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Bolt connections are widely used in construction and engineering to securely join structural elements. These connections are essential for distributing loads across components and ensuring that structures can withstand external forces. The planned failure of these bolts is of great importance in steel safety barriers (SSBs), as it can directly influence the height of the guardrail and the working width of the SSB during the vehicle impact, which consequently affects the crash consequences. Therefore, it is of great importance to determine the bolt response until fractures under different strain rates. For that purpose, experimental tensile tests of low-strength steel rods of grade 4.6 were conducted at various strain rates (0.0025–25 s−1) until fracture. Test specimens were photographed during the testing, and by means of image processing, input data for calculation of true stresses and strains up to the point of fracture were extracted. Based on the experimental data, material parameters were determined for the Cowper–Symonds model, enabling precise numerical simulations of these connections at various strain rates. A validation study was also performed successfully. [ABSTRACT FROM AUTHOR]

This work presents an analysis of the relationship between strength parameters determined in the laboratory and the results of a cone penetration test with pore water pressure measurement (CPTU) of waste soils in the "White Seas" area in Cracow. Anthropogenic soil is an alkaline waste formed during the production of soda ash and deposited in the area of the former Solvay Sodium Plant factory in Cracow, Poland. Due to the large area of the land and numerous investment plans and completed buildings, there was a need to identify reliable functional relationships enabling the determination of the strength parameters of these soils based on the results of the CPTU. Statistical analysis showed that the best correlation with the test results was provided by two logarithmic functions in which the dependent variables were the effective friction angle and effective cohesion. The dependent variable for both cases was the corrected cone resistance qt. The functional relationship combined data from labour-intensive, long-lasting and costly laboratory measurements with quick and less expensive measurements, i.e., in situ CPTUs. The obtained relationships enable the determination of the strength properties of the subsoil of these anthropogenic soils. [ABSTRACT FROM AUTHOR]

This study investigates the impact of nanomaterials on soil strength parameters. This project is carried out according to laboratory tests to determine the impact of nano-silica on the compressive strength and plasticity properties of soil. This project covers the operation of injecting nano-silica into the remoulded soil of Yazd University region, and performing the CPT test as the executive studies in addition to the analysis of nanoparticles by SEM (scanning electron microscope) and AFM (atomic force microscope) images of soil samples. These tests are done for two methods with and without nanomaterials, and then the results are compared. According to the results, nano-silica increases the Plastic Limit (PL) slightly and Liquid Limit (LL) considerably; hence, the addition of nano-silica will increase the Plasticity Index (PI) of soil. Following the increase in nano-silica, the soil compressive strength is also increased; the more the curing time increases, the more the compressive strength will be enhanced. The average rate of increase in compressive strength with time will be increased by increasing the percentage of nano-silica. Based on the results of field and laboratory tests for the injection of nanomaterials and according to silica cementation between soil particles, the nano-silica injection has resulted in the increased CPT strength of soil; hence it is offered as a suitable solution. [ABSTRACT FROM AUTHOR]

The aim of this study is to determine the effect of changes in the phase composition of Al2O3–Si3N4 ceramics that were obtained using the method of mechanochemical solid-phase grinding on their resistance to the process of long-term thermal exposure, accompanied by the processes of oxidation and softening. The relevance of this research consists of determining the influence of the phase composition of ceramics on the change in their strength and thermophysical parameters, on the basis of which, we can draw a conclusion about the optimal composition of composite ceramics that have great prospects in the field of fire-resistant, heat-resistant, or radiation-resistant structural materials. During this study, the dynamics of the changes in the phase transformations of the xAl2O3–(1−x)Si3N4 ceramics, with variations in the ratio of the components, initiated by the thermal annealing of the samples, was established. According to the assessment of the phase transformations with variations in the ratio of the components, it was found that thermal annealing in an air environment at an Al2O3 concentration in the order of 0.3–0.5 M leads to the formation of an orthorhombic Al2(SiO4)O phase and an elevation in its contribution at concentrations above 0.5 M, which causes a rise in the thermophysical parameters and resistance to high-temperature degradation. During the heat resistance tests, it was found that the formation of the composite ceramics with the Si3N4(SiO2)/Al2(SiO4)O/Al2O3 phase composition results in an increase in the stability of their strength properties when exposed to thermally induced oxidation, which has a negative impact on their resistance to softening and a decrease in hardness. Moreover, the presence of the Al2(SiO4)O phase in the composition of the ceramics causes a slowdown in the processes of thermal oxidation of the Si3N4 phase under prolonged temperature exposure, alongside an increase in the degradation resistance of strength properties by more than 4–7 times, in comparison with the softening data established for single-component ceramics. [ABSTRACT FROM AUTHOR]

Cement clay interlocking (CCI) hollow bricks have been used as a construction material in many developed and developing countries. Many emerging and underdeveloped nations have utilised cement clay interlocking (CCI) hollow bricks as building materials. In India, Andhra Pradesh local makers prepare these cement clay interlocking (CCI) hollow bricks by simply mixing clay, cement, and sand in a traditional method, without following strict design criteria or rules. Previous research has demonstrated that the mechanical characteristics of CCI hollow bricks gathered from various locations in detailed manner respect to hand books on Civil Engineering as per Indian Standards. Bricks from one region had compressive strengths that were significantly lower than the other region Indian Community Standards. Various methods were employed in this investigation to enhance the mechanical characteristics of CCI bricks. New mix patterns were created with the use of sand, cement, and fly ash in this research paper.

Ketogenic diets (KDs) are an alternative to improve strength performance and body composition in resistance training participants. The objective of this review and meta-analysis is to verify whether a ketogenic diet produces an increase in the strength of resistance-trained participants. We have evaluated the effect of the ketogenic diet in conjunction with resistance training on the strength levels in trained participants. Boolean algorithms from various databases (PubMed, Scopus, and Web of Science) were used. Meta-analyses were carried out, one on the 1-RM squat (SQ), with 106 trained participants or athletes, and another on the 1-RM on the bench press (BP), evaluating 119 participants. We did not find significant differences between the groups in the variables of SQ or BP, although the size of the effect was slightly higher in the ketogenic group. Conclusions: KDs do not appear to impair 1-RM performance; however, this test does not appear to be the most optimal tool for assessing hypertrophy-based strength session performance in resistance-trained participants. [ABSTRACT FROM AUTHOR]

This work presents an analysis of the relationship between strength parameters determined in the laboratory and the results of a cone penetration test with pore water pressure measurement (CPTU) of waste soils in the “White Seas” area in Cracow. Anthropogenic soil is an alkaline waste formed during the production of soda ash and deposited in the area of the former Solvay Sodium Plant factory in Cracow, Poland. Due to the large area of the land and numerous investment plans and completed buildings, there was a need to identify reliable functional relationships enabling the determination of the strength parameters of these soils based on the results of the CPTU. Statistical analysis showed that the best correlation with the test results was provided by two logarithmic functions in which the dependent variables were the effective friction angle and effective cohesion. The dependent variable for both cases was the corrected cone resistance qt. The functional relationship combined data from labour-intensive, long-lasting and costly laboratory measurements with quick and less expensive measurements, i.e., in situ CPTUs. The obtained relationships enable the determination of the strength properties of the subsoil of these anthropogenic soils.

The present study explores the intricate relationship between the geotechnical and mineralogical properties of lithomargic clays in the Uttara Kannada region of south India. Lithomargic clays, characterized by their unique composition of clay minerals and calcareous content, play a crucial role in the geotechnical behavior of soils. The study aims to provide a comprehensive understanding of the interplay between the mineralogical composition and engineering characteristics of lithomargic clays, shedding light on their suitability for various construction and infrastructure projects. The research methodology involves a systematic analysis of lithomargic clay samples collected from different locations in the Uttara Kannada region. Geotechnical investigations, including particle size distribution, Atterberg limits, unconfined compressive strength (UCS), California bearing ratio (CBR) and triaxial tests, are conducted to assess the engineering properties of the clays. Concurrently, mineralogical analyses, such as X-ray diffraction (XRD) and scanning electron microscopy (SEM), are employed to identify and quantify the clay mineral constituents within the samples. The findings of this study reveal correlations between specific mineralogical features and geotechnical behaviors of lithomargic clays. Understanding these relationships is crucial for predicting the response of these clays to different engineering applications, including slope stability, foundation design and embankment construction. The research contributes valuable insights to the scientific and engineering communities, aiding in the informed utilization of lithomargic clays in geotechnical projects in the Uttara Kannada region and beyond. The outcomes of this investigation, such as the correlation of geotechnical properties with the variation in minerals in various sample locations, enhance our understanding of the complex nature of lithomargic clays, providing a foundation for more sustainable and effective engineering practices in the geologically diverse landscapes of south India. [ABSTRACT FROM AUTHOR]

The aim of this study is to determine the effect of changes in the phase composition of Al2O3–Si3N4 ceramics that were obtained using the method of mechanochemical solid-phase grinding on their resistance to the process of long-term thermal exposure, accompanied by the processes of oxidation and softening. The relevance of this research consists of determining the influence of the phase composition of ceramics on the change in their strength and thermophysical parameters, on the basis of which, we can draw a conclusion about the optimal composition of composite ceramics that have great prospects in the field of fire-resistant, heat-resistant, or radiation-resistant structural materials. During this study, the dynamics of the changes in the phase transformations of the xAl2O3–(1−x)Si3N4 ceramics, with variations in the ratio of the components, initiated by the thermal annealing of the samples, was established. According to the assessment of the phase transformations with variations in the ratio of the components, it was found that thermal annealing in an air environment at an Al2O3 concentration in the order of 0.3–0.5 M leads to the formation of an orthorhombic Al2(SiO4)O phase and an elevation in its contribution at concentrations above 0.5 M, which causes a rise in the thermophysical parameters and resistance to high-temperature degradation. During the heat resistance tests, it was found that the formation of the composite ceramics with the Si3N4(SiO2)/Al2(SiO4)O/Al2O3 phase composition results in an increase in the stability of their strength properties when exposed to thermally induced oxidation, which has a negative impact on their resistance to softening and a decrease in hardness. Moreover, the presence of the Al2(SiO4)O phase in the composition of the ceramics causes a slowdown in the processes of thermal oxidation of the Si3N4 phase under prolonged temperature exposure, alongside an increase in the degradation resistance of strength properties by more than 4–7 times, in comparison with the softening data established for single-component ceramics.

An industrial by-product known as fly ash is produced when coal is burned for electricity production and is considered an environmental pollutant. A comprehensive fly ash utilisation programme must be implemented to reduce environmental pollution, including numerous factors at different levels. Fly ash's geotechnical qualities, including its specific gravity, permeability, internal angular friction, and consolidation characteristics, make it ideal for structural fill, particularly on clay soils, when building highways and embankments. Much research has been conducted on how fly ash affects soil stability. In order to determine the impact of fly ash addition on soil properties, this inquiry reviewed a few of these papers and conducted a critical assessment. This study also looked at combining fly ash and clay soil. Numerous investigations indicate that fly ash generally improves soil stability, notably when analysing CBR values and soil permeability, and reduces volumetric changes in the soil. The ground becomes compact due to particle size and form and a decrease in volumetric dilatation. Because the additives to the hardened soil do not dissolve, the soil's behaviour continues to be modified. [ABSTRACT FROM AUTHOR]

An appreciable quantity of cement is consumed as binder for masonry mortar, which has resulted in cost escalation and high energy consumption in building construction, in addition to contributing to greenhouse gas emissions. On the other hand, disposal of waste lignocellulosic materials as agricultural residues persists as an unsolved technical problem creating environmental pollution. This paper proposes an effective solution for these two critical issues. Coir fiber, when used as a reinforcement material in cement, was found to be effective in enhancing the mechanical properties of the binder. The application of coir fiber reinforcement on strong, moderate, and weak masonry mortars with respect to strength criteria is examined in this study. ANOVA analysis was carried out to examine the level of significance of coir fiber reinforcement on the flexural and compressive strengths of masonry mortar. The findings from the study revealed that 0.5% coir fiber reinforcement enhanced flexural strength of strong mortar by 18%–22%, moderate mortar by 21%, weak mortar by 10%, and compressive strength of strong mortars by 16%–19% by contributing strength in the early curing period. Moreover, coir fiber–reinforced mortars satisfied the compressive strength criteria required of strong mortar (7.5 to 10 N/mm2), moderate mortar (5 N/mm2), and weak (3 N/mm2) mortar for its application as mortar on masonry walls in accordance with Indian standards. The strength of masonry in compression, flexure, and shear determines how well masonry operates structurally. Cement-based structures are strong in compression but are prone to shrinkage cracks over a span of 30 years due to its weakness in tension. Flexural strength is an indirect indicator for measuring tension. Coir fiber imparts tensile strength to the matrix when used as reinforcement in cement mortar. Fiber networking dissipates the tensile stresses that develop in mortar during flexure and would bridge the gap in a better way. This prolongs the life of buildings and maintains ecological equilibrium by preventing the need for periodic repair and maintenance, which reduces cost, time, and labor. The use of fibers in mortar for plastering is found to be more beneficial in enhancing the strength of a masonry structure than adding fibers to blocks. Coir fiber content of 0.25% and 0.5% (10 mm length) by weight of cement was found to be effective at enhancing the early flexural strength of cement mortar. Coir fiber–reinforced plaster cement can be made available ready to use in bags of 25 or 50 kg for a crack-free plastered surface on ceilings and internal and external walls. [ABSTRACT FROM AUTHOR]

In this research, a multilayer feed-forward backpropagation error neural network has been used to predict the strength parameters of a concrete sample containing different additives. To achieve the most optimal neural network structure, the strength parameters of the concrete have been evaluated for different neural network arrangements. Control criteria are the use ofnumerical values of performance, the correlation between training functions, validation and,testing in the neural network, gradient and results of regression diagram to determine the most optimal neural network structure. It was found that the function of the neural network largely depends on its geometric structure. Revealed by the research findings, the most optimal prediction of the neural network has occurred in the case of using three layers with 30 neurons in each layer in the neural network. In this case, the numerical value of the neural network performance and the regression were obtained as 58.5 × (10-9) and 0.9846 , respectively. By determining the optimal neural network, different percentages of concrete raw materials based on the pre-performed experimental study are introduced to the selected neural network and the considered resistance parameters are predicted through residual analysis. According to the results, the differences between the predicted values of the neural network and the numerical values of the experimental study concerning the parameters of compressive, flexural, and tensile strength were also found to be equal to 1.68%, 1.92%, and 0.21%, respectively. Such a slight difference reflects the optimal accuracy of the chosen neural network in predicting the strength parameters.

This work investigates the behavior of a silty clay stabilized with 3, 6, 9, and 12 % of ground granulated blast-furnace slag (GGBS), respectively, and 1 % of quicklime used as an activator. The influence of the composite (Quicklime - GGBS) on the immediate behavior of the silty clay is studied by examining the Atterberg limits, the maximum dry density, the optimum moisture content, and the immediate bearing index. The evolution, at different curing periods (1, 7, and 28 days), of the mechanical characteristics of the treated soil, namely unconfined compressive strength, cohesion, and internal angle of friction is also studied. The increase, up to a dosage of 9%, of the GGBS content, leads to an increase in the optimum moisture content, the immediate bearing index, the unconfined compressive strength, and shear strength parameters. Paradoxically, a decrease in the plasticity index and the maximum dry density was observed.

The present study explores the intricate relationship between the geotechnical and mineralogical properties of lithomargic clays in the Uttara Kannada region of south India. Lithomargic clays, characterized by their unique composition of clay minerals and calcareous content, play a crucial role in the geotechnical behavior of soils. The study aims to provide a comprehensive understanding of the interplay between the mineralogical composition and engineering characteristics of lithomargic clays, shedding light on their suitability for various construction and infrastructure projects. The research methodology involves a systematic analysis of lithomargic clay samples collected from different locations in the Uttara Kannada region. Geotechnical investigations, including particle size distribution, Atterberg limits, unconfined compressive strength (UCS), California bearing ratio (CBR) and triaxial tests, are conducted to assess the engineering properties of the clays. Concurrently, mineralogical analyses, such as X-ray diffraction (XRD) and scanning electron microscopy (SEM), are employed to identify and quantify the clay mineral constituents within the samples. The findings of this study reveal correlations between specific mineralogical features and geotechnical behaviors of lithomargic clays. Understanding these relationships is crucial for predicting the response of these clays to different engineering applications, including slope stability, foundation design and embankment construction. The research contributes valuable insights to the scientific and engineering communities, aiding in the informed utilization of lithomargic clays in geotechnical projects in the Uttara Kannada region and beyond. The outcomes of this investigation, such as the correlation of geotechnical properties with the variation in minerals in various sample locations, enhance our understanding of the complex nature of lithomargic clays, providing a foundation for more sustainable and effective engineering practices in the geologically diverse landscapes of south India.

Myokines represent important regulators of muscle metabolism. Our study aimed to explore the effects of a cyclical ketogenic reduction diet (CKD) vs. a nutritionally balanced reduction diet (RD) combined with regular resistance/aerobic training in healthy young males on serum concentrations of myokines and their potential role in changes in physical fitness. Twenty-five subjects undergoing regular resistance/aerobic training were randomized to the CKD (n = 13) or RD (n = 12) groups. Anthropometric and spiroergometric parameters, muscle strength, biochemical parameters, and serum concentrations of myokines and cytokines were assessed at baseline and after 8 weeks of intervention. Both diets reduced body weight, body fat, and BMI. Muscle strength and endurance performance were improved only by RD. Increased musclin (32.9 pg/mL vs. 74.5 pg/mL, p = 0.028) and decreased osteonectin levels (562 pg/mL vs. 511 pg/mL, p = 0.023) were observed in RD but not in the CKD group. In contrast, decreased levels of FGF21 (181 pg/mL vs. 86.4 pg/mL, p = 0.003) were found in the CKD group only. Other tested myokines and cytokines were not significantly affected by the intervention. Our data suggest that changes in systemic osteonectin and musclin levels could contribute to improved muscle strength and endurance performance and partially explain the differential effects of CKD and RD on physical fitness. [ABSTRACT FROM AUTHOR]

Approximately 30 million tons of tailings are being stored each year at the KGHMs Zelazny Most Tailings Storage Facility (TSF). Covering an area of almost 1.6 thousand hectares, and being surrounded by dams of a total length of 14 km and height of over 70 m in some areas, makes it the largest reservoir of post-flotation tailings in Europe and the second-largest in the world. With approximately 2900 monitoring instruments and measuring points surrounding the facility, Zelazny Most is a subject of round-the-clock monitoring, which for safety and economic reasons is crucial not only for the immediate surroundings of the facility but for the entire region. The monitoring network can be divided into four main groups: (a) geotechnical, consisting mostly of inclinometers and VW pore pressure transducers, (b) hydrological with piezometers and water level gauges, (c) geodetic survey with laser and GPS measurements, as well as surface and in-depth benchmarks, (d) seismic network, consisting primarily of accelerometer stations. Separately a variety of different chemical analyses are conducted, in parallel with spigotting processes and relief wells monitorin. This leads to a large amount of data that is difficult to analyze with conventional methods. In this article, we discuss a machine learning-driven approach which should improve the quality of the monitoring and maintenance of such facilities. Overview of the main algorithms developed to determine the stability parameters or classification of tailings are presented. The concepts described in this article will be further developed in the IlluMINEation project (H2020).

The ability to conduct conventional triaxial compression tests on multiple identical specimens is restricted by available sample quantity, sample homogeneity, as well as testing duration. Multistage triaxial testing is an alternative method to tackle these issues by using a single specimen sheared under different confining stresses to attain the strength parameters. Although there are widely accepted procedures to decide when to stop each shearing stage and proceed to the next stress level, the applicability of these procedures on different soil types is still a question. This study examines the applicability of combinations of two multistage triaxial testing procedures (Rational Procedure and Minimum Slope) under two different deviator stress conditions (Sustained or Cyclic) during confining stress increase. The outcome is compared to conventional triaxial test results for undrained and drained shearing of reconstituted specimens of high-plasticity Ankara Clay. Out of the four options, the rational procedure with cyclic deviator loading and minimum slope with cyclic deviatoric loading conditions, are found to give the most accurate strength parameters in reference to single-stage test results. The maximum number of the shearing-reconsolidation sequences applicable before strength loss is also investigated for each multistage triaxial testing procedure.

Physical properties and mechanical parameters of intact rocks are essential in defining geomechanical characteristics of rock masses. The latter are fundamental in the geotechnical design and numerical modelling of engineering-geological applications involving slope stability analyses as well as the design of dams, foundations, tunnels, open and underground mines, nuclear storage repository etc. Time and financial constraints of many projects often do not allow to perform all the laboratory tests necessary for physical-mechanical characterization of the rock matrix. In these cases, existing published data are the only tools for appropriate definition of the geomechanical characteristics of the intact rocks and subsequent development of engineering-geological performances.This paper reports the values of major physical properties and mechanical parameters for several intact rock samples of limestone, collected from the Central Apennines region (Italy). The main physical properties measured for the rock samples are unit weight, density, and porosity. The mechanical parameters derived from the laboratory tests on the samples include uniaxial compressive strength, cohesion, friction angle, tensile strength, elastic modulus, and Poisson's ratio. Only for a few of samples, the index parameters (point load index) and the dynamic characteristics (P-wave velocity) were also measured. The laboratory tests for these samples were performed following the standards by the International Society for Rock Mechanics (ISRM).

The freezing technique has been employed for a long time to strengthen the mechanical properties of intact rock and rock mass; however, it has not received as much attention as it deserves. This paper thoroughly reviews the effect of freezing on the essential mechanical properties, including uniaxial compressive strength, tensile strength, and Young’s modulus. The laboratory tests include the determination of density, ultrasound speed propagation, and strength parameters such as uniaxial compressive strength, tensile strength, and Young’s modulus. According to previously published results, the strength of different rocks such as marl, limestone, sandstone, tuff, granite, and marble increased significantly due to freezing when the samples were tested in frozen conditions. However, there is variation in strength increase based on rock type. It is outlined here that freezing increases rock strength by a factor of 4 in porous rock and by a factor of 1.8 in crystalline rock. Additionally, Young’s modulus increases with a decrease in temperature; however, a further decrease in temperature from -10 to -20 °C has no effect on Young’s modulus. Moreover, mathematical modelling for frozen rock has been reviewed comprehensively. It was found that porosity, the density of rock grains, density of water, residual unfrozen water content, minimum unfrozen water content at freezing point, material parameters, the initial temperature of rock, crystal size, orientation and alignment of minerals, and the loading rate are the most critical parameters that influence frozen rock strength.

Slope failure is a recurring natural hazard in the western margin of the Main Ethiopian Rift and especially around the Debre Sina area. To minimize the damage caused by failure events, a detailed investigation of landslide-prone areas identified using numerical modelling plays a crucial role. The main aim of this study is to assess the stability of slopes and to evaluate and compare safety factors calculated by the different available numerical methods. Stability analyses of slopes prone to different types of failures were performed with different techniques. The stability was assessed for slopes of complex geometry composed of aphanitic basalt, porphyritic basalt, tuff, and colluvium (poorly sorted clayey sand to silty sand) using the limit equilibrium method and the shear strength reduction method based on finite elements. Furthermore, numerical analysis was done under static and pseudo-static loading using the horizontal seismic coefficient to model their stability during a seismic event. Satellite images were used to select failure-prone slopes based on slope properties and identified past landslides, as well as to derive structural and geological information for the numerical models. The slope stability analysis indicates that the studied slopes are unstable, and any small-scale disturbance will further reduce the factor of safety and cause failure. The slope stability of landslide prone hills in the study area strongly depends on the saturation conditions and the seismic load. [ABSTRACT FROM AUTHOR]

The subject of this paper is the evaluation of the use of waste material, which is the native soil. On the example of the base ground taken from the village of Lipie (Podkarpackie voivodeship), soil-aggregate mixtures were prepared with a different degree of addition of natural aggregate. The study analysed the quantitative and qualitative parameters of the prepared mixtures and assessed their physical and mechanical properties to determine their suitability for the construction of nfrastructural facilities. It should be noted that most specifications recommend the use of primarily aggregate mixtures. The paper presents the results of a study analysing the effect of aggregate admixture to the native soil on selected physical and strength properties of the mixtures developed. The obtained results confirmed the validity of research on the use of soil-aggregate mixtures for construction purposes. [ABSTRACT FROM AUTHOR]

Various adverse effects and hydro-mechanical failures of soil are the dominant effects of global warming. At the same time, rapid industrial development has produced several by-products on a large scale. The reuse of industrial residues in different engineering fields without compromising the technical characteristics is propitious from the engineering, environmental, ecological and economic points of view. Phosphogypsum (PG) can be used as an alternative civil engineering material as it is rich in calcium sulphate, although it contains some radioactive molecules. Researchers are continuing to investigate the utilisation of PG by mixing it with other traditional materials to convert into alternative materials when the radioactive minerals are within the permissible limits. However, the contamination effect can be reduced by treating with citric acid. This review paper presents details of the increase in strength parameters and permeability of PG when combined with other wastes materials used in different geotechnical fields.

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With the increasing global demand for clean and renewable energy sources, many underground hydropower caverns are built in deep mountain valleys in high-stress regions. The evolution of the mechanical properties of the surrounding rock of underground caverns under high-stress excavation requires urgent investigation. According to the deep-buried granite in the underground caverns of the Shuangjiangkou hydropower station, triaxial tests under confining pressures of 10, 30, 40, and 50 MPa were conducted by the MTS815 rock mechanics test system. Based on the stress–strain curve, the evolution law of the strength parameters of rock samples with the crack volume strain and energy with the energy consumption ratio under different confining pressures was analyzed. Our results showed that the stress–strain curve of the sample is divided into five stages with four characteristic points: the closed point, initiation point, volume expansion point, and peak point. The strength of each stage increases with an increase in the confining pressure. In addition, the failure of this granite is characterized by apparent shear failure. The internal friction angle and the cohesion increase rapidly with the increase in the crack volume strain, and they gradually tend to be constant. Furthermore, the confining pressure profoundly influences energy evolution during the loading in the stable and unstable crack growth stages. In these stages, total energy, dissipated energy, and elastic strain energy increase with an increase in the confining pressure. Finally, the energy consumption ratio can represent the preliminary criterion of rock failure in terms of energy. With the increase in the confining pressure, the energy consumption ratio of rock samples gradually increases to approximately 1.0 at the peak stress point. The research results can provide a reference for the instability prediction of surrounding rock masses of high-stress underground caverns.

The main goal of this research is to study the failure behavior of cement-fiber-treated sand under triaxial direct tension condition tests. Thus, a new loading system and triaxial cell was designed and built for tensile loading. Samples were prepared with content cement of 3 and 5% (dry wt.) of the sand, while two types of polypropylene fibers 0.024 m in length and 23 μm and 300 μm thick were added at 0.0% and 0.5% (dry wt.) of the sand and cement mixture. After a seven-day curing period, the samples were loaded under triaxial direct tension tests under confining pressures of 100, 200, and 300 kpa in drained conditions. Stress-strain behavior, changes in volume and energy absorbed by cement-fiber reinforced sand were measured and compared with the results of other studies. Adding fibers resulted in reduced peak deviatoric stress and increased residual deviatoric stresses of the cement-fiber reinforced sand, with changes from brittle to ductile behavior. The initial stiffness and stiffness at 50% maximum tensile stress of the samples is decreased with the addition of fibers and with an increase in fiber diameter, the reduction rate of this stiffness is more evident. The absorbed energy for fibers with a thickness of 23 μm is less than fibers with a thickness of 300 μm. The effect of adding fibers to strength parameters showed that the cohesion intercept decreases, while the internal friction angle increases. [ABSTRACT FROM AUTHOR]

A significant increase in effective stress can be induced in hydrate-bearing reservoirs when the depressurization method is applied. A series of drained triaxial shear tests were performed on hydrate-bearing sediments with various hydrate saturations to investigate their mechanical characteristics under effective confining pressures of up to 20 MPa. The results show that significant particle crushing of the host sand occurs during shearing under high pressures, and there is no remarkable effect of hydrate saturation on the degree of particle breakage. As the effective confining pressure increases, the stress–strain curves of the hydrate-bearing specimen transformed from strain-softening to strain-hardening. The peak stress ratio and internal friction angle of the sediments gradually decrease and tend to be constant with the increased confining stress, whereas the cohesion in hydrate-bearing sediments exhibits an increasing tendency. The critical state line (CSL) of hydrate-bearing sediments in the e-lnp′ space under low-to-high effective confining pressures intersects with the normal consolidation line under the same hydrate saturation. Furthermore, the CSL moves upward and rotates clockwise as the hydrate saturation increases. [ABSTRACT FROM AUTHOR]

In this research, the potential improvement of some geotechnical characteristics of soft clay soil using the low Calcium fly ash was evaluated. (These characteristics include unit weight, shear strength, compaction characteristics and soil plasticity characteristics). In addition, the X-ray diffraction test was performed to measure the mineralogical changes in the soft clay soil when the low Calcium fly ash is added. The ordinary Portland cement was used to activate the fly ash. The total percent of flash and cement was10% to investigate the variation in the effectiveness of activation. The optimum moisture content that which computed by the compaction test was adopted in the rest of the experimental program. The test results revealed that the cement could be used to improve the activating of the fly ash efficiently. The maximum value of dry density was marginally affected due to activation from 1.747 to 1.738 g/cm3 along with a corresponding change in optimum water content from 17.45 to 15.5 %. The soil cohesion parameter increased from 188 to 206 kN/m2 whereas the angle of internal friction rose from about 56.7o to 59.1o. Finally, the results of the unconfined compression test reveal that the cement-activated fly ash could present better results than those obtained from a 28-days curing cement.

This paper presents the impact of selected essential aspects of geological structure on the state of slope stability as assessed by changes in the safety factor (SF). The engineering geological slope features that were analysed include: (i) changes in soil cohesion and internal friction angle, (ii) presence of a weak soil layer and its span, (iii) structural discontinuity (i.e. fault), (iv) soil permeability properties and water conditions (i.e. groundwater level, long and heavy rainfall). A certain scheme of slope stability calculations has been proposed for a case involving complex geological conditions. The numerical modelling of a hypothetic slope was performed using the shear strength reduction method based on the finite element method.

Based on the triaxial test results of 30 types of rocks, by analysing the confining pressure function and defining a new plastic internal variable, the evolution laws of the strength parameters and shear dilation angle with a defined plastic internal variable are studied, and the corresponding evolution models are established. First, the complete stress-strain curves of 30 types of rocks are collected from published literature; from these curves, the critical equivalent plastic strains under different confining pressures are extracted. With the confining pressure and critical equivalent plastic strain data of the 30 types of rocks, fitting is performed for 23 different functions. The results demonstrate that the three-parameter allometric power-type function is the best to serve as the confining pressure function to define the plastic internal variable. Second, the strength and plastic strain data of the 30 types of rocks are extracted and transformed into the strength and plastic internal variable data. By analysing the evolution laws of the strength parameters considering the plastic internal variable, the Gaussian function is adopted to uniformly characterise the variation in the strength parameters with the plastic internal variable. Third, the shear dilation angle, confining pressure and plastic strain data of the 30 types of rocks are extracted and transformed into shear dilation angle, confining pressure and plastic internal variable data. By analysing the evolution law of the shear dilation angle considering the confining pressure and the plastic internal variable, a negative exponential function is adopted to uniformly characterise the nonlinear evolution of the shear dilation angle. Finally, the proposed evolution models of the strength parameters and the shear dilation angle are integrated into ABAQUS. By comparing the simulated complete stress-strain curves with the experimental curves of the different rock types, it is verified that the proposed models can be used to correctly simulate the nonlinear deformation and failure of different rock types. This research overcomes the shortcomings of the existing models and has wide application prospective. [ABSTRACT FROM AUTHOR]

Sandy soils constitute a large part of the soils of the northern part of Iran. The construction of structures on these soils will have some problems due to a lack of proper strength properties. On the other hand, in recent years, bottles of polyethylene terephthalate (PET) plastics, such as water and soda bottles, have led to the emergence of an environmental threat due to their prolonged durability in the environment. The utilization of these materials for soil improvement seems to be a sustainable approach. In this research, the effect of recycled PET on the mechanical properties of Babolsar sandy soil is investigated through an extensive experimental analysis carried out using direct shear and Consolidated Drained (CD) triaxial compression tests. Various concentrations of PET were mixed to sand with 3%, 5%, and 7% cement contents. The curing time and relative density of samples were 7 days and 70%, respectively. The results showed that the addition of this fiber improved strength parameters such as cohesion and internal friction angle. Furthermore, the effect of the fiber was not significant with an increase in cement content in samples. The samples with 3% cement showed better results in both direct shear and triaxial tests. By adding 0.5% and 1% PET fibers to the samples containing 3% cement at 100 kPa pressure, the ratio of strength in direct shear tests increased by 13% and 24%, respectively, and increased in the triaxial test by 50% and 93%, respectively. [ABSTRACT FROM AUTHOR]

The quality of designed structures embedded in rocks is strongly related to rock strength parameters of intact rock. Measuring different parameters from tests could be very expensive in designing phase of projects. Estimating some parameters from other ones can reduce costs and time of project procedure. In this paper, the relationships between static and dynamic parameters of marls are studied by using the single and multiple linear regressions. For this purpose, several marl core samples from Seydoon region, Khoozestan Province in Iran are collected and tested. Some equations with sufficient correlation have been obtained to predict the engineering parameters of marls, especially the uniaxial compressive strength (UCS).

The slopes of open-pit mines are often at risk of failure. To identify this hazard, stability analyses are performed. An important element of these stability analyses is the reliable selection of input parameter values for the calculations. This selection is difficult because the slopes of the open pit are disturbed by mining activities. In such conditions, rheological processes, intensified by weathering, develop in open-pit slopes. This study is aimed at setting the strength parameters for the stability analysis of open-pit slopes with a developed slide process, using the random set method. The study was performed on the example of the open pit of the Bełchatów lignite mine, central Poland. A four-stage methodology, according to the random set method, was proposed. The methodology covered the following: site investigation, sensitivity analyses, shear strength reduction (SSR) analyses using numerical calculations, and probability analyses of the factor of safety (FoS) calculation results. The setting of the input parameters took into account the peak and residual strength parameters for each lithological unit in the physical model of the open-pit slope. Samples for laboratory tests were taken from the cores of nine test boreholes. The sensitivity analysis included all peak and residual strength parameters for each lithological unit in the body. As a result of the sensitivity analysis, specific strength parameters were adopted that would have a great impact upon the results of the calculations. Selected sets of parameter values were then used for the FoS calculations. The resultant FoS values revealed the probable slide planes. The positions of the slide planes were consistent with the interpreted slide surfaces based on the control boreholes and terrain observations. Knowledge of the slide planes positions and the values of the strength parameters enabled the designing of a securing approach for this landslide, and the taking of preventive measures to reduce this risk.

Utilizing bentonite in composites such as concrete mixture is one of the practical approaches for adsorption of heavy metals. The mixture of bentonite and normal concrete is known as bentonite plastic concrete (BPC). This type of concrete is commonly utilized as the material of cutoff walls under earth dams with the aim of minimizing or preventing water seepage. Plastic concrete should possess high workability and consistency since it is poured into trenches by tremie pipe; this fact highlights the importance of predicting the slump of BPC. Different strength parameters of BPC such as compressive strength and elastic modulus can be predicted by utilizing prediction models. This information is exceedingly useful for modifying mixing design of BPC which results in reducing the cost and time of constructing a project. Consequently, it is vital to propose models that can predict the parameters of BPC with high precision. In this research, 158, 169, and 119 data records respectively for slump, compressive strength of cubic samples (f' c,cube), and elastic modulus (E c) of BPC were collected from literature in order to propose prediction models. Three soft computing methods of artificial neural network (ANN), Multivariate adaptive regression splines (MARS), and M5 model tree (M5Tree) were utilized and compared in this paper. Then, parametric studies were conducted to study the effect of different variables such as silty clay addition, bentonite dosage, water content, and curing time on the outputs (i.e., slump, f' c,cube , and E c). Results indicate that ANN models are more accurate than the other models for prediction of all three parameters. The water variable produces the greatest effect on the slump of BPC while the sand variable has the least influence. In addition, both for f' c,cube and E c models, variables of cement and curing time have the maximum and minimum impact on the outputs, respectively. • Three datasets of Slump, f' c,cube , and E c of BPC were gathered from the literature. • Three methods of ANN, MARS, and M5Tree were compared. • ANN models were more precise than the other models. • The parametric studies were performed to investigate the behavior of ANN models. • The sensitivitsy analysis showed the influence of input parameters on models output. [ABSTRACT FROM AUTHOR]

A new method is proposed in order to estimate the shear strength of schistosity planes in slate in terms of Mohr–Coulomb cohesion and internal friction angle. The procedure consists in carrying out the Brazilian method under different loading-foliation angles, for which experimental tests were achieved in slates from the northwest of the Iberian Peninsula (Spain). The experimental fracture patterns were analytically studied and justified by simulating the stress field in the discontinuity planes contained in the whole sample, taking into account the first failure registered in the tests. By combining experimental and analytical studies and a procedure based on the representation of the threshold state of stresses—in the elastic regime—in the failure plane, it is possible to estimate the foliation's strength envelope through a lineal adjustment according to the Mohr–Coulomb criterion and, thus, to characterize the layering. Finally, the proposed procedure was validated by the direct shear test. The cohesion and the internal friction angle obtained with this convenctional test were very close to that calculated by the proposed method, verifying the methodology developed by the authors. This procedure may be interesting in various engineering applications, either in the study of the properties of cleavage in slate, which is commonly used as an industrial rock, or in dam foundations, underground excavations and slope engineering, since one of the main failures in civil engineering is due to sliding along weak planes. [ABSTRACT FROM AUTHOR]

Abstract It is established that the strength of frozen soil exhibits apparent nonlinearity in the p–q plane. As the mean stress p increases, in certain experimental conditions, the strength of frozen soil increases rapidly and then reduces gradually; however, in certain other conditions, the strength increases gradually and then reduces rapidly. The former phenomenon is said to be of the "front peak" type, and its critical confining pressure is relatively smaller. The latter phenomenon is said to be of the "back peak" type, and its critical confining pressure is relatively higher. Only a few cases are considered as "symmetric"; these exhibit forms analogous to a parabola opening downward. Based on these observations, it is determined that the temperature, soil type, salt content, strain rate, thawing cycle times, and particle size of the sample determine the type of the strength curve. With the present level of research, most of the strength criteria can consider only one of the three types. Thus, a new strength criterion that can be simultaneously applied to the three types of strength-changes, and the corresponding strength criterion in the deviatoric plane are proposed. Moreover, two concepts—"calculated cohesive force (c 0)" and "calculated internal frictional angle (φ)" of frozen soil—are proposed as fundamental mechanical parameters for various strength criteria. Highlights • The strength variation of frozen soil on the compressed meridional plane is both nonlinear and asymmetrical. • The asymmetry of strength of frozen soils on the meridional plane can be classified into three types: "front peak," "symmetric," and "back peak." • The concepts of "calculated cohesive force (c 0)" and "calculated internal frictional angle (φ)" of frozen soil are introduced. On this basis, we propose a series of strength criteria for frozen soil in stress space. [ABSTRACT FROM AUTHOR]

The article presents research results of the strength parameters of HPC achieved in various research conditions. The research was carried out on substantially different samples, both as to the size as the slenderness ratio. Moreover, the assessment of the effect of speed of a load on strength parameters as well as other factors which in a significant way show the difference in the strength values was made. For comparison, the results were also applied to the relations known in ordinary concrete.

The effect of capillary water caused by heavy rainfall and groundwater level fluctuations can induce the erosion and collapse of island reef coral sand foundations. Here, the effects of water content (ω) on the shear strength parameters of coral gravelly sand are analyzed at the macro and micro scales by laboratory consolidated-drained triaxial compression and nuclear magnetic resonance tests. Furthermore, particle breakage characteristics of coral gravelly sand under the static load are discussed. With increasing ω, (1) the internal friction angle increases slightly (ω; (3) with an increase from 5.4% to 21.3%, the bound water content remains almost unchanged; (4) the capillary water content is the main factor impacting the apparent cohesion; (5) the increase in free water content is the internal cause of the decreasing internal friction angle of coral gravelly sand with ω > 11.1%; and (6) the particle breakage increases, and there is an approximately linear relationship between the median particle diameter (d50) and relative breakage index (Br). The established physical model can reflect the influence of water content and plastic work and describe the evolution law of particle breakage.

Defining relationships among the soil parameters and strength properties have become a popular research topic among the soil mechanics researchers in recent years. As conducting laboratory tests are quite tiresome and time-consuming, investigating interconnection and correlation among the soil parameters using collected data will help to understand and predict the characteristics of soil effortlessly. This research aims at stating regression and product moment correlation analysis between the strength parameters and index properties of the soils of Karnaphuli river tunnel project site. Around 120 borings were done in that site to determine both the index and strength properties of the soil in the laboratories. In this paper, multiple linear regression analysis was developed for the cohesion and liquid limit along with the collected explanatory variables and correlation analysis was done to quantify the direction and strength of the linear association. This equation supports to adopt different characteristics of the soils of Karnaphuli River and additionally a statistical significance of correlation among different soil parameters have also been unfolded. Finally, the equation is compared with some of commonly used classical soil mechanics equation to determine the acceptability of this correlation. [ABSTRACT FROM AUTHOR]

Occurred in the offshore of SW Taiwan on 26 December 2006 with a magnitude of 7, the Pingtung earthquake had triggered numbers of submarine landslides. This event provides an excellent opportunity to incorporate the back analysis approach to evaluate the in situ shear strength parameters. According to the chirp sonar images of the seabed near the SW Xiaoliuqiu obtained before and after the earthquake were adopted to establish the slope profile and identified the location of a circular sliding surface. Consequently, the in situ, effective strength parameters under the critical condition can be calculated by back slope stability analysis. Submarine sediment sampler was obtained via gravity sampling method and the laboratory tests were performed to determine the index properties and strength parameters. Test results indicate the cored sediment has the characteristics of normally consolidated (NC) clay. The effective friction angle (Φ') is 15.3° with cohesion (c') of 19.4 kPa. The effective and total stress methods were used to perform the back analysis. The strength parameters derived from back analysis of effective and total stress methods all indicate values approach the CIU triaxial tests results. Consequently, the representativeness of the marine sediment characteristics obtained from laboratory tests is identified. The total stress approach yields an undrained strength ratio cu\ σ'ν0 of 0.26 which well fit the ratio used in geotechnical practice for estimating NC clay. According to the analytical approach, the landslide was applied seismic forces (seismic coefficient kh = 0.14) and generated excess pore pressure of 31 kPa at the sliding surface. [ABSTRACT FROM AUTHOR]

Copyright of Acta Scientiarum Polonorum. Formatio Circumiectus is the property of Wydawnictwo Uniwersytetu Rolniczego im. Hugona Kollataja w Krakowie and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Scientiarum Polonorum. Formatio Circumiectus is the property of Wydawnictwo Uniwersytetu Rolniczego im. Hugona Kollataja w Krakowie and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A large number of micro cracks，holes and other defects appear in the rock material because of the complexity of its natural formation process.In order to study the interaction mechanism between the cavities and the effect of the cavities on the mechanical behavior of rock，the uniaxial compression tests were conducted on the sandstone samples with the different geometric arrangements of holes and the diameters of the side holes to obtain their strength，deformation and fracture evolution laws. The result demonstrates that both the peak strength and elastic modulus of the samples show the trend of first decrease then increase with the increase of the angle. The minimum and maximum values reach at α=30° and α=90°；the peak strength and elastic modulus show a gradually decrease with the increase of the diameter of the side hole. The damage form of the sandstone containing double circular cavities is affected by the angle and the side hole diameter，mainly in the three aspects of crack initiation forms of the samples，the fracturing behavior of the central hole and the coalescence mode of the double circular cavities. The interaction between the central hole and the side hole gradually increases and then gradually decreases with the increase of the angle，the increase of the diameter of the side hole can also enhance the interaction between the central hole and the side hole，and this has been confirmed in the void coalescence. [ABSTRACT FROM AUTHOR]

The presence of cracks significantly influences the engineering properties of unsaturated residual soil, particularly under external air pressure fluctuation (i.e. Δua). A formula is developed that integrates existing crack depth theories with factors such as soil shear strengths, effective stress parameters, effective tensile strength reduction coefficients, and environmental changes like infiltration and evaporation. In addition, a further equation is deduced to determine the surface flow rate cracking value Q0, which can reflect the influence of seasonal climate on the matric suction of the surface soil. Our findings reveal that crack depth is quite reactive to short-term fluctuations in external air pressure, effective stress parameters and evaporation intensity, with remarkable increases in crack depth linked to these variations. The theoretical depth of soil crack increases by 0.12 ∼ 0.27m when the external air pressure fluctuation (i.e. Δua) is 3 kPa. Soils subjected to climatic conditions crack only when Q>Q0, and early cracking of soils under Δua>0 is conditioned by increasing infiltration and effective cohesion or reducing evaporation. The variation rule of the theoretical crack depth calculated in this research shows consistency with the previous equations, and the model predictions at Δua = 3kPa are proved to match well with the measured results of the practical engineering subjected to various climate environment factors.

In this study, the relationship between the properties of the wood and kraft pulp fibers as well as paper characteristics of 27-year-old trees, lodgepole pine (Pinus contorta) and Scots pine (Pinus sylvestris), was assessed. All trees had been grown in Latvia, within the same forest type, Myrtillosa. Wood density, year ring width, chemical composition and cross-sectional cell wall dimensions were measured. Fiber characteristics were determined, and handsheets were made for all samples from unbeaten kraft pulp. The results showed that the amount of latewood had a positive correlation with wood density for both species and with further positive impact on the paper burst index. Also, slight differences in cross-sectional dimensions were observed. Lodgepole pine provided paper with higher burst strength than Scots pine. Since the former is of higher density, less wood per volume is needed to produce a ton of pulp, and results showed a higher pulp yield in the case of lodgepole pine.