Cylindrical Apparatus Research Articles

Effects of low clay content on the anisotropic behavior of sand-clay mixtures: laboratory investigation using TSHCA

Undrained behavior of sandy soil with fines content is a challenge in geotechnical research. In this article, the effect of low clay content (plastic Kaolin) on the anisotropic behavior of sand is studied. In the technical literature, there are different data about the effect of fine particles (generally high percentage), but there are not enough studies on low fines content (especially plastic fines) and anisotropic conditions. For this purpose, 30 undrained tests are performed using a torsional shear hollow cylindrical apparatus (TSHCA) with constant (αo) and (b) values on Firoozkuh sand. The specimens had Kaolin contents of 0, 3, 5, 7 and 10%, and the inclination angle (αo) is varied from 15o to 60o. The specimens are prepared by dry deposition method and are consolidated under P'c= 100 and 200 kPa. The results of the experiments show that increasing the (αo) leads to more contractive behavior in sand. By adding clay particles to the host sand up to 3%, the peak strength of the specimen is increased (7% and 6% for α=15°and 30°, respectively), and then with the increase of clay content up to 10%, the strength of the specimen is decreased (33% and 22% for α=15°and 30°, respectively). But at α = 60o, with the addition of 5% clay, decrease in the peak strength is observed (about 15%) and with a further increase in the clay content, unlike the angles of 15o and 30o, increase in the peak strength of the specimen is observed, so that at 10% clay, the strength of the specimen is higher than the host sand (about 7%), which can be attributed to the cohesion nature of the clay particles. With the increase of clay content, anisotropy degree is decreased. In other words, with the increase of fines content, the anisotropic behavior is decreased.

An anisotropic hypoplastic model for clays considering the non-coaxial behavior

Previous experimental tests on clays have confirmed the non-coincidence of principal strain increments with principal stress axes even though the stress rate is colinear with the current stress. To simulate the non-coaxial behavior of saturated clay subjected to monotonic proportional or non-proportional loading with constant principal stress rate directions, an anisotropic hypoplastic model is presented in this paper. The model is proposed by incorporating an improved anisotropic asymptotic state boundary surface (ASBS) and a non-coaxial asymptotic strain rate direction into the original explicit-ASBS hypoplastic model. The non-coaxial flow results from a non-coaxial stress rate defined by a Gram-Schmidt orthogonalization process based on a reference stress tensor. The capability of the proposed model is demonstrated by simulating the test data performed in hollow cylindrical apparatus (HCA) on Wenzhou clay and Shanghai clay with different drainage conditions and initial consolidation states. In addition, a series of numerical stress probing tests have been conducted to gain further insights into the properties of the proposed model.

Coking of high-viscosity water-containing oil

Objectives. A characteristic feature of oil production is an increase in the volume of highviscosity bituminous oil. In Russia, technologies based on the use of water vapor are used for their extraction. The use of such technologies leads to a large amount of water in the product stream from the production well. Preparation of oil for processing involves its stabilization, desalination, and dewatering. Since the densities of the extracted oil and the water contained in it are comparable, traditional preparation schemes for processing of high-viscosity bituminous oil are ineffective. One of the possible solutions to the problem involving such oil in the fuel, energy, and petrochemical balance is to use a coking process at the first stage of its processing. This aim can be achieved by studying the influence of the process conditions of coking high-viscosity water-containing oil on the yield and characteristics of the resulting products.Methods. Coking of oil with a density of 1.0200 g/cm3 at 50 °C and with 18 wt % water content was carried out in a laboratory installation in a “cube.” A hollow cylindrical apparatus was used as a reactor and was placed in a furnace. The temperature and pressure in the reactor were maintained at 500–700 °C and 0.10–0.35 MPa, respectively.Results. An increase in the coking process temperature results in an increase in the amount of gaseous products, a decrease in the amount of the coke generated, and a higher dependence of the amount of liquid products on temperature with a maximum yield at 550–600 °C. The process temperature also affects the composition of liquid products. At a lower temperature, the amount of gasoline and kerosene fractions in liquid products is higher. With an increase in pressure, a higher amount of gaseous products, coke, and low-molecular-weight hydrocarbon fractions in liquid products could also be obtained. The characteristics of the coke produced in the coking process are similar to those of commercially produced grades. It is noted that when coking water-containing oil, up to 98% of the emulsion water goes with liquid products, and the remaining amount of water remains in the formed coke.Conclusions. Results showed the possible application of the coking process at the initial stage of processing high-viscosity bituminous oil. In this case, the dewatering stage is significantly simplified since the technological scheme of delayed coking allows the separation of the gasoline fraction from water.

Development of environmental measures to reduce the dusty emissions of stone coal in loading and unloading works

Now Russia is one of the worlds leading coal producers. Particles inevitably pass into an aerosol state, forming dust, which is subsequently emitted into the atmosphere during the extraction, crushing, sorting and transportation of coal. This dust negatively affects the health of workers in the mining industry, as well as the population of the residential area. In this regard, the question arises about the effective air cleaning in the working area from coal dust and reducing its concentration. The work purpose is to develop a comprehensive cleaning of gas-air emissions from coal dust in the working area where it is transported. The main task is to create an additional degree of air purification from coal dust. For this purpose, a vortex absorber was used, which is a cylindrical apparatus in which a contact element with perforated holes is located. The geometric dimensions of the absorber and its main parameters have been determined. The absorber developed by the authors has shown very good results as a device for the final purification of gas-air emissions. The efficiency of trapping small solid particles in the presented scheme reaches 99%. At the same time, as a result of the introduction of this installation, effective air purification from dust particles with a diameter of about 0.2 microns is carried out and the coal briquettes production is increased by 144 tons per year.

Experimental Study on the Dynamic Modulus and Damping Ratio of Compacted Loess under Circular Dynamic Stress Paths

Dynamic loads such as earthquakes and traffic will simultaneously generate vertical dynamic stress and horizontal shear stress in the foundation soil. When the vertical dynamic stress amplitude is twice the horizontal shear dynamic stress amplitude, and the phase difference between them is 90°, a circular dynamic stress path is formed in the τzθd ~ (σzd − σθd)/2 stress coordinate system. To simulate the stress state of soil in the area of the circular dynamic stress path caused by bidirectional dynamic stress coupling, a series of tests of compacted loess under the action of a circular dynamic stress path were carried out using a hollow cylindrical torsion shear apparatus. The effects of the mean principal stress, dry density, and deviatoric stress ratio (the ratio of deviator stress to average principal stress) on the dynamic modulus and damping ratio of compacted loess were mainly studied. The test results show that, under the action of the circular dynamic stress path, the larger the mean principal stress is, the larger the dynamic compression modulus and dynamic shear modulus are. The dynamic compression modulus increases obviously with increasing dry density, but the dynamic shear modulus increases only slightly. When the deviator stress ratio increases from 0 to 0.4, the dynamic compression modulus and dynamic shear modulus increase to a certain extent. In addition, the greater the dry density and deviatoric stress ratio are, the greater the initial dynamic compression modulus and initial dynamic shear modulus of the compacted loess. The dynamic compression damping ratio of compacted loess increases with increasing mean principal stress, but the dynamic shear damping ratio decreases with increasing mean principal stress. Dry density basically has no effect on the dynamic compression damping ratio and dynamic shear damping ratio of compacted loess. When the dynamic strain exceeds 1%, the greater the deviatoric stress ratio is, the smaller the dynamic compression damping ratio and the dynamic shear damping ratio are. The research results can provide reference for the study of dynamic modulus and damping ratio of loess under special stress paths.

Stiffness degradation of natural soft foundation in embankment dam under complex stress paths with considering different initial states

Under cyclic loads, such as wave, earthquake, and traffic load, the direction of the principle stress axis rotates continuously in the soft foundation of embankment dam. However, the research conducted on stress-strain and stiffness characteristics of soft foundation in embankment dam under complex loads considering principal stress rotation was limited. In this paper, the deformation property of natural soft clay was investigated, with considering different inclined consolidation angles ζ and different intermediate principal stress coefficients b, by using GDS hollow cylindrical apparatus (HCA). It can be concluded from the test that, with the cycle number increasing, there are obvious differences in the axial stress-strain curves under different cycles, and the same as the torsional stress-strain curves under different cycles; the development of soil strain path is greatly affected by ζ value; the stiffness is significantly affected by ζ value and b value.

Calculation of Interphase Mass Transfer in a Spray Flow Produced by a Nozzle with Account of Crisis

This paper describes the numerical model and the results of calculating the interphase mass transfer in a two-phase flow generated by atomizing a liquid in a gas using a nozzle. The proposed mathematical model is based on differential equations of unsteady flow in a compressible medium, complemented by the equation of mass transfer from gas to droplets. The popular explicit Lax–Wendroff scheme is used for transition to difference analogs of continuity and phase motion equations. Axial profiles of droplet and gas velocities and gas impurity concentrations in a free spray cone are calculated and presented together with radial profiles of impurity concentrations in a two-phase flow through a cylindrical apparatus, taking into account early drag crisis of droplets and crisis of interphase mass transfer, as well as the features of turbulent friction in gas, discovered in previous experiments. The calculation established the dependencies of the gas flow rate, the concentration of gas impurities at the outlet of the apparatus, and the amount of impurities absorbed by the liquid from the height and cross-sectional area of the apparatus.

Progressive Freeze Concentration of Coconut Water and Use of Partial Ice Melting Method for Yield Improvement.

Coconut water is a highly nutritious liquid food which is a by-product of the desiccated coconut industry. Freeze concentration is the most suitable concentration method for coconut water since the low-temperature operation for concentration does not deteriorate the original quality of coconut water. Suspension freeze concentration (SFC) and progressive freeze concentration (PFC) are the available FC methods, and SFC is a complex and expensive method compared with PFC. PFC is a novel freeze concentration technique to concentrate liquid food by using a simple system. The limitation of PFC is the lower product yield than SFC, and to overcome the problem, the partial ice-melting technique can be used. A simple cylindrical apparatus was used for PFC which consists of a sample vessel, agitator system, and a cooling bath (at −23°C ± 2°C temperature). The final concentration of the liquid product was directly affected by the apparatus agitator speed and sample vessel dipping speed. PFC agitator speed of 290 rpm and dipping speed of 1.3 cm h−1 were reported as the optimum operating conditions to achieve the highest concentration for the PFC apparatus used in this study. Using optimized agitation speed and dipping speed, coconut water was concentrated up to Brix 8.5° from the initial concentration of Brix 3.5°. PFC coconut water achieved 73.56% of total yield, 2.42 of concentration ratio, 0.7° of ice phase concentration, and 0.08 of effective partition coefficient. The partial melting technique was successfully explored by recovering initial ice fractions with high solute concentrations, and the total yield was improved up to 80%.

Расчет межфазного массообмена в факеле распыла форсунки с учетом кризиса

A numerical model and the results of calculation of the interfacial mass transfer in a two-phase flow formed by spraying a liquid in a gas with a nozzle are described. The basis of the proposed mathematical model is the differential equations of the nonstationary flow of a compressible medium supplemented by the equation of mass transfer from a gas to droplets. Going over to the difference analogues of the equations of continuity and phase motion, we used the well-known explicit Lax-Vendroff scheme. Herein, the axial profiles of the velocities of droplets and gas, concentrations of gas impurity in a free spray flow, as well as radial profiles of impurity concentrations in a two-phase flow through a cylindrical apparatus are calculated and presented accounting the early drag crisis of droplets, the mass-transfer crisis and the turbulent friction characteristics in gas discovered in previous experiments. Calculations show dependences of the volumetric gas flow, concentration of the gas admixture at the apparatus output, and the amount of impurity absorbed by a liquid on the height and cross-section area of the apparatus.

A strength criterion for frozen clay considering the influence of stress Lode angle

To investigate the influence of stress Lode angle on frozen soil, a series of directional shear tests was conducted on artificial frozen clay at three temperatures (–6, –10, and –15 °C) and five stress Lode angles (θσ= –30°, –16.1°, 0°, 16.1°, and 30°) using a hollow cylindrical apparatus. An elliptical function was proposed according to the strength envelope evaluation with the mean principal stress (p) in the p–q plane. In addition, generalized nonlinear strength theory (GNST) was introduced in the π plane to describe the evolution of the strength envelope with increasing mean principal stress. Then a strength criterion for frozen clay in three-dimensional principal stress space was proposed by combining strength functions in the p–q and π planes. The temperature effect was also introduced into the strength criterion. The proposed strength criterion can predict the multi-axial strength characteristics of frozen clay and reveal the influence of the stress Lode angle.

Railroad ballast behavior in triaxial compression tests with and without geogrid

This paper highlights recent laboratory studies at Emperor Alexander I St. Petersburg State Transport University, using large-scale cylindrical triaxial apparatus, which helped quantify the geogrid performance in railway ballast. The triaxial shear strength tests were conducted on ballast with and without geogrid. Effect of geogrid layers quantity on the ballast stress-strain behaviour were studied. The experimental results indicate that the geogrids have improved ballast bearing capacity up to 25%.

Seepage test by HCA for remolded kaolin

Permeability is an import character of soil, especially in excavation and tunnelling. Hollow cylindrical apparatus (HCA) is often used to determine soil anisotropy, particularly soil strength and stiffness under different directions of major principal stress, so complex stress paths can be simulated and the corresponding soil properties can be examined. It can also be used to determine the permeability coefficient if a special mode is added, therefore the seepage test can be expected. Owing to no seepage test has been conducted by HCA before, the complete procedure of HCA seepage tests after static and dynamic loading are respectively studied. And the seepage stability stage is discussed since only data in this stage are valid and reliable for permeability calculation. The results show that:1) when the difference in average permeability coefficient within unit time (3600 seconds) less than 2% in 24h, it is reliable to take the average permeability coefficient in this period as the ultimate permeability in static seepage test; 2) for dynamic test, if the average permeability in 3600 seconds varies with 5% in 24h, the average permeability coefficient in this period can be taken as the ultimate value. Research in this paper provides a solid foundation for HCA seepage test under complex stress paths.

Analysis of a feasible field THAI pattern by the derivation of scaling criteria and combustion experiments

Abstarct Toe-to-heel air injection (THAI) process is considered as a potential enhanced oil recovery (EOR) method for heavy oil production. For physical simulation of THAI process in laboratory conditions, the simplified scaling criteria of THAI process were derived and a novel three-dimensional cylindrical apparatus was used to construct the new THAI pattern in this study. Equation analysis and dimensional analysis (Buckingham π-theorem) were applied to deduce the whole dimensionless groups, and sensitivity of the coefficients described with their distortion coefficients were used to obtain the influential weights and the simplified scaling criteria. STARS module in Computer Modeling Group (CMG) was used to verify the feasibility of the THAI pattern by two models, which represent the reservoir prototype and the 3D apparatus respectively. With an effective simulation of experimental results, a reasonable data set was obtained, and then those values were upscaled for simulation of field THAI process by the simplified scaling criteria. The experiment results showed that the horizontal well was well protected by a slant distribution of coke zone and the other parameters about oil production (such as the high temperature swept volume, oil production rate and recovery) were still satisfactory. The similarity of variation process of temperature field, oil saturation distribution and production performance between the laboratory results and THAI simulation in reservoir prototype showed the validity of the scaling criteria and indicated that a feasible field THAI process with a large combustion chamber upon horizontal well can be predicted to achieve.

Minimizing the mass of a flat bottom of cylindrical apparatus

In the bodies of cylindrical apparatuses that operate under pressure, one of the weak elements is a flat bottom whose thickness is increased by 4…5 times in comparison with the wall thickness. This is due to the fact that the bottom is exposed to a more unfavorable bending deformation compared to the wall that «works» on stretching. In order to reduce specific metal consumption for the bottom, we propose the optimization of the shape of a radial cross-section by a rational redistribution of the material: to increase thickness of the bottom in the region of its contact with the wall and to significantly reduce it in the central zone. To describe a variable thickness of the bottom, we applied the Gauss equation with an arbitrary parameter that determines the intensity of change in the thickness in radial direction. We have obtained a general solution to the differential equation of the problem on bending a bottom at a given law of change in its thickness, which is represented using the hypergeometric Kummer’s functions. A technique for concretizing the resulting solution was proposed and implemented, based on the application of conditions of contact between a cylindrical shell and a bottom. The solution derived was used to minimize the mass of the bottom. We have designed a zone of transition from the bottom to the wall whose strength was verified by the method of finite elements under actual conditions.

Effect of drained static shear on cyclic deformation behavior of K0-consolidated sand

The K0-consolidated soil elements beneath structures like quay walls, bridge abutments, cut and cover tunnels and similar structures may be subjected to static shear involving the rotation of the principal stress prior to cyclic loading, which results in the presence of initial shear stress. A hollow cylindrical apparatus was employed and a series of drained cyclic tests was conducted to examine the effects of the initial shear stress induced by drained static shear prior to the application of cyclic loading. Both the initial vertical stress and the initial torsional shear stress were considered in the drained cyclic deformation behavior. The experimental observations indicate that the initial vertical stress accelerates the accumulation of vertical permanent strain during the first 100 cycles only when the initial vertical stress exceeds the value corresponding to the K0-consolidated stress state. The average growth rate of strain increases due to the presence of the initial torsional shear stress. A Critical Static Shear Line (CSSL), initiating from the K0-consolidated stress state in the (σz−σθ)−2σzθ plane, divides the volume change responses into contraction and dilation in subsequent cyclic loading. To account for the combined effects of the initial vertical stress and the initial torsional shear stress on the deformation behavior, a modified model is proposed to predict the vertical permanent strain.

Numerical simulation of the two-phase flow produced by spraying a liquid by a nozzle

A numerical experiment on the simulation of the two-phase flow formed during spraying of a liquid by a nozzle has been described. The radial and axial velocity profiles of the droplets and gas in the free spray and in the two-phase flow through a cylindrical apparatus have been calculated and represented taking into account the early drag crisis of droplets and peculiarities of turbulent friction in the gas, which was detected in previous experiments. The distinguishing feature of the numerical model of the two-phase flow is that it employs the differential equations describing the nonstationary flow of a compressible gas as the initial equations. In transition to their difference analog, the familiar Lax–Wendorff algorithm has been used. A comparison of the results of calculations based on this model with experimental data has demonstrated their concordance.

Cyclic strength of saturated sand under bi-directional cyclic loading

Subject to cyclic loading due to ocean waves and earthquakes, both the shear stress and axial cyclic stress need to be accounted for in the analyses of stress state and cyclic strength. For laboratory soil test, the loading condition can be simulated by performing hollow cylindrical apparatus test, and also the effects of ratios and phase angles between dynamic axial and horizontal shear stress can be considered. In the present study, the maximum shear stress amplitude of soil element is defined as a measure of cyclic strength. Based on the theoretical analysis and experimental tests, this study investigates the influence from the ratios and phase angles on the number of load cycles leading to liquefaction failures. In addition, the characteristics of pore water pressure development are also studied. The theoretical and experimental results indicate that the ratios and phases between the axial dynamic load and torsional dynamic load significantly affect the dynamic strength of sands. Moreover, ratios and phases between the axial dynamic load and torsional dynamic load influence the accumulation speed of pore water pressure significantly. Nevertheless, when the pore water pressure is normalized, the sensitivity of their influences on the pore water pressure development cannot be identified.

Effect of Air Flow Velocity in Smoldering Combustion with Opposed Propagation on Cellulosic Material

Smoldering combustion is a phenomenon that is quite unique, because it is a flameless combustion. This smoldering phenomenon can be a hazard, because of it's characteristics. The characteristic of smoldering combustion is slow, low-temperature, flameless and sustained combustion. This phenomenon can occur on cellulose material both organic and non-organic. Smoldering combustion in organics material can cause a wildland fires, both in surface and inside the soil. This phenomenon in organics material was studied using tobacco material and found that ignition temperatures of 380-620oC were observed. This reaserch was conducted in small scale, vertically oriented smoldering cylindrical apparatus, with varied air flow and from-up ignition (downward propagation). The oxidizer which contacted with the bottom surface of tobacco, was forced in certain volumetric flow rate. A constant power to igniter is applied until the temperature of tobacco 10mm from the igniter reached 500oC. The main observation of this research is temperature distribution, mass loss rate and optical density from the resulting smoke. The temperature records in this research were measured by six type-K thermocouples. The mass loss rate of the tobacco in this research were masured by digital scale in real time. The optical density from the released smoke in this research were measured by opacity meter, which transmitted intensity value, converted into optical density value. Air flow variations used in this research were 1, 3, 5, 7, and 9 liter per minute (LPM). The result of this research showed that air flow is an important factor in the process of smoldering combustion. The ignition position and direction of air flow affect direction of propagation. In this research the propagation occured in two direction. In the first process, the propagation of smoldering front was in downward direction. Nevertheless, after the smoldering front reached the bottom surface of tobacco, heat released by ember were accumulated. The air flow from the bottom of the tube forced the combustible mixture to move upwards and then followed by the upward propagation of smoldering front.

Motor and Hippocampal Dependent Spatial Learning and Reference Memory Assessment in a Transgenic Rat Model of Alzheimer's Disease with Stroke.

Alzheimer's disease (AD) is a debilitating neurodegenerative disease that results in neurodegeneration and memory loss. While age is a major risk factor for AD, stroke has also been implicated as a risk factor and an exacerbating factor. The co-morbidity of stroke and AD results in worsened stroke-related motor control and AD-related cognitive deficits when compared to each condition alone. To model the combined condition of stroke and AD, a novel transgenic rat model of AD, with a mutated form of amyloid precursor protein (a key protein involved in the development of AD) incorporated into its DNA, is given a small unilateral striatal stroke. For a model with the combination of both stroke and AD, behavioral tests that assess stroke-related motor control, locomotion and AD-related cognitive function must be implemented. The cylinder task involves a cost-efficient, multipurpose apparatus that assesses spontaneous forelimb motor use. In this task, a rat is placed in a cylindrical apparatus, where the rat will spontaneously rear and contact the wall of the cylinder with its forelimbs. These contacts are considered forelimb motor use and quantified during video analysis after testing. Another cost-efficient motor task implemented is the beam-walk task, which assesses forelimb control, hindlimb control and locomotion. This task involves a rat walking across a wooden beam allowing for the assessment of limb motor control through analysis of forelimb slips, hindlimb slips and falls. Assessment of learning and memory is completed with Morris water maze for this behavioral paradigm. The protocol starts with spatial learning, whereby the rat locates a stationary hidden platform. After spatial learning, the platform is removed and both short-term and long-term spatial reference memory is assessed. All three of these tasks are sensitive to behavioral differences and completed within 28 days for this model, making this paradigm time-efficient and cost-efficient.

An experimental design approach for investigating and modeling wax deposition based on a new cylindrical Couette apparatus

ABSTRACTThe authors report an experimental study carried out through a newly developed Couette apparatus on evaluating the influence of important operating factors such as wall oil temperature, temperature difference (△T) and flow rate. It is found that wax crystal solubility coefficient, temperature gradient, and sheer stress at the wall play leading roles on the internal mechanism. CFD software is adopted for numerical calculation and the result agrees well with the distribution of the flow and temperature field in actual pipelines so that precise parameter values under related experimental conditions are obtained. An improved dynamic wax deposition model considering the enhance effect of resin and asphaltene as well as static deposition condition is established with an average error of 5.6%. Thus the feasibility of the method based on the new apparatus for further research is implied.