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Determining the properties of mine waste dump material is very difficult, it is caused by the difference of dimension between the laboratory equipment and field material size distribution. This study aims to determine the material properties from mine waste dump material using back analysis method after failure was occurred. The back analysis method is based on a trial and error concept which focuses on failure geometry and it is conducted by varying the cohesion and friction angle until the safety factor was less than 1.0. The laboratory results showed a 66.2 kPa change as well as a 48.8°friction angle deviation in mine waste dump material properties, while the back analysis indicated 33.7 kPa and 27.4°. It means, there is a reduction in the value. Therefore, the increasing in these properties are expected to allow the redesign of heap stability.

The mechanical indices used to describe the anisotropy of layered rock mass are numerous and difficult to be measured. Take the medium - thick horizontal layered limestone rock mass as an example, rock mechanical tests, engineering geological survey, field tests, numerical back-analysis were done to obtain transverse isotropic deformation parameters and strength indices. Normal and transverse moduli of elasticity of rock mass could be preliminarily confirmed by rock uniaxial compression tests, RQD, and empirical formula. Then vertical compression testing of layered rock mass, vertical and horizontal plate bearing tests, and numerical back-analysis were conducted to determine the other deformation parameters. These parameters include normal and transverse moduli of elasticity, normal and transverse Poisson’s ratio, and shear modulus of the rock mass. The cohesion and internal friction angle of the rock mass were then confirmed by direct shear and shear testing. Test results of bidirectional elasticity modulus showed the obvious anisotropy of the layered rock mass. Engineering application indicated that vault settlement was the main deformation mode of the horizontally layered surrounding rock. This differed from the homogeneous rock. Rock falling and delamination readily occurred in the arch of the tunnel.

This paper tested the viscosity of prepreg in the automatic placement process, and conducted the probe and placement-90° peel tests through the test systems. The law of variation of prepreg viscosity during the laying process was studied through these tests under different conditions by taking the peel force to intuitively and quantitatively characterise the viscosity of the prepreg. The results show that this viscosity is inversely proportional to the laying rate, proportional to the laying pressure, and quadratic to the laying temperature. Then, peel tests were simulated to validate both the correctness of the peel test and that of the probe test data fitting the two-line cohesion model. On this basis, a response surface test for laying and peeling was designed. Taking viscous peel force as the response target, the laying process parameters were optimised and the significance of their influence was further studied. The error between the test value and the predicted value of the maximum viscous peel force is 3.03%.

Taking the red clay from Guilin, China as the object, this paper prepares red clay samples with different initial water contents, extracts the crack parameters from the images on the samples under cyclic drying and wetting through image processing, and analyzes the laws of crack development. In addition, parallel red clay samples were subject to shrinkage tests and direct shear tests under the same cyclic drying and wetting. Based on the test results, the authors discussed the laws of shrinkage deformaiton and strength change for the samples under cyclic drying and wetting, and examined the relationship between cracking, shrinkage properties, and strength detiroation of the red clay. The results show that: (1) With the growing crack rate, the volume shrinkage ratio constantly declined; the area shrinkage ratio was generally decreasing, but the decrement was not obvious in local places (in some places, the area shrinkage ratio even increased); the shrinkage coefficient generally declined, (2) Through the five dry-wet cycles, it was learned that the cohesion and internal friction angle of red clay strength can be quantified using the crack rate. This finding lays the basis for judging soil strength based on crack rate, and solving actual engineering problems with the red clay.

Species vary extensively in geographic range size and climatic niche breadth. If range limits are primarily determined by climatic factors, species with broad climatic tolerances and those that track geographically widespread climates should have large ranges. However, large ranges might increase the probability of population fragmentation and adaptive divergence, potentially decoupling climatic niche breadth and range size. Conversely, ecological generalism in large-ranged species might lead to higher gene flow across climatic transitions, increasing species' cohesion and thus decreasing genetic isolation by distance (IBD). Focusing on Australia's iconic

Pin piles have been principally utilized to uphold components of footing to counteract the static and dynamic loadings. Pin piles have been utilized adequately in numerous uses of ground improvement to increase the bearing capacity of soil. The purpose of this study is to observe the behaviour of different types of soil when pin piles were inserted in the vicinity of square footing. The diameter of pin pile, edge distance and pile to pile distance were taken as variables to study the effect of pin pile. Both the soil behaves differently to the pin piles. Although, the insertion of pin piles in clayey soil is difficult but as clays are sensitive to the settlement the pin piles can play a vital role in improvement in load bearing capacity even inserted up to shallow depth. Pin piles also show significant improvement to restrict the lateral movement of cohesion less particles of sandy soil. This paper holds the comparison of both clayey and sandy types of soil subjected to pin piles insertion in the periphery of existing footing through a laboratory model.

An improved grain-based numerical manifold method (NMM) is developed to investigate deformation and damage of intact rocks at the meso‑scale. The grain boundaries are embedded into the numerical manifold method using a random Voronoi tessellation technique to approximate the microstructure of rocks at the meso‑scale. To enhance efficiency, an improved contact loop updating algorithm is proposed, which only preserves the corners of polygonal blocks and deletes the rest of the loop boundary nodes, thus greatly reducing the number of loop nodes involved in contact retrieval. An interface contact model considering cohesion and tensile strength between rock grains is incorporated into the numerical manifold method to simulate fracturing. With the newly developed grain-based numerical manifold method, Brazilian tests and uniaxial compression tests are numerically simulated to validate failure pattern and macroscopic response against laboratory tests. Sensitivity analysis is conducted using the proposed model to further investigate the influence of different number of grains and different stiffness ratio on the macroscopic response of rocks. The results indicate that the improved grain-based numerical manifold method can be effectively used to study deformation, damage and fracturing of rocks at the meso‑scale.

A discrete element method (DEM) calibration for a flexible wheat straw model for simulating direct shear test of wheat straw was investigated. The calibration process uses DEM simulated Design of Experiment (DOE) of a three-point bending test, DEM parameters initialised from previous cantilever beam test, and uniaxial compression test of wheat straw. Wheat straw samples from physiologically matured Winter wheat straw (Triticum aestivum) material were used to estimate shape of a flexible wheat straw model and to obtain material testing data. Using the DEM simulated DOE of a three-point bending test, a regression meta-model was established between particle contact Young's modulus, and bond Young's modulus and Poisson's ratio. An optimisation procedure that minimised a global error relative to the test data was utilised to determine the DEM parameters of particle contact Young's modulus, bond Young's modulus, and Poisson's ratio. From the three-point bending test of wheat straw (length of 55 mm, a diameter of 2.81 mm, and a thickness of 0.35 mm), and DOE based optimisation procedure, the DEM predicted Young's modulus of flexible wheat straw at a percent relative error (RE) of 3.11% compared to test data. Using the optimised DEM parameters of the flexible wheat straw model, the direct shear box test was simulated using the flexible fibre DEM model, as a validation experiment. DEM successfully simulated the direct shear behaviour of wheat straw from the ASTM laboratory direct shear box test, predicting wheat straw angle of internal friction (RE of 1.67%) and apparent cohesion close to zero.

Recent years have witnessed several accidents associated with tunnel face failure in cobble-rich soil in the city of Chengdu, China. Due to its lack of cohesion, cobble-rich soil can be easily disturbed by shield tunneling. Based on the general conditions of the Chengdu Metro Line 1 project, the mechanisms of face failure of tunnels in cobble-rich soil driven with earth pressure balance (EPB) machines are studied. Specifically, we present results of tests carried out using a laboratory reduced-scale model of EPB tunneling operations in cobble-rich soil. The failure kinematics and limit face pressures are presented and analyzed. Then a three-dimensional (3D) discrete-element method (DEM) model, which is able to simulate the main EPB excavation processes is employed to gain further insight into the mechanisms of face failure in cobble-rich soil. Comparisons of these results with the observations based on previous studies are discussed. The results reveal a fundamentally different tunnel-face failure mechanism in cobble-rich soil in contrast with that in clayey or sandy soils. It shows that the ground movement during face failure is sudden in cobble-rich soil, which is different from the progressive mechanism in frictional–cohesive materials. The observed sinkhole at surface takes the shape of an oval, and the failure zone behind tunnel face extends almost as far as that ahead of the face, which is different from the observations in previous studies. The failure zone is found to be wider than that of sandy soils in both the transverse and longitudinal directions.

Due to the rapid industrialization and the development of the economy in each country, the demand for energy is increasing rapidly. The coal mines have to pace up the mining operations with large production to meet the energy demand. This requirement has led underground coal mines to go deeper with more difficult conditions, especially the mining hazards, such as large deformations, rockburst, coal burst, roof collapse, to name a few. Therefore, this study aims at investigating and predicting the stability of the roadways in underground coal mines exploited by longwall mining method, using various novel intelligent techniques based on physics-based optimization algorithms (i.e. multi-verse optimizer (MVO), equilibrium optimizer (EO), simulated annealing (SA), and Henry gas solubility optimization (HGSO)) and adaptive neuro-fuzzy inference system (ANFIS), named as MVO-ANFIS, EO-ANFIS, SA-ANFIS and HGSO-ANFIS models. Accordingly, 162 roof displacement events were investigated based on the characteristics of surrounding rocks, such as cohesion, Young's modulus, density, shear strength, angle of internal friction, uniaxial compressive strength, quench durability index, rock mass rating, and tensile strength. The MVO-ANFIS, EO-ANFIS, SA-ANFIS and HGSO-ANFIS models were then developed and evaluated based on this dataset for predicting roof displacements in roadways of underground mines. The results indicated that the proposed intelligent techniques could accurately predict the roof displacements in roadways of underground mines with an accuracy in the range of 83%–92%. Remarkably, the SA-ANFIS model yielded the most dominant accuracy (i.e. 92%). Based on the accurate predictions from the proposed techniques, the reinforced solutions can be timely suggested to ensure the stability of roadways during exploiting coal, especially in the underground coal mines exploited by the longwall mining.

Motivated by the exponential growth and the huge success of cloud data services bring the cloud common place for data to be not only stored in the cloud, but also shared across multiple users. Our scheme also has the added feature of access control in which only valid users are able to decrypt the stored information. Unfortunately, the integrity of cloud data is subject to skepticism due to the existence of hardware/software failures and human errors. Several mechanisms have been designed to allow both data owners and public verifiers to efficiently audit cloud data integrity without retrieving the entire data from the cloud server. However, public auditing on the integrity of shared data with these existing mechanisms will inevitably reveal confidential information—identity privacy—to public verifiers. In this paper, we propose a novel privacy-preserving mechanism that supports public auditing on shared data stored in the cloud. In particular, we exploit ring signatures to compute verification metadata needed to audit the correctness of shared data. With our mechanism, the identity of the signer on each block in shared data is kept private from public verifiers, who are able to efficiently verify shared data integrity without retrieving the entire file. In addition, our mechanism is able to perform multiple auditing tasks simultaneously instead of verifying them one by one. Our experimental results demonstrate the effectiveness and efficiency of our mechanism when auditing shared data integrity. Keywords: Public auditing, privacy-preserving, shared data, cloud computing

Despite a long period of post-crisis recovery, the COVID crisis caught the EU in a precarious state. The policy and institutional innovations during the financial crisis tempered the macroeconomic imbalances that had caused the crisis. Nevertheless, the EU was left with a strong trend of divergence in economic and social performance because of the lack of sufficiently strong reforms at EU and national levels. But the lessons of the previous crisis were learned. This time around, the EU-level policy and institutional innovations were decisive. The fiscal capacities of the hard-hit countries were strengthened quickly. Green and digital transformation will require a major new wave of innovation in the corporate sector in the EU. This, in turn, critically hinges on improving the quality of public and private institutions and advancing with the implementation of major reforms at the EU level, such as the digital single market or Capital Market Union. Implementing these reforms fully, and preventing later reversals is a key to stemming the trend of economic and social divergence, thus strengthening the coherence of the EU.

High-performance anti-friction coatings are applicable for various applications. The main complications in fabricating such coatings are acquiring desired properties such as low coefficient of friction and high wear resistance while maintaining structural integrity and cohesion. Most state-of-the-art commercial coatings cannot endure severe conditions for extended periods resulting in stunted efficiency and an unsafe environment. In this work, we designed high-performance anti-friction coatings which incorporate ingredients that display robustness and high structural cohesion. An effective and economical method was established that could synthesize the coating consisting of high-temperature ceramics such as BN and SiC; friction modifiers were hybridizing graphite and α-zirconium phosphate. The analysis showed that the coatings exhibited exceptional lubrication performance at room temperature. The coating was annealed at 300 °C and was stable under a wide temperature range of 37-300 °C. The lowest average coefficients of friction for our coated steel sample were 0.107 and 0.169 in air and seawater, respectively. Compared to the coefficient of friction values of a blank non-coated steel sample, reductions of 76.22% in air and 45.48% in seawater percentages were achieved. This work will advance future coating designs with enhanced properties for a wide range of tribological applications including anti-friction coating applications.

A 1/20 scale experimental dozer push test rig was designed and constructed to quantify the expected production rates (loose cubic metres per hour) for dozers operating in hard rock bulk push applications. The particle size distribution of the material employed in the test rig was modelled on a fragmented muckpile representative of that for a typical surface copper/gold mine overburden. A commercially available road base material was found to be highly representative of site conditions. Buckingham Pi theory was applied to mathematically develop factors for scaling up dozer productivity parameters, including blade loads and push times. Dozer production rates were investigated for various dozing distances and slope angles. A series of instantaneous productivity curves were produced which are applicable for use in hard rock dozer push operations. Currently, it is difficult to estimate dozer push productivity in hard rock environments due to dozer productivity correction factors that are empirical in nature and provide only discrete, end-point values for a range of operating conditions. The productivity curves produced demonstrate that dozer productivity declines rapidly over the range of 10 m to 40 m. As such, it is recommended that efficient bulk dozing operations in hard rock mining blocks should not exceed 40 m dozing distance. Further testing of muckpile conditions with increased clay and moisture content would be beneficial in order to better understand and quantify the effects of cohesion on hard rock dozer push productivity.

Chalk breaks easily when subjected to human action such as mechanical handling, earthworks operations or pile installation. These actions break the cemented structure of chalk, which turns into a degraded material known as putty, with lower strength and stiffness than the intact chalk. The addition of Portland cement can improve the behaviour of chalk putties. Yet, there are no studies determining the tensile strength of chalk putty–cement blends, the initial stiffness evolution during the curing time and other design parameters such as friction angle and cohesion of this material. This paper addresses this knowledge gap and provides an interpretation of new experimental results based on the dimensionless index expressed as the ratio between porosity and volumetric content of cement (η/Civ) or its exponential modification (η/Civa). This index aids the selection of the amount of cement and density for key design parameters of compacted chalk putty–cement blends required in geotechnical engineering projects such as road foundations and pavements, embankments, and also bored concrete pile foundations.

This study was conducted to determine the characteristics of claystone at the Sebamban Syncline by carrying out geology—geomechanics and geochemistry approach. The aim of this is to provide the latest information on characteristics of claystone at the Sebamban Syncline. Results of the study showed that the provenance of Warukin claystone was from recycled orogen. This was corroborated by the geochemical data which stated that the claystone was composed by clay-sized quartz minerals. Clay-sized quartz minerals indicate that there has been a long process of transport and weathering of the quartz minerals that have high resistance, until they become clay-sized. The other geochemical data result is the absence of minerals from volcanic rocks that appear at the beginning of the Bowen series, which have fragile property. Mg is the fragile element that was not found and the mineral is an element binding in montmorillonite, so the presence of the montmorillonite in claystone of the Sebamban Syncline was also not found. Geomechanical data result shows that claystone had strength of around 100 kPa with internal friction angle of about 14° and cohesion of about 29 kPa.

Enzyme-induced carbonate precipitation (EICP) is a promising method for the improvement in soil properties. In this study, a model test using a meter-scale soil model was carried out to investigate the feasibility and performance of using the EICP method for the improvement in silty sand. Crude urease derived from soybeans was used for the catalyzation of urea decomposition in the EICP process. Industrial-grade calcium chloride and fertilizer urea were used for the soil treatment. In the treatment process, 1.5 pore volume treatment liquid (3/4 0.67 mol/L urea-calcium chloride solution and 1/4 crude urease liquid) was circulated in the soil model through four perforated pipes as one treatment time. The soil model was treated with totally 5 times. The results showed that the average calcium carbonate content in the soil was around 0.5%. The content was relatively high in the area between the injection/extraction pipes and close to the pipes. Penetration tests with a cone-shape penetrometer were conducted in the soil model. It was found that the penetration resistance in the soil model increased with more treatment times. The distribution of penetration resistances was also consistent with the distribution of calcium carbonate content in the soil model. Soils samples were taken from the model box for triaxial CD tests after the treatments. There were 5.4 ~ 34.7% improvements in the peak deviatoric stresses as compared with the untreated soil. The friction angle increased from 24.0° to 28.9°, and cohesion increased from 0 to 3.5 kPa. The SEM and XRD analysis also demonstrated the presence of CaCO3 produced in the soil. The experimental results indicated that the EICP method had the potential to be used for the improvement in silty sand in engineering projects.

When considering the friction and bonding force between the back of the retaining wall and the horizontal fill behind the wall, the principal stress of the soil element near the vertical back of the retaining wall is no longer vertical and horizontal but deflects to a certain extent. When the surface of the backfill becomes inclined, the principal stress of the soil behind the wall deflects in a more complicated way. In this paper, the cohesion of the soil element in the fill with an inclined surface is assumed, and the formulas for calculating the active and passive earth pressures of the retaining wall with inclined cohesive backfill are derived by rotating the principal stress of the soil element behind the wall. The proposed method is compared with the existing algorithm, and the influences of the inclination and the cohesion of the fill are analyzed. The results show that the proposed method is more universal. Both the active and passive earth pressures increase rapidly with the increase of the inclination of the fill. The active earth pressure and its horizontal component decrease with the increase of the cohesion of the fill, while the passive earth pressure and its horizontal component increase with the increase of the cohesion of the fill.

In this research, Discontinuous Deformation Analysis (DDA) is extended to analyze shear characteristics of unsaturated soil by separately considering capillary suction and adsorption suction at micro-scale. First, the developed matric suction model is validated by comparing simulation results with the analytical solution. Then, the shear characteristics of unsaturated cohesionless soil are simulated and compared with experimental results. The “peak effect” of the shear strength is reproduced, and it is quantitively explained by the proposed micro parameter CSN (number of the capillary bridge). Further, in the high suction range of cohesive soil, adsorption suction is the dominant factor for apparent cohesion. As the contact area of the clay layer decreases slightly in the high suction range, adsorption suction controls shear strength, therefore, there is seldom a “peak effect” of the shear strength for cohesive soil. The extended DDA provides an innovative approach to analyze the micro mechanism of matric suction in a wide suction range.

Given the difficulty in quantifying the interparticle forces, both experimentally and numerically, most studies have considered only the humidity effect in powder caking. In this work, the interparticle forces in caked powders were quantified using the simplified Johnson-Kendall-Roberts (JKR) model to account for all the material and environmental factors that influences powder caking. The cohesion energy density, which is the ratio of cohesive energy to volume of the particle, was used as the indicator of caking in powders. Simulated force chain network was used to track the relay of interparticle forces (IPFL) under compression. The model was validated experimentally by using caked isomalt powder. At a consolidation pressure of 9 kPa, an increase in moisture from 6 to 8% increased the predicted IPFL from 0.41 to 1.31 N while the experimentally measured IPFEL ranged from 0.33 to 1.11 N. The corresponding cohesion energy density varied from 4.05 to 6.98 MJ/m3. This study shows the potential of using cohesion energy density as the predictor and indicator of powder caking. The conditions at which a powder is stored can be related to the cohesion energy density which then can be used as an input parameter for analyzing the caking behavior.

Rock failure criteria are key input parameters for models designed to better understand the stability of volcanic rock masses. Cohesion and friction angle are the two defining material variables for the Mohr-Coulomb failure criterion. Although these can be determined from laboratory deformation experiments, they are rarely reported. Tabulated data for volcanic rocks, calculated using published triaxial results, show that cohesion and friction angle decrease with increasing porosity. If porosity is known, these empirical fits can provide laboratory-scale cohesion and friction angle estimations. We present a method to upscale these parameters using the generalised Hoek-Brown failure criterion, discuss the considerations and assumptions associated with the upscaling, and provide recommendations for potential end-users. A spreadsheet is provided so that modellers can (1) estimate cohesion and friction angle and (2) upscale these values for use in large-scale volcano modelling. Better constrained input parameters will increase the accuracy of large-scale volcano stability models.

The dependence of powder flowability on particle cohesion can often be captured by a dimensionless Bond number, however, whether the same is true for powder spreadability remains unclear. This paper thus presents a particle-scale study on the spreading of cohesive fine powders for additive manufacturing, focusing on the combined effect of particle size and surface cohesiveness. With an experimental validated model, detailed analysis revealed two competing mechanisms due to geometrical constraint and interparticle cohesion. For small particles that allows multiple particles across blade clearance, layer homogeneity is largely maintained before deteriorating sharply, while for large particles that forming a mono-layered packing structure, an optimum homogeneity can be obtained at a moderate level of particle cohesion. The efficacy of increasing blade clearance to improve layer quality was also evaluated. This study can help to identify a critical set of powder descriptors that defines spreading performance.

Calibration and validating are very important to DEM models especially for lunar soil. A review of present lunar soil models, evolutions, calibrations and verifications was executed. The result showed that most scholars used trial-and-error method to calibrate the parameters, but did not sum up a calibration law; in terms of validating, most scholars only focused on the internal friction angle and cohesion, but did not care about the elastic–plastic performance and adaptation. In this study, a systematic method was established instead of single-methods specifically for the calibration and validating of lunar soil DEM models. This is a multi-step method based on triaxial compression test. First, the alterable constitutive law previously proposed by the authors was used, and the influence law of each parameter on the peak stress difference and the position of failure point was analyzed and summed up for calibration. Second, the stress–strain curve was adjusted to coincide highly with Scott's test curve using loose real lunar soil. Third, the internal friction angle and cohesion under both loose and dense conditions were compared with the optimal estimated values to verify the shear strength. Fourth, the elastic–plastic behavior under dense condition was compared with Scott’s test result to verify the adaptation of density. Finally, two application simulations were executed to verify the practicability. By referring the systematic method, the purpose of parameter calibration is more explicit, and the validation is more comprehensive.

Based on the review of regulations and press releases of EU institutions, the content of changes in the cohesion policy in 2021–2027 was revealed in comparison with the period 2014– 2020. The conclusion is made about the preservation of a significant role of the cohesion policy in the EU’s activities and high volume of its allocations from the EU Budget. The author sees an element of novelty in the synthesis of well-known methods and principles of supranational regulation of the socio-economic development of the EU territories – the budget method, the principle of financial conditionality and the open method of coordination. Particular attention is paid to the decision to reorient a third of the allocations of European regional policy funds for programs of transition to a circular and climate-neutral economy in 2021–2027. The explanation of such strong link between the goals of regional policy and the ecological and climatic goals of the EU is proposed. Namely, the success of the «Europe 2020» Strategy only in terms of climate benchmarks, according to the author, gives to the official Brussels a reason to see the potential to increase the effectiveness of regional policy.

To explore the reinforcement effects of different reinforcement methods, kraft paper was used as reinforcement material, and shear tests were carried out in sand to study the reinforcement effects of kraft paper perpendicular and parallel to the shear plane. The test results show that the two reinforcement methods can effectively improve the strength of sand and the orthogonal reinforcement form is more superior. The existence of reinforced materials greatly improves the cohesion of sand, but does not significantly improve the internal friction angle. The width of reinforcement material has little effect on the reinforcement effect and shows different variation laws under different reinforcement forms.

Ordinary Kriging (OK) is one of the geostatistical methods, which were used in the variation types of mapping, which related to the soil. Compliment by semi variogram models, OK has become one of the most sought out method for the digital mapping, which applied Geographical Information System (GIS) as a main approach. Four semi variogram models, which are spherical, exponential, circular and gaussian would be applied to determine the best model for the mapping purposes, with Root-Mean-Squared-Error (RMSE) as a performance indicator. The value of the cohesion and clay percentage will be based according to the related depth. Each semi variogram model will be applied to determine the best model for each depth, whether it is cohesion or clay percentage, and producing a map, as a result. This mapping would be an alternative to the geological mapping, whereby it would show the range of the cohesion and clay percentage values rather than soil types.

The Hoek–Brown failure criterion has developed into the most widely used system for estimating rock mass strength in rock engineering. The reason lies in its unique framework for integrating the strength properties of intact rock and geological observations in the field. While the determination of intact rock properties from laboratory tests is relatively straightforward, quantifying the relevant geological characteristics remains challenging. Strength degradation relations play a central role in the Hoek–Brown failure criterion by downgrading the strength properties of intact rock, based on quantitative measures of rock mass quality and disturbance, to estimate the strength properties of the rock mass. In this independent review, the origin and evolution of the Hoek–Brown failure criterion and the associated strength degradation relations and rock mass characterization methods are discussed. Common methods for estimating rock mass cohesion, friction angle and deformation modulus are presented. The effect of parameter uncertainty on the reliability of estimated rock mass properties is investigated. Understanding the basis and development of the Hoek–Brown failure criterion is essential for proper use of the system within its limits of applicability and with realistic expectations of reliability.

The design of grouting engineering in practice is either based on conventional soil mechanics or empirical procedures ignoring the effect of degree of saturation (water content). In this study, a series of laboratory-pressurized grouting tests were conducted on unsaturated sand to reveal the influence of soil water content on the grouting characteristics. With combination of direct shear tests at constant water content, water retention tests as well as microscopy observations, the mechanisms that controlling the strength and in turn the grouting characteristics in unsaturated sand were interpreted from the perspective of water–air interface. It was found that the non-monotonic phenomena of grouting characteristics (injectability and diffusion characteristics) with increasing water content were strongly dependent on the shear strength, which is influenced by the apparent cohesion induced by capillary mechanisms relating to the water–air interface. The threshold value of the injectability and diffusion pattern is corresponding to the boundary of the two transition zones (two different desaturation mechanisms) in the water retention curve. In the primary transition zone, the water phase is interconnected with air bulbs entrapped. With the drainage of bulk water in the large pores, the amount of water menisci increases, generating larger and larger surface tension force between particles. Therefore, less and less grout was injected as the bearing capacity and shear strength increase. However, in the second transition zone, with the drainage of menisci water, the menisci area of each pores decreases, inducing less and less surface tension force. Thus, more and more grout was injected as the bearing capacity and shear strength decrease. It is hoped that the work in this study will facilitate researching the grouting mechanisms in unsaturated soil, thus optimizing the grouting parameters in engineering practice.

Slope stability in reservoirs depends on time-dependent triggering factors such as fluctuations of the groundwater level and precipitation. This paper assesses the stability of reservoir slopes over time, accounting for the uncertainty of the shear strength and hydraulic parameters. An intelligent surrogate model has been developed to reduce the computational effort. The capability of two machine learning algorithms, namely Support Vector Regression and Extreme Gradient Boosting, is considered to obtain the relationship between geomechanical parameters and the factor of safety. The probability of failure of a hypothetical reservoir slope is estimated employing Monte Carlo simulations for different scenarios of drawdown velocity. A sensitivity analysis is conducted to investigate the influence of the geomechanical parameters, regarded as random variables, on the probability of failure. The results revealed that the coefficient of variation in the effective friction angle and the correlation between effective cohesion and friction angle have the highest impact on the probability of failure. The intelligent surrogate model can predict the factor of safety of reservoir slopes under rapid drawdown with high accuracy and enhanced computational efficiency.

Tin (Sn) mining has disrupted some part of Gyel’A’ and Kantoma ecosystem with characteristic mine tailings, deep pits, abandoned mine excavations, mine ponds, deforestation, etc. To permit continual mining of tin, protection and subsequent beneficial use of the mined land, there is need for backfilling/reclamation. Hence, accurate modeling of backfilling materials is required. In this study, possible backfilling materials such as normal soil and mine tailings samples were modeled by integrating geotechnical parameters with statistical tools. The result revealed that; normal soil samples (Gyel’A’C and KantomaC) have more percentage of fines and well graded than the mine tailings (Gyel’A’1 and Kantoma1). Quick undrained triaxial result showed that kantoma C (18.344) and Gyel’A’C (16.26) have higher shear strength than Kantoma1 (12.657) and Gyel’A’1 (0.9935). Mine tailings have lower coefficient of compressibility but more permeable than normal soils. Statistically, strong positive correlation exist between the geotechnical parameters moisture content (M/c), void ratio (e), porosity (η), undrained cohesion ( $$\complement$$ ), angle of internal friction ( $$\varphi$$ ), optimum moisture content (OMC %), maximum dry density (MDD) and shear strength. Non-significant strong correlation exists between shear strength and all the parameters except angle of internal friction ( $$\varphi )$$ . Principal component analysis showed that apart from permeability and particle size distribution; moisture content, void ratio, porosity, angle of internal friction, optimum moisture content, maximum dry density and shear strength are the dominant parameters that determines the suitability of the choice of backfilling material unlike undrain cohesion.

New sustainable ground improvement techniques have been recently required for applications in onshore and offshore geotechnical structures. The Microbiological Induced Calcite Precipitation (MICP) method is a ground improvement technique that results from a natural biogeochemical process in order to create a soil cemented framework. The biocementation resulted from this method has been shown to produce a reasonable increment in soil’s mechanical properties such as strength and stiffness. This study focused on evaluating the mechanical behavior of a biocemented uniform sand by using the MICP method. Three different cemented levels were produced in a laboratory scale by varying the amount of a chemical solution (cementation solution) percolated through the specimens. The experimental outcome from a set of triaxial tests performed at three different confining pressures (100 kPa, 200 kPa, and 400 kPa) demonstrated that the MICP method produced an increment in strength with a peak in the deviatoric stress when compared to the uncemented soil, changing the cohesion intercept from nearly 0 kPa to 75 kPa. Furthermore, the stress-dilatancy response indicated that a fully structural degradation is achieved at large plastic strains, differently from what is usually observed in chemically artificially cemented blends, like soil–cement and soil–lime.

In mining engineering, coal and gas outburst is extremely dangerous dynamic disaster, which will cause serious casualties and property losses. As a method to predict coal burst, the drilling cutting method has been widely used in coal mines. The drilling cutting weight is an important index of the drilling cutting method. In theoretical calculation, scholars usually assume that the coal is isotropic and homogeneous before drilling to deduce the formula of drilling cutting weight. However, in actual mining engineering, drilling cutting is usually carried out in the plastic coal body in front of the working face. Therefore, in the present study, the theoretical formula of the drilling cutting weight in the plastic coal mass is deduced, as well as in the elastic coal mass. The results show that the drilling cutting weight calculated based on the deduced formula increases with the increase of drilling depth in the plastic coal mass, which is consistent with the field measurement results. The fragmentation degrees of coal around the drilling hole are also considered by introducing cohesion, which changes linearly along the radial direction of the drilling hole. The results show that the smaller the cohesion, the greater the drilling cutting weight. The calculation formula for drilling cutting in elastic coal mass is also given. The dilatancy effect of coal around the drilling hole is also considered by introducing expansion coefficient n, which changes linearly along the radial direction of the drilling hole. There is a good match between the theoretical calculation results and the laboratory test results. The obtained results are helpful for the prediction and prevention of coal burst.

Hydro-chemical erosion has a great effect on the micro-structure morphology and macroscopic mechanical properties of the rock mass. In this paper, direct shear test system was used to study the hydro-chemical effect on the shear strength characteristics of limestone fractures. Besides, morphology parameters of the fracture under different chemical solutions were also analyzed through three-dimensional laser scanning and electron microscope imaging. Experimental results showed that after hydro-chemical erosion, the profile mean square root deviation Sq, the profile area ratio Rs, the profile peak point density Spd increased, while the slope mean square root Sdq decreased. Combined with scanning electron microscope (SEM) images, it is found that due to the hydro-chemical erosion, the roughness of limestone fracture surface, the discreteness of height distribution of the asperities and the JRC2D values increased, but the slope of asperities decreased. There was a good exponential relation between the decrease percentage of limestone internal friction angle and soaking time, and a logarithmic relation between the decrease percentage of cohesion and soaking time. According to the gray correlation method, the influencing factors were ranked in descending order as follows: normal stress, soaking time and pH values. In addition, the JRC2D value had a negative linear correlation with internal friction angle and cohesion of limestone fracture.

This paper focuses on the effects of the COVID-19 pandemic and its repercussions on the EU’s Cohesion Policy. We will analyse the regional and territorial problems created by the COVID-19 crisis and the influences it had on the new developments of the Cohesion Policy. The evolution of the Cohesion Policy will be addressed, particularly the development of conditionality. The developments on the European Multiannual Financial Framework and the regional policy following the recent developments of the European response to the COVID-19 crisis and the new role of Regions will also be examined. The aim of the paper is to identify and characterise the effects of the pandemic on the European Regions and its repercussions for the development of the new Cohesion Policy and its governance model. The need for a more flexible Cohesion Policy and the opportunities afforded to the Regions and the evolution of the European Union Multilevel Governance Framework, that come from the recent developments on the proposed European Recovery Plan are also reflected

During a freezing method for rock crosscut coal uncovering (RCCU), the mechanical properties of the frozen coal–rock interface have a significant impact on coal-body stability. To investigate characteristic and development mechanism of freezing strength of frozen coal–rock interface, a series of direct shear tests were conducted on frozen coal–rock interface under various testing temperatures, moisture contents in coal and normal stresses. The test results showed that the strength of the frozen coal–rock interface was affected by the moisture content in coal. The larger the moisture content was, the greater strength of the interface was. When the testing temperature was −10°C, the freezing strength increased from 75.46 to 267.42 kPa with the moisture content increasing from 3% to 9%. The ice cementing strength at the interface also increased with testing temperature decreasing. It increased from 6.44 to 73.34 kPa with the testing temperature decreasing from −2°C to −10°C when the moisture content was 5% and the normal stress was 200 kPa. With the increase of normal stress, the residual strength of the frozen coal–rock interface increased. When the moisture content in coal was 9% and the testing temperature was −10°C, the residual strength of the interface increased from 40.68 to 132.28 kPa with the normal stress increasing from 100 to 400 kPa. The testing temperature had no obvious influence on the friction coefficient and the cohesion of residual strength. When the moisture content in coal was 5%, the cohesion of residual strength increased from 23.39 to 98.7 kPa and the friction coefficient of residual strength fluctuated between 0.49 and 0.63 with the testing temperature decreasing from −2°C to −10°C. The relationship between the shear strength and the normal stress followed the Mohr–Coulomb law.

The effects of backfill cohesion on the seismic behavior of a retaining wall are discussed on the basis of a series of 1 g shaking table model tests. The model test results show that a retaining wall having cohesive backfill soil is more stable than a wall without it. The following aspects are observed in the cases of cohesive backfill soil from a detailed analysis using the measured seismic active earth pressure acting on the retaining wall: 1) the existence of a stable region at the top part of the backfill soil, 2) the increase in shear force acting on the boundary between the back face of the wall and the backfill soil, and 3) the mobilization of cohesion along the failure plane in the backfill soil. The existence of a stable region results in reductions in both the driving force and the overturning moment, while it tends to disappear under a high seismic load. The increase in shear force acting on the back face of the wall contributes to an increase in the resistant moment against the overturning of the wall with respect to the base of the footing, and it mobilizes even under a high seismic load. Mobilized cohesion along the failure plane contributes to the support of the soil wedge, resulting in a decrease in the seismic active earth pressure. It also continuously mobilizes even under a high seismic load. These observations indicate that giving consideration to the backfill cohesion when calculating the seismic active earth pressure leads to the rationalization of the evaluation of the seismic performance of the retaining wall even though further study is required, namely, carrying out the validation in the prototype scale and setting the applicable conditions for the seismic design.

Cracks resulting from cyclic wetting and drying of expansive soils create discontinuities and anisotropy in the soil. The representative elementary volume (REV) defined by the continuous-media theory cannot be applied to cracked expansive soils that are considered discontinuous media. In this study, direct shear tests of three different scales (30 cm2, 900 cm2, 1963 cm2) and crack image analysis were carried out on undisturbed soil samples subjected to drying-wetting cycles in-situ. The REV size of expansive soil was investigated using the crack intensity factor (CIF) and soil cohesion. The results show that soil cohesion decreased with increasing sample area, and the development of secondary cracks further exacerbated the size effect of sample on cohesion of the soil. As shrinkage cracks developed, the REV size of the soil gradually increased and plateaued after 3–5 cycles. Under the same drying-wetting cycle conditions, the REV size determined using soil cohesion (REV-C) is 1.75 to 2.97 times the REV size determined using CIF (REV-CIF). Under the influence of shrinkage cracks, the average CIF is positively correlated with the REV size determined using different maximum permissible errors, with the coefficient of correlation greater than 0.9. A method for determining the REV-C based on crack image analysis is proposed, and the REV-C of expansive soil in the study area under different exposure times is given.

This study investigates the effect of initial water content on the pore pressure response and undrained shear behavior of K0 consolidated reconstituted clay. A series of K0 consolidated undrained triaxial compression tests were conducted on reconstituted Lianyungang clay. Results were compared to those obtained by isotropic consolidated undrained triaxial tests. The testing results showed that the K0 consolidated undrained strength envelope of reconstituted soil content is a straight line passing through the origin regardless of the initial water content. The initial water content would affect the undrained strength of K0 consolidated clay as decreased normalized undrained shear strength was observed with clay at higher initial water content. The slope C of normalized pore pressure and stress ratio is affected by the consolidation method, where C is found to be a soil constant for K0 consolidated clay and the value would be higher with clay under K0 consolidation. The pore pressure increases with increasing initial water content at a certain axial strain under given consolidation pressure, and the difference in excess pore pressure increases with the increasing consolidation pressure. Pore pressure coefficient at failure (Af) increases as the initial water content increases, where a trendline can be well fitted between the pore coefficient at failure and the ratio of initial water content to the liquid limit of clay. The undrained strength indexes, i.e., effective cohesion and effective internal friction angle have decreasing tendency with increasing initial water content; however, changes in the total strength indexes of soil in this study are insignificant with varying initial water content.

Compacted layers of expansive soils are used in different engineering projects, such as subgrades, engineered clay barriers, and buffers for radioactive waste disposal. These layers are exposed to a variety of stresses and wetting conditions during field serviceability. Coupling between hydraulic and mechanical repeated loading provides insight understanding to the induced progressive deformation of expansive clay. This study was conducted to investigate the hydromechanical behavior of unsaturated compacted expansive clay under repeated loading–unloading (RLU) conditions. Two series of one-dimensional (1D) oedometer tests were conducted under controlled matric suction up to 1500 kPa using the axis translation technique (Fredlund soil-water characteristic curve device, SWC-150). The first test series was carried out at different levels of controlled matric suction for non-repeated loading–unloading (NRLU) cycles. RLU cycles were applied in the second test series at different repetitive-stress levels and under different levels of matric suction. The results indicated increasing axial wetting strain ea(s), axial swell pressure σs(s), compression index Cc(s), and swell index Cs(s) with suction reduction. The estimated load–collapse (LC) curves obtained from NRLU series (LCN) and RLU series (LCR) indicated increasing yield stress σy(s) with increasing suction. This is attributed to the developed apparent cohesion between soil particles, which in turn rigidifies the material response. Applying repetitive loading induced a notable reduction of compression index Cc(s) at the same level of suction, whereas swell index Cs(s) seems to be independent of repetitive loading. Finally, repetitive loading exceeding initial yield stresses results in plastic hardening and, hence, enlargement of yield stress locus (i.e. LCR curve).

Made available in DSpace on 2021-06-25T10:31:48Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 The fundamental mechanisms controlling shear strength and deformability behavior of clay-fiber mixtures have still not been well established, nor the constraints that may affect their performance of shearing under different drainage conditions. This study aims to understand the behavior of a clay soil mixed with polypropylene fibers using results from drained and undrained triaxial compression tests, and to provide necessary calibration data for a shear strength prediction model. In drained tests, shear strength increased with fiber inclusion for a given mean effective stress, represented by an increase in apparent cohesion. In the undrained tests, the shear strength was not affected by pore water pressure generation. Results from the drained and undrained tests indicate that the fiber content had a greater influence on the apparent cohesion than on the friction angle. Drainage affected the improvement in the peak shear strength of fiber-reinforced soils, with superior improvement in the drained tests. As the percent improvement in shear strength decreased with increasing effective confining stresses for both tests, the difference in behavior in the drained and undrained tests was attributed to the strain at failure, with failure occurring at large strains in the drained tests but at smaller strains in the undrained tests. UFSCar - Federal University of Sao Carlos Department of Civil Engineering UNESP - São Paulo State University School of Engineering at Bauru UCSD – University of California at San Diego UNESP - São Paulo State University School of Engineering at Bauru

To commercialize the biocementation through microbial induced carbonate precipitation (MICP), the current study aimed at replacing the costly standard nutrient medium with corn steep liquor (CSL), an inexpensive bio-industrial by-product, on the production of urease enzyme by Sporosarcina pasteurii (PTC 1845). Multiple linear regression (MLR) in linear and quadratic forms, adaptive neuro-fuzzy inference system (ANFIS), and genetic programming (GP) were used for modeling of process based on the experimental data for improving the urease activity (UA). In these models, CSL concentration, urea concentration, nickel supplementation, and incubation time as independent variables and UA as target function were considered. The results of modeling showed that the GP model had the best performance to predict the extent of urease, compared to other ones. The GP model had higher R2 as well as lower RSME in comparison with the models derived from ANFIS and MLR. Under the optimum conditions optimized by GP method, the maximum UA value of 3.6 Mm min–1 was also obtained for 5%v/v CSL concentration, 4.5 g L–1 urea concentration, 0 μM nickel supplementation, and 60 h incubation time. A good agreement between the outputs of GP model for the optimal UA and experimental result was obtained. Finally, a series of laboratory experiments were undertaken to evaluate the influence of biological cementation on the strengthening behavior of treated soil. The maximum shear stress improvement between bio-treated and untreated samples was 292% under normal stress of 55.5 kN as a result of an increase in interparticle cohesion parameters.

Jet grouting methods have recently become one of the soil enhancement technologies utilized to provide strength improvement and solve most problems of weak soils. In this study, a full-scale 1 m diameter and 5 m length jet grout (soilcrete) column was constructed in the field with a water-to-cement ratio of 1 and 400 bar pressure injections. A mechanical, physical, and microstructural investigation was performed on jet grout samples taken from six different depths (0.0, 0.5, 1.0, 1.5, 2.0, and 2.5 m) and at the same depth at five different locations, including the center. For normal conditions, samples were prepared for six periods to study dry and saturated conditions. The following tests are performed on each sample: compressive strength index (I-s) in all conditions, water absorption, density, porosity, and interface friction. Additionally, SEM was performed on selected samples to investigate the microstructures of jet grout columns (JGCs). The test results showed that the I-s varies with depth, and within the same depth, the variation is approximately 20%. Other properties also vary with depth and location; for example, the average percentage of water absorption and porosity are considered minimum values at the same location, which are 53 and 30%, respectively. However, the interface friction angle of organic soil-cement grout gains 48 degrees and 10 kPa cohesion. The theoretical part of this study is to predict the diameter of JGC in organic soil.

The geotechnical behavior of fly ash mixed with lime and alccofine is discussed in this paper. The specimens were prepared and cured using the burlap technique for 7, 14, and 28 days. The results of this study showed that the unconfined compression strength, split tensile strength, California bearing ratio, and flexural strength of a fly ash containing 6% lime and 2% alccofine (referred to as the “reference mix”) improved as the curing time increased. After the durability cycles, the reference mix showed a significant increase in the unconfined compressive strength. For the unconsolidated undrained and consolidated drained triaxial tests, the deviator stress and cohesion increased while the friction angle decreased as the curing time increased. The volumetric strain response of the reference mix shows an initial compression followed by large dilation. In the consolidated drained test, the dilatancy behavior of the reference mix suppressed, as the curing time increased. The improved behavior of the fly ash–lime–alccofine mix could boost the construction of rural roads.

The friction peak that occurs in tire-road sliding when the contact changes from wet to dry was previously attributed to capillary cohesion, van der Waals attraction, and surface roughness, but the detailed mechanisms have yet to be revealed. In this study, friction and static contact experiments were conducted using a custom-built in situ optical microtribometer, which allowed us to investigate the evolution of the friction, normal load, and contact area between a polydimethylsiloxane (PDMS) film and a silicon nitride ball during water volatilization. The friction coefficient increased by 100%, and the normal force dropped by 30% relative to those in the dry condition during the wet-to-dry transition. In static contact experiments, the probe indentation depth increased, and the normal load decreased by ∼60% as the water evaporated. Combining the friction and static contact results, we propose that the large friction peak that appeared in this study can be attributed to the combined effects of increased adhesive capillary force and increased plowing during the wet-to-dry transition.

Geotechnical structures, design of embankment, earth and rock fill dam, tunnels, and slope stability require further attention in determining the shear strength of soil and other parameters that govern the result. The shear strength of soil commonly obtained by conducting laboratory testing such as Unconfined Compression Strength (UCS) Test and Unconsolidated Undrained (UU) Test. However, random errors and systematic errors can occur during experimental works and caused the findings imprecise. Besides, the laboratory test also consuming a lot of time and some of them are quite costly. Therefore, soft computational tools are developed to improve the accuracy of the results and time effectively when compared to conventional method. In this study, Artificial Neural Network (ANN) was employed to develop a predictive model to correlate the moisture content (MC), liquid limit (LL), plastic limit (PL), and liquidity index (LI) of cohesive soil with the undrained shear strength of soil. A total of 10 databases was developed by using MATLAB 7.0 - matrix laboratory with 318 of UCS tests and 451 of UU tests which are collected from the verified site investigation (SI) report, respectively. All the SI reports collected were conducted in Sarawak, Malaysia. The datasets were split into ratio of 3:1:1 which is 60:20:20 (training: validation: testing) with one hidden layer and eight hidden neurons. The input parameter of Liquidity index (LI) has shown the highest R-value (regression coefficient) which are 0.926 and 0.904 for UCS and UU model, respectively. In addition, the predictive models were tested and compare with the predicted and observed cohesion obtained from the collected experimental results. In summary, the ANN has the feasibility to be used as a predictive tool in estimating the shear strength of the soil.

Fine-grained calcareous silt interlayers with a non-uniform thickness are distributed discontinuously in the hydraulically reclaimed foundation of island-reefs in the South China Sea. Because of their high compressibility and low strength, these interlayers commonly cause differential foundation settlement and result in the cracking of buildings, which poses a potential safety hazard. In this study, consolidated-drained triaxial shear tests were conducted to investigate the effect of fines content (FC) on the shear strength of calcareous sand. The brittleness index and dilatancy coefficient were introduced to quantify the strain-softening and dilatancy of calcareous sand. The mechanism by which the FC affects the calcareous sand strength was revealed in terms of the particle shape and soil structure. Under a constant effective confining pressure, an increase in FC led to a gradual decrease in peak strength, a weakening of strain-softening characteristics, less dilation, and a linear decrease in apparent cohesion for calcareous sand. The internal friction angle of calcareous sand peaked at a FC of 10%. Compared with quartz sand, calcareous sand has the more irregular particle shape. An increase in FC weakened the interlocking between calcareous sand particles, which decreased the shear strength. The research results are of great significance for slope stability analysis and for the foundation treatment of island reefs.

The author examines the Kosovo crisis in the context of the pluralisation and democratisation of Slovenian society in the 1980s and early 1990s. This issue became a catalyst not only for the repositioning of structures of party leadership in relation to Belgrade, but also with respect to general public debates. By charting individual stages of the critical decade of 1981-1991, the author presents Slovenian perceptions of Kosovo's political, economic, and social issues, first through the works of neo-Marxist critics and later through the activism of a group of left-liberal intellectuals, which included the provision of legal support and a high-profile social action related to the violations of Kosovar Albanian human rights. The author discusses the constraints encountered by this brief attempt to establish a pan-Yugoslav civil society initiative. At the same time, he shows how the complexities of the Kosovo crisis were used to coalesce the Slovenian nation into flight from Yugoslavia. Bibliografija: str. 220-222. Abstract. ARRS, Raziskovalni programi, SI, Sredozemlje in Slovenija ARRS, Raziskovalni projekti, SI, Jadranske socialne države. Socialne politike v transnacionalni obmejni pokrajini od sredine 19. do 21. stoletja.