Volumetric Compressibility Research Articles

Volumetric and isentropic compressibility behaviour of ionic liquid, tetrapropylammonium bromide in some inorganic salts aqueous systems at T = (293.15 to 318.15) K

ABSTRACT In this work, to obtain evidence about the salting-out effect, a set of thermophysical properties, namely, density and speed of sound measurements were determined for the systems containing the ionic liquid tetrapropylammonium bromide and some inorganic salts at temperatures from T = 298.15 to 318.15 K and ambient pressure. For the investigated systems, the apparent molar volumes and apparent molar isentropic compressibilities at infinite dilution have been calculated at each temperature using the Masson equation. For all of the systems investigated the intermolecular interactions are weaker and also increase regularly with an increase in temperature. The values of TPAB are both negative and positive. For low concentrations, the isentropic compressibilities decrease with an increase in temperature. At a fixed temperature, the isentropic compressibilities also decreased with an increase in concentration of the solute.

ОЦЕНКА КОНТАКТНЫХ НАПРЯЖЕНИЙ ПРИ ВНЕДРЕНИИ УДАРНИКА В ПРОЧНЫЙ ГРУНТ

Finite formulas have been derived for evaluating contact stresses in a rigid impactor penetrating a soil, taking into account the friction in the framework of the local interaction model. In analyzing dynamic deformation of the soil, its volumetric compressibility, shear resistance and initial strength are accounted for. The obtained evaluations of resistance to penetration of an impactor into the soil are based on a quadratic relation between the stress normal to the impactor surface and impact velocity. The authors have pioneered in deriving finite expressions for coefficients of a trinomial approximation as a function of experimentally determined physical-mechanical parameters of the soil - a dynamic compressibility diagram (a shock adiabat) and a yield strength - pressure diagram. Impact compressibility of soils is described based on Hugoniot's adiabat - a linear relation between shock wave velocity and mass velocity of the medium particles behind the shockwave front. Plastic deformation obeys the Mohr - Coulomb yield criterion with a constraint on the limiting value of maximal tangential stresses according to Tresca's criterion - the Mohr - Coulomb - Tresca plasticity condition. An earlier obtained analytical solution of a one-dimensional problem of a spherical cavity expanding at a constant velocity from a point in a half-space occupied by a plastic soil medium is used. A formula for determining critical pressure (a minimal pressure required for the formation of a cavity, accounting for internal pressure in the framework of Mohr - Coulomb's yield criterion) is also used, which generalizes a known solution for an elastic ideally plastic medium with Tresca's criterion. The derived formulas have been verified by comparing their results with the available data from experiments on the penetration of a steel conical impactor into a frozen sandy soil. It is shown that the disagreement between the numerical and experimental results is within 10%.

The Influence of Atmospheric Pressure on Air Content and Pore Structure of Air-entrained Concrete

To study the effect of atmospheric pressure on the properties of fresh and hardened air-entrained concrete, three kinds of air entraining agents were used for preparing air-entrained concrete in the plateaus (Lhasa, 61 kPa) and the plains (Beijing, 101 kPa). Air content, slump, compressive strength and pore structure of the three air-entrained concretes were tested in these two places. It is found that the air content of concrete under low atmospheric pressure (LAP) is 4%-36% lower than that of concrete under normal atmospheric pressure (NAP), which explaines the decrease of slump for air-entrained concrete under LAP. Pore number of hardened concrete under LAP is reduced by 48%-69%. While, the proportion of big pores (pore diameter >1 200 μm) and air void spacing factor are increased by 1.5%-7.3% and 51%-92%, respectively. The deterioration of pore structure results in a 3%-9% reduction in the compressive strength of concrete. From the results we have obtained, it can be concluded that the increase of critical nucleation energy of air bubbles and the decrease of volumetric compressibility coefficient of air in the concrete are responsible for the variation of air content and pore structure of concrete under LAP.

Centrifuge testing to investigate effects of partial saturation on the response of shallow foundation in liquefiable ground under strong sequential ground motions

Induced partial saturation is one of the novel techniques to increase the liquefaction resistance of saturated sandy ground. Nonetheless, a limited number of experimental studies are available on the delineation of this method. Moreover, the performance of induced partial saturation under sequential ground motions is poorly understood. Dynamic centrifuge experiments are carried out to investigate the effects of partial saturation on the response of shallow foundation resting on liquefiable ground under sequential ground motions. Centrifuge models consist of two distinct shallow foundations and associated superstructures resting on a liquefiable uniform sand layer. The drainage-recharge method is used to induce partial saturation in the model ground. Compressibility change of pore fluid and alteration of ground permeability because of induced air voids, affect the deformation mechanism of the ground-foundation system. Assessment of maximum potential volumetric compressibility of pore fluid because of induced air voids is essential to understand the effectiveness of induced partial saturation. Centrifuge test results signify that the induced partial saturation reduces the overall deformation of the foundation-structure system. However, slightly amplified kinematic seismic demand is observed at superstructures in case of partially saturated ground in comparison with fully saturated ground.

Investigation of the Thermodynamic Properties in Aqueous Solutions Containing d-Fructose and Some Imidazolium-Based Ionic Liquids at Different Temperatures

To investigate the interactions present in aqueous {d-fructose + ionic liquids 1-butyl-3-methylimidazolium bromide or 1-octyl-3-methylimidazolium bromide or 1-octyl-3-methylimidazolium chloride} solutions, volumetric compressibility and viscometric properties of these systems have been studied at temperatures T = 288.15–318.15 K and atmospheric pressure. The positive and increasing values of transfer volume and transfer partial molar isentropic compression with increasing ionic liquid concentration indicated predominance of ionic–hydrophilic interactions in these systems. The calculated hydration number showed dehydration of fructose in the presence of studied ionic liquids. Further, the interaction and cavity volumes were computed using the scaled particle theory.

Mechanical behavior of low-rank bituminous coal under compression: An experimental and numerical study

The mechanical behavior of coal has an important influence on coal reservoir stimulation and the dynamic change of coal reservoir permeability during coalbed methane (CBM) production. Generally, coal is regarded as an elastic-brittle material, which is reasonable when the surrounding stress is small. However, with the increasing depth of CBM exploitation, the in-situ stress increases continuously, so the coal will inevitably show some plastic behavior. In this work, the typical low-rank bituminous coal from the Baode CBM block on the eastern margin of the Ordos Basin was selected to carry out uniaxial and triaxial compression tests under various confining pressures (Pc) for further investigation of mechanical behavior. The results show that, as a complex porous material, the coal samples have a series of deformation responses during the loading process, which can be classified into four phases. Both the yield stress (σy) and the peak stress (σpeak) increase nonlinearly as Pc increases. Additionally, with increasing Pc, the elastic modulus (E) increases at a decreasing rate, while the Poisson's ratio (ν) decreases at a decreasing rate. Moreover, a change from volumetric compressibility to dilatancy in the coal was clearly observed in the tests, and the stress at the onset of dilation (σd) is also significantly influenced by Pc. Finally, based on irreversible thermodynamics and empirical support, a coupled elastoplastic damage constitutive model for low-rank bituminous coal was established by introducing the non-associated plastic flow laws and the damage evolution rules; the numerical simulation result of the model is in good agreement with the experimental measurements. This model can be used for further investigation of the mechanical properties of coal reservoirs under different in-situ stress conditions during the exploitation of CBM.

Compressibility of arterial wall – Direct measurement and predictions of compressible constitutive models

Volumetric compressibility and Poisson's ratios of fibrous soft tissues are analyzed in this paper on the basis of constitutive models and experimental data. The paper extends the previous work of Skacel and Bursa (J Mech Behav Biomed Mater, 54, pp. 316–327, 2016), dealing with incompressible behaviour of constitutive models, to the area of compressibility. Both recent approaches to structure-based constitutive modelling of anisotropic fibrous biomaterials (based on either generalized structure tensor or angular integration) are analyzed, including their compressibility-related aspects. New experimental data related to compressibility of porcine arterial layer are presented and compared with the theoretical predictions of analyzed constitutive models. The paper points out the drawbacks of recent models with distributed fibres orientation since none of the analyzed constitutive models seems to be capable to predict the experimentally observed Poisson's ratios and volume change satisfactory.

Mechanical properties and associated seismic isolation effects of foamed concrete layer in rock tunnel

Foamed concrete has a good energy absorption capability and can be used as seismic isolation material for tunnels. This study aims to investigate the mechanical properties and associated seismic isolation effects of foamed concrete layer in rock tunnel. For this, a series of uniaxial/triaxial compression tests was conducted to understand the effects of concrete density, confining stress and strain rate on the mechanical properties of foamed concrete. The direct shear tests were also performed to investigate the effects of concrete density and normal stress on the nonlinear behaviors of foamed concrete layer-lining interface. The test results showed that the mechanical properties of foamed concrete are significantly influenced by the concrete density. The foamed concrete also has high volumetric compressibility and strain-rate dependence. The peak stress, residual stress, shear stiffness and residual friction coefficient of the foamed concrete layer-lining interface are influenced by the foamed concrete density and normal stress applied. Then, a crushable foam constitutive model was constructed using ABAQUS software and a composite exponential model was also established to study the relationship between shear stress and shear displacement of the interface, in which their parameters were fitted based on the experimental results. Finally, a parametric analysis using the finite element method (FEM) was conducted to understand the influence of foamed concrete layer properties on the seismic isolation effect, including the density and thickness of the layer as well as the shear stiffness and residual friction coefficient of the interface. It was revealed that lower density and greater thickness in addition to smaller shear stiffness or residual friction coefficient of the foamed concrete layer could yield better seismic isolation effect, and the influences of the first two tend to be more significant.

Generalized Liquid-Based Damping Device for Passive Vibration Control

This paper presents a liquid-based device with fluid-induced damping, stiffness, and inertia effects. The proposed concept is modeled and experimentally studied. A lumped parameter fluid dynamics approach is used to model the flow-induced energy dissipation, inertia, and volumetric compressibility. It is shown that the developed five-state nonlinear dynamic model can be modified to represent a range of previously established models. A reference set of model parameters is determined from the calibration data obtained from a novel device demonstrator. The model’s functional and parametric changes are shown to enable the device specializations, which can approximate simpler as well as ideal devices such as dampers, springs, and inerters. This work also demonstrates that the interaction between all three principal fluid effects opens routes to dynamic device tuning and frequency-selective damping.

Evaluating 2D numerical simulations of granular columns in level and gently sloping liquefiable sites using centrifuge experiments

The response of a layered liquefiable soil profile, with granular columns as a mitigation strategy, was evaluated via numerical and centrifuge modeling. Comparisons were made for a level site containing a single granular column and for a pair of gentle slopes, one of which was mitigated with a network of dense granular columns. The results reveal the abilities and limitations of two state-of-the-art soil constitutive models. All simulations were performed in 2-dimensions using: 1) the pressure-dependent, multi-yield-surface, plasticity-based soil constitutive model (PDMY02); and 2) the bounding surface, plasticity-based, Manzari-Dafalias (M-D) soil constitutive model, both implemented in OpenSees. Numerical model parameters were previously calibrated via element testing. Both constitutive models under-predicted PGA near the surface at different distances from the granular column, but they better predicted spectral accelerations at periods exceeding 0.5 s (particularly M-D). The M-D model generally predicted seismic settlements well, while PDMY02 notably underestimated soil's volumetric compressibility and strains. Both models accurately predicted the peak value and generation of excess pore pressures during shaking for the unmitigated slope, leading to a successful prediction of lateral deformations. However, lateral movement of the treated slope was poorly predicted by both models due to inaccuracies in predicting the dissipation rate in the presence of drains. Both models came close to predicting the performance of gently sloping, liquefiable sites when untreated. But further advances are required to better predict the rate of excess pore pressure dissipation and seismic performance when the slope is treated with granular columns.

Force Field Benchmark of the TraPPE_UA for Polar Liquids: Density, Heat of Vaporization, Dielectric Constant, Surface Tension, Volumetric Expansion Coefficient, and Isothermal Compressibility.

The transferable potential for a phase equilibria force field in its united-atom version, TraPPE_UA, is evaluated for 41 polar liquids that include alcohols, thiols, ethers, sulfides, aldehydes, ketones, and esters to determine its ability to reproduce experimental properties that were not included in the parametrization procedure. The intermolecular force field parameters for pure components were fit to reproduce experimental boiling temperature, vapor-liquid coexisting densities, and critical point (temperature, density, and pressure) using Monte Carlo simulations in different ensembles. The properties calculated in this work are liquid density, heat of vaporization, dielectric constant, surface tension, volumetric expansion coefficient, and isothermal compressibility. Molecular dynamics simulations were performed in the gas and liquid phases, and also at the liquid-vapor interface. We found that relative error between calculated and experimental data is 1.2% for density, 6% for heat of vaporization, and 6.2% for surface tension, in good agreement with the experimental data. The dielectric constant is systematically underestimated, and the relative error is 37%. Evaluating the performance of the force field to reproduce the volumetric expansion coefficient and isothermal compressibility requires more experimental data.

Sensitivity Study of Input Parameters for Seepage Flow Simulations using Parallel Computers

This paper describes a comprehensive sensitivity study that was performed using high performance parallel computers to understand the importance of input parameters to a transient partially saturated finite element seepage analysis for a levee with separate soil layers of sand, silty sand, and clay. Seepage flow in this paper refers to the type of flow of water that occurred through the failed levees in New Orleans, Louisiana, USA, as a result of Hurricane Katrina. The input parameters tested were saturated hydraulic conductivity, volumetric compressibility, residual moisture content, saturated moisture content, and two van Genuchten unsaturated flow parameters. The output data compiled to show the sensitivity of the input parameters were the simulation times (days) to achieve 25%, 50%, and 75% of the steady-state values of pore pressure at the toe of the levee beneath its blanket, flow rate through the landside flux section, and the level of saturation in the levee. The use of high performance parallel computers enabled the running of thousands of scenarios using different values for the input variables. A sensitivity investigation of this magnitude has not been previously performed. The results of this investigation indicated that the more sensitive soil parameters were the saturated hydraulic conductivity and the volumetric compressibility. The unsaturated van Genuchten parameters of the landside blanket had a larger than anticipated impact on the duration of time to achieve steady state. This practical example is an excellent success story for high performance computing in that running a given simulation for a couple of hours on thousands of processors in parallel replaced over a year work using a PC.

Application of high resolution geophysical prospecting to assess the risk related to subsurface deformationin Mexico City

Abstract. In the eastern sector of Mexico City the sub soil consists of high contrasting sequences (lacustrine and volcanic inter bedded deposits) that favor the development of erratic fracturing in the surface causing damage to the urban infrastructure. The high-resolution geophysical prospecting are useful tools for the assessment of ground deformation and fracturing associated with land subsidence phenomena. The GPR method allowed to evaluate the fracture propagation and deformation of vulcano-sedimentary sequences at different depths, the main electrical parameters are directly related with the gravimetric and volumetric water content and therefore with the plasticity of the near surface prospected sequences. The active seismology prospection consisted in a combination of Seismic Refraction (SR) and Multichannel Analysis of Surface Waves (MASW) for the estimation of the velocity of the mechanical compressive (P) and the shear (S) waves. The integration of both methods allowed to estimate the geomechanical parameters characterizing the studied sequence, the Poisson Ratio and the volumetric compressibility. The obtained mechanical parameters were correlated with laboratory measured parameters such as plasticity index, density, shear strength and compressibility and, GPR and seismic profiles were correlated with the mapped fracture systems in the study area. Once calibrated, the profiles allowed to identify the lithological contact between lacustrine and volcanic sequences, their variations of thicknesses in depth and to assess the deformation area in the surface. An accurate determination of the geometry of fracturing was of the most importance for the assessment of the geological risk in the study area.

Poisson׳s ratio of arterial wall – Inconsistency of constitutive models with experimental data

Poisson׳s ratio of fibrous soft tissues is analyzed in this paper on the basis of constitutive models and experimental data. Three different up-to-date constitutive models accounting for the dispersion of fibre orientations are analyzed. Their predictions of the anisotropic Poisson׳s ratios are investigated under finite strain conditions together with the effects of specific orientation distribution functions and of other parameters. The applied constitutive models predict the tendency to lower (or even negative) out-of-plane Poisson׳s ratio. New experimental data of porcine arterial layer under uniaxial tension in orthogonal directions are also presented and compared with the theoretical predictions and other literature data. The results point out the typical features of recent constitutive models with fibres concentrated in circumferential–axial plane of arterial layers and their potential inconsistence with some experimental data. The volumetric (in)compressibility of arterial tissues is also discussed as an eventual and significant factor influencing this inconsistency.

Numerical and Centrifuge Modeling of Seismic Soil–Foundation–Structure Interaction on Liquefiable Ground

AbstractThe effective mitigation of the liquefaction hazard requires an improved understanding of the consequences of liquefaction in terms of ground shaking, permanent displacement, and building performance. In this paper, results from centrifuge experiments of a shallow-founded structure on liquefiable sand are used to evaluate the predictive capabilities of a state-of-the-art numerical tool. Solid-fluid, fully-coupled 3D nonlinear numerical simulations were performed using the PDMY02 soil model implemented in a software modeling domain. The numerical model captured excess pore pressures and accelerations well in the free-field, but largely underestimated volumetric settlements due to loss of water during shaking. This was associated with the drastic increase in soil hydraulic conductivity when approaching liquefaction, which was not taken into account numerically, as well as the underestimation of soil volumetric compressibility. The contribution of volumetric strains to total building settlement was, ...

Experimental and Numerical Investigations on Strength and Deformation Behavior of Cataclastic Sandstone

This work is devoted to characterization of the deformation and strength properties of cataclastic sandstones. Before conducting mechanical tests, the physical properties were first examined. These sandstones are characterized by a loose damaged microstructure and poorly cemented contacts. Then, a series of mechanical tests including hydrostatic, uniaxial, and triaxial compression tests were performed to study the mechanical strength and deformation of the sandstones. The results obtained show nonlinear stress–strain responses. The initial microcracks are closed at hydrostatic stress of 2.6 MPa, and the uniaxial compressive strength is about 0.98 MPa. Under triaxial compression, there is a clear transition from volumetric compressibility to dilatancy and a strong dependency on confining pressure. Based on the experimental evidence, an elastoplastic model is proposed using a linear yield function and a nonassociated plastic potential. There is good agreement between numerical results and experimental data.

Cam Clay–Coupled Consolidation Analysis of Field Instrumented Preloading Program

AbstractA surcharge preloading program for an 8-story hotel building at Philadelphia International Airport in Pennsylvania provided an opportunity to examine the merits of coupled consolidation analysis. Close agreement between the measured and predicted responses in pore pressures, settlement magnitude, and rate are attributed to the use of the modified cam clay model for soft Delaware River organic silt. A conventional consolidation analysis utilizes single volumetric compressibility and permeability coefficients rather than ones which vary with the actual stress level as demonstrated by consolidation testing. This results in an appreciable divergence from the measured values. The modified cam clay model clearly captures the actual nonlinear stress-strain behavior of the soft, organic silt layer.

Experimental study of poromechanical behavior of saturated claystone under triaxial compression

This paper presents experimental results of drained and undrained triaxial compression tests of saturated Meuse–Haute/Marne claystone. The emphasis is to study the evolution of pore pressure with growth of microcracks and the effect of pore pressure on mechanical behavior. Basic mechanical responses are first investigated through drained triaxial compression tests, showing nonlinear stress strain relations, volumetric dilatancy and pressure sensitivity. In undrained triaxial compression tests, the pore pressure exhibits a transition from increase to decrease due to the transition from volumetric compressibility to dilatancy caused by the growth of microcracks. The failure surfaces, determined by total stress and Terzaghi’s effective stress under undrained condition, are compared with the one under drained condition.

석션드레인공법을 적용한 연약지반의 침하 특성

기존 성토재하 방식의 연약지반 개량공법에서 제기된 여러 가지 문제에 의해 진공압 재하방식의 개량공법이 개발되었으며, 국내 적용사례가 증가하고 있다. 현장에서의 침하관리시 동일한 하중을 재하하였을 경우의 진공압재하공법과 성토재하공법에 대한 침하량 비교 연구가 진행되어 왔다. 본 연구에서는 두 공법의 발생침하량에 관한 이론 및 사례 연구를 수행하였다. 그 결과 연약지반 개량을 위해 진공압이 적용되면 내향의 수평변위가 발생하고 동일한 하중재하 대비 침하량이 감소하였다. Hooke의 탄성이론을 바탕으로 한 경우 0.54~0.67, 국내 설계기준에서는 0.50~0.75, 과거 국내 시공사례를 바탕으로 한 경우 0.91, 실내시험을 바탕으로 한 경우 0.81, 탄성론과 체적압축계수법을 바탕으로 한 경우 0.75, 최근 국내 대심도 시공 사례의 경우 0.77~0.93의 범위를 보이는 것으로 나타났다. A vacuum pressure method has been developed to solve many problems in the conventional surcharge method such as embankments, and its application has increased in the country. Recently, to control target settlements in the field, there have been many studies on the comparison of settlements between vacuum pressure method and surcharge load method in the same conditions. In this study, the settlement characteristics of soil subjected to vacuum pressure and surcharge pressure are discussed. The results indicate that if vacuum pressure is applied to the improvement of soft ground, there will be inward lateral displacement and the vacuum pressure will induce generally less settlement than a surcharge load of the same magnitude. The range of settlement reduction ratio is 0.54~0.67 based on Hooke's law, 0.91 based on field cases, 0.81 based on laboratory oedometer tests, 0.75 based on the theory of elasticity and coefficient of volumetric compressibility and 0.77~0.93 in its recent applications to the thick soft ground.

Effect of carbide powder characteristics on the PVT behavior of powder injection molding compounds

Effect of powder concentration and particle size distribution of highly filled cemented carbide compounds on their pressure–volume–temperature (PVT) characteristics and thermal properties was investigated. PVT data of compounds containing up to 50 vol.% of powder evaluated on a high-pressure mercury dilatometer reveals that the pressure influences both detected phase transitions, but it causes a different effect on the melting and crystallization of the material only for the higher transition (corresponding to binder components with melting temperatures 100 and 107 °C). The discrepancies in specific volumes at an applied pressure diminish with increasing powder content, whereas melting temperatures – derived from differential scanning calorimetry – remain unaffected. Volumetric thermal expansion coefficient and compressibility are linearly and exponentially, respectively, dependent on pressure. Further, the variance in the particle size distributions of carbide compounds resulted in shifts in both volumetric thermal expansion coefficients and compressibility values.