Ultimate Shear Stress Research Articles

Blasting safety criterion of existing high speed railway tunnel over tunnel

Drilling and blasting method is still an important method in the current tunnel excavation construction. Controlling the vibration effect of blasting during construction and its influence on the upper span tunnel is the key problem in tunnel construction. Based on Chongqing Science City tunnel excavation blasting project, combined with the tunnel blasting vibration monitoring and testing, this paper analyzes the propagation attenuation law of tunnel blasting vibration along the rock mass, and studies the load characteristics of the explosion stress wave propagating to the existing high-speed railway tunnel. Considering the influence of the buried depth of the blasting source, a mathematical prediction model of the attenuation law of the upper span existing high-speed railway tunnel caused by tunnel blasting is established. Based on the dynamic finite element numerical calculation method, the influence of blasting vibration on the structure of the existing high-speed railway tunnel under construction is analyzed, and the propagation and attenuation law of blasting vibration along the tunnel contour is studied. Based on the ultimate tensile stress criterion, the ultimate shear stress criterion and the Mohr criterion, and compared with the results obtained from the numerical simulation, the blasting safety criterion model of the existing high-speed railway tunnel over the tunnel is established.

Bond-slip models on interfacial behavior between Fe-SMA and steel in hygrothermal environments

Strengthening the existing steel structures to enhance performance can prolong their service life and reduce carbon emissions. Previous studies have employed iron-based shape memory alloy (Fe-SMA) to adhesively and actively retrofit long-span steel bridges in practice, achieving satisfactory repair efficiency. Nonetheless, concerns persist regarding the long-term performance of Fe-SMA-bonded parent structures, principally stemming from the performance degradation of the adhesives in hygrothermal environments. In this study, the damage evolution and debonding mechanisms of Fe-SMA/steel single-lap joints (SLJs) in hygrothermal environments are investigated through 54 lap-shear tests. The evolutionary process of Fe-SMA strain and shear stress within the overlapping zone is assessed, varying with aging time and adhesive type under shear load. Furthermore, the bond-slip models of the Fe-SMA/steel SLJs are put forward, which change with the aforementioned influencing factors in hygrothermal environments. The lap-shear tests demonstrate that the ultimate shear stress of SLJs is transmitted approximately up to 50 mm away from the initial end, with shear stress developing swiftly towards the free end during this phase. In hygrothermal environments, the effective overlapping length of the SLJs is highly contingent on the material properties of adhesives, improving with the prolonged aging time. This study proposes bond-slip models that describe the interfacial performance between Fe-SMA and steel, accounting for the detrimental influence of temperature, humidity, plastic deformation of components and strain relaxation. The experimental outcomes can guide the analysis of the debonding characteristics of Fe-SMA-bonded structures, and the theoretical study can provide reliable predictions for the service performance of reinforcement systems in hygrothermal environments.

Viscoelastic creep model and parameter inversion of bond interface in steel plate reinforced tunnel lining

The interface filler material (epoxy resin) used for reinforcing tunnel linings with steel plates exhibits time-dependent mechanical properties, commonly referred as creep behavior. The creep behavior of the filler material will significantly influence the long-term service performance of the reinforced tunnel, especially considering the design service life scale of 100 years. This paper presents an experimental test and mathematical modelling to illustrate the creep mechanical behavior of bond interfaces within shield tunnels reinforced with steel plates. It was observed that in the initial moments of stress application, the bond interface demonstrates an instantaneous response through elastic strain and on-set of creep deformation stage at maximum stress value. Three stages can be characterized in the creep deformation process: the decay creep stage, the steady-state creep stage and the accelerated creep stage. In the accelerated creep stage, the bond interface rapidly deteriorated after experiencing 90 % of the ultimate shear stress for 186 hours or 90 % of the ultimate tensile stress for 96 hours. Based on the fractional-order calculus theory and drawing inspiration from the modeling principles of classical component combination models, a constitutive equation that accurately characterizes the creep mechanical behavior of the bond interface between steel plates and concrete linings was formulated. The model parameters are inversely computed using the principle of least squares and the accuracy of this model is validated through a comparison with the results of the creep tests.

Influence of protein-fat emulsion from turkey skin and plant raw materials on the quality of cooked sausages

The study examined the impact of a protein-fat emulsion (PFE) derived from turkey skin and green buckwheat flour on the quality of cooked sausages. The aim was to investigate how the addition of PFE affects various characteristics of the sausage. The experiments demonstrated that adding PFE up to 30% while stirring for up to 8 minutes at 10°C improved the sausage structure. This was evidenced by an increase in pH values to 6.5, water binding capacity to 71.2%, and ultimate shear stress to 321.86 Pa. It was observed that stuffing temperature and mixing time influenced pH, water binding capacity, and ultimate shear stress. The study identified the optimal production conditions and determined the maximum amount of PFE that can be added to sausages. Additionally, it was found that green buckwheat flour enhances the structure of the minced meat, raises pH, and increases water-binding capacity. Furthermore, PFE was noted to improve the appearance and flavor characteristics of the sausages. These findings highlight the potential of these new ingredients to enhance the quality of cooked sausages in the food industry.

Research on the formation of the structure of dairy desserts with a combined composition of raw materials under the influence of technological factors

Subject of study. Dairy products are complex in chemical composition and have a complex of various properties that affect the quality of the fnished product, in particular, its structure. Consumer demands for food quality are constantly growing, which leads to the improvement of technological processes. Therefore, the study of the influence of technological factors in the production of dairy products for dessert purposes on the formation of their structure is an urgent issue. The study aimed to investigate the influence of technological factors, in particular, different temperature regimes of packaging on the structure of the fnished product. The results. The article presents the results of studies on the formation of the structure of pudding and cream packaged at different temperatures. It has been shown that the flow curves of dairy desserts, characteristic of thixotropic systems, change their structure under the influence of mechanical loads. It was found that samples of dairy desserts packaged immediately after thermomechanical processing had a lower thixotropy coefcient compared to samples packaged after cooling. It was found that the viscosity of the retentate-based milk dessert was 10-20 % lower than that of a similar product based on butter. In addition, the viscosity values for retentate-based pudding were 20- 30 % higher than for cream. Conclusions. It has been proved that the temperature of the packaging of dairy desserts, as one of the decisive technological factors, has an impact on the formation of the structure, and, as a result, on the quality of the fnished product. For example, to produce dairy desserts with a consistency typical of pudding or cream, it is necessary to pack at a temperature of at least 65°C. At the same time, the viscosity and ultimate shear stress for cream should be in the range of 55...75 Pa-s and 70...100 Pa, respectively, for pudding - 117...124 Pa-s and 90...110 Pa, respectively. Key words: dairy desserts, creams, puddings, combined composition of raw materials, temperature conditions, packaging, structure, rheological indicators, quality.

INFLUENCE OF ELECTROMAGNETIC TREATMENT ON HYDRAULIC CHARACTERISTICS OF HOT PIPELINES DURING NEWTONIAN AND NON-NEWTONIAN PETROLEUM SYSTEMS TRANSPORTATION

This work examines the influence of radio-frequency (RF) electromagnetic (EM) influence on the hydraulic characteristics of hot pipelines for the transport of petroleum Newtonian and non-Newtonian systems.Newtonian and non-Newtonian petroleum and their rheological properties before and after RF EM exposure, as well as the hydraulic characteristics of hot petroleum pipelines for pumping selected petroleum, were selected as objects of study.As a result: a methodology for petroleum processing has been developed that corresponds to industrial practice in the operation of petroleum pipelines; empirical dependences of petroleum viscosity on temperature were obtained in the form of piecewise exponential functions. The influence of RF EM exposure on the thixotropic properties of petroleum and the values of ultimate shear stresses was assessed. A decrease or complete disappearance of hysteresis loops after RF EM exposure to petroleum and a decrease in the maximum shear stress for non-Newtonian petroleum were revealed.By using the software developed by the authors, «Hydraulic calculation of isothermal and non-isothermal petroleum pipelines (GRINT)», the processes of pipeline transport of petroleum treated with EM fields were modeled, taking into account the obtained empirical dependencies. An assessment of the influence of RF EM exposure on the hydraulic characteristics of «hot» pipelines was carried out. It has been established that after RF EM exposure to petroleum, the zone of stable operation of a «hot» petroleum pipeline increases and the required pressure for pumping the same volume of petroleum decreases.

The influence of shear surface quality on the mechanical properties of long-span prestressed continuous rigid-frame bridge

PurposeThe long-span continuous rigid-frame bridges are commonly constructed by the section-by-section symmetrical balance suspension casting method. The deflection of these bridges is increasing over time. Wet joints are a typical construction feature of continuous rigid-frame bridges and will affect their integrity. To investigate the sensitivity of shear surface quality on the mechanical properties of long-span prestressed continuous rigid-frame bridges, a large serviced bridge is selected for analysis.Design/methodology/approachIts shear surface is examined and classified using the damage measuring method, and four levels are determined statistically based on the core sample integrity, cracking length and cracking depth. Based on the shear-friction theory of the shear surface, a 3D solid element-based finite element model of the selected bridge is established, taking into account factors such as damage location, damage number and damage of the shear surface. The simulated results on the stress distribution of the local segment, the shear surface opening and the beam deflection are extracted and analyzed.FindingsThe findings indicate that the main factors affecting the ultimate shear stress and shear strength of the shear surface are size, shear reinforcements, normal stress and friction performance of the shear surface. The connection strength of a single or a few shear surfaces decreases but with little effect on the local stress. Cracking and opening mainly occur at the 1/4 span. Compared with the rigid “Tie” connection, the mid-span deflection of the main span increases by 25.03% and the relative deflection of the section near the shear surface increases by 99.89%. However, when there are penetrating cracks and openings in the shear surface at the 1/2 span, compared with the 1/4 span position, the mid-span deflection of the main span and the relative deflection of the cross-section increase by 4.50%. The deflection of the main span increases with the failure of the shear surface.Originality/valueThese conclusions can guide the analysis of deflection development in long-span prestressed continuous rigid-frame bridges.

Vibration reduction effect of retaining pile structure under the action of damping hole—A case study

In the context of mitigating the impact of blasting-induced seismic waves on excavation processes and reducing the vibrational load on retaining pile structures, this study examines the influence of predetermined damping hole parameters on the damping effect. It also evaluates the protective efficacy of damping holes on retaining pile structures. Leveraging the foundation pit project at the Julong Avenue Station of Wuhan Metro Line 7 as a reference, on-site blasting construction was monitored to obtain vibration velocities at the top of the retaining pile structure. A numerical calculation model for blasting in the foundation pit was established using LS-DYNA software, and its reliability was verified through the integration of on-site monitoring data at the top of the retaining pile. Multiple damping hole excavation schemes were devised, and their effects on the damping effectiveness were analyzed with respect to various parameters. Safety criteria for the stability of the retaining pile structure were proposed based on the ultimate tensile stress criterion, ultimate shear stress criterion, and Mohr’s criterion. Under the optimized scheme, the dynamic response characteristics of the retaining pile structure were analyzed, and the practical application effects on-site were observed. The research findings indicate that the depth, spacing, and number of damping holes have a significant impact on the damping effect. The safety criterion for the vibrational velocity of the retaining pile structure during blasting is determined to be 26.10 cm/s. Under the optimized scheme, the vibrational velocities at various monitoring points on the retaining pile structure all fall within the safe range, with a maximum reduction rate of 30.9%.

Modelling the centrifugal mixing process of minced meat to optimise the production of chopped meat semi-finished products

One of the most important problems in ensuring the quality of mincemeat preparation in the production of sausages is the effective structuring of components and mixing of their ingredients. To solve this problem, researchers added a multifunctional admixture based on whey protein in the process of centrifugal mixing of the components, which determined the composition of the factor space of the investigated process. Based on the results of the research, the effective content of whey protein, sodium alginate, and soy fiber in the developed recipe was proven, which showed high characteristics in terms of fat-retaining and moisture-retaining ability, digestibility, pH level – activity, and other parameters. The developed formulation made it possible to improve the general indicator of the balance of amino acids in the product and increase the functional-technological and quality parameters of the developed products. The physical and mechanical characteristics of the obtained meat product were evaluated based on the results of physical and mathematical modelling. Modelling was carried out using Federman-on-Buckingham's second similarity theory and the "dimension theory" method, which allows the processing of the obtained experimental data in the form of a criterion equation, which was compiled using Froude, Euler, and Sherwood criteria. The purpose of this study was to obtain dependencies between such process factors as product density, the coefficient of dynamic viscosity of the technological medium, the ultimate shear stress, the change in the concentration of the main impurities of lactic acid in the raw material, the value of the diffusion coefficient and the coefficient of mass transfer in the loading mass, the weight of one load of products, the angular frequency of rotation of the screws of the minced meat mixer, the radius of the rotating working bodies, the characteristic size of the products after grinding. Using the complex criterion equation and the developed program, we find a recommended set of operating mode parameters for preparing minced meat under the conditions of centrifugal influence on the mixing process and the action of the specified factors.

Investigation into the interface bond between polyurethane concrete and steel plate

PurposePolyurethane concrete (PUC), as a new type of steel bridge deck paving material, the bond-slip pattern at the interface with the steel plate is not yet clear. In this study, the mechanical properties of the PUC and steel plate interface under the coupled action of temperature, normal force and tangential force were explored through shear tests and numerical simulations. An analytical model for bond-slip at the PUC/steel plate interface and a predictive model for the shear strength of the PUC/steel plate interface were developed.Design/methodology/approachThe new shear test device designed in this paper overcomes the defect that the traditional oblique shear test cannot test the interface shear performance under the condition of fixed normal force. The universal testing machine (UTM) test machine was used to adjust the test temperature conditions. Combined with the results of the bond-slip test, the finite element simulation of the interface is completed by using the COHENSIVE unit to analyze the local stress distribution characteristics of the interface. The use of variance-based uncertainty analysis guaranteed the validity of the simulation.FindingsThe shear strength (τf) at the PUC-plate interface was negatively correlated with temperature while it was positively correlated with normal stress. The effect of temperature on the shear properties was more significant than that of normal stress. The slip corresponding to the maximum shear (D1) positively correlates with both temperature and normal stress. The interfacial shear ductility improves with increasing temperature.Originality/valueBased on the PUC bond-slip measured curves, the relationship between bond stress and slip at different stages was analyzed, and the bond-slip analytical model at different stages was established; the model was defined by key parameters such as elastic ultimate shear stress τ0, peak stress τf and interface fracture energy Gf.

RHEOLOGICAL FEATURES OF LIQUID IN MICROCRACKED CHANNELS WITH THE “MICROCRACK-LIQUID” EFFECT DISPLAYED

Based on experimental and theoretical studies in plane-radial and plane-parallel microcracks, a previously unknown pattern called “microcrack-liquid” effect was established for the first time, that when viscous liquids move in a microcrack at h<hcr, anomalous properties appear, and when anomalous liquids move, rheological parameters increase, at h>hcr these effects disappear. It was revealed that the reason for the manifestation of anomalous properties of Newtonian liquids and the enhancement of the rheological properties of non-Newtonian systems when they move in microcapillary cracks is the new microcrack effect of the “microcrack-liquid” system. The established critical values of crack opening for the studied viscous oils are 160 μm at a temperature of 303 K. Keywords: microcrack opening, non-Newtonian fluids, ultimate shear stress, structural viscosity, microcrack-liquid effect.

Analyzing cyclic shear behavior at the sand–rough concrete interface: An experimental and DEM study across varying displacement amplitudes

AbstractPile foundations frequently endure dynamic loads, necessitating an in‐depth examination of the cyclic shear properties at the pile–soil interface. This study involved a series of cyclic direct shear (CDS) tests conducted on sand and concrete with irregular surface, utilizing varying displacement amplitudes (1, 3, 6, and 10 mm) and joint roughness coefficients (0.4, 5.8, 9.5, 12.8, and 16.7). Discrete Element Method (DEM) models, informed by experimental data, facilitated mesoscopic mechanical response analyses. Findings indicate that the sand–concrete interface undergoes softening, with hysteresis loops' morphology dependent largely on displacement amplitude. A maximum ultimate shear stress corresponds to a specific critical surface roughness, while the initial tangent modulus escalates with increased concrete roughness. Volume variations of the specimen inversely correlate with displacement amplitude and directly with surface roughness. As displacement amplitude expands, there is a reduction in the maximum shear stiffness and an elevation in the maximum damping ratio. Empirical formulas for the surface roughness and normalized shear stiffness were proposed. Larger displacement amplitudes result in more substantial shear bands and heightened energy dissipation, yet the incremental energy ratio remains largely unaffected. Predominant energy dissipation mechanisms include both slip and rolling slip, with the former surpassing the latter in energy dissipation capacity. The anisotropy directions of contact normal, normal contact forces, and tangential contact forces consistently fluctuate with shear direction alterations.

Linear Cutting Performance Tests and Parameter Optimization of Poplar Branches Based on RSM and NSGA-II

To reduce the cutting force and cutting energy consumption during the operation of tree-climbing pruning machines for poplar trees, a linear cutting test bench device for branches was designed according to the growth characteristics of poplar branches and pruning forestry requirements in this study. Firstly, the cutting mechanical analysis of poplar branches was carried out to explore the significance parameters affecting the cutting force, and then the cutting performance test and parameter optimization of poplar branches was carried out through the response surface method (RSM). The test results indicated that cutting speed, tool edge angle and tool back angle had significant effects on the ultimate shear stress, cutting power consumption per unit area, and the branch damage rate of poplar branches, and the established regression equation demonstrated high goodness of fit. Meanwhile, a second-order regression mathematical model was developed between ultimate shear stress, cutting the power consumption per unit area of the cut and the branch damage rate, and the significance parameter. The non-dominated Sorting Genetic Algorithm II (NSGA-II) was used for multi-objective optimization computation to obtain the optimal combination of cutting parameters as 3.02 m/s for cutting speed, 15° for tool edge angle, and 3° for tool back angle. In this case, the ultimate shear stress, cutting power consumption per unit area, and branch damage rate of poplar branches were small, which were 346.63 kPa, 9.35 mJ/mm2, and 12.36%, respectively. Through the test verification, it can be seen that the relative error between the verification test and the predicted value of model was less than 7%. Moreover, under a cutting tool edge angle of 15°, the ultimate shear stress, cutting power consumption per unit area, and branch damage rate were, respectively, reduced by 17.29%, 14.98%, and 34.21% compared with those under a cutting tool edge angle of 20°, which verifies the validity and reliability of the test results and the research method. This study can provide data support and reference for the research and development of energy-efficient poplar tree-climbing pruning equipment and related branch-cutting performance tests.

Effects of Cutting Parameters on the Shearing Properties of Oilseed Rape (Brassica Napus L.) Shoots in Harvesting

Highlights Cutting parameters affect the shearing properties of ultimate shear stress and specific shear energy of oilseed rape shoots harvesting. The oilseed rape shoots harvester blade was optimized using a central composite design (CCD) experimental test. The interaction term of blade thickness and oblique angle significantly affect the ultimate shear force and specific shear energy. Provide a reference for designing oilseed rape shoots harvesting machinery. Abstract. Oilseed rape (Brassica napus L.) shoots are used as an edible nutritious and healthy vegetable. However, there is little information for the effects on cutting parameters on the oilseed rape stalk shearing properties to harvest fresh shoots. This study used the single factor method and response surface methodology (RSM) along with central composite design (CCD) to examine the effects of the blade operating and structural parameters, such as the blade loading velocity, the bevel angle, the oblique angle, and the thickness, on the response variables of ultimate shear stress and specific shear energy. The RSM analysis results demonstrated that the interaction term of blade oblique angle and thickness affect the response variables. Optimized operating and geometry parameters for minimizing response variable values were 195 mm min-1 for loading velocity, 16.4° for bevel angle, 16.3° for oblique angle, and 3.2 mm for thickness. Moreover, under these optimal parameters, the ultimate shear stress and specific shear energy were reduced by 31.37% and 40.95%, respectively, compared to the cutting parameters of the prototype harvester. This study concluded that the appropriate cutting parameters could effectively decrease the shear force and energy requirements, which provided a vital basis for designing and developing the cutting device for the oilseed rape shoots harvester. Keywords: Cutting parameters, Oilseed rape shoots, Shearing experimental test, Specific shear energy, Ultimate shear stress.

Modified Gypsum-Cement-Pozzolan Concrete for 3DCP

3D concrete printing (3DCP) is an innovative and promising method for constructing buildings and structures. Compositions of fine-grained concrete based on Portland cement are widely used as raw material mixtures in this technology. An alternative to the use of cement binder is the use of gypsum-cement-pozzolan binder, which can significantly reduce the cost of the finished product and, accordingly, increase its competitiveness. The raw material mixtures based on gypsum-cement-pozzolan binder presented on the construction market do not fully meet the requirements of 3DCP. Achieving optimal performance of gypsum-cement-pozzolan mixtures in 3DCP is possible by regulating the content of fine aggregate in the composition of fine-grained concrete, as well as the use of multicomponent modifying additives. The purpose of this work is to develop modified gypsum-cement-pozzolan concretes for 3DCP based on optimization of aggregate content and multifunctional additive, providing optimal rheotechnological properties of raw mixtures and technological characteristics of finished products. The formation of samples during experimental studies was carried out using the layer-by-layer extrusion method on a workshop construction 3D printer “AMT S-6044”. Modified gypsum- cement-pozzolan concretes have been developed for 3DCP with increased ultimate shear stress of the mixture (87.6 Pa), dimensional stability (23 cm), average composite density (1920 g/m3), flexural strength (8.4 MPa) and compression (30.6 MPa) and water resistance (0.85). The possibility of targeted regulation of the structure and properties of gypsum-cement- pozzolan mixtures and concrete due to the synergistic effect of the components of the developed multifunctional complex additive, including an aqueous solution of a polycarboxylate ether, a copolymer based on carboxylic acid esters, and a homogeneous mixture of oligoethoxysiloxanes, has been proven. The results obtained are consistent with the results of the differential thermal analysis of modified gypsum-cement-pozzolanic stone.

STRUCTURE FORMATION OF IRON-CONTAINING DISPERSIONS OF ORGANOMONTMORYLONITE

The aim of the work is to study the processes of structure formation of organomontmorillonite in iron-containing dispersions by studying the rheological and colloid-chemical properties of such systems. To modify the surface of montmorillonite, a cationic surface-active substance, a quaternary ammonium salt, hexadecyltriammonium bromide, was used. With the help of X-ray diffraction analysis, we confirmed the penetration of molecules of surface-active substances into the interlayer space of the mineral and its increase to 1.86 nm during the modification mineral surfactant/ cation exchange capacity (S/CEC)=1. The analysis of the results of rheological studies showed that the changes in the characteristics of montmorillonite dispersions depending on the concentration of surfactants are extreme and reach a maximum (6.7 Pa) at the degree of modification of the mineral S/CEC=0.3. The high values of ultimate shear stress confirm the formation of a continuous network between the mineral particles with an "edge–face" orientation. When the surfactant content in the system increases, the ultimate shear stress of the suspension gradually decreases and reaches practically zero values. These results lay the foundation for determining the optimal parameters for the synthesis of iron-containing dispersions based on organomontmorillonite. nZVI was obtained by its reduction on the solid surface of organomodified montmorillonite from a solution of iron(II) sulfate salt. X-ray diffraction data confirmed the fixation of nZVI on the surface of organophilized montmorillonite. Analysis of the results of rheological studies showed that changes in the characteristics of dispersions of iron-containing material based on organomontmorillonite depending on the content of nZVI are extreme and reach a maximum at (6.8 Pa) when the iron content in the sorbent is 0.01 mass fraction in the solid phase of the sorbent. When the content of nZVI is increased to 0.05 mass fraction of the solid phase of the sorbent, it is possible to obtain dispersions with high values of ultimate shear stress (3.3 Pa) and clearly expressed hysteresis loops, which indicates the formation of thixotropic structures and confirms the possibility of its use in permeable reaction barriers. Experimental data confirm that with an increase in the content of nZVI above 0.1 mass fraction in the samples, the ultimate stress and plastic viscosity decrease, which leads to the failure of the suspensions. These results lay foundation for determining the optimal parameters of sorbents synthesis and regulation of their properties by changing the hydrophilic-hydrophobic balance of source systems.

Shear stability and resistance design of novel vertically-flexible stiffened steel plate shear walls

Steel plate shear walls (SPSWs) have been widely employed in practical engineering projects. The steel plates inevitably endure axial loads due to the gravitational forces and structural settling. However, vertical pre-compressive loads have detrimental effects on the buckling behavior and shear resistance of the steel plates. Instead of strengthening the SPSWs to resist the vertical loads, a new type of vertically-flexible stiffened steel plate shear wall (VFS-SPSW) is proposed to minimize these adverse effects. The incorporation of hollow steel tube reduces the vertical compressive stiffness of the VFS-SPSW, leading to a decrease in the proportion of axial compressive loads transmitted to the steel plate wall from the boundary frame. Consequently, this feature facilitates the installation of VFS-SPSW without the necessity of awaiting the completion of the upper structure. In this paper, finite element (FE) analysis is conducted to obtain a threshold out-of-plane bending stiffness ratio for the stability of the VFS-SPSW. Subsequently, a formula for threshold out-of-plane bending stiffness ratio is proposed, including parameters of the ratio of torsional to bending stiffness and aspect ratio of the subpanel. Then, the anchoring mechanism of hollow steel tube to the tensile field of the steel plate is investigated. The threshold in-plane anchor stiffness ratio is defined to ensure the full development of the tension field in the steel plate. A formula for predicting this ratio is proposed by theoretical and numerical analysis. Finally, the reduction factor of vertical compressive stiffness for the VFS-SPSW at the threshold in-plane anchor stiffness ratio is calculated. The results indicate that the vertical compressive stiffness of the VFS-SPSW, which meets the threshold stiffness design requirements, can be decreased to below 50% of the traditional stiffened SPSW, while ensuring that the reduction in ultimate shear stress remains within the limit of 5%.

Технология инъекционной изоляции пластовых выработок угольных шахт

The basic composition of technological suspension (TS) for injection grouting of the edge part of the coal seam has been developed. The investigated water-solid TS actively show structural characteristics at different velocities of flat flow in the fracture. An increase in the TS concentration and introduction of ash-slag into the composition provides nonlinear growth of dynamic (ultimate) shear stress τ0 and is accompanied by a jump of its value in the range of water-solid ratio from 0.35 to 0.4. The schemes of grouting operations for different categories of coal seams stability have been developed, which differ in the application of spray-insulating coating, collector connection scheme and the evacuation system for the injection boreholes. Monitoring of the operating parameters with current operational assessment of the massif fracturing degree allows to control the flow movement and the TS injection pressure, reducing the solution losses while improving the quality of injection isolation.

Experimental investigation on corroded stud connectors under strain rates effect

Shear connectors have been widely used in bridge and steel engineering to transfer the dynamic load effect between the neighbour elements. The shear connectors are exposed to moist air, and corrosion is unavoidable. An experimental investigation was conducted on the shear behaviour of corroded stud connectors with growing strain rates to study the effects of corrosion and strain rate on the shear capacity. Four series of specimens with different corrosion rates were tested. The electronic accelerating method was used to fabricate corroded studs with target corrosion rates. The corroded studs were loaded with five loading speeds to investigate the strain rate effects on the shear capacity. The fractured surfaces show that the corroded stud connectors have more tensile deformation in the loading process and a higher strain rate enhances the shear fracture other than tensile fracture. Based on the statistics of load-slip curves, we found that stud connectors with higher corrosion rates are more sensitive to dynamic load. However, corrosion cannot decrease the ultimate shear stress based on the minimum cross-section. For all corrosion rates, the relative ultimate shear strength grows with strain rate with a fixed growth rate.

Исследование реологических характеристик рыбного фарша из объектов аквакультуры

The paper dwells on the prospects of using the methods of extrusion processing of products based on minced fish. It is noted that one of the promising methods is the method of cold extrusion and co-extrusion. The research aims to identify theoretical and experimental patterns of changes in the rheological characteristics of minced aquaculture fish (carp and silver carp) and analyze them in relation to extrusion processes. The dependences of the rheological characteristics of minced fish samples on the influencing parameters in a wide temperature range from –5 to +25 °C have been studied. The values of the ultimate shear stress and the penetration depth of minced fish have been determined on a conical plastometer KP-3, viscosity – on a rotational viscometer Brookfield DV–II+Pro, and adhesive ability – on a laboratory unit for determining the stickiness of the material. Based on the data of minced fish chemical composition theoretical dependences of the effective viscosity on the shear rate gradient have been obtained. Similar dependences have been obtained experimentally in a wide temperature range. The analysis of these dependencies has shown their qualitative coincidence for the usual conditions for producing minced fish, but there are quantitative differences due to the technology for preparing minced aquaculture fish. The rheological characteristics of minced fish have been analyzed for the studied temperature range. It has been determined that the temperature range from –2.5 to 0 °C is the most appropriate for cold extrusion processes. In this area the value of the effective viscosity of minced fish and its adhesive ability are minimal, which is decisive for implementing extrusion processing. The good formability of the product has also been noted under these conditions. A further research direction is to identify the influence of technological additives on the formability of minced aquaculture fish, to reduce the smell of fish, and to eliminate undesirable oxidative processes. Developing new types of fish products with innovations in form, texture, colour and composition remains relevant. The prospects of the co-extrusion method which allows creating new innovative fish products with functional properties have been confirmed.