scholarly journals Modeling of Minimum and Maximum Void Ratios of Granular Soils

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Xiaoxu Qian ◽  
Xin Liu ◽  
Zhiwei Shao ◽  
Yunqiang Shi ◽  
Siqing Zhang ◽  
...  
Keyword(s):  
Size Distribution ◽  
Analytical Methods ◽  
Void Ratio ◽  
Experimental Tests ◽  
Experimental Results ◽  
Granular Soils ◽  
Soil Permeability ◽  
Empirical Relationships

Determining the maximum and minimum void ratios of granular soils is very important because it can be correlated with engineering behaviors such as soil permeability. Empirical relationships can be used for determining the void ratio, but they have many limitations related to the shape and the size distribution of the grains. Analytical methods improve the empirical relationships. In this paper, we present enhancements to the model of Chang et al. by combining the model of Youd et al., as Chang–Youd models, to make it more convenient and also to extend its usage to be suitable for determining the maximum void ratio. The Chang–Youd models are verified with experimental tests performed by the authors. Compared with the experimental results in the literature, the Chang–Youd models are also effective but more convenient and practical.

Characterization of dual-structure pore-size distribution of soil

2009 ◽  
Vol 46 (2) ◽  
pp. 129-141 ◽  
Author(s):  
X. Li ◽  
L. M. Zhang
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Void Ratio ◽  
Experimental Results ◽  
Dual Porosity ◽  
Porosity Structure ◽  
The Relationship ◽  
Comprehensive Study

The microporosity structure of soil provides important information in understanding the shear strength, compressibility, water-retention ability, and hydraulic conductivity of soils. It is a soil characteristic that depends on sample preparation method and wetting–drying history. A comprehensive study of the microporosity structure of a lean clay with sand was conducted in this research to investigate variations of the microporosity structure during compaction, saturation, and drying processes. Scanning electron microscopy was used to observe the microporosity structure of soil sample surfaces. Mercury intrusion porosimetry was used to measure the microporosity structure quantitatively by showing the relationship between cumulative pore volumes and pore radius. The experimental results show that a dual-porosity structure (i.e., interaggregate pores and intra-aggregate pores) forms during the compaction process. The interaggregate pores are compressible and the associated volume is closely related to the final void ratio of the compacted sample. Changes to interaggregate pores is dominant during compaction, but changes to intra-aggregate pores is dominant during saturation and drying. Based on the experimental results, a dual-porosity structure model was developed by relating the pore-size distribution to the void ratio. Consequently, the pore-size distribution at any void ratio can be predicted.

Laboratory permeability tests on sand: influence of the compaction method on anisotropy

1989 ◽  
Vol 26 (4) ◽  
pp. 614-622 ◽  
Author(s):  
Robert P. Chapuis ◽  
Denis E. Gill ◽  
Karsten Baass
Keyword(s):  
Void Ratio ◽  
Soil Mass ◽  
Granular Soils ◽  
Anisotropy Ratio ◽  
Soil Permeability ◽  
Compacted Soils ◽  
Anisotropy Index ◽  
Preparation Mode ◽  
Hydraulic Anisotropy ◽  
Compaction Method

New laboratory results are presented on how densification influences the hydraulic anisotropy of a sand. Results are given for two compaction modes. Tests were performed at different densities in order to derive the curves kv(e) and kh(e). The samples were statically compacted in the first series and dynamically compacted in the second series. The ratio rk = kh/kv is different for the two series. It is higher than 1 for static compaction and lower than 1 for dynamic compaction. Thus, the anisotropy ratio of granular soils can take several values for the same void ratio, depending on the preparation mode. Even if the anisotropy ratios differ, the first invariant of the hydraulic conductivity tensor, 11k, is found to be a function of e only for this sand, regardless of the densification mode. The evolution of an adimensional anisotropy index, I1k/kv, versus a density index, Ie, is compared for the sand and a dispersed clay. The evolutions are nearly identical, which means that the hydraulic anisotropy of natural homogeneous soils may be similar for sediments having settled in still water and influenced subsequently by gravity only. From an engineering viewpoint, a reasonably good fit is obtained between experimental results and predictive charts. The results also demonstrate that the high apparent anisotropy often found either in natural or in compacted soils is not induced mainly by deposition or compaction but rather is due to nonuniformity or segregation in the soil mass. Key words: soil, permeability, anisotropy, laboratory, compaction.

Yaw Galloping of a TLWP Platform Under High Speed Currents by Analytical Methods and its Comparison With Experimental Results

2017 ◽  
Author(s):  
Francisco Lamas ◽  
Miguel A. M. Ramirez ◽  
Antonio Carlos Fernandes
Keyword(s):  
High Speed ◽  
Production Systems ◽  
Experimental Tests ◽  
Experimental Results ◽  
Analytical Methodology ◽  
New Approach ◽  
Laboratory Facilities ◽  
Polynomial Curve ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Analyses

Flow Induced Motions are always an important subject during both design and operational phases of an offshore platform life. These motions could significantly affect the performance of the platform, including its mooring and oil production systems. These kind of analyses are performed using basically two different approaches: experimental tests with reduced models and, more recently, with Computational Fluid Dynamics (CFD) dynamic analysis. The main objective of this work is to present a new approach, based on an analytical methodology using static CFD analyses to estimate the response on yaw motions of a Tension Leg Wellhead Platform on one of the several types of motions that can be classified as flow-induced motions, known as galloping. The first step is to review the equations that govern the yaw motions of an ocean platform when subjected to currents from different angles of attack. The yaw moment coefficients will be obtained using CFD steady-state analysis, on which the yaw moments will be calculated for several angles of attack, placed around the central angle where the analysis is being carried out. Having the force coefficients plotted against the angle values, we can adjust a polynomial curve around each analysis point in order to evaluate the amplitude of the yaw motion using a limit cycle approach. Other properties of the system which are flow-dependent, such as damping and added mass, will also be estimated using CFD. The last part of this work consists in comparing the analytical results with experimental results obtained at the LOC/COPPE-UFRJ laboratory facilities.

scholarly journals Numerical and experimental evaluation of masonry prisms by finite element method

2017 ◽  
Vol 10 (2) ◽  
pp. 477-508 ◽  
Author(s):  
C. F.R. SANTOS ◽  
R. C. S. S. ALVARENGA ◽  
J. C. L. RIBEIRO ◽  
L. O CASTRO ◽  
R. M. SILVA ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
High Strength Concrete ◽  
Numerical Models ◽  
High Strength ◽  
Experimental Tests ◽  
Experimental Results ◽  
Concrete Blocks ◽  
Micro Modeling ◽  
Modeling Strategy

Abstract This work developed experimental tests and numerical models able to represent the mechanical behavior of prisms made of ordinary and high strength concrete blocks. Experimental tests of prisms were performed and a detailed micro-modeling strategy was adopted for numerical analysis. In this modeling technique, each material (block and mortar) was represented by its own mechanical properties. The validation of numerical models was based on experimental results. It was found that the obtained numerical values of compressive strength and modulus of elasticity differ by 5% from the experimentally observed values. Moreover, mechanisms responsible for the rupture of the prisms were evaluated and compared to the behaviors observed in the tests and those described in the literature. Through experimental results it is possible to conclude that the numerical models have been able to represent both the mechanical properties and the mechanisms responsible for failure.

scholarly journals The relationship between aerosol and cloud drop number concentrations in a global aerosol microphysics model

2009 ◽  
Vol 9 (1) ◽  
pp. 3207-3241 ◽  
Author(s):  
K. J. Pringle ◽  
K. S. Carslaw ◽  
D. V. Spracklen ◽  
G. M. Mann ◽  
M. P. Chipperfield
Keyword(s):  
Size Distribution ◽  
Cloud Droplet ◽  
Global Scale ◽  
Rate Of Change ◽  
The Arctic ◽  
Aerosol Size Distribution ◽  
Percentage Error ◽  
Empirical Relationships ◽  
Wide Range ◽  
Global Mean

Abstract. Empirical relationships that link cloud droplet number (CDN) to aerosol number or mass are commonly used to calculate global fields of CDN for climate forcing assessments. In this work we use a sectional global model of sulfate and sea-salt aerosol coupled to a mechanistic aerosol activation scheme to explore the limitations of this approach. We find that a given aerosol number concentration produces a wide range of CDN concentrations due to variations in the shape of the aerosol size distribution. On a global scale, the dependence of CDN on the size distribution results in regional biases in predicted CDN (for a given aerosol number). Empirical relationships between aerosol number and CDN are often derived from regional data but applied to the entire globe. In an analogous process, we derive regional "correlation-relations" between aerosol number and CDN and apply these regional relations to calculations of CDN on the global scale. The global mean percentage error in CDN caused by using regionally derived CDN-aerosol relations is 20 to 26%, which is about half the global mean percentage change in CDN caused by doubling the updraft velocity. However, the error is as much as 25–75% in the Southern Ocean, the Arctic and regions of persistent stratocumulus when an aerosol-CDN correlation relation from the North Atlantic is used. These regions produce much higher CDN concentrations (for a given aerosol number) than predicted by the globally uniform empirical relations. CDN-aerosol number relations from different regions also show very different sensitivity to changing aerosol. The magnitude of the rate of change of CDN with particle number, a measure of the aerosol efficacy, varies by a factor 4. CDN in cloud processed regions of persistent stratocumulus is particularly sensitive to changing aerosol number. It is therefore likely that the indirect effect will be underestimated in these important regions.

Determination of Thermal Conductivity of Soils: A Need for Computing Heat Loss Through Buried Submarine Pipelines

1982 ◽  
Vol 22 (04) ◽  
pp. 558-562 ◽  
Author(s):  
P.C. Rawat ◽  
S.L. Agarwal
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Crude Oil ◽  
Rheological Properties ◽  
Heat Loss ◽  
Experimental Results ◽  
Dry Density ◽  
Empirical Relationships ◽  
Thermal Conductivities

Abstract An important parameter required for computing heat loss through buried submarine pipelines transporting crude oil is the thermal conductivity of soils. This paper describes an apparatus designed for determination of the thermal conductivity of soils at the desired moisture/ density condition in the laboratory under steady-state conditions. Experimental results on the three soils studied show that thermal conductivity increases as dry density increases at a constant moisture content and that it increases as water content increases at constant dry density. These results confirm the trends isolated earlier by Kersten. The experimental results are compared with the available empirical relationships. Kersten's relation is observed to predict the thermal conductivity of these soils reasonably. The predictions from Makowski and Mochlinski's relation (quoted by Szilas) are not good but improve if the sum of silt and clay fractions is treated as a clay fraction in the computation. Introduction Submarine pipelines are used extensively for transporting crude oil from offshore to other pipelines offshore or onshore. These pipelines usually are steel pipes covered with a coating of concrete. They often are buried some depth below the mudline. The rheological properties of different crude oils vary, and their viscosities increase with a decrease in temperature. Below some temperature, the liquid oil tends to gel. Therefore, for efficient transportation, the crude must be at a relatively high temperature so that it has a low viscosity. The temperature of the soil/water system surrounding a submarine pipeline is usually lower than that of oil. This temperature difference induces heat to flow from the oil to the environment, and the temperature of the oil decreases as it travels along the length of the pipeline. One must ensure that this temperature reduction does not exceed desirable limits dictated by the rheological properties of oil and by the imperatives of efficient economic properties of oil and by the imperatives of efficient economic transportation. Thus the analytical problem is to predict the temperature of crude in the pipeline some distance away from the input station. To do so, knowledge of the overall heat transfer coefficient for the pipeline is required, for which, in turn, it is necessary to know the thermal conductivities of the oil, the pipeline materials and its coating, and the soil. This paper presents thermal conductivities of soils determined in the laboratory under steady-state conditions and also presents a comparison of the test results of three soils with values determined from existing empirical relationships. Literature Review Heat moves spontaneously from higher to lower temperatures. In a completely dry porous body, transmission of heat can take place not only by conduction through the solid framework of the body and the air in the pores but also by convection and radiation between the walls of a pore and by macro- and microdistillation. In soils, however, it can be ascribed essentially to conduction, a molecular phenomenon that can be expressed in terms of experimentally determined coefficients of conductivity or resistivity, although these actually may include microdistillation and other mechanisms. SPEJ p. 558

Experimental Investigation of Flowrate Irregularity in Rotary Gear Pumps

1992 ◽  
Author(s):  
G. Mimmi
Keyword(s):  
Experimental Investigation ◽  
Flow Rate ◽  
Experimental Tests ◽  
Periodic Variation ◽  
Experimental Results ◽  
Gear Pump ◽  
Gear Pumps ◽  
Hot Film ◽  
Instantaneous Flow Rate ◽  
External Gear Pump

Abstract In a previous paper the author proposed a method to reduce the periodic variation in flow rate for an external gear pump. To verify the experimental results, a series of experimental tests on a expressly realized gear pump, was carried out. The pump was equipped with relieving grooves milled into the side plates. The tests were done on a closed piping specifically realized and equipped for measuring the instantaneous flow rate of the fluid through a wedge-shaped hot film probe.

scholarly journals Determining efficiency of cycloid reducers using different calculation methods

2019 ◽  
Vol 290 ◽  
pp. 01008
Author(s):  
Milos Matejic ◽  
Mirko Blagojevic ◽  
Ileana Ioana Cofaru ◽  
Nenad Kostic ◽  
Nenad Petrovic ◽  
...  
Keyword(s):  
Comparative Analysis ◽  
Analytical Methods ◽  
Common Property ◽  
Experimental Results ◽  
Calculation Methods ◽  
Wide Range ◽  
Pros And Cons ◽  
Gear Trains ◽  
Central Gear ◽  
The Way

Cycloid reducers are gear trains which can be classified as planetary transmissions. These transmissions have a very wide range of uses in industry in transporters, robots, satellites, etc. This research presents a comparative analysis of three analytical methods for determining cycloid drive efficiency. The paper explores every mathematically formulated method and compares them to experimental results from literature. The presented methods for determining efficiency have a common property, in that they all determine losses due to friction on the bearing cam surface of the shaft, the rollers of the central gear and the output rollers. The calculation of efficiency values is done for standard power values. The methods differ primarily in the way they calculate losses. For each method of calculating efficiency there is an analysis of pros and cons. The paper concludes with suggestions as well as possible directions for further research.

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