Loose Medium Research Articles

Application of ferromagnetic materials for technological processes thermal regime stabilization (Review)

The research focuses on the technological and auxiliary equipment used in various industries that require maintaining a specific narrow temperature range. The study aims to critically analyze the potential use of structural elements made of ferromagnetic materials with a second-kind phase transition temperature (Curie temperature or Curie point) in high-performance, knowledge-intensive industries, particularly the chemical industry. These materials correspond to the required temperature of the processed or transported liquid or loose medium. The technological processes using the magnetothermal effect and the corresponding designs of equipment are considered: heat exchange, heat and mass exchange, mechanical and hydromechanical, equipment for processing thermoplastics, as well as other devices used in various branches of industry, in particular chemical, food and microbiological, in thermal energy, metallurgy, agriculture, medicine and construction. It is shown that the specified method of ensuring the required thermal regime is suitable for use primarily in large-tonnage continuous production. As the conducted studies have shown, the proposed approach to stabilizing the heat flow of various technological and auxiliary equipment is effective and quite promising. The indisputable advantage of the corresponding method is to ensure a certain temperature of the working parts of the equipment with high accuracy, however, this method is quite difficult to implement on the existing equipment, which is mostly made of magnetic materials (steel, cast iron). Therefore, to implement the proposed method in practice, it is necessary to develop new equipment designs or to subject existing samples to deep modernization. At the same time, there may be difficulties associated with the search for existing or the creation of new ferromagnetic materials with the required thermomagnetic properties for the manufacture of appropriate structural elements of technological and auxiliary equipment. However, in certain cases, the proposed method of maintaining the specified temperature of the processed media may become the most appropriate (primarily in fine chemical technology, biotechnology, pharmaceuticals, precision instrument manufacturing, microelectronics, and medicine).

Mechanism of thermal gravimetric difference between simulated and experimental of coal group components

Understanding the molecular mechanism underlying coal's thermal gravimetric behavior is crucial for advancing efficient and clean coal utilization technology, a task that remains challenging to address experimentally. ReaxFF molecular dynamic simulation has been widely applied across various systems and materials, particularly excelling in simulating combustion and pyrolysis processes with complex coal models. It is necessary to establish more connections between simulation and experiment, and to analyze and discuss the differences between them. This will lay the foundation for the reliability of simulation results in revealing experimental phenomena. In this study, coal was divided into four components using a full component classification method: the dense medium component, loose medium component, heavy component, and light component. The connections of the simulated and experimental thermal gravimetric behaviors of the coal group component skeletons were conducted, and founding the inconsistencies in the later stages of the curves. To understand these discrepancies, the test environments were analyzed, identifying the behavior of tar free radicals generated during pyrolysis as a key factor influencing the thermo-gravimetric curve. To mitigate the influence of tar free radicals and reduce the observed differences, a correction coefficient was introduced into the calculation formula for the yield of non-volatile products, achieving an improved alignment between the simulated and experimental thermo-gravimetric curves. This study significantly advances the application of ReaxFF molecular dynamics simulation in elucidating the mechanisms of coal pyrolysis.

Evaluation of accurate measurement methods for radon exhalation rate with advection effect and application in field

In decommissioning of a uranium tailings pond, radon exhalation rates on a beach surface should meet regulatory standards. Accurate measurements of the radon exhalation rate are demanded. However, current studies fail to consider the impact of advection under temperature variations or pressure gradients caused by gas movement on measurements using an accumulation chamber. Two proposed methods were therefore evaluated to accurately measure radon exhalation rates on the loose medium surface under advective conditions. Repeated experiments were conducted on a laboratory experimental platform filled with uranium tailings sand under advective flow rates of 0.03 and 0.3 L/min to validate the stability and reliability. Deviations between measured and true values were 0.1–6.1 % and 6.3–29.2 % for the two methods, respectively. Subsequently, numerical simulation was used to analyze defects of traditional methods and mechanisms of the new methods. In a field study, all methods were compared, and a predictive map of radon exhalation rates was created using interpolated data from 20 random sites using the new method. Results from the proposed methods, compared with traditional ones, were closer to true values under advective conditions, and accurate assessment of beach surface treatment was expected.

STUDY OF THE CHARACTERISTICS OF VIBRORHEOLOGICAL MODELS OF BULK RAW MATERIALS IN THE WORKING AREA OF A VIBROCENTRIFUGAL MIXER

Determining the movement of loose media in vibrating equipment (in particular, vibratory volume processing, grinding, separation) is a rather complex task of dynamics, which has not been fully investigated to date. The reason for this is the cumbersomeness of the mathematical description of the dynamics of the fluid medium, simplifying hypotheses and assumptions, the linearity of the models, which do not always adequately reflect the real physics of the investigated vibrational process. In recent years, vibration mechanics and vibrorheology have played an important role in the emerging new direction of applied vibration theory - the theory of vibration processes and devices. This theory examines the regularities of the impact of vibrations in various mechanical systems. It also covers the theory of machines where vibration is used for useful purposes. Vibrorheology is a branch of mechanics that studies the change under the influence of vibration in the rheological properties of bodies in relation to slow forces, as well as the corresponding slow movements of bodies. In recent years, vibration mechanics and vibrorheology have gained significant importance in a new direction of applied vibration theory - the theory of vibration processes and devices. This branch investigates the patterns of creation and influence of vibrations in various mechanical systems; it also covers the theory of machines where vibrations are used for useful purposes. Using the models mentioned below, it was possible to describe the chaotic movement of a layer of loose medium under the influence of vibration. These movements have been well studied in liquid media and have also been successfully studied in loose media. This further confirms the possibility of modeling the slow movements of a loose medium using analogies related to the movements of a viscous liquid.

Experimental Compaction of a High-Silica Sand in Quasi-Static Conditions

In the compaction process, an uneven densification of the powder through the entire height of the die is a major problem which determines the strength properties of the final product, which vary throughout the entire volume. The aim of this investigation was to determine the distribution of the forming pressure inside the die and to visualise the differences in compaction. To determine the pressure inside the die during the compaction process, the deformation on the die surface was measured by means of strain gauges. However, in order to visualise the densification of high-silica sand during the compaction process, an X-ray tomograph was used, which permits one to visualise the interior of the die. The authors developed an analytical model of how the change in internal pressure influences the change in stresses arising on the outer surface of the die, and, as a result, the friction force. It has been observed that the highest values of pressure as well as the highest concentrations of the loose medium are found closest to the punch and decrease with distance from the punch. Moreover, based on the measurements of deformation, a dependence of the pressure distribution on the value of friction forces was observed, which prompted further analysis of this phenomenon. As a result, tests to determine the coefficient of friction between the die and the loose medium were carried out. This made it possible to describe the pressure distribution inside the die, based on the pressure applied and the height of the die.

ANALYSIS OF THE METHODS OF STABILITY CALCULATING OF LANDSLIDE SLOPES

Purpose. Analysis of the methods of stability calculating of landslide slopes and their further development in European normative documents. Methodology. Variants of methods for calculating the stability of slopes by different authors are considered. Various definitions of the functional were adopted in variational methods, and then the minimum was found. In M. M. Gersevanov’s method, the functional was the sum of horizontal forces that acted on an array of hypothetical soil. In the method of Y. I. Solovyov, the functional is the ratio of the work of the forces that maintain the slope to the work of the forces that shift to the movement. In Kopashi’s method, it is the sum of vertical loads that act on the sliding surface in a loose medium. In the abbreviated Terzaghi’s method, the minimum ratio of the moment of the holding forces to the moment of the forces that shift the slope is sought. Findings. Domestic and foreign scientists have successfully studied the strength and stability of slopes. This is a complex task determined by the need to simultaneously take into account two main factors: relief and gravitational force. The basis for determining the stability of slopes is the idea that the stressed state of rocks in the upper part of the earth’s crust is formed by universally acting gravitational and tectonic forces. The relief of the earth’s surface makes a significant contribution to the redistribution of stresses. Originality. Eurocode 7 recommends the possibility of performing a preliminary calculation of the natural slope using characteristic values, which gives an approximate idea of ​​the value of the overall reliability factor before the start of design. Practical value. Areas located directly on slopes are often used as construction sites. The bases for the foundations of buildings and structures are soil massifs that are in difficult engineering and geological conditions. Landslides are a geological process that occurs on any part of a slope or slope as a result of a disturbance in the balance of rocks when the steepness of the slope increases as a result of water washing, the weakening of the strength of rocks due to weathering or rewetting by precipitation and groundwater, the effect of seismic shocks, construction and economic activities of people. Determining the stability factor is a necessary condition for concluding that the slopes can be used for construction.

Mathematical model of the snow mass transportation process in the snowblower rotor

Introduction. The complexity and laboriousness of determining the functional dependencies between the structural elements of a rotary snowplow and the developed snow mass when conducting experimental studies on a physical model of a rotary snowplow necessitates the development of mathematical models that make it possible to describe as accurately as possible the processes of interaction between the elements of a rotary snowplow and snow mass. The method of research. A mathematical model of the process of transporting snow mass in a rotor, in which snow is represented as a loose medium, including a set of individual particles, was developed using the method of discrete elements. When constructing a mathematical model, the problems of identifying mass and surface forces acting in the ‘rotor - snow mass’ system were solved. The principle of the location of a group of particles in the interblade space of the snowplow rotor and the choice of the method for analyzing the mathematical model are substantiated.Results. The implementation of this mathematical model on a computer made it possible to obtain the numerical values of the forces of the normal reaction of the rotor casing at each moment of time, which allows developing new and improving existing design schemes, reasonably choosing the design and technological parameters of the rotor of a snow blower.Discussion and conclusion. The proposed mathematical model and the equations of motion, compiled on its basis, make it possible to unambiguously determine the values of all forces acting on the snow mass during its transportation in the rotor of a rotary snowplow. The model under consideration makes it possible to simulate a snow mass in the interblade space of a more complex configuration and a set of particles that have an irregular distribution in size and relative position.

Safe and Efficient Recovery Technique of Horizontal Isolated Pillar under Loose Tailings Backfill; A Case Study in a Zinc-Lead Mine

The presence of loose medium backfill above the horizontal pillar will technically hinder the efficient recovery of the pillar since the improper design and preserved roof protection layer height will potentially lead to casualties and equipment damage caused by large area collapse of filled tailings as well as roof fall accidents. In this study, a safe and efficient technique for the recovery of isolated pillars under loose tailings backfill was carried out via field investigation, theoretical analysis, numerical simulation, and analytic hierarchy process using the isolated pillars in the 855 middle sublevel of Hongling Zinc-Lead Mine, Chifeng, Inner Mongolia, as a practical engineering background. Current studies have revealed that the optimal scheme for an isolated horizontal pillar recovered via the cut-and-fill stoping of a drift vertical to ore body strike involves preserving a 1.0-m roof protection layer above the crown pillar combined with a spaced mining extraction sequence. This design minimizes ore dilution and losses during the pillar extraction process under safe operation. Our research results provide theoretical and technical support for the safe and efficient recovery of isolated pillars under loose tailings backfill in similar mines.

Hierarchical porous N-TiO2/carbon foam composite for enhancement of photodegradation activity under simulated sunlight

Nitrogen doped TiO2 (N-TiO2) photocatalyst was synthesized via sol-gel combined with low temperature reflux method using urea as nitrogen source. Hierarchical porous carbon foam (HPCF) with the characteristics of micro/mesopores and micron-sized macropores was made by steam activation of a new type of thin-walled carbon foam which was produced from the loose medium component of coal. N-TiO2/HPCF was synthesized by loading N-TiO2 onto the HPCF via impregnation method. The synthesized catalysts were characterized by N2 adsorption, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), diffuse reflection spectrometry (DRS) and photoluminescence spectroscopy (PL). Phenol was used as a simulated pollutant in wastewater to evaluate the photodegradation performances of naked TiO2, N-TiO2 and N-TiO2/HPCF. The N-TiO2/HPCF composite removed 97 % of phenol in 2 h of simulated sunlight irradiation and displayed the highest photocatalytic activity, which was 4.9 times that of N-TiO2 and 10.8 times that of naked TiO2. The enhanced activity of N-TiO2/HPCF can be ascribed to the combination of both extended visible light adsorption of N-TiO2 and the concentrating effect brought by HPCF. This work demonstrates a facile approach to synthesis an inexpensive and efficient N-TiO2 coated coal-based carbon foam for the treatment of wastewater.

Flat problem to determine the forces of destruction of pieces n disintegrators while being grabbed in thick layer

Purpose. Research on analytical dependences of destructive stresses, acting on a piece of non-isometric shape at quasi-static deformation of a relatively thick layer of rock mass in disintegrators, on parameters of the piece shape, the pieces spatial orientation, also on the relative piece size in layer, taking into consideration the discrete nature of contact force application. Methodology. The flat scheme of a non-isometric shaped piece contacts in a thick layer of rock mass is obtained by composition of the central rectangular piece and the round pieces of average size for the given layer. The distribution of stress components in the layer of loose rock mass is accepted on the basis of the classical theory of elasticity and the theory of loose medium. The geomechanics criterion showing relationship of equivalent destructive stress and ultimate compressive strength of rock is used as a criterion of piece destruction in complex stress state. All force schemes of the piece loading are reduced to three-point bending schemes and two-point shear schemes, both across the long and the short sides of the piece. The most dangerous loading scheme is determined from the analysis of the mentioned schemes for each particular case. Dimensionless parameterization is applied both to specify the geometric parameters of pieces and to analyze the resulting destructive stresses. Findings. Analytical dependences of equivalent destructive stresses for an oblong piece are obtained depending on the piece relative length, the relative piece size in the rock layer, the angle of piece orientation relative to the direction of the maximum main stress and the side thrust coefficient in the layer. It has been set that lamellar pieces, especially those smaller than the average size for the layer, are destroyed mainly from the implementation of bending schemes across the long side, the shape of their fragments is improved by reducing the pieces relative length. Increasing the uniformity of the force field in the working zone of disintegrator also leads to improvement in the shape of fragments. On the other hand, as the shape of the piece approaches the isometric one, as well as when the piece relative size in layer raises, the probability of implementing shear schemes increases and the probability of implementing bending schemes decreases, including with a deterioration in the fragments shape compared to the original piece. At the same time, larger values of destructive stresses for the lamellar smaller pieces are proved analytically compared to the isometric bigger ones, all other things being equal. Originality. The versatility of application of the three-point bending scheme of a non-isometric shaped piece in combination with the two-point scheme of its shear for analysis of its destruction in the thick layer of rock mass is substantiated. For the first time, the dependences of equivalent destructive stresses for the non-isometric piece on its relative length, its relative size in layer, the angle of deviation of the pieces main axis from the main stress direction and on the side thrust coefficient in the layer have been obtained. Practical value. The results obtained allow making reasonable choice of parameters of disintegrators operational parts for destruction of materials in the thick layer, as well as predicting the change in lamellar pieces fraction during disintegration process. They give the possibility to determine key parameters of operational parts for new designs of disintegrators. This creates the basis for the development of calculation techniques for operational parts of modern samples of crushing and grinding equipment.

Electrospun carbon nanofibers from PAN and a loose medium component of coal as binder-free electrodes for supercapacitors

BackgroundDespite the significant progress of co-spinning strategy to prepare 1D hierarchical porous carbon nanofibers, reducing raw material cost and improving specific surface area (SSA) utilization ratio still needs further improvement. MethodsThe binder-free and flexible carbon nanofibers (CNFs) are fabricated using a blend of polyacrylonitrile (PAN) and a loose medium component (LMC) of coal via electrospinning, followed by pre-oxidation and carbonization process. Significant findingsLMC, an effective pore-enhancing modifier for CNFs, can increase pore volume and improve electrochemical performance while retaining the basic characteristics of good pore structure and pore size distribution (PSD). The prepared materials have higher SSA utilization, mainly due to the dominant pore distribution of 0.9 nm and the special fibrous properties, which are different from ordinary porous carbon. The supercapacitor electrodes prepared from LCNF3 possess a high specific capacitance (227.4 F g−1 at 1 A g−1) and outstanding cycling stability (104.3% capacitance retention after 10,000 cycles). This work provides a new perspective for increasing the pore volume of CNFs prepared by electrospinning and realizing coal's high value-added utilization.

Study on Single Jersey Knitted Fabrics Made from Cotton/ Polyester Core Spun Yarns. Part I: Thermal Comfort Properties

This study focused on the effect of core- sheath ratio, twist and loop length on the thermal comfort properties of single jersey knitted fabrics produced from 100% cotton, 80:20 and 60:40 cotton/polyester core spun yarns. Thermal properties like air permeability, water vapor permeability, thermal conductivity and thermal resistance properties were analyzed with low, medium and high twist and also with loose medium and tight structured fabrics. Box behnken, three level - three variable factorial design software has been used to study the interactive effect of core- sheath ratio, twist and loop length on the thermal comfort properties of single jersey knitted fabrics and response surface equations were derived and design variables were optimized. ANOVA test model reveals the statistical significance of variables on thermal properties with high F-value and low p-values. From this study it is observed that the decrease in cotton ratio decreases the fabric thickness, becomes lighter and more porous with higher thermal conductivity, air permeability, water vapour transmission rate and less thermal resistance. Increase in twist and tight loop structure makes thicker and less porous fabric with higher thermal resistance and lesser air permeability, water vapour transmission rate and thermal conductivity.

Experimental study on the migration and expansion of liquid nitrogen in loose media with different dip angles

ABSTRACT The goaf is the main disaster area for natural fires in mines, and liquid nitrogen has become an essential medium for fire prevention in goafs due to its excellent cooling and inerting properties.At present, there is no in-depth research on the transport and vaporization of liquid nitrogen after injection into the goaf, and it is impossible to quantitatively evaluate the cooling inerting effect after liquid nitrogen injection. To address the above problems, this project proposes to carry out the following research: to study the effects of different inclination angles on the transport and vaporization of liquid nitrogen and temperature distribution in the loose medium in confined space by monitoring the temperature field changes during the pressure injection of liquid nitrogen in the loose medium in confined space.The results show that the temperature field distribution is very uneven after liquid nitrogen is injected into the loose medium in the restricted space.It is found that the vaporization rate of liquid nitrogen decreases with the increase of diffusion time and diffusion area, and the instantaneous vaporization rate of liquid nitrogen decreases with the larger inclination angle under the same injection position. Compared with the horizontal state, the maximum vaporization rate decreased 84.79% when the maximum inclination angle was 15°, which indicates that the vaporization rate was greatly affected by the inclination angle of the surface. In the vertical direction of the experimental box, the cooling area of liquid nitrogen in the experimental box is mainly concentrated within 0.05 m height from the bottom of the experimental box, and the changes of the “cooling restricted zone” after liquid nitrogen injection into the goaf are further explained during the experiment.It is found that the “cooling restricted zone” mainly exists in the upper part of the goaf, under the inclined condition, and the area increases with the increase of the inclination angle, so the increase of the angle is not conducive to the effective cooling effect of liquid nitrogen.The research results of the project will help to improve the theory of liquid nitrogen fire prevention in mines and provide theoretical support for the fire prevention technology of liquid nitrogen direct injection in goafs.

Designing a system that removes metallic inclusions from bulk raw materials on the belt conveyor

Modern industrial technologies require raw materials of high purity from suppliers, especially due to the possible presence of inclusions of heterogeneous metals in them. The existence of metallic inclusions of heterogeneous metals in the raw materials leads to equipment failure, a decrease in the quality of output products, and, consequently, large financial losses. Since the main method of transporting raw materials in the industry is still a conveyor belt, this imposes additional conditions to control and remove metallic inclusions. For various reasons, current methods for removing metallic inclusions in the conveyor belt do not fully meet the needs of modern production. The main issue related to existing removal systems is the lack of intelligent interaction between these systems and the absence of information exchange between systems that detect and remove metallic inclusions. An alternative method for removing metallic inclusions of heterogeneous metals from loose medium has been proposed, which implies the tandem operation of the system that detects metallic inclusions and the system that removes them. The tandem operation of the two systems makes it possible to exchange information about a detected metallic inclusion and, as a result, to more flexibly use tools for the removal of metallic inclusion depending on the size and location of the metallic inclusion relative to the conveyor belt axis. At the same time, the control unit of the removal system makes it possible to control the conveyor belt itself, which allows the removal of complex metallic inclusions using the reverse of the electric drive of the belt, as well as enables a control check of the fact of removal. The developed algorithm of the removal system was implemented in the programming environment TIA-Portal. The introduction of this removal system could reduce the number of metallic inclusions in raw materials by 15‒20 %; moreover, its application is not limited to only one sector of the national economy

Thermodynamic characteristics of methane adsorption about coking coal molecular with different sulfur components: Considering the influence of moisture contents

Sulfur groups are very susceptible to adsorption onto coking coal. In this study, three major organic sulfides of coking coal were extracted and identified by experiments. Then, coal molecules containing sulfide groups were respectively constructed via simulation. The adsorption isotherm curves of methane under different moisture contents were created. The experimental results show that thiophanthren, methyl-dibenzothiophene and dimethyl-naphthothiophene are the main organic sulfides found in coking coal. The simulation results indicate that the presence of moisture will cause the methane adsorption capacity to decrease sharply, which is mainly affected by the H/C ratio. With increasing of moisture content, the adsorption capacity of water molecules to coal molecules is stronger than that of methane molecules. The heat of methane adsorption, meanwhile, has no obvious relationship with moisture contents, but is mainly affected by S/C ratio. The adsorption heat of coal with an appreciable moisture content is less than that of coal without moisture. When the moisture content reaches a certain limit value (4%), its influence on the heat of methane adsorption is very small. The order of the heat of methane adsorption is dense medium component (DMC) > heavy component (HC) ＞ loose medium component (LMC). Water molecules easily combine with the chemical bonds on the surface of coal molecules and the hydrophilic functional groups inside. The heat of adsorption is mainly influenced by differences in the degree of coalification, but not by the various components extracted. When water is present, the adsorption capacity of methane is reduced to some extent, causing the adsorption system to methane coal molecules to reach equilibrium and release less heat. The results of this study were offer a quantitative understanding of the adsorption and thermodynamic properties of coal molecules with complex structures after extraction.

On the porosity of ridge keel (with reference to V.V. Kharitonov’s paper)

The article discusses whether the model of loose granular medium is applicable to the analysis of physical processes in the ridge keel. It is argued that the model is not valid for dealing with a number of problems such as the evolution of the ridge keel. It is also suggested that the decrease in keel porosity in time is primarily caused by thermodynamic factors.

EFFECTS OF STRUCTURE HEIGHT ON SEISMIC DEMAND OF MOMENT-RESISTING REINFORCED CONCRETE FRAMES CONSIDERING SOIL-STRUCTURE INTERACTION

Forces and displacements induced in a building due to structural responses to earthquake excitation are called seismic demands which depend upon the input motion, structural characteristics, site effects and the interaction of structure with soil. Structural response of three laterally non-controlled moment-resisting reinforced concrete frame structures with three different soil conditions are have been investigated in this paper. The soil conditions include loose soil, medium soil and rigid ground. The soil-structure interaction of low-, mid- and high-rise frame structures with the above mentioned soil types was analysed by performing nonlinear response history analyses. A set of eleven earthquake motions was employed in the analyses and maximum structural seismic demands for the frame structures were calculated. It was found that pressure-independent relatively loose sandy soils are not very critical for low-rise structures. On the other hand, pressure-independent relatively loose sandy soils and pressure-independent medium sandy soils are highly critical for mid-rise and high-rise structures, respectively. Categorisation of the soils is performed based on the value ranges of a series of constitutive parameters. Further, fixity of the base is most effective in controlling storey displacements until approximately one-third of the structure height. Medium soil leads to highest maximum base shears in low-rise structures while fixed-base and medium cases, and fixed base state control the behaviours of mid-rise and high-rise structures, respectively.

Diffusion Behavior of Polymer Grouting Materials in Sand and Gravel

The study aims to experimentally investigate the diffusion behavior of an expanding polymer grouting material in sand, gravel, and a sand-gravel mixture. In situ grouting tests were performed using the hole-sealing grouting method. Diffusion characteristics of the polymer grouted in the sand are analyzed through numerical analysis, and the results show that diffusion mainly depends on the size of pores and particles of the medium. In terms of the diffusion pattern, the loose medium mainly exhibited penetration and diffusion, while splitting diffusion occurred in finer grained media.

Experimental Study on Grouting Reinforcement Mechanism of Heterogeneous Fractured Rock and Soil Mass

To explore the grouting reinforcement mechanism of heterogeneous rock and soil in a fault fracture zone, based on the F2 fault grouting project of Yonglian Tunnel, the filling area composed of loose and soft media in the fault is defined as the advantageous grouting diffusion region, which is divided into loose and weak diffusion regions according to the slurry diffusion form. A self-developed grouting reinforcement test system is used to carry out grouting reinforcement tests on the heterogeneous rock and soil. The existence of the advantageous diffusion region can effectively improve the reinforced body strength. The slurry in the reinforced body containing the loose medium mainly expands outwards in the form of first infiltration and then compaction, and the slurry vein mainly remains in the advantageous diffusion region. The slurry in the reinforced body containing the soft medium mainly diffuses in the form of compaction splitting, which can form thicker splitting of the grouting veins. When the reinforced body is destroyed, the body containing the loose medium is mostly conically fractured, indicating complete lithology and homogeneous material. Moreover, the reinforced body containing the soft medium always forms a penetrating crack along the slurry vein or near the grouting vein. Focusing on the heterogeneous stratum consisting of fault breccia and soft plastic fault gouge, controllable slurry dynamic adjustment, same-hole multi-sequence sub-gradient grouting, and localized grouting control are proposed. The grouting control method is applied to the case of Yonglian Tunnel, and a superior grouting reinforcement effect is achieved.

The interface mechanical properties and breakage analysis of the flexible isolation layer under ore drawing from a single funnel

The interface mechanical properties and the breakage analysis of the flexible isolation layer under the condition of single funnel ore drawing is an important research topic for the theory of loose medium flow under the flexible isolation layer. To grasp the distribution characteristics and variation rules of the force system from the microscopic level and to provide a theoretical basis for the strength design of the flexible isolation layer in the new mining method, the tensile stress and the compressive stress of the isolation layer are measured using a physical experiment, and the interface mechanical properties and rupture conditions of the isolation layer are analysed. The results showed the following conclusions: (1) Horizontally, with the increase in the distance between the measuring points and the centre point in the isolation layer, the tensile stress value of the isolation layer first increased and then decreased, while the compressive stress only decreased; the friction showed a trend of decreasing first, increasing later and decreasing again. (2) Longitudinally, the tensile stress value and the compressive stress value of the isolation layer increased with an increase in the descending height, while the friction first increased and then decreased with an increase in the descending height. (3) The isolation layer in the cavity is affected by the supporting force, and the variation in the supporting force received by the isolation layer in the noncavity region is the same as the compressive stress. (4) The isolation layer is most easily broken when h = 110 cm and s = 29.863 cm.