical behaviour and the energy evolution of prepeak unloading damage

Deep high-stress roadway excavation under unloading disturbance inevitably leads to damage deterioration of the surrounding rock, which poses a serious threat to its stability. To explore the energy characteristics of white sandstone damaged by peak front unloading, uniaxial compression tests were conducted on damaged rock samples. The results show that the peak strength and modulus of elasticity of the rock sample gradually decrease with increasing damage degrees. The external work input energy, releasable elastic strain energy and dissipation energy all decreased with increasing damage. Damage evolution curves and equations of the rock samples were obtained based on the damage instantiation model established by the principle of energy dissipation and release. The effects of unloading damage on the fracture characteristics of the rock samples were analysed from both macro and microscopic viewpoints, and the results showed that a micro fracture in the rock is transformed from brittle–ductile damage, while macroscopic damage occurs in the form of a "shear"-"splitting"-"mixed shear-splitting" damage process. This paper has certain research and reference value for understanding the damage evolution characteristics of rocks with peak front unloading damage.

Damage Analysis of Chemically Corroded Sandstone Under Cyclic Impacts and Axial Static Pressure

To explore the influence of cyclic impact and axial static pressure on the damage of chemically corroded sandstone, a series of cyclic impact tests were conducted on white sandstone by using the Split Hopkinson Pressure Bar. Besides, the longitudinal sections and fractures of samples were observed with the scanning electron microscope for the purpose of investigating the damage characteristics and structural changes of sandstone subjected to the coupling of force and chemistry. The results show: (1) When pH of the solution is 7, the number of cyclic impacts and stress peaks of specimens increases, and the specimens respond with a significantly high resistant strength. (2) The stress wave transmission coefficient of sandstone decreases gradually with the increase of the number of cyclic impacts, while the reflection coefficient shows a tendency of "decreasing firstly and then increasing". (3) Cylindrical specimens with a certain axial static pressure present an "X" shaped conjugate failure under cyclic impact. When axial static pressure is too large or there is excessive impact, the "X" shaped conjugate undergoes shear to a state of broken cones. (4) The vertical section and fracture surface damage degree of white sandstone soaked in the sodium sulfate solution is more serious than that in the sodium sulfate solution.

Fracture evolution and failure characteristics of sandstone under freeze-thaw cycling by computed tomography

Long-term freeze-thaw (F-T) action causes the expansion of the fracture network in rock mass with ice-filled joints, triggering more serious engineering geological disasters. This study explores F-T damage effects and loading failure in double-fractured white sandstones with different saturation types (saturated and ice-filled). Saturated intact, saturated fractured, and ice-filled fractured sandstones were subjected to F-T cycle tests and uniaxial compression tests. Three-dimensional images of the specimens under various F-T cycles and stress states were obtained using computed tomography. The evolution in fracture morphology was evaluated visually, with pore network model parameters used for quantitative characterisation. Sandstone fractures evolved according to four main processes: frost-heave cracking, progressive expansion of damage, rock bridge penetration under load, and shear failure. The proportion of connected pores was used to estimate the influences of F-T cycling on pore-structure connectivity and fracture expansion in different specimen layers. During F-T cycling, pore characteristics vary according to size: micropores (equivalent radius < 100 μm) account for >60% of pores and increase in number more than pores of other sizes. Mesopores (100–500 μm) gradually decrease in number but their volume fraction remains >70%. Macropores (500–1000 μm) have the greatest increase in volume fraction. Early F-T cycling induces the connection of pore throats, while later cycling accelerates their expansion. Hydrostatic pressure increases are the leading cause of damage in ice-filled fractured sandstone, which exhibits greater variations in porosity, heterogeneity coefficient, and pore-throat parameters under F-T cycling than saturated fractured sandstone. The results provide insight into fracture evolution and failure characteristics in fractured rock masses with different saturation types (saturated and ice-filled) in cold regions.

Experimental Study on the Mechanical Properties of Triaxial Compression of White Sandstone under the Coupling Action of Chemical Corrosion and Temperature

In order to study the chemical corrosion and temperature coupling effect on the triaxial compression mechanical properties of white sandstone, first, the white sandstone is soaked in acidic, neutral, and alkaline solutions respectively in different temperatures, after that, triaxial compression tests were carried out on the treated white sandstone, then, the strength and deformation of white sandstone after coupling action are analyzed, finally, the chemical corrosion and temperature coupling mechanism is studied. The results show that: At the same temperature (below 100°C),the triaxial compressive strength of the specimens in acidic and alkaline environments is lower than that in neutral environments. In the same chemical (acid or alkali) environment, the triaxial compressive strength of the specimen decreases with the increase of temperature (below 100°C); In a neutral environment, with the increase of temperature (below 100°C),the triaxial compressive strength of the specimen decreases slowly and basically remains unchanged. Below 100°C, the damage of rock caused by temperature is small and can be ignored; Different chemical (acid or alkali) environment can degrade rock damage and reduce its triaxial compressive strength. Temperature mainly affects the rate of chemical reaction, which damages the rock and reduces its strength.

The prospecting strategy for a deep Cu-Ag ore deposit in Poland – An anatomy of success

The article presents the prospecting strategy implemented by Miedzi Copper Corporation in search for new Cu-Ag ore deposits of the Kupferschiefer type. Sediment-hosted stratiform copper deposits in Poland occur mostly in the Fore-Sudetic Monocline, in the contact zone between the continental red beds (Rotliegend) and Zechstein marine sediments. The ore-bearing series consists of white sandstone (Weissliegend), copper-bearing shale (Kupferschiefer) and carbonates (Zechstein Limestone). The southern-central part of the Fore-Sudetic Monocline is a well-known Lubin-Sieroszowice mining area, where mining operations are conducted at the depths up to 1300 m below surface. However, due to significant depletion of shallower reserves, deep Cu-Ag mineralisation have recently become a subject of interest. Several basic problems had to be resolved in order to reach for such deposits: finding indicators suggesting the presence of rich mineralisation; more precise identification of the current geothermal field in the area of the Fore-Sudetic Monocline; and the availability of modern technologies which would allow safe and economic operation of a deep underground mine. In 2011, Miedzi Copper Corporation initiated its exploration programme focused on deep Cu-Ag ore deposits, based on known prognostic areas in the vicinity of palaeorises and contacts between oxidised and reduced facies, as copper mineralization occurs at the rims of oxidised areas, on the reduced side of the redox boundary. Exploration programme has led to the documentation of three new deep deposits: Nowa Sól, Sulmierzyce North and Mozów, two of which were identified in areas previously described as prospective by the Polish Geological Institute.

Diagenetic alteration and geochemical evolution during sandstones bleaching of deep red-bed induced by methane migration in petroliferous basins

Bleaching of red-bed sandstones is an important process related to the organic-inorganic interactions and diagenetic alteration, playing an important role in reservoir heterogeneity and carbon cycle in petroliferous basins. Distinguishing from the aeolian red-bed in the outcrop, a case study of deep red-bed of fluvial facies was conducted on the Permian Xiashihezi Formation, NE Ordos Basin, China. Four diagenetic facies can be identified as red, brown, green and white sandstones (RS, BS, GS, WS) with typical diagenetic alteration and geochemical characteristics. Thereinto, diagenetic alterations are dominated by clay minerals and carbonate cements including calcite and siderite. Carbon and oxygen isotopes showed a synergistic decreasing trend from RS, BS to WS with the increase of altered degree. The unaltered RS retained abundant early hematite, smectite and calcite, while strongly bleached WS had lowest feldspar but extensive kaolinite and illite, and manganese-rich calcite. Medium-altered BS and GS are characterized by late magnesium-rich siderite and chlorite coating respectively. The isotopic data, fluid inclusions and modeling indicated that CH4 is the important causal fluid for sandstones bleaching. Diagenetic alteration and geochemical evolution in deep red-bed of fluvial facies was influenced by upward-fining sedimentary sequence, open/closed diagenetic system and natural gas migration. The geochemical behaviors of Fe are responsible for the diversity of diagenetic facies. Fe2+ from redox between Fe3+ and CH4, integrated Mg2+ released from the transformation of smectite to illite into magnesium-rich siderite, or into chlorite in coarser sandstones in relatively open system. Extensive CH4-rich reducing fluids were oxidized to acidic fluids in the more open diagenetic system with coarser grained sandstones, resulting in the intense dissolution and the high-quality reservoirs distributed in the lower sequence of fluvial facies. Furthermore, CH4 oxidation by Fe(III) in deep red-bed can be extremely important CH4 sink and expected to potential sites of geological carbon sequestration.

Energy Dissipation and Failure Characteristics of Layered Composite Rocks under Impact Load

Horizontal layered composite rock samples composed of white and black sandstones with large differences in physical and mechanical properties were tested to explore the dynamic characteristics of layered composite rocks under impact load. Using the split Hopkinson pressure bar test system, the dynamic compression tests of two incident states of stress waves, that is, stress waves from white sandstone to black sandstone (W⟶B) and from black sandstone to white sandstone (B⟶W), were designed and carried out under different impact velocities. Combining the ultrahigh‐speed photography system and digital photogrammetry for deformation measurement (DPDM), we obtained the stress wave propagation characteristics, failure characteristics, and particle size distribution characteristics of broken rocks of the composite rocks under the two conditions. The experimental results were compared and analyzed, while stresses and strength conditions at the interface of the composite rock samples were theoretically assessed, yielding the following main findings. The energy dissipation pattern of composite rock had an obvious strain rate effect. The reflected energy and fragmentation energy density of composite rock increased approximately as quadratic functions of the incident energy. Affected by the wave impedance matching relationship, the W⟶B and B⟶W samples were significantly different in terms of the stress wave shape, energy dissipation, average particle size, and fractal dimension of the broken rocks at low impact velocities. However, with an increase in the impact velocities, the two gradually shared the same behavior. When composite rock samples deformed and failed, the macrocracks mostly initiated from the white sandstone. When the crack tip stress of the white sandstone at the interface exceeded the strength of the weakened black sandstone, the crack continued to develop through the two‐phase rock interface due to the difference in Poisson’s ratios. The damage degrees and failure modes of the two parts of composite rocks were different: black sandstone was prone to tensile splitting with local shear failure, while white sandstone exhibited shear failure with local tensile splitting. The damage degree of white sandstone exceeded that of black sandstone.

Quantifying the Mechanical Properties of White Sandstone Based on Computer Fractal Theory

The work presented in this paper was conducted to quantify the relationship between the pore characteristics and mechanical properties of white sandstone. The study include tests carried out under the coupling effects of chemical corrosion, temperature, nuclear magnetic resonance, and mechanical tests. Computer fractal theory was employed to describe and quantify the characteristics of the growth of pores in white sandstone under the same coupling effect. A custom developed program code, in the MATLAB software platform, was used for calculating the growths of the pores in white sandstone when subjected to coupling effects. The correlation between the computer fractal dimension of the growth of the pores in rock and characteristics of mechanical damage was accordingly analyzed. The results showed that when the temperature was set at a level lower than 100°C, it caused damage to the rock and strength reduction, primarily due to the rates of chemical reactions, the generation, and evolution of pores in the rock mass under the coupling effects of chemical corrosion and temperature. Overall, it was observed that the higher the value of the computer fractal dimension, the higher the growth of the pores, and the lower the uniaxial compressive strength of the white sandstone.

Optimal Proportion of Similar Materials and Rockburst Tendency of White Sandstone

To explore the tendency of rockburst, a similar material ratio was optimised based on white sandstone. Quartz sand, iron powder, gypsum, cement, retarder, and a water‐reducing agent were used as the main materials. The orthogonal test design principle was used to determine the four‐factor and four‐level orthogonal test design with the quartz sand content, iron powder content, gypsum‐cement ratio, and sand particle size as the influencing factors. Uniaxial compression tests and tensile tests were conducted on similar material models. The tensile strength and elastic modulus were analysed, the significance of each influencing factor was investigated, and the test results of the similar materials were fitted. The optimal ratios of the similar materials of white sandstone were found to be quartz sand content of 36%, iron powder content of 1.9%, gypsum‐cement ratio of 1.8 : 1, and sand particle size of 2–4 mm. The physical and mechanical properties of the similar materials were consistent with those of white sandstone. The mechanical properties of the similar materials were compared with those of the original rock. By judging the rockburst propensity and verifying the index, it is concluded that the similar materials can effectively simulate the characteristics of white sandstone, which is an ideal similar material of rockburst, and they all show strong rockburst propensity. The rock specimens with optimal proportions were produced, and the internal energy changes and rockburst mechanisms of the model at different temperatures were discussed. The results show that the rockburst process is closely related to energy, such as thermal energy and elastic strain energy, and the rock failure process can be divided into three main stages: energy accumulation, microcrack formation and propagation, and crack penetration and bursting. It provides an experimental basis for the preparation of rockburst similar materials that are more in line with the actual situation of the project and provides a basis for discussing the energy criterion of rockburst.

New minerals and the first mineral occurrences in the Kupferschiefer (U, REE, HgS, chloride minerals PtAs2, Pt(Sb,Bi)2, PtBi2), Poland, and their genetic meaning

Abstract Main U minerals in the Lubin and Polkowice mines in decreasing order of abundance are: uraninite, brannerite, metazunerite, metauranospinite, uranospinite, thucholite, monazite-huttonite, coffinite, and becquerelite. All these minerals are associated mainly with noble metal mineralization at the redox interfaces. Main minerals of REE are: (i) brannerite, monazite-huttonite in Noble Metals Bearing Shale (NMBS), (ii) florencite in Mo-Re shales and (iii) minor phospates in Cu-black shales derived from oxidation of organic matter. The latter, however, are controlling no more than 1/5 of the REE budget. Chloride minerals and sulphates are ubiquitous phases associated with Cu sulphides. They are represented by chlorargylite, cotunnite and penfieldite. Halite and sylvite form cubic inclusions in gypsum, up to 3 mm in chevrel compound, where they occur together with thiosulphates, anna-bergite and erithrite and Ni-Co-diarsenides. Sylvite is most common in lensoidal accumulations of semi massive kaolinite + chalcocite + gypsum at the contact between black shale and the top part of white sandstone. Such lenses have been traced over a distance of up to 30 m in the Lubin West and Polkowice East mines. Sylvite and halite have been so far overlooked during investigations of the Kupferschiefer because of applying standard cuƫng and polishing procedures using water as a lubricant. The Au content in native gold may reach exceptionally up to 97.40 wt% in a dolomitic reef from the Lubin West Mine. Gold forms four characteristic micro to nano-textures. Organic matrix of thucholite indicates correlation of Pt-Ni-V suggesting substitution of Pt in tetrapyrrole ring. Sperrylite, geversite and insizwaite appear at the western perimeter of Cu-sulphide deposit, where the redox gradient is so strong that almost all organic matter is gone. Platinum has forms its own minerals trapped in microfractures in anilite-digenite-spionkopite-yarrowite-bornite composite grains present in the reddened NMBS. Celestine-barite solid solution is one of the main accessory minerals in the Kupferschiefer. It has Sr/Ba ratio around 2.5 and 7.5. Euhedral uraninite associated with celestine-barite yielded U/Pb age of 84 ± 1 Ma, based on four grains measurements.

A new species of Utricularia Sect. Orchidioides (Lentibulariaceae) from the Amotape-Huancabamba Zone of North Peru

A new species of Utricularia Section Orchidioides: Utricularia amotape-huancabambensis sp. nov. (Lentibulariaceae), endemic to Northern Peru is described and illustrated. It is known from two populations so far, both located in the Province Bongará, Dpto. Amazonas at ca. 2200 m altitude. The new species inhabits the páramo of the low white sandstone plateaus, an extension of the southern branches of the Condor mountain range in the southeastern part of the Amotape-Huancabamba phytogeographic zone. A diagnosis, description, etymology and an identification key covering the Andean and selected similar species of the section are presented. The distribution, habitat, ecology, associated flora, preliminary conservation status, an observed hybridization with sympatric U. unifolia and the affinities of the new species with other related taxa are discussed. The new species is known from two close-by populations in the same region and likely affected by anthropic pressure. Threatening changes in land use, resulting in habitat fragmentation or loss or changing water regimes in the course of climate change will have severe consequences for the sensitive páramo ecosystem and thus the populations of U. amotape-huancabambensis. Therefore, this new spectacular species of Utricularia is preliminarily considered Critically Endangered (CR).

Red sandstone as raw material of Baden culture (Late Copper Age) grinding stones (Balatonőszöd - Temetői dűlő site, Hungary), with a review of the red sandstone formations of SW Hungary

Balatonőszöd - Temetői dűlő is one of the largest excavated and longest-lived sites of the Late Copper Age Baden Culture in Hungary, where 500 lithic finds were registered. In the site finds belonging to the late Middle Copper Age Balaton-Lasinja Culture and the Late Copper Age Boleraz Culture were found too.&#x0D; This paper presents petrographic and geochemical analyses of stone utensils, mostly of grinding stones, made of red, or discoloured white sandstones.&#x0D; Almost all sandstone artefacts are upper and lower stones of grinding equipment and polishers, as well as objects whose function is not known, worked and non-worked fragments; boulders of raw material are also in the studied set.&#x0D; The detailed petrographic and geochemical methods applied here are polarized light microscopy and a distribution study of the framework grains in thin section, and ICP-OES and ICP-MS as bulk rock chemical methods. The results were compared to published petrographic and geochemical data.&#x0D; Most of the studied artefacts were made of the rocks of the Red Sandstone and Siltstone Member of the Balaton Highland Sandstone Formation, especially from the mature type sandstone in which quartz is predominant, and which is almost free of feldspar. This type is characteristic of the confines of the Southern Balaton Highland and the lower part of the formation in the Northern Balaton Highland.&#x0D; A minor part of the studied artefacts - red or purple, purplish grey sandstones - originates from the sandstones of the Jakabhegy Sandstone Formation (Western Mecsek mountains).

Petrography, Mineralogy, and Geochemistry of Combustion Metamorphic Rocks in the Northeastern Ordos Basin, China: Implications for the Origin of “White Sandstone”

Since the Quaternary period, tectonic uplift and river erosion in the northeastern Ordos Basin (northwest China) have exhumed numerous coal seams, creating the conditions for the development of coal fires following their spontaneous combustion or other types of ignition (e.g., lightning strikes). Coal fires activity is testified by the widespread occurrence of combustion metamorphic rocks. In this study, thin section analyses, scanning electron microscopy, X-ray diffraction (XRD), X-ray fluorescence (XRF), and inductively coupled plasma mass spectrometry (ICP-MS) were used to investigate in detail the mineralogical and geochemical characteristics of combustion metamorphic rocks in the Jurassic succession of the northeastern Ordos Basin. The samples collected in localities distributed over an area of about 8000 km2 were analyzed to determine their mineral association, revealing the presence of tridymite, cristobalite, mullite, and cordierite that are typically produced in pyrometamorphic reactions. XRF and ICP-MS analyses revealed that combustion metamorphic rocks are iron-enriched. Investigations in the study area also highlighted the occurrence of a peculiar, porous, and permeable white sandstone that appears often associated with clinkers or coal seams. It is composed of quartz and feldspar grains and cemented by kaolinite. It is here suggested that the white color of this sandstone could be due to coal fire-related kaolinization of a sandstone protolith produced by the acidic low-temperature hydrothermal circulation of rain waters during times of coal fire activity.

The response to the rebuttal on the revised stratigraphy of the Bida Basin, Nigeria: New observations.

The late Cretaceous Bida Basin lithostratigraphy was carried out in order to establish a correlation between the northern (Bida area) and the southern part (Lokoja area) of the basin. The detailed fieldwork carried out over four years involved field description and mapping of outcrops in the entire basin. The study showed that the basin is underlain by mainly continental sedimentary rocks with minor occurrence of marginal/shallow marine to freshwater flood-plain deposits. The basin fill is characterised mostly by several cycles of amalgamated and/or stacked alluvial fans of the Bida/Lokoja Formation directly overlying the Basement Complex. The study revealed that the Lokoja/Bida Sandstone is overlain directly by the oolitic/pisolitic ironstone of the Agbaja/Sakpe Formations, which, in turn, is succeeded by fine to medium grained, grey and white sandstones, siltstones, grey clays, carbonaceous silts and shales, and ubiquitous concretionary ironstone bands of the Patti/Enagi Formation. Given the current detailed investigation, this study suggests that contrary to the rebuttal published, the Agbaja Ironstone is not the youngest formation in the basin. This study further revealed that the sequence of rocks and fossils used to define the Patti Formation and its probable age do not exist on Mount Patti in Lokoja, rather they are found along excavated road sections, quarries and boreholes around the Ahoko Village. Based on the detailed field work and sedimentological investigations, this study hereby proposes that the name ‘Patti Formation’ be changed to ‘Ahoko Formation’.

Experimental study on mechanical characteristics of unloaded damaged white sandstone before peak

In order to study the problem of deformation and failure caused by rock unloading during excavation and mining, a three-axis loading-unloading-uniaxial reloading mechanics with different confining pressures and different initial axial pressures was applied to white sandstone specimens with the RMT-150 testing machine characteristic test. The damage and weakening mechanisms of white sandstone specimens during triaxial loading, unloading, and uniaxial reloading were analyzed. The experimental results show that the peak strength of the specimen has a linear relationship with the confining pressure. The greater the confining pressure, the higher the peak strength of the white sandstone specimen. The peak strength of the specimen and the initial axial compression load ratio (the ratio of the initial axial compression to the triaxial peak load intensity) and the porosity have a 3rd-order polynomial relationship. The damage and weakening of the strength of the rock specimen are related to the load history. The greater the initial axial pressure, the faster the reloaded specimen from the crack closure to the elastic deformation under steady-state damage to the accelerated elastic-plastic deformation under accelerated damage, and the smaller the peak load strength after unloading the specimen. In addition, combined with the loading history of rock, a strength weakening calculation method based on the loading process state is proposed. After verification, this method is feasible.

Landslide susceptibility mapping and rock slope stability assessment using frequency ratio and kinematic analysis in the mountains of Mgulat area, Northern Ethiopia

Landslides, mainly triggered by rainfall, are one of the most common natural hazards in the northern and central highlands of Ethiopia, resulting in the loss of human life and property. As part of the Ethiopian highlands, Mgulat Mountain (88.6 km2) is a typical example for the occurrence of landslides and associated damages. The main aim of this research was to generate landslide susceptibility map (LSM) for the first time by considering various causative factors typical for the Mgulat Mountain area. The methods used include frequency ratio (FR) and kinematic analysis (KA) supported by GIS tools. The research involved conventional fieldwork (e.g., geological mapping, landslides inventory) and analysis and interpretation of images. From the geological mapping, major rock units were identified: quaternary deposit, basalt, red sandstone, tillite, and white sandstone. A total of 220 landslides (15.45 km2) were identified in the study area from field survey, Google Earth and aerial photo interpretation. Five causative factors (lithology, slope steepness, distance from drainage, land use-land cover (LULC), and slope aspect) were selected based on their contribution to landslide initiation as the landslide conditioning factors for generation of the LSM. From the five causative factors, lithology and slope steepness were found to be influential as landslide conditioning factors. Specifically, lithology (red sandstone and tillite), distance to stream (0 to 300 m), LULC (bare land and settlement), and slope steepness (> 25°) have FR > 1, indicating a high relationship with landslide occurrence. Based on the generated LSM, five susceptibility classes or zones were identified (very low, low, moderate, high, and very high susceptibility). The area of each class as percentage of total area was found to be 19.53, 24.15, 22.57, 18.74, and 15.01%, for the very low to the very high class, respectively. The results of KA show potentially and marginally planar, topple, and wedge failures. The generated LSM can serve as an important tool or guide for further land-use planning and to prevent and mitigate landslide-related risks. Consequently, to consider cost-effective and technically sound mitigation measures, detailed and site-specific multidisciplinary investigations are recommended.

Dynamic Mechanical Properties and Energy Dissipation Analysis of Sandstone after High Temperature Cycling

In order to study the effect of high temperature cycling on the physical and mechanical properties of rock materials, a box-type resistance furnace was used to conduct high temperature cycling at 400°C 10 times on sandstone specimens in coal mine, and the impact compression tests under 8 loading rates were carried out using a split Hopkinson bar (SHPB) device. Results showed that, with the increase of cycle times, the gray white sandstone specimen gradually showed reddish brown spots, and the volume of specimen increased, while the mass, density, and longitudinal wave velocity decreased; in addition, the volume increase rate, the mass decrease rate, the density decrease rate, and the longitudinal wave velocity decreased rate with cycle times showed quadratic function relationship. The dynamic compressive stress-strain curve of sandstone specimens subjected to high temperature cyclic action under impact load was obviously different from that under normal temperature. The dynamic elastic modulus was obviously larger than that under static load. The failure mode of dynamic and static specimens showed brittleness and ductility characteristics, respectively. In the SHPB test, the impact pressure, reflected energy, transmitted energy, and absorbed energy of the rock specimen all increased linearly with the increase of incident energy. The dynamic compressive strength, elastic modulus, and strain rate of sandstone specimens were positively correlated with the incident energy, while the dynamic strain showed negative correlation.