Influence Of Void Ratio Research Articles

Numerical simulation of rainfall-induced deformations of embankments considering the coupled hydro-mechanical behavior of unsaturated soils

This paper presents numerical simulations of the deformation response of unsaturated embankments subjected to rainfall infiltration using a coupled hydro-mechanical constitutive model for unsaturated soils. The constitutive model accounts for the influence of degree of saturation on the stress–strain behavior and the influence of void ratio on the water retention behavior. The constitutive model was implemented in the finite difference program FLAC, calibrated using triaxial test data, and validated using measurements of wetting-induced deformations of embankment models from centrifuge tests. The validation demonstrates that the constitutive model can capture the coupled hydro-mechanical behavior of unsaturated soils under wetting conditions. Simulations of the hydro-mechanical response of unsaturated embankments subjected to rainfall infiltration indicate that the differential settlement across the top surface of the embankment between the centerline and shoulder increases significantly during rainfall infiltration, which could result in severe damage to overlying transportation infrastructure. As the rainfall infiltration increases, shear strains accumulate and form a potential failure surface at a shallow depth of approximately 2 m from the slope surface. Insights into the hydro-mechanical response of unsaturated embankments subjected to rainfall infiltration gained will be useful for considering climate change effects in design and construction of compacted embankments.

A model predicting mechanical properties of asphalt mixtures considering void ratio and loading conditions

The void ratio is an essential parameter in asphalt mixture design, which significantly affects asphalt mixtures' mechanical properties and road performance. The prediction model for mechanical properties will be established based on the Computed tomography (CT) scanning, strength, and fatigue test results in this research to reveal the relationship between the asphalt mixtures' mechanical properties and void ratio. Firstly, the voids' transverse and longitudinal distribution characteristics in asphalt mixtures of different gradations were investigated based on CT scanning. Then, the influences of void ratio, loading rates on the strength, and the impacts of void ratio and stress levels on the fatigue life were investigated by conducting indirect tensile tests. Finally, the mechanical properties prediction model was established for void ratio and loading conditions. Further, the feasibility of the model is verified in conjunction with existing research results. The results show that the void ratio calculated based on CT scanning is about 1.15 times the measured void ratio in the water weight method. The number of voids was uniformly distributed in the range of 15 mm∼50 mm in height and 10 mm∼40 mm in radius of the specimen. The asphalt mixtures' strength decreases with increasing void ratio and increases with increasing loading rate. The asphalt mixtures' fatigue life declines with increasing void ratio and stress level. The correlation coefficients of the established strength and fatigue prediction models were 0.963 and 0.976, respectively. The relative error between the measured strength, fatigue life, and predicted results is about 10.75% and 11.27%, respectively. This research provides a basis for designing high-performance asphalt mixtures by establishing the relationship between asphalt mixtures' microscopic and mechanical characteristics.

Study of Noise Reduction and Sound Absorption Performance of Drainage Asphalt Pavement Based on Indoor Tire Accelerated Falling Method

In order to study the noise reduction and sound absorption performance of drainage asphalt pavement and porous asphalt concrete (PAC) and the difference of noise reduction and sound absorption effects of conventional AC pavement, single-layer and double-layer PAC pavements are compared and analyzed by improving the indoor noise test of tire accelerated falling method, and then the sound absorption coefficient of single-layer and double-layer PAC pavement is further tested using the standing wave tube method. Based on the standing wave interference principle of sound, the sound absorption characteristics of drainage asphalt pavement are described, the influence of void ratio on the sound absorption coefficient of PAC pavement is analyzed, and the data model between the void parameters and sound absorption coefficient is established. The results show that: (1) using the improved indoor tire accelerated falling method and using the sound level meter to measure the A-weighted sound pressure level and 1/3 octave frequency spectrum of noise under three distance conditions, the noise value of drainage asphalt pavement is 2 to 5 dB(A) lower than that of traditional AC pavement, and the noise reduction ability decreases with the increase of distance from the sound source and increases with the increase of void ratio. The sound absorption coefficient curve of drainage asphalt pavement is measured using the standing wave tube double transfer function method. The average sound absorption coefficient of PAC specimens decreases with the decrease of the void fraction. (2) The sound absorption coefficient curve of single-layer PAC pavement presents a “single peak type”. The sound absorption peak frequencies of a single layer 4 cm-thick PAC pavement and 10 cm-thick PAC pavement are around 1100 Hz and 800 Hz respectively. The corresponding frequencies of the sound absorption peaks of the two specimens are within the common frequency range of traffic noise, which is helpful to alleviate traffic noise. (3) Through CT scanning and three-dimensional reconstruction software, the void parameters of the PAC specimen are obtained, and the sound absorption coefficient prediction model is established. The sound absorption coefficient calculated by the model has a high correlation with the measured value of standing wave tube method, which verifies the accuracy of the sound absorption coefficient model in predicting the sound absorption characteristics of drainage asphalt pavement.

Construction and Programming of Bivariate Model for Unsaturated Soil Seepage Calculation

The seepage calculation of unsaturated soil has always been an important subject in the field of geotechnical engineering, and it greatly influences the stability of geotechnical engineering. Currently, most of the unsaturated soil seepage calculation formulas consider only the saturation. In fact, the seepage of the soil is also affected by other factors, such as pore size. Therefore, considering the influence of void ratio in the seepage calculation of unsaturated soil is worthy of further investigation. In this study, a seepage function of unsaturated soil, which considers the influence of dry density and saturation, was constructed and introduced into ABAQUS program. An engineering case was calculated, and the difference between the results considering two variables and that only considering saturation was compared and analyzed. The analysis of the results indicates that this function can better characterize unsaturated seepage, and its subprogram is applicable.

Modeling unimodal/bimodal soil-water retention curves considering the influence of void ratio under capillarity and adsorption

Modeling unimodal/bimodal soil-water retention curves considering the influence of void ratio under capillarity and adsorption

Sample preparation of dense granular materials Influence of void ratio e and coordination number Z* on the mechanical behaviour at failure

This paper presents a Discrete Element Method (DEM) study of assemblies of 5041 frictional discs, with periodic boundary conditions and confined by an external isotropic load. In order to generate samples with different internal state variables like the void ratio and coordination number, we present two different numerical procedures. The first technique, which has been widely used in the literature for many years, consists in controlling the coefficient of friction between particles to adjust the density of the samples, which directly influences the coordination number. The second technique is inspired by the previous one but adds an extra step of dynamic mixing with intergranular contacts lubrication. This makes it possible to control quasi independently the void ratio and the coordination number in the case of dense samples. These two types of samples are subjected to simple shear to analyse the influence of the sample preparation procedure on their macroscopic mechanical behaviour.

The Effect of Structural and Process Parameters on the Effective Properties of Polymer Composites Reinforced by Fiber-rod and Three-dimensional Weaving

Weaving structure and manufacturing characteristics have close relationships with the mechanical properties of polymer composite reinforced by fiber-rod and three-dimensional (3D) weaving (PCFR3DWs). The Eshelby-Mori-Tanaka inclusion theory and the stiffness volume average method are proposed herein to predict the effective properties of PCFR3DWs. The elastic properties of compound weaving composites (CWCs) and unidirectional weaving laminate composites (UWLCs) of PCFR3DWs were thereby calculated. The effect of the fiber-rod array interval (D) and fiber-rod diameter (d) on the elastic properties of PCFR3DW UWLCs and CWCs were investigated and discussed. Furthermore, considering the characteristics of manufacturing process, the influences of yarn packing factor and void ratio on the stiffness properties of CWC were studied as well. Experiments and finite element analysis (FEA) validated the calculation model, with good agreement between the experimental, FEA and calculation results. The D greatly affected some of the elastic constants of the PCFR3DWs, while d had little effect on the elastic constants other than the longitudinal Young’s modulus. The yarn packing factor had significantly effect on the stiffness properties of the composites, while the influence of the void ratio was negligible. Moreover, the fracture mechanism of PCFR3DW was evaluated based on the experimental test result. This work will facilitate the design of PCFR3DWs by providing insight into the relationships between the various stiffness properties, weaving structure, geometric parameters and procedure parameters of the components that affect macroscale performance.

Pengaruh Void Ratio dan Permeabilitas Beton Terhadap Kuat Tekan Beton Porous Dengan RCA

The infrastructure development raises the potential of old building destruction and demolition. This fact will results an environmental damage if construction waste is not being properly utilized. One type of construction waste that can be utilized is concrete waste. To apply sustainable development, concrete waste can be reused and recycled into aggregate in the form of RCA (Recycled Coarse Aggregate). Natural Coarse Aggregates (NCA) and RCA are processed into 0.5-1 cm, 1-2 cm, and 0.5-2 cm sizes and later mixed with cement paste into porous or pervious concrete. Porous concrete is a non-structural concrete which is water-permeable and has large pores. This study aims to determine the effect of RCA on the velue of concrete compressive strength, the most optimal concrete variation, and the influence of void ratio and permeability to the compressive strength of porous concrete. The result reported that RCA affects the compressive strength,, it can be proven that any variation of aggregate size, concrete variation with 0% RCA has the higher value than the 100% RCA one. The optimum concrete condition is in variation of 50% RCA at aggregate size 0.5-2 cm. The compressive strength value is 10.211 MPa. This is due to the more diverse aggregates affecting the concrete density. The larger the pores of the concrete (void ratio), the permeability value will be higher and the higher void ratio and permeability of concrete, the value of the compressive strength of porous concrete will be lower.

Influence of void ratio on phase change of thermal energy storage for heat pipe receiver

In this paper, influence of void ratio on phase change of thermal storage unit for heat pipe receiver under microgravity is numerically simulated. Accordingly, mathematical model is set up. Numerical method is offered. The liquid fraction distribution of thermal storage unit of heat pipe receiver is shown. Numerical results are compared with experimental ones in Japan. Numerical results show that void cavity prevents the process of phase change greatly. PCMmelts slowly during sunlight periods and freezes slowly during eclipse periods as the void ratio increases. The utility ratio of PCM during both sunlight periods and eclipse periods decreases obviously as the void ratio increases. The thermal resistance of void cavity is much higher than that of PCMcanister wall. Void cavity prevents the heat transfer between PCM zone and canister wall.

Hydraulic and Mechanical Behavior of Unsaturated Silt: Experimental and Theoretical Characterization

AbstractA series of experiments were performed to investigate the hydraulic and κk(Sr)=bk(1−SrSr−Srirr)1/dk, R=DR, WTmechanical behavior of an unsaturated silt obtained from the Yellow River Delta. To identify the key factors that influence the soil-water characteristics (SWC), an experimental program was designed to study the SWC of the soil at different void ratios and vertical pressures. It was shown that an that that apparent hysteresis phenomenon occurred on the SWC curves when the soil experienced drying/wetting cycles. It was also shown that the influence of void ratio on the SWC was significant, and the stress state influenced the SWC only through changing the void ratio. Isotropic compression tests were conducted at different constant matric suctions, using a suction-controlled double cell triaxial apparatus. The soil under shearing showed apparent dilatant and softening behavior, in a way similar to medium to dense sand. In addition, the hardening effect of matric suction was significant, and bo...

Influence of void ratio on thermal stress of PCM canister for heat pipe receiver

Influence of void ratio on thermal stress of PCM (phase change material) canister for heat pipe receiver under microgravity is numerically simulated. LiFCaF2 (80.5–19.5 mol%, melting point: 763 °C) PCM is used as a latent thermal energy storage medium for its high latent heats of fusion. Accordingly, mathematical model and numerical method are offered. A judgment for convergence is accomplished. Numerical results show that the thermal stress in PCM canister increases as void ratio increases. Void cavity prevents the heat transfer between canister wall and PCM zone during both sunlight and eclipse periods. The temperature gradient is very significant when void ratio reaches the maximum. So the lifetime of heat pipe receiver may decrease as void ratio increases. The corresponding maximum thermal stress of different void ratios during eclipse periods is lower than that during sunlight periods. If the designed material of PCM canister can satisfy the strength during sunlight periods, it must be safe and reliable during eclipse periods and the necessary overall performance can be maintained. The research results can be used to guide designing the PCM canister for heat pipe receiver.

Influence of Void Ratio on Phase Change in Thermal Storage Canister of Heat Pipe Receiver

In this paper, with both void cavity and phase change considered, influence of void ratio on phase change in thermal storage canister of heat pipe receiver under microgravity is numerically simulated. Accordingly, physical and mathematical models are built. A solidification–melting model upon the enthalpy–porosity method is specially provided to deal with phase changes. The change of liquid fraction with respect to void ratio and the liquid fraction distribution of different void ratios in a thermal storage canister of a heat pipe receiver are shown. Numerical results are compared with experimental ones. Research results indicate that the void cavity prevents the process of phase change significantly. Phase-change material (PCM) melts slowly during sunlight periods and freezes slowly during eclipse periods as void ratio increases. The utility ratio of PCM during both sunlight periods and eclipse periods decreases obviously as the void ratio increases. The void cavity prevents the heat transfer between the PCM zone and canister wall. The void cavity blocks the processes of both melting and solidification during cycle orbital periods.

Influence of void ratio on phase change of thermal energy storage for heat pipe receiver

In this paper, influence of void ratio on phase change of thermal storage unit for heat pipe receiver under microgravity is numerically simulated. Accordingly, mathematical model is set up. A solidification-melting model upon the enthalpy-porosity method is specially provided to deal with phase changes. The liquid fraction distribution of thermal storage unit of heat pipe receiver is shown. The fluctuation of melting ratio in PCM canister is indicated. Numerical results are compared with experimental ones in Japan. The results show that void cavity prevents the process of phase change greatly. PCM melts slowly during sunlight periods and freezes slowly during eclipse periods as void ratio increases. The utility ratio of PCM during both sunlight periods and eclipse periods decreases obviously with the improvement of void ratio. The thermal resistance of void cavity is much higher than that of PCM canister wall. Void cavity prevents the heat transfer between PCM zone and canister wall.

Influence of Parameters of Insulation Layer on Performance of Vacuum Heat Insulation Oil Pipe

Influences of void ratio of glass fiber cloth, conductivity of glass fiber cloth, number of of insulation layer and emissivity of aluminium foil on apparent heat conductivity of vacuum heat insulation oil pipe are calculated based on the experiment plat in master machinery plant of Liaohe Petroleum Exploration Bureau. The results show that apparent heat conductivity of vacuum heat insulation oil pipe is inverse ratio to void ratio of glass fiber cloth, and is proportional to conductivity of glass fiber cloth and emissivity of aluminium foil. At vacuum condition, 6 layers is appropriate.

Influence of void ratio on thermal performance of heat pipe receiver

In this paper, influence of void ratio on thermal performance of heat pipe receiver under microgravity is numerically simulated. Accordingly, mathematical model is set up. Numerical method is offered. The temperature field of Phase Change Material (PCM) canister is shown. Numerical results are compared with numerical ones of National Aeronautics and Space Administration (NASA). Numerical results show that the temperature gradient increases significantly and the utility ratio of PCM decreases obviously as void ratio increases. Void cavity influences the process of phase change greatly. PCM melts slowly during sunlight periods and freezes slowly during eclipse periods as void ratio increases. The thermal resistance of void cavity is much bigger than that of PCM canister wall. Void cavity prevents the heat transfer between PCM zone and canister wall. The temperature gradient of PCM zone is very significant with the effect of void cavity. So the thermal stress of heat pipe receiver may increase, and the lifetime may decrease as void ratio increases.

An experimental study on the hazard assessment and mechanical properties of porous concrete utilizing coal bottom ash coarse aggregate in Korea

This study evaluates quality properties and toxicity of coal bottom ash coarse aggregate and analyzes mechanical properties of porous concrete depending on mixing rates of coal bottom ash. As a result, soundness and resistance to abrasion of coal bottom ash coarse aggregate were satisfied according to the standard of coarse aggregate for concrete. To satisfy the standard pertaining to chloride content, the coarse aggregates have to be washed more than twice. In regards to the result of leaching test for coal bottom ash coarse aggregate and porous concrete produced with these coarse aggregates, it was satisfied with the environment criteria. As the mixing rate of coal bottom ash increased, influence of void ratio and permeability coefficient was very little, but compressive and flexural strength decreased. When coal bottom ash was mixed over 40%, strength decreased sharply (compressive strength: by 11.7–27.1%, flexural strength: by maximum 26.4%). Also, as the mixing rate of coal bottom ash increased, it was confirmed that test specimens were destroyed by aggregate fracture more than binder fracture and interface fracture. To utilize coal bottom ash in large quantities, it is thought that an improvement method in regards to strength has to be discussed such as incorporation of reinforcing materials and improvement of aggregate hardness.

Mechanical Properties of Municipal Solid Waste

Abstract This paper deals with the compressibility and shear strength of Municipal Solid Waste (MSW) as measured in the laboratory. The waste studied was recovered from Bandeirantes Sanitary Landfill (São Paulo, Brazil) and is about 15 years old. More than 50 % by weight of MSW is organic paste and as much as 17 % is plastic and other strip materials. Consolidation and drained and undrained triaxial compression tests were performed in reconstituted waste specimens of large dimensions and with different unit weights considering both saturated specimens and specimens tested at natural moisture content. It is shown that the MSW exhibits a pronounced secondary compression; the influence of void ratio and stress on secondary compression index is discussed and compared with available data from MSW and soft soils. Typical stress-strain curves are presented and some peculiarities are shown, as the absence of failure even at large strains, up to 30 %, implies the need of deriving shear strength envelopes based on strain. The influence of saturation and of unit weight on shear strength is also addressed as well as the shear strength mobilization that shows that the friction tends to be fully mobilized at strains of about 20 %, while the cohesion intercept starts to be mobilized at strains of 10% and even more and a limiting value could not be observed in the strain range attained in the tests. The development of pore water pressures in the undrained tests and the variation of undrained shear strength with effective confining pressure are also addressed.

Reply to the discussion by A. Eliadorani and Y.P. Vaid on "Effect of undrained creep on instability behaviour of loose sand"

The discussers stated that the definition used in the note is “misleading.” According to the Oxford Advanced Learner’s Dictionary, the word “misleading” means “giving the wrong idea or impression and make them believe something that is not true.” The definition of instability is clearly defined and used consistently in the note. Therefore, we fail to see in which way it is “misleading.” If the discussers’ disagreement is on the term “undrained creep” or whether the instability should be called creep induced instability, we have explained in the note that the same term has been used and similar behaviour has been studied by Arulanandan et al. (1971) and Sheahan (1995) before for other types of soil. The discussers also stated “drained perturbation will not cause instability” and “there is only one instability line.” This may not be generally true, as it has been observed by a number of researchers (Eckersley 1990; Sasitharan et al. 1993; Chu et al. 2000, 2003b) that instability can occur under drained conditions and the instability line is not unique, but affected by many factors (Imam et al. 2002; Yang 2002). Creep is one of the factors and is studied in this note. The influence of void ratio on the instability line is also illustrated in Fig. 3 of the discussed note.

Modeling on coupled heat and moisture transfer in freezing soil using mixture theory

A set of perfect constitutive equations including the coupling effects of heat transfer and moisture migration is constructed for freezing soil, after analyzing its thermomechanic properties, in the framework of continuum mechanics and mixture theory. By applying the theory, the influence of void ratio on frost heaving is studied after proposing a criterion for formation of layered ice; the results obtained coincide with experimental data available in the literature. The temperature distribution of freezing soil is analyzed, the controlling equation deduced appears to be a nonlinear Burgers type equation with varying boundaries, which presents a theoretic foundation for studying the nonlinear effects of heat-moisture migration in the freezing process.