A new approach to DEM simulation of sand production

Cui, Yifei; Nouri, Alireza; Chan, Dave; Rahmati, Ehsan

doi:10.1016/j.petrol.2016.05.007

Cited by 96 publications

(31 citation statements)

References 16 publications

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“…More importantly, stress effects on SFCCs and its hysteresis loop of sand specimens are much smaller than those of clay specimens. This is probably because that the stress‐induced change in pore size distribution is smaller in sand due to its smaller compressibility (Cui et al, 2016). As shown in Table 2, the void ratio of sand only decreases by 1.5% with increasing the confining stress from 30 to 200 kPa.…”

Section: Resultsmentioning

confidence: 99%

Stress Effects on Soil Freezing Characteristic Curve: Equipment Development and Experimental Results

Mu¹,

Zhou

et al. 2019

Vadose Zone Journal

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Core Ideas A triaxial apparatus is developed to measure stress‐dependent SFCC. Unfrozen water content of clay and sand increases with increasing confining stress. Stress effects on the SFCC of clay are more significant than sand. The soil freezing characteristic curve (SFCC) defines the relationship between soil temperature and unfrozen water content. This curve is important for predicting water flow and heat conduction in frozen soils, as well as freezing heave and thawing settlement. So far, SFCCs reported in the literature were usually determined at zero stress. To investigate stress effects on SFCC, a stress‐ and temperature‐controlled triaxial apparatus was developed in this study. The unfrozen volumetric water content was measured using a newly developed noninvasive time domain reflectometry (TDR) probe. The new apparatus was used to measure SFCCs of two typical soils (i.e., clay and sand) at different stress conditions (i.e., 30, 100, and 200 kPa). Each specimen was subjected to compression, and then a cycle of freezing and thawing. As expected, for both soils, the saturated water content prior to freezing was smaller at higher stresses because of compression. During the subsequent freezing and thawing, the soil specimen at a higher stress was able to retain more liquid water than that at a lower stress. The higher unfrozen water retention capacity at higher stresses is mainly because the pore size of a soil specimen becomes smaller during compression. Hence, more water can retain a liquid state due to the enhanced capillarity. On the other hand, stress effects on the SFCC were found to be more significant for clay than for sand. This is likely because the stress‐induced change in pore size distribution is larger in clay due to its higher compressibility.

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Section: Resultsmentioning

confidence: 99%

Stress Effects on Soil Freezing Characteristic Curve: Equipment Development and Experimental Results

Mu¹,

Zhou

et al. 2019

Vadose Zone Journal

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“…A DEM model is generated by using 2 horizontal and 1 cylindrical rigid wall with a radius of 25 mm and height of 100 mm, as shown in Figure . Potyondy and Cundall stated that for a sample with a constant Young's modulus E s , the normal stiffness K sm of each particle m is calculated as

K_{sm} = 4 R_{m} E_{s}

where R m is the radius of each particle m . To obtain the optimum calculation speed, the simulation here increases the particle radius to 1 mm but maintains the same Young's modulus (7 × 10 9 Pa in the current simulation) compared with the isotropic compression test.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…Significant errors in the calculated porosity will result when the measurement sphere includes only 4 or fewer particles . On the other hand, inaccurate permeability calculations result when part of the measurement sphere lies outside the sample . As shown in Figure , the criterion for the distance d between the measurement sphere and the boundary wall, in the radial direction, is calculated as shown in the following equation:

d > \frac{Δs}{2}

where ∆ s is the total displacement of the boundary wall in one of the principle directions under the maximum applied boundary stress during the entire simulation.…”

Section: Numerical Resultsmentioning

confidence: 99%

Coupling of solid deformation and pore pressure for undrained deformation—a discrete element method approach

Cui

Chan

Nouri

2017

Num Anal Meth Geomechanics

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Summary This paper presents a numerical scheme for fluid‐particle coupling that uses the discrete element method by taking into consideration solid deformation and pore pressure generation. A new water particle element is introduced to calculate pore water pressure due to porosity changes. The water particle element has the same size and shape as the solid element and experiences the same amount of deformation. On the basis of the effective stress principle at the element contact, the total force is equal to the sum of the force transmitted through the solid element contact and the water particle force due to pore water pressure. Analytical solutions of traditional soil mechanics problems, such as isotropic compression and consolidated triaxial undrained test, are used to quantitatively validate the proposed model. The numerical results show good agreement between the model and the analytical solutions. The model therefore provides an effective method to calculate pore pressure in a porous medium in discrete modeling.

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“…The measurement sphere is a built-in tool in PFC3D to help the user measure quantities such as coordination number, porosity, and strain rate in a specific measurement volume at the current state [12]. The diameter of the measurement sphere should be large enough and it should include at least 20 particles in calculating the average values [13].…”

Section: Measurement Modelmentioning

confidence: 99%

“…Several measurement spheres of 117, 118 and 120 are determined based on the varation of coordination number and porosity for calibrating the localization of shear surface when the increase is larger than 50%. The volumetric strain can be calculated by measuring the volumetric strain rate in a measurement circle [13]. The variation of the volumetric strain determines the contraction or dilation behavior of the material.…”

Section: Variations Of the Porosity Coordination Number And Volumetrmentioning

confidence: 99%

Application and Analysis of Measurement Model for Calibrating Spatial Shear Surface in Triaxial Test

Zhang

Qiu

Zhang

et al. 2017

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. Discrete element method has great advantages in simulating the contacts, fractures, large displacement and deformation between particles. In order to analyze the spatial distribution of the shear surface in the three-dimensional triaxial test, a measurement model is inserted in the numerical triaxial model which is generated by weighted average assembling method. Due to the non-visibility of internal shear surface in laboratory, it is largely insufficient to judge the trend of internal shear surface only based on the superficial cracks of sheared sample, therefore, the measurement model is introduced. The trend of the internal shear zone is analyzed according to the variations of porosity, coordination number and volumetric strain in each layer. It shows that as a case study on confining stress of 0.8 MPa, the spatial shear surface is calibrated with the results of the rotated particle distribution and the theoretical value with the specific characteristics of the increase of porosity, the decrease of coordination number, and the increase of volumetric strain, which represents the measurement model used in threedimensional model is applicable.

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A new approach to DEM simulation of sand production

Cited by 96 publications

References 16 publications

Stress Effects on Soil Freezing Characteristic Curve: Equipment Development and Experimental Results

Stress Effects on Soil Freezing Characteristic Curve: Equipment Development and Experimental Results

Coupling of solid deformation and pore pressure for undrained deformation—a discrete element method approach

Application and Analysis of Measurement Model for Calibrating Spatial Shear Surface in Triaxial Test

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